Current State of Knowledge of the Anticancer Properties of Polyphenolic Compounds from Garlic (Allium sativum L.)

Garlic (<i>Allium sativum</i> L.) belongs to the <i>Allium</i> genus and is one of the main bulbous plants consumed fresh, powdered, or cooked. Numerous studies have shown that garlic exhibits antihyperlipidaemic, antioxidant, anti-inflammatory, cardiovascular disease preventive, antihypertensive, antibacterial, antiviral, antifungal, antiparasitic, antidiabetic, anticarcinogenic, hepatoprotective, immunomodulatory, and hypoglycaemic effects. Moreover, studies on polyphenols detected in garlic reveal strong anticancer properties in various cell lines. The aim of this review is to summarise the current state of knowledge regarding the anticancer properties and shared molecular mechanisms of action of garlic-derived polyphenolic compounds. Our analysis demonstrates that the polyphenol content in garlic is highly variable and depends on numerous factors, including the part of the plant, processing methods, place of cultivation, and other conditions. Additionally, garlic contains polyphenols that exhibit anticancer activity in preclinical models, the properties of which have been demonstrated in in vitro studies. The anticancer mechanism of action varies depending on the type of polyphenol. Several polyphenols from garlic such as e.g., catechin, quercetin, and kaempferol activate peroxisome proliferator-activated receptors, which appear to contribute to at least part of garlic's anticancer activity. The primary mechanism of garlic's anticancer properties relies on reactive oxygen species-dependent toxicity and/or apoptosis, and Nrf2 is also implicated in the mechanism of action of garlic polyphenols. Our review provides evidence that under in vitro conditions, polyphenols present in garlic may exhibit anticancer properties. Garlic is not only a valuable culinary ingredient but also a natural medicine. Regular consumption in moderate amounts may offer numerous health benefits.