In a recent review published in Nutrients, researchers evaluate the associations between medicinal plants, the gut microbiome, and cancer.
Study: The Interplay between Medical Plants and Gut Microbiota in Cancer. Image Credit: PattPaulStudio / Shutterstock.com
Background
Previous studies have shown that the gut microbiome, a dynamic colony of bacteria, varies according to certain factors like diseases, diet, antibiotics, and hygiene. Diabetes, cardiovascular diseases, obesity, and cancer are implicated in gut dysbiosis, which disturbs the natural balance between the host and bacteria.
According to several studies, certain plants have anticancer qualities and can regulate the gut microbiome. In the present review, researchers review existing data on the beneficial effects of medicinal plants on the gut microbiome and cancer.
Health benefits of medicinal plants
Biologically active chemicals in medicinal plants include flavonoids, phenolic acids, alkaloids, tannins, terpenoids, organosulfur compounds, and coumarins. These chemicals exhibit a wide range of beneficial properties including anti-inflammatory, antioxidant, antibacterial, and antineoplastic activity.
Medicinal plant usage has been linked to reduced local and systemic gut inflammation, as well as a reduced risk of illnesses such as type 2 diabetes and colon cancer. Polyphenols are bioactive substances that include flavonoids such as isoflavones, anthocyanins, stilbenes, tannins, and lignans. Anthocyanins are anti-inflammatory and antioxidant compounds found in specific fruits and vegetables such as blueberries, eggplants, potatoes, and carrots.
Isolated from broccoli, glucoraphanin possesses antibacterial and anticancer effects. Vascular plants, which are distinguished by lignified tissues known as xylem, promote beneficial bacteria and enhance gut microbial diversity.
Association between medicinal plants, gut microbiota, and cancer
Gut dysbiosis, which often develops alongside metabolic disorders, is associated with a reduced abundance of beneficial microbes such as Roseburia, Lactobacillus, Eubacterium, and Akkermansia muciniphila, as well as an increased abundance of pathogenic microorganisms such as Bacteroidetes and Ruminococcus gnavus. Diet-related molecules reviving gut microbiota such as dietary fibers and evodiamine, as well as prebiotics and probiotics, can have a positive effect on humans and prevent carcinogenesis.
Natural molecules like evodiamine (EVO), which is an alkaloid in Evodia rutaescarpa, and resveratrol (RES), which is present in grapes, peanuts, wine, and berries, play crucial roles in apoptosis. EVO and RES act by inhibiting nuclear factor kappa B (NF-KB) and allowing B-cell lymphoma 2 (Bcl-2) to exert its proapoptotic effect. Anthocyanins exert antioxidant effects, thereby reducing reactive oxygen species (ROS) and interleukin-6 (IL-6) levels, as well as inflammation.
EVO can also inhibit cycloxygenase-2 (COX-2), prostaglandin E2 (PGE-2), and nitric oxide synthase. As a result, EVO inhibits neovascularization and colorectal cancer cell proliferation through phosphorylated signal transducer and activator of transcription 3 (pSTAT-3) inhibition.
Daidzein, which is isolated from soybeans, is metabolized by the gut microbiota to form equol. Equol exerts neuroprotective, anticancer, antiestrogenic, and antiangiogenetic effects and downregulates the expression of vascular endothelial growth factor (VEGF).
Equol also lowers Ki67 and Cyclin D1/Cyclin E1 expression and increases caspase-3 levels, which promote the arrest of the growth phase of the cell cycle. Vachellia tortilis can inhibit Klebsiella, Staphylococcus aureus, and Pseudomonas aeruginosa in vitro, as well as exert cytotoxic effects, particularly on hepatocellular carcinoma cells.
β-glucans found in mushrooms, oats, and barley have several anticancer and antimicrobial effects, in addition to modulating the gut microbiome and immunity. In vitro studies have shown that baicalin and wogonoside from Scutellaria baicalensis were converted into baicalein and wogonin, both of which are associated with anticancer effects in colon cancer.
Green tea polyphenols derived from the leaves of Camellia sinensis also have anti-inflammatory and antioxidant properties. Polyphenols reduce inflammation-related oxidative stress on gut microorganisms and provide a carbon source for the metabolism of bacteria.
Additionally, polyphenols can inhibit the proliferation of Campylobacter jejuni, Bacillus cereus, Escherichia coli, Clostridium perfringens, Legionella pneumophila, and Helicobacter pylori through cell membrane disruption. Green tea polyphenols can also induce the overproliferation of Faecalibacterium, Bifidobacterium, Eubacterium, and Roseburia, which increases short-chain fatty acid (SCFA) level, suppresses lipopolysaccharide synthesis and, consequently, potentiates the immune response.
Citrus fruits including Citrus reticulate, Citrus sinesis, Citrus depressa, Citrus aurantium, and Citrus tangerine contain nobiletin, which exhibits cytotoxic properties against colon cancer cells. Lycopene, a carotenoid found in red fruits and vegetables like tomatoes, acts through the regulation of growth factor signals, induction of cell cycle inhibition, and stimulation of apoptosis.
Lycopene upregulates the proapoptotic protein Bcl-2 and p53 tumor suppressor expression. Quercetin, a flavonoid found in vegetables and fruits, shows pro-oxidant and antioxidant properties, suppressing calcineurin pathway activation and inhibiting angiogenesis. Sulforaphane (SF), isolated from broccoli, regulates gene expression, blocks NF-KB activity, and exerts antiandrogenic effects.
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