Quantification of total polyphenols, antioxidants, anthocyanins and secondary metabolites by UPLC VION IMS QTOF MS/MS analysis in green and red lettuce cultivars

Lettuce is an important leafy vegetable and an excellent source of phytochemicals in human diets. However, the metabolic levels in different green and red type lettuce varieties are not fully explored. Therefore, it is important to explore and identify the selected health promoting secondary metabolites in green and red type lettuce varieties with having different phenotypic characteristics. In this study, we explored the selected secondary metabolites, total polyphenol, antioxidants activities, total flavonoids and anthocyanin contents in 32 lettuce varieties of green and red color. The results showed that green and red type lettuce varieties showed a significant difference in lactupicrin, chlorogenic acid, caffeoylmalic acid, syringic acid and quercetin 3-D-galactoside. Selected metabolites showed a significant variation in green and red type lettuce varieties depends upon different color and phenotypic characteristics. Total flavonoids and anthocyanin contents were found more in red type lettuce varieties while the total polyphenols and total antioxidants were found significantly higher in green type lettuce varieties. Tentative identified 78 metabolites with online databases, the published literature and standards including phenolic acid, flavonoids and glycosylated flavonoids. The metabolomic profiling was present at significantly difference in green and red type lettuce varieties which suggested the significant variation between green and red type lettuce varieties to secondary metabolism. This study provides a selection of lettuce varieties for further studies on the basis of color and phenotypic characteristics for improving the nutritional value, quality and yield of lettuce.