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Introduction
What if I told you that a handful of tiny greens could help protect you against cancer? The study "Can Edible Sprouts Be the Element of Effective Chemoprevention Strategy?" by Grudzinska et al. (2023) explores how these humble little sprouts might just be your new secret weapon in the fight against cancer.
The Power of Sprouts: Small but Mighty
Sprouts may look like they belong in a salad and nowhere else, but don't let their appearance fool you. They’re bursting with powerful compounds that could help protect your body at the cellular level.
Grudzinska and her team dove deep into the science and found that sprouts, especially those from cruciferous vegetables like broccoli, radish, and cabbage, are loaded with bioactive compounds. These aren’t just any nutrients—they’re the kind that have serious cancer-fighting potential.
Here's What the Study Found
Let’s get straight to the exciting stuff. Here’s what the research uncovered about the role of sprouts in cancer prevention:
1. Rich in Glucosinolates
2. Antioxidant Powerhouses
3. Boosting Detoxification Enzymes
4. Supporting Immune Function
5. Inhibiting Tumor Growth
How to Get These Benefits
It’s simple—start eating more sprouts. These powerful greens can easily become a regular part of your diet. Here are a few ways to enjoy them:
Want to Learn More? Dive Into the Research
Curious about the details? Check out the full study written below, titled "Can Edible Sprouts Be the Element of Effective Chemoprevention Strategy?" by Grudzinska et al. (2023). It’s packed with information on how sprouts work at a molecular level to help protect you from cancer. The more you know, the more you'll want to keep these greens in your diet.
Conclusion
Sprouts are more than just a garnish—they’re a powerful tool in the fight against cancer. The science is clear: these tiny greens are loaded with compounds that protect your cells, boost your immune system, and help your body detoxify. So why not make them a regular part of your diet?
At The Sprouting Company, we make it easy for you to get started. Our sprouting kits are designed for simplicity, so you can grow fresh, nutritious sprouts right at home. Take control of your health, one sprout at a time.
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Full Study: Edible Plant Sprouts: Can edible sprouts be the element of an effective chemopreventive strategy? - A systematic review of in vitro and in vivo study
By Marta Grudzinska, Agnieszka Galanty, and Pawel Pasko
Abstract
Background
Cancer is a disease that seriously and increasingly threatens human health and life, affecting various organs such as breast, lung, colon and rectum, prostate, or stomach. Because of that, it is important to find appropriate chemopreventive agents that can prevent the development of cancer in humans. One such method may be a healthy diet rich in vegetables and fruits, including sprouts, which have recently gained popularity due to their health-promoting properties and easy cultivation process.
Scope and Approach
This systematic review aims to collect the results of all published studies on the chemopreventive potential of sprouts of various edible plants to select the most promising species for further research. This paper focused on the impact of sprout extracts on cancer cells in vitro, as determined by the inhibition of tumor cell proliferation, growth, and viability, or apoptosis stimulation, with special interest in the results of in vivo and human studies. The influence of different cultivation conditions and biofortification with selenium and probiotics on the activity of sprouts was assessed. Attempts were also made to indicate the main compounds responsible for sprouts’ biological activity.
Key Findings and Conclusions
Most results suggest that sprouts may play a role in chemoprevention, as a part of the daily diet, with especially encouraging effects observed for broccoli sprouts. However, further research on cultivation conditions, safety profile, the impact of Se-enrichment, or pharmacokinetic studies are necessary to assess the effectiveness of sprouts as chemopreventive agents in humans.
Introduction
Cancer is one of the most serious health concerns worldwide, with the most common new cases of the disease comprising breast, lung, colon and rectum, prostate, skin, and stomach cancers. WHO estimated that about 30% of cancer deaths, linked to different harmful behavioral activities such as high body mass index, low fruit and vegetable intake, lack of physical activity, and also tobacco and alcohol abuse, could be preventable. One of the ideas to prevent cancer development at early stages is an intervention based on a specially composed diet, rich in fruits and vegetables, including sprouts. Sprouts of various edible plants have gained popularity in recent years. A definite advantage of sprouts is their wide availability and the possibility of purchasing them in most grocery stores around the world. Sprouts are easy to grow, inexpensive examples of functional food, harvested at an early stage of plant growth, and intended for eating as a whole, with the seeds. As soon as the growing of the sprouts begins, the production of bioactive components instantly increases, making them a richer source of nutrients and phytochemicals compared to plants at later stages of development. These include compounds from different chemical groups with proven cytotoxic, antioxidant, and anti-inflammatory potential, such as sulfur compounds (glucosinolates and their derivates – isothiocyanates), flavonoids (i.e., isoflavones, flavanols, anthocyanins), phenolic acids, lignans, carotenoids, betacyanins, or stilbenes. It should also be emphasized that the amount of antinutritive compounds in sprouts (e.g., enzyme inhibitors, phytic acid) decreases significantly in comparison to the seeds, which means that sprouting processes significantly improve digestibility and nutrient utilization by organisms.
Chemoprevention is understood as the process of inhibiting, reversing, or preventing the development of cancer in humans. Chemopreventive agents should be non-toxic and easily applicable on a large scale. These include a wide range of medicinal and edible plants, among which sprouts of the latter, containing a variety of easily absorbed nutrients and phytochemicals, meet these expectations. Especially in recent years, there has been a clear increasing tendency in the number of publications concerning the chemopreventive activity of sprouts of edible plants, emphasizing the importance of the topic.
This review aims to evaluate the role that edible plant sprouts may play in chemoprevention. We focused on the impact of sprout extracts directly on cancer cells in vitro as determined by the inhibition of tumor cell proliferation, growth, and viability, or apoptosis stimulation, with special interest in the results of in vivo and human studies. As it is known that chronic inflammation is associated with tumor development by stimulating tumor cell proliferation, metastasis, or suppressing the immune response, this aspect was included in the review. To better address the subject of the review, different efforts to modulate the content of phytochemicals in the sprouts, translating into their chemopreventive potential, were included as well.
Materials and Methods
This systematic review was conducted in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. The following databases were searched: PubMed, Scopus, and Google Scholar, and the data was collected until the end of December 2022. The keywords used were "sprouts" in combination with "anti-cancer", "anti-tumor", "apoptosis", "chemopreventive", "anti-inflammatory", and "cytotoxic". There were no time limits, and the language used in the articles was English. Due to the large number of records in the Google Scholar database, the method of searching by keywords contained in the title (allintitle formula) was used. The inclusion criteria were research articles that described the chemopreventive activity of edible plants’ sprouts extracts in vitro and in vivo. The exclusion criteria were review articles, articles describing the activity of pure compounds found in the sprouts, and studies in which the sprouts of inedible plants were used. Moreover, works describing solely the antioxidant activity of the sprouts were also excluded, as this aspect has been often reviewed. 2761 articles were selected for review in the first stage of the search. Then, the article selection process was carried out using the Rayyan software, where 1064 duplicates were removed, 1697 articles were used for further screening, and finally 108 articles were selected. The details of the search method are presented in Fig. 1.
Cytotoxic Activity in Vitro
The in vitro cytotoxic activities of the sprouts are presented in Table 1 and graphically summarized in Fig. 2. The experiments were conducted on cancer cells of various tissue origins, with the predominance of human cell lines, and only two of animal origin (murine colorectal CT26 and prostate Mat-Ly-Lu). Almost half of the cell lines used in the studies were of gastrointestinal origin, while about 40% of the cell lines used were of urogenital origin. These types of experiments seem to be justified, as the sprouts consumed may exert their effects directly on the gastrointestinal tract cancer cells, while hormone-dependent prostate cancer cells may be affected by phytoestrogens (e.g., isoflavones), which are structurally similar to natural hormones. Isoflavones and sulfur compounds, present in the sprouts, can also affect the functioning of thyroid gland cancer cells, although this interesting direction of studies is represented by only 2% of the reviewed experiments. The remaining 10% of the studies comprised the effects of sprouts on lung, melanoma, leukemia, or osteosarcoma cells, the choice of which does not seem to be clearly justified, in terms of potential chemoprevention. As far as sample preparation is concerned, sprouts were extracted with different solvents, most often methanol, ethanol, or water, and only a few studies conducted simulated in vitro digestion of sprouts, which, in turn, is a method that better reflects the actual behavior of sprouts after their consumption by humans. Therefore, it is important to use the in vitro digestion method more widely in the study of the chemopreventive activity of sprouts.
Most of the results obtained during the studies included in this review indicate that the cytotoxic activity of sprouts, expressed as IC50, falls within the range 50–500 μg/mL, which can be classified as moderate (21–200 μg/mL) and weak (201–500 μg/mL) activity, according to the criteria of the National Cancer Institute and Geran protocol. However, in three cases, the sprouts of fenugreek (Trigonella foenum-graecum L.), red clover (Trifolium pratense L.), and broccoli (Brassica oleracea var. italica Plenck) were highly cytotoxic to breast MCF-7 and MDA-MB-231, and thyroid FTC133 cancer cells, with IC50 values of 2.5, 14.8, and 16.9 μg/mL, respectively. On the other hand, a few of the sprouts tested, e.g., mung bean or peanut, revealed activity above 501 μg/mL, which classified them as not active. Interestingly, in some cases, a significant increase in cytotoxic activity was observed after the elongation of incubation time.
Apart from the effectiveness, the search for chemopreventive agents should also be accompanied by the determination of their safety. Preliminary safety studies can be performed on non-cancerous cells of appropriate tissue origin, and may indicate the selectivity of the examined product. Only a few of the reviewed studies included this aspect and examined the sprouts' effect also on normal cells, namely: kale sprouts on Nthy-ori 3–1, kohlrabi sprouts on BJ, radish sprouts on NIH3T3, fenugreek sprouts on Vero, red clover sprouts on HUVEC, peanut sprouts on BdFC, rutabaga sprouts on CHO–K1, and broccoli sprouts on FL83B cells. These results suggest that most of the tested sprouts are safe for normal cells, up to concentrations as high as 800 μg/mL. The exception is the study on fenugreek sprouts, which were as toxic to normal Vero cells as to cancer MCF-7 cells (IC50 2.5 μg/mL). The safety of two cultivars of radish (cv. Rebel and cv. Bolide), alfalfa (Medicago sativa), and fenugreek sprouts was proven with the use of HL60 leukemia cells; however, the use of cancer cells in this model makes the result questionable. Also, very few studies mentioned the use of a reference positive control, examples of compounds used are cisplatin, triton X-100, concanavalin A, and docetaxel. The standard incubation time during the cytotoxic experiments was 24 h, but in some cases, the activity was determined also after 48, or even prolonged 72 h of exposure.
