Changes in secondary metabolites during growth and development of milk yam (Ipomoea digitata L.) tubers

Abstract

Milk yam is a medicinal plant having therapeutic as well as nutraceutical potential. This study was aimed on quality evaluation of milk yam tubers during its different growth stages so as to assess its optimum maturity and harvesting stage. Milk yam vine cuttings having two nodes were raised in polybags and depotted carefully after tuber formation at tri-monthly intervals for a period of two years and subjected to quantitative phytochemical analysis. Tubers harvested at twenty one months after planting recorded optimally high alkaloids (0.83 mg AE g-1), saponins (9.50 mg DE g-1) and flavonoids (0.54 mg QE g-1); moderate glycosides (1.40 µg g-1) and phytosterols (1.18 mg g-1). Hence, twenty one months after planting is identified as optimum maturity stage for harvesting the tubers with better quality.