Current perspectives on the Nutrient composition and health benefits of yams (Discorea species)

Abstract

Yams (Discorea spp) are food security crops which serve as invaluable food sources of energy, micronutrients and phytochemicals with numerous health benefits. They show a lot of genetic and compositional diversity. New biologically active compounds are being identified from wild yams. This review focuses on the nutrients, and phytochemicals found in yam species and their health benefits. The B group of vitamins, vitamin C, pro-vitamin A; copper; manganese; isoflavones; steroidal saponins; alkaloids; terpenes; and anthocyanidins are found in different species of yams. Wild yams such as Discorea villosa and Discorea hispida are used in ethnomedicine because of their phytochemical content. Diosgenin, dioscorin, dioscin dihydrodiscorine protodioscin, methyprotodioscin, prosapogenin, epifzelechin, glucopyranoside, phytoestrogen and allantoin are bioactive phytochemicals that may be found in yams. They are valuable as anti-cancer, anti-mutagenic, anti-inflammatory, anti-diabetic, anti-ageing lipid lowering and hepatoprotective agents. Other claims based on traditional uses of yams have not been scientifically substantiated. Dioscorea species are likely to contain other unidentified secondary metabolites. Discorea species with other health promoting bioactive compounds should be identified; modern techniques should be used to extract yet unidentified compounds in Discorea and the food use and health benefits of yam species should be optimized.