Allium vegetables: Traditional uses, phytoconstituents, and beneficial effects in inflammation and cancer

The genus Allium comprises of at least 918 species; the majority grown for dietary and medicinal purposes. This review describes the traditional uses, phytoconstituents, anti-inflammatory and anticancer activity, and safety profile of six main species, namely Allium sativum L. (garlic), Allium cepa L. (onions), Allium ampeloprasum L. (leek), Allium fistulosum L. (scallion), Allium schoenoprasum L. (chives) and Allium tuberosum Rottler (garlic chives). These species contain at least 260 phytoconstituents; mainly volatile compounds—including 63 organosulfur molecules—, saponins, flavonoids, anthocyanins, phenolic compounds, amino acids, organic acids, fatty acids, steroids, vitamins and nucleosides. They have prominent in vitro anti-inflammatory activity, and in vivo replications of such results have been achieved for all except for A. schoenoprasum. They also exert cytotoxicity against different cancer cell lines. Several anticancer phytoconstituents have been characterized from all except for A. fistulosum. Organosulfur constituents, saponins and flavonoid glycosides have demonstrated anti-inflammatory and anticancer activity. Extensive work has been conducted mainly on the anti-inflammatory and anticancer activity of A. sativum and A. cepa. The presence of anti-inflammatory and anticancer constituents in these two species suggests that similar bioactive constituents could be found in other species. This provides future avenues for identifying new Allium-derived anti-inflammatory and anticancer agents.