The sprouts used in the studies were grown most often for 5–12 days. In two studies, sprouts grown for 25 days were used; however, they should be classified rather as microgreens. In some cases, the sprouts were grown in special conditions, e.g., in the light of different wavelengths, which is discussed later in this review. The plant that has been most extensively studied in terms of cytotoxic activity is broccoli belonging to the Brassicaceae family.
As far as the mechanisms of cytotoxic activity are concerned, some studies indicated the pro-apoptotic potential of the sprouts. Methanol extracts of radish sprouts tested on lung adenoma cells panel, differing in p53 expression, showed significant cytotoxic effects, dependent on the cell type. The sprouts clearly reduced the viability of H1299 and Calu-6 cells (p53-deleted) by inducing apoptosis, which depends on p53 status, but no effect was observed for non-cancerous NIK3t3 cells and A549 cells (expressing a p53 mutant lacking the C terminus). Water extracts from 5- and 7-day-old sprouts of mustard (Brassica juncea), turnip (B. rapa), and cauliflower (B. oleracea) showed strong cytotoxic effects on PC-3 prostate cancer cells. The sprouts caused an increase in the amount of reactive oxygen species, which could be a direct cause of cell death, and DNA fragmentation, which indicates apoptosis. Moreover, all the extracts caused a significant increase in the G0 fraction of the PC-3 cells in cell cycle analysis. In one study, flaxseed (Linum usitatissimum L.) sprouts ethanol extract significantly reduced the growth of estrogen-receptor-negative MDA-MB-231 and estrogen-receptor-positive breast cancer cells MCF-7, while being harmless to non-cancerous MCF-10A cells. The extract stimulated apoptosis in the cancer cells, observed as an increased upregulation of p53 mRNA. Mung bean (Vigna radiata L.) sprouts extract induced apoptosis in cervix adenocarcinoma (HeLa) and hepatocellular carcinoma (HepG2) cells, in 56.6% and 55.4%, respectively, after 24 h of treatment. The tested extract arrested HeLa cells in G0/G1 phase of the cell cycle, when compared to the untreated cells. Interestingly, the difference was observed in the expression of apoptosis and tumor suppressor-related genes, in the tested cells the extract stimulated the expression of cdk-inhibitors, p21, p53, and p27 in HeLa cells, while in HepG2 cells only p53 expression was enhanced. Pro-apoptotic effects were also observed for lentil (Lens culinaris Medik.), yellow and green pea (Pisum sativum L.) methanol extracts in human colon carcinoma Caco-2 cells, manifested as DNA fragmentation, cell surface blebbing, apoptotic bodies, cell membrane destabilization, but also the increase in caspase-3 activity. What is important, the extracts from sprouting plants were more active compared to extracts from non-sprouted plants. Studies on the Poaceae family report on the pro-apoptotic activity of wheat sprout hydroalcoholic extracts and confirm their ability to inhibit the activity of the 20s proteasome and induce apoptosis in Caco-2 and HeLa cancer cells. Ki et al. observed a significant decrease in viability in human hepatic, lung, gastric, and bone cancer cell lines, related to cell cycle arrest, apoptosis, and caspase-dependent cell death by the dichloromethane fraction of Triticum aestivum sprouts. In another study, black and white varieties of glutinous rice (Oryza sativa L.) sprouts methanol extracts were analyzed. Among all tested cancer cells: human T-lymphocyte (Jurkat), melanoma (SK-MEL-2), hepatocellular carcinoma (HepG2), and colorectal carcinoma (HCT116), Jurkat cells were the most susceptible to the effect of black glutinous rice sprouts, which was observed as the decrease in their proliferation. Moreover, black glutinous rice sprouts extract from 10 to 15 and 20–25-day-old sprouts at concentrations of 200 μg/mL significantly induced apoptosis of 30.5% and 31.2%, respectively, in comparison to untreated cells (15.9%).
The summary of in vitro activity of sprouts on various cancer cell lines and their mechanisms of action are presented in Table 1.
Chemopreventive/Anti-Cancer Activity in Vivo
Although the vast majority of the studies included in this review were performed in vitro, a number of in vivo studies also described the interesting chemopreventive potential of the sprouts. Details of the in vivo studies are gathered in Table 2 and graphically summarized in Fig. 2.
Mammary Cancer
Broccoli sprouts powder, added to the diet, reduced the risk of developing estrogen receptor (ER)–negative mammary cancer in HER2/neu mice and their pups, and the combination of sprouts with green tea polyphenols significantly reduced tumor weight and volume, compared with the control group. The volume of the tumor in the experimental group decreased about five times, when compared to the control. Combined use of broccoli sprouts with green tea polyphenols was more effective in inhibiting the cell cycle and promoting apoptosis in mice with ER-negative mammary tumors by regulating B-cell lymphoma 2 and Bcl-2-associated X protein, in comparison to broccoli sprouts or green tea polyphenols administered alone. It is worth mentioning that tumor weight and volume were reduced to a greater extent when broccoli sprouts were administered than with green tea polyphenols, therefore, it can be suggested that sprouts, whose activity is enhanced by the presence of polyphenols, are mainly responsible for the above-mentioned effect. Broccoli sprouts prevented the development of mammary cancer not only in mice fed with the sprouts but also in their offspring, and epigenetic regulation was the basis for this effect. The supply of broccoli sprouts in the prenatal period showed the strongest protective effect, when compared to the animals supplemented after birth and before the onset of puberty. On the other hand, the administration of the sprouts to adult mice did not inhibit the tumorigenesis process. Arora et al. tried to explain the mechanism of the chemopreventive effect of broccoli sprouts against mammary cancer development in the offspring of the mice mothers administered with the sprouts. The diet rich in broccoli sprouts affected the activity of histone deacetylases and DNA methyltransferase, as well as changes in the genes, responsible for the key processes in carcinogenesis.
