Changes in major flavonols and quercetin glycosides upon sprouting in onion cultivars

Abstract

Objective: This study was carried out to demonstrate the effect of sprouting on the major flavonols and quercetin glycosides in onion powders developed from four onion cultivars (Punjab White, Punjab Naroya, PRO-6 and Commercial) of Indian Origin. Methods: The major flavonols summing up total flavonoids and quercetin glucosides comprising up to the total quercetin glucoside concