Effects of 1-methylcyclopropene treatment on phenolic metabolism in postharvest Gynura bicolor DC

Abstract

We examined the effects of 10 μ L−1 1-methylcyclopropene (1-MCP) treatment on phenolic metabolism in postharvest Gynura bicolor DC stored at 20 ± 2 °C. The results indicated that 1-MCP treatment stimulated the biosynthesis of flavonoids and anthocyanins but inhibited that of lignin by regulating gene expression and enzyme activity. Specifically, 1-MCP treatment increased the contents of cinnamic acid, kaempferol, rutin, and chlorogenic acid by upregulating the expression of GbPAL, GbCHS, GbDFR, GbANS and GbUFGT, and decreased the ferulic acid content by downregulating the expression of GbC4H, GbCOMT, GbF5H and GbCCoAOMT. A correlation heatmap suggested close relations between individual phenolics and gene expression. The resulting accumulation of phenolics enhanced 2,2-diphenyl-1-picrylhydrazyl hydrate radical (DPPH·) and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS·+) scavenging ability and ferric ion-reducing antioxidant power (FRAP). Furthermore, 1-MCP treatment decreased electrolyte leakage and inhibited the activity of peroxidase and polyphenol oxidase, alleviating the risks of phenolics degradation and the increase in superoxide anion (O2·−) and H2O2 levels. In summary, 1-MCP treatment increased the contents of total phenolics, flavonoids, and anthocyanins by stimulating gene expression, and retarded the risk of phenolic degradation, thus delaying senescence of G. bicolor leaves.