Prostate Cancer
Broccoli sprouts after oral administration in mice have a significant inhibitory effect on the development of prostate cancer. In TRAMP mice fed with broccoli sprouts, a significant inhibition of prostate tumor growth was observed, the induction of pro-apoptotic proteins and the Nrf2/ARE pathway and the simultaneous inhibition of the Akt/mTOR cascade are probably responsible for this effect. In another study, a decrease in the incidence of prostate cancer and the expression of the HDAC3 protein was observed in TRAMP mice. Interesting results of an experiment using kale (Brassica oleracea) sprouts on the LNCaP xenograft model (hormone-dependent human prostate cancer) were described. Although no reduction in tumor size was achieved, the supplementation of diet with kale sprouts resulted in the inhibition of tumor necrosis, decrease in hemorrhage, and induction of vascular maturation, compared to the control group. The sprouts also caused the inhibition of pro-angiogenic factors such as matrix metalloproteinase (MMP), placental growth factor (PIGF), basic fibroblast growth factor (bFGF), at the same time anti-angiogenic factor angiostatin was stimulated.
Miscellaneous
Munday et al. confirmed that an aqueous extract of broccoli sprouts sprouts inhibits the development of bladder cancer in rats. The sprouts
stimulated the activity of antioxidant enzymes such as GST and NQO1 in
the bladder. The authors concluded that this activity is due to iso-
thiocyanates present in the extract, the equivalents of which were
determined in a greater amount (2–3 times more) in urine than in
plasma.Broccoli sprouts extracts standardized for the content of sulforaph-
ane, reduced the incidence of skin cancer by 50% after topical appli-
cation in mice after exposure to UV radiation (details in Table 2) (Dinkova-Kostova et al., 2006). Wheat sprouts significantly inhibited the growth of melanoma in a mouse model using B16 cells, and this effect was comparable to the effect of cisplatin used as a reference drug. The authors suggested that the anticancer effect in this case was due to the immunomodulatory effect caused by the wheat sprouts, which significantly increased the concentration of IL-12 and IFN-γ in mice (Ki et al., 2017). Mung bean sprouts turned out to be more effective than mung bean seeds in limiting the development of colon cancer, induced with 1,
2-dimethylhydrazine (DMH), in rats. Although it seems not credible, the authors claim that the activity of the sprouts was comparable to 5-fluorouracil (Kabr ́e et al., 2022).
Anti-Inflammatory Activity
In Vitro
Kang et al. (2021) investigated the anti-inflammatory effect of Actinidia arguta sprout water extract on LPS-induced HT-29 colorectal cancer cells at a wide concentration range of 10–200 μg/mL. The obtained results indicated a protective effect of the extract on HT-29 cells by decreasing IL-6 expression and increasing cell viability, even at the lowest concentration (10 μg/mL) tested. It was shown that the level of pro-inflammatory IL-6 was reduced in the cells treated with the extract at the concentration of 100 μg/mL. In another study, 6-day-old onion (Allium cepa L.) sprouts were used, from which a water extract was made (sample I), the filtrate (sample II), and a methanolic extract from the filtrate remaining after steam distillation were also used. The results showed that sample I had a dose-dependent anti-inflammatory effect (77.9% inhibition of hydroperoxides activity induced by lipoxygenase), similar activity was shown by sample II (inhibition up to 80% concentration), and the methanol sample had no noticeable anti-inflammatory activity (Takahashi & Shibamoto, 2008). One of the studies focused on the anti-inflammatory properties of a partially purified extract of ginseng sprouts (PGE) and sprout extract enriched with compound K (CKE), which is a ginsenoside biotransformed metabolite. CKE was more effective in reducing the level of nitric oxide (NO) and the amount of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β compared to PGE. In turn, PGE showed stronger antioxidant activity than CKE (Baik et al., 2021).
The anti-inflammatory activity of broccoli sprouts was examined in a few studies. It has been proved that broccoli sprouts inhibited the formation of advanced glycation end products, and the use of 1% broccoli sprout extract on HUVEC cells prevented the formation of reactive oxygen species (ROS) (Sotokawauchi et al., 2018). The sprouts reduced the amount of pro-inflammatory cytokines such as TNF-α and IL-6 and increased the production of anti-inflammatory cytokines such as IL-10 (Olszewska et al., 2020). In turn, in the cyclooxygenase (COX) inhibition experiment, the extract from 7-day-old broccoli sprouts showed anti-inflammatory activity with IC50 81 μg/mL, which was a better result compared to the seed extract and mature broccoli (IC50 109 and 127 μg/mL, respectively). Interestingly, the activity of the sprouts was also higher than the reference drugs, i.e., aspirin (IC50 140 μg/mL) and flufenamate (IC50 198 μg/mL) (Shams et al., 2017).
