Increased polyphenols and antioxidant activity of rice bean (Vigna umbellata L.) sprouts induced by Methyl Jasmonate: the promotion effect of Methyl Jasmonate on rice bean sprouts

Abstract Rice bean (Vigna umbellata L.) sprouts are richer in metabolites and biological activities after germination. The total polyphenol and total flavonoid contents were analyzed during the sprouting process. The antioxidant activities of the sprouts were tested using 1,1-diphenyl-2- picrylhydrazyl radical (DPPH) screening assay. To determine the reason for increased activity, quantitative analysis of 8 flavonoids, in the germination process of methyl jasmonate (MeJA)-treated and control groups, was performed using high-performance liquid chromatography coupled with diode array detection (HPLC/DAD) and partial least squares discriminant analysis (PLS/DA). The metabolites in MeJA-treated beans shows that addition of 100.0 μmol MeJA significantly increased the total flavonoid and polyphenol contents during the sprouting process. DPPH screening assay and analytical results show that MeJA has a significant influence on the production of secondary metabolites in sprouts between the 4th and 6th days, thereby inducing increased antioxidant activity. Flavonoids rutin, kaempferol-3-O-rutinoside, daidzin, and genistin are further identified as the main contributors to the increased DPPH screening activity.