In Vivo
Details of all animal experiments are presented in Table 2. The above-mentioned in vitro study on Actinidia arguta sprout water extract was completed by an experiment on brain tissues of mice with inflammation induced by the administration of LPS. The extract administered orally effectively reduced the amount of pro-inflammatory cytokines such as IL-6 and TNF-α, and the expression of p-JNK and p-NF-κB proteins involved in the inflammatory response (Kang et al., 2021).
In an experiment conducted by Venkateshwarlu et al. (2016), mung bean sprouts’ anti-arthritic activity was assessed in rats. The sprouts significantly attenuated the biochemical changes induced in rats by the administration of complete Freund’s adjuvant, reduced the amount of pro-inflammatory cytokines such as TNF-α and IL-1β in serum in higher doses (500 mg/kg), while lower doses (250 mg/kg) did not prove to be significantly active. The MDA level was also reduced, and total reduced glutathione (GSH) content was increased, as well as myeloperoxidase (MPO) activity.
An ointment containing 5% of peanut sprouts ethanol extract administered to mice with induced contact dermatitis showed anti-inflammatory activity, observed as a decrease in skin lesions (desquamation and thickening of the skin) and in the activity and level of biomarkers of inflammation: COX-2 and nerve growth factor (NGF) (Choi et al., 2015). One study also confirmed the anti-inflammatory activity of ethyl acetate extract of alfalfa sprouts, which caused a reduction in the amount of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in the serum and increased the survival rates of mice (Hong et al., 2009). In vivo studies were also carried out using a specially prepared mixture from red bean (Phaseolus vulgaris L.) sprouts. In rats with carrageenan-induced hind paw edema, the mixture reduced the volume of edema and increased rat mobility, thus exerting an anti-inflammatory effect correlated with the content of phenolic compounds (Winarsi et al., 2020).
One study evaluated the effects of barley sprouts on alcohol-induced liver damage in mice, mediated by inflammation and oxidative stress. The sprouts inhibited the synthesis of TNF-α, pro-inflammatory interleukins IL-6 and IL-1β, and exerted a protective effect on the liver damaged by alcohol, which confirms their anti-inflammatory properties (Lee et al., 2016). The anti-inflammatory effect of buckwheat sprouts was confirmed in a study involving LPS-stimulated mice. Oral administration of buckwheat sprout ethanol extracts resulted in a decrease in the level of pro-inflammatory cytokines (IL-6 and TNF-α). A protective effect on the liver was also demonstrated, in which damage was induced by glucosamine/LPS (Ishii et al., 2008).
Human Studies
Only a few of all researched articles concerned the chemopreventive potential of sprouts tested in humans, and the majority of the studies concerned broccoli sprouts. The details of all experiments are presented in Table 3.
The study by Atwell et al. (2015) was the first to provide evidence for the possibility of using broccoli sprout extract with myrosinase, which was used to release sulforaphane from its precursor glucoraphanin, to study their chemopreventive activity in humans. The main objective of this study was to compare the bioavailability of sulforaphane after the consumption of fresh sprouts and sprouts’ extract. The amount of sulforaphane metabolites in the plasma and urine of people consuming fresh broccoli sprouts was three times higher compared to those who were administered extract from broccoli sprouts, proving the lower bioavailability of sulforaphane from the extract compared to the consumption of sprouts alone. Two studies concerned the anti-inflammatory potential of broccoli sprouts, either included in a diet or in a form of powdered broccoli sprouts standardized for sulforaphane content, observed as a decrease in the amount of IL-6 and C-reactive protein (López-Chillón et al., 2019; Mirmiran et al., 2012). Interestingly, broccoli sprouts powder, applied to patients with type 2 diabetes, significantly reduced the amount of C-reactive protein in the serum, while IL-6 and TNF-α were decreased only slightly (Mirmiran et al., 2012).
In a study conducted on breast cancer patients, administered broccoli sprout extracts standardized for isothiocyanates, anti-cancer activity was demonstrated with low toxicity and high compliance. Changes in the levels of breast cancer biomarkers were not statistically significant after the intervention; however, researchers observed an upward trend in cleaved caspase 3 amount, pro-apoptotic activity, and stimulation of the immune system through the activation of lymphocytes and neutrophils (Wang et al., 2022). A 28-day oral administration of broccoli sprout extract containing sulforaphane to patients with a history of melanoma and atypical skin lesions inhibited the progression of skin cancer and UV-induced damage. In addition, oral administration of sprouts was well tolerated, and sulforaphane concentrations achieved in skin and plasma were dose-dependent (Tahata et al., 2018).
Broccoli sprouts eaten daily in an in vivo study reduced Helicobacter pylori colonization of the gastrointestinal tract, attenuated the expression of TNF-α and IL-1β, and improved the aftermath of infection in mice and humans. This study proved the protective effect of broccoli sprouts on the gastric mucosa and, therefore, their chemopreventive effect against gastric cancer, a risk factor for which is H. pylori infections (Uemura et al., 2001; Watanabe et al., 1998; Yanaka et al., 2009).
Influence of Biofortification and Cultivation Conditions of Sprouts
Some efforts have been made to enhance the phytochemical content and the activity of the sprouts. Two of the most common approaches include the biofortification process and the modification of cultivation conditions, and the effects of such studies are described below and graphically summarized in Fig. 3.
Biofortification or biological fortification of edible plants is one of the major tools in the production of functional foods. This refers to nutritionally enhanced food with increased bioavailability. The process of sprouts’ fortification using different essential and trace elements or microbes provides the possibility to modulate the synthesis of bioactive components and pharmacological potential (Rehman et al., 2021). Apart from this, some studies also verified the influence of different factors, e.g., the time of harvesting or light condition, used during sprouts cultivation, on the synthesis of bioactive compounds and their activity.
Selenium-Enriched Sprouts – The Results From the In Vitro and In Vivo Studies
Plants from the Brassicaceae family have a high ability to accumulate selenium (Se) compounds, which in turn contributes to an increase in their cytotoxic and anti-inflammatory activity, and in the concentration of active compounds such as glucosinolates and isothiocyanates. In addition, Se increases plant tolerance to stress, stimulates growth, and affects homeostasis and photosynthesis. For this reason, sprouts enriched with Se compounds are extensively studied.
The anti-cancer potential of Se-enriched sprouts has been demonstrated in various studies. For example, Se-enriched chickpea sprouts, added as flour to the diet of immune-suppressed mice xenografted with colorectal cancer, reduced tumor growth and promoted apoptosis through the overexpression of cell surface death receptors. Similarly, radish sprouts enriched with Se showed a reduction in breast cancer incidence in rats.
Sulphur-Enriched Sprouts
A sole study focused on the effect of sulphur enrichment on the activity of the sprouts. Twelve-day-old sprouts of cabbage, radish, and broccoli grown in soil supplemented with sodium thiosulphate showed higher antiproliferative activity against HepG2 (viability decreased by 22–35%) and CT26 cells (viability decreased by 34–59%) compared to the control sprouts grown without sulphur salt (cells viability ~100%). Researchers suggested that the higher content of glucosinolates (a 2–5 fold increase) could have contributed to this increase in activity (Kestwal et al., 2011).
Probiotic or Potentially Probiotic Cultures-Enriched Sprouts
In a study by Zakłos-Szyda et al., (2020), chickpea sprouts were fermented with Lactobacillus casei 0979 bacteria and incubated with β-glucosidase, which resulted in an increase in isoflavonoid synthesis, followed by enhanced antioxidant and anti-inflammatory activity. Lactic fermentation of sprouts induced by L. casei 0979 can increase the content of isoflavones, which was confirmed by the study conducted by Budryn et al. (2019). In relation to human breast cancer cells (MCF-7), the sprouts inhibited migration and induced apoptosis, but at lower concentrations, they stimulated cell proliferation; therefore, it is important to choose the right extract dose. Clover sprouts have the ability to inhibit the migration of MDA-MB-231 and MCF-7 breast cancer cells by influencing membrane stiffening, regulation of N-cadherin, E-cadherin, and MMP-9 at the transcriptional level, intracellular ROS generation, adhesion, or vascular endothelial growth factor (VEGF) secretion. It is worth noting that in this experiment, the authors carried out lactic fermentation of sprouts with Lactobacillus casei 0979 in order to increase the content of polyphenols and convert glycosides to aglycones (Zakłos-Szyda & Budryn, 2020). Their previous study confirmed the affinity of isoflavones obtained from red clover to ERβ, which in turn reduced proliferation and migration of cancer cells (Budryn et al., 2018). Although the L. casei 0979 strain cannot be considered as probiotic, as no clinical studies have been published so far, the results of the above-mentioned studies seem promising.
Light Conditions
Light is an important factor affecting the development of plants, their growth, and the synthesis of active compounds. One study showed an increase in isoflavone synthesis in soybean sprouts grown in light, which was not observed in sprouts grown in darkness. Moreover, light had a positive effect on the anti-inflammatory activity of the sprouts compared to those grown in darkness (Eum et al., 2020). In another study, chickpea (Cicer arietinum L.) and lupine (Lupinus luteus L.) sprouts were cultivated under total darkness, normal light, and LED light of various colors (blue, red, yellow, and green). In chickpea sprouts, yellow LED light significantly increased the content of isoflavones, while green LED light resulted in the lowest values. Conversely, in lupine sprouts, the opposite effect was noted. Chickpea sprouts exhibited more cytotoxic activity against prostate DU-145 and PC3, and breast MCF7 and MDA-MB-321 cancer cells, compared to lupine sprouts. Notably, these sprouts were selective and did not affect normal cells (Galanty, Zagrodzki, et al., 2022). Another study found that garlic sprouts grown in the absence of light increased the activity of certain inflammatory markers in macrophages, which may be due to the high content of α-linolenic acid in the sprouts (Gdula-Argasińska et al., 2017).
Germination Time
Several studies have explored the effect of cultivation time on the activity of sprouts. One study found that 8-day-old rutabaga sprouts had the best antiproliferative effects on HepG2 cells, while 10–12-day-old kohlrabi sprouts had higher levels of beneficial phenolic compounds but lower levels of anti-nutritive components such as progoitrin (Paśko et al., 2021). In chickpea and lupine sprouts, the highest accumulation of isoflavones was observed in 10-day-old chickpea sprouts, which also showed significant cytotoxic activity against certain cancer cells. For alfalfa sprouts, the content of polyphenols peaked on the 11th day, and the most pronounced cytotoxic activity was observed in 7-day-old sprouts (Ibrahim et al., 2020).
Content of CO2
The modification of CO2 content in the air during the germination of sprouts has shown interesting results. Elevated CO2 levels during the germination of garden cress (Lepidium sativum) sprouts positively correlated with increased cytotoxic activity against human cancer cell lines, particularly bladder cancer cells. However, anti-inflammatory activity decreased under elevated CO2 conditions (Alotaibi et al., 2021). In broccoli sprouts, increased CO2 levels led to higher anticancer markers such as quinone reductase and GST in Hepa 1c1c7 cells. Elevated CO2 also increased myrosinase activity, leading to greater cytotoxic and anti-inflammatory activity of the sprouts (Almuhayawi et al., 2020). Additionally, elevated CO2 during the germination of alfalfa sprouts increased the levels of flavonoids, phenols, vitamins, and stimulated photosynthesis, which enhanced antioxidant and anti-inflammatory activities (Almuhayawi et al., 2021).
Miscellaneous
In one study, 4-day-old soybean sprouts were subjected to increased hydrostatic pressure (150 MPa), which increased their anti-inflammatory activity, resulting in the ability to inhibit NO synthesis (Kim et al., 2020).
The only study on the modification of sprout growth parameters conducted in vivo was performed on peanut sprouts grown on a substrate of fermented sawdust (PSEFS). Sprouts administered orally (20 mg/kg) showed an anticancer effect by reducing the growth rate of bladder cancer in mice injected with T24 cells, and this effect was comparable to that of cisplatin (5 mg/kg). It is worth noting that the sprouts did not show toxicity in the form of weight loss or changes in the blood parameters in the tested mice. However, no experiment was performed using control sprouts grown in normal conditions, so it is not possible to assess whether the use of a substrate of fermented sawdust significantly improves the anticancer activity of peanut sprouts (Park et al., 2020).
Other Interesting Studies
In Vitro
An interesting study was carried out by Tabassum and Ahmad (2018), who developed a nanoemulsion containing Nigella sativa sprouts extract. The developed nanoemulsion showed high stability during storage, and its use resulted in a decrease in the viability and the number of forming colonies of human liver carcinoma cells (HepG2) and an increase in ROS activity and chromatin condensation. Importantly, the prepared nanoemulsion was not toxic to normal WRL-68 cells. The results of the study confirmed that the nanoemulsion could be an effective carrier for the N. sativa sprout extract, which has cytotoxic activity against HepG2 cells.
Another interesting study was conducted by Gawlik-Dziki et al. (2014), who examined the cytotoxic activity of extracts (simulated in vitro digestion) from bread, in which part of the flour (2%) was replaced with powdered broccoli sprouts, against human stomach cancer AGS cells. High cytotoxic activity observed indicated that broccoli sprouts retain their biological activity even after they are processed into bread. In a similar study by Aborus et al. (2018), three types of cereal sprouts (spelt, oat, wheat) were subjected to simulated gastrointestinal digestion in vitro. The fractions obtained from oat sprouts had the highest content of phenols and antioxidant activity, while the spelt fractions had the highest content of pigments such as carotenoids and chlorophylls. The fraction obtained after digestion of wheat had significant anti-inflammatory activity, similar to oat sprouts.
Human Studies
In a study by Hong et al. (2021), an extract composed of Ligularia stenocephala Matsum. & Koidz leaves and rye sprout (Secale cereale L.) (TEES-10®) was prepared and administered to voluntary participants in a randomized clinical trial to investigate the effect on gingivitis after oral administration. Participants were receiving TEES-10® capsule twice a day for 4 weeks. The results suggest that TEES-10® reduced the incidence of gingivitis in patients after 4 weeks of use, demonstrating the anti-inflammatory potential of rye sprouts present in the extract. However, it is worth noting that it is difficult to assess to what extent this activity was caused by the presence of sprout extract.
Compounds Responsible for Sprouts' Activity
Various biologically active compounds present in the sprouts are responsible for their activity, among which organosulfur compounds such as glucosinolates, and flavonoids, especially isoflavones, seem to be the most important in the context of chemopreventive activity of the sprouts. Glucosinolates, characteristic of the plants from the Brassicaceae family, have been well studied and described in a number of recent reviews. They reveal biological activity after the hydrolysis by the enzyme myrosinase and conversion to nitrile compounds, isothiocyanates, or cyanides.
Several studies describe that the active ingredients responsible for the action against cancer cells in broccoli sprouts are isothiocyanates, including sulforaphane. Sulforaphane has been widely tested for cytotoxic activity, which was thoroughly described in some recent reviews. In one study, sulforaphane extracted from 7-day-old broccoli sprouts showed a strong pro-apoptotic effect on MDA-MB-231 breast cancer cells by down-regulating the Bcl-2 gene (anti-apoptotic) transcription and up-regulating the pro-apoptotic Bax gene, caspase-3, caspase-8, and caspase-9. Another study confirmed that sulforaphane isolated from broccoli sprouts had a significant dose-dependent antiproliferative effect against gastric cancer cells.
Another group of compounds important in the context of sprouts' activity are isoflavones, often present in plants of the Fabaceae family, and structurally similar to the female hormone 17-β-estradiol. The pharmacology of isoflavones and their role in chemoprevention have been summarized in many previous reviews. Among the most active isoflavones, genistein, daidzein, and glycitein should be mentioned, which are present, e.g., in soy. There are also other flavonoids and various phenolic compounds, which are especially responsible for antioxidant and anti-inflammatory activity of sprouts.
Limitations of the Studies Included in the Review
Regarding the in vitro studies, there are several shortcomings. Most of the cell lines used in experiments, such as those of gastrointestinal, breast, prostate, or thyroid origin, are well-justified in terms of potentially including sprouts in the daily diet. However, some studies described the effects of sprouts on lung, melanoma, leukemia, or osteosarcoma cells, the choice of which does not seem clearly justified in terms of potential chemoprevention. This issue relates both to the route of sprouts' administration, which are eaten, and to the phytochemicals present in the sprouts, which, apart from their direct impact on the gastrointestinal tract, can influence some hormone-sensitive cells (e.g., breast or thyroid).
Although most of the sprouts extracts examined were well-defined in terms of their phytochemical content, only a few studies provided the determination of potential relationships or correlations between the amount of phytochemicals detected and the observed effects. Additionally, there is no data on the in vitro passive or active transport of sprouts extracts, which could be obtained by using, for example, a Caco-2 cell transport model. This could give preliminary information on the bioavailability of the compounds present in the sprouts extracts and enable their preselection for further animal studies.
Most studies did not include non-cancerous cells as a reference for the safety or selectivity of the sprouts, which should be a crucial step in the experimental design of such studies. Moreover, no reference compound was used during the cited studies, which could enable the comparison of activity and serve as an indicator of the proper course of the experiment. The results of the studies generally lack information on prolonged exposure of cancer cells to sprouts, as most studies used only standard 24 or 48 hours of incubation time. It would be interesting to observe the effect of sprouts over time, as it could increase their effectiveness, which is particularly important in terms of sprouts as an element of the daily diet.
The determination of sprouts' impact on other aspects of cell functioning was rarely found in the studies cited. Most studies focused only on cell viability, while other crucial aspects, such as proliferation or migration, which are essential for the effective elimination of cancer cells, were ignored. Similarly, mechanistic studies were scarce, with only a few authors describing the effect of sprouts on apoptosis stimulation or cell cycle arrest. These aspects should be studied more thoroughly in the future.
Despite the enormous number of in vitro studies performed so far on the activity of sprouts towards cancer cells, most of their results indicate moderate or weak cytotoxic potential. However, even moderate activity of sprouts can still provide a chemopreventive effect when eaten regularly. Further studies should also verify the concomitant treatment with sprouts and cytostatic drugs, determining the final effect as synergistic or antagonistic. Such experiments should also be performed in animal models, and their results could provide more information on the effectiveness of such treatment in the future.
Regarding the biofortification experiments, the vast majority of studies were based on selenium fortification, while other important elements (e.g., iodide, zinc), the deficiency of which is also frequently occurring, were not taken into account. The results of the impact of selenium-biofortified sprouts, although interesting, were obtained mostly from in vitro studies performed by only three research groups. This aspect should be explored more thoroughly, with other elements and further in vivo studies.
Some other minor issues that should be indicated as the weaknesses of the cited studies include: i) the proper definition of sprouts – some of the material cultivated for a longer period should be classified as microgreens; ii) the problem of translating the doses used in the in vitro studies to the real amount of sprouts included in the diet; iii) the credibility of some studies where the results for sprouts were comparable to cytostatic drugs used as a reference; iv) unclear data on the superiority of using fresh sprouts or sprouts' extracts in in vivo studies.
Conclusion
The number of published reports on the chemopreventive properties of sprouts from edible plants belonging to various families strongly indicates that this type of food attracts significant and growing scientific attention. The results of the studies cited in this review suggest that sprouts from the Brassicaceae family are the most extensively examined group (49% of all research items included in this review) in terms of their potential use in chemoprevention. Among them, broccoli sprouts deserve special attention, as the results of human studies showed their chemopreventive and anti-inflammatory activity. Studies on sprouts from the Fabaceae family comprise over 25% of all research items included in this review, indicating these sprouts as a group of special interest for the future.
However, it is interesting to note that the chemopreventive effect or the impact of cultivation conditions observed for the sprouts within each family, or even genus, differed significantly, suggesting that experimental conditions should be individually planned for each species.
Despite some limitations and weaknesses, most of the results included in this review seem to suggest that sprouts may play a role in chemoprevention as a part of the daily diet, with especially encouraging effects observed for broccoli sprouts. However, some issues should be further explained or deepened, particularly: i) optimization of sprouts cultivation conditions, providing a controlled amount of bioactive compounds; ii) safety profile of sprouts, conducted both in vitro on non-cancerous cell lines and in vivo on healthy animals; iii) the impact of selenium or other elements enrichment of sprouts on their activity; iv) relationships between the phytochemical content of sprouts and their activity; v) pharmacokinetic studies of sprouts extracts.
In conclusion, research on the chemopreventive activity of sprouts of edible plants is a direction worth developing. With their easy and inexpensive cultivation and visual attractiveness, sprouts may become an important element of a chemopreventive strategy in the future.
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Grudzinska, M., Błaszczak, W., Piekarska, A., & Narwojsz, A. (2023). Can edible sprouts be the element of effective chemoprevention strategy? Trends in Food Science & Technology, 134, 182-193. https://doi.org/10.1016/j.tifs.2023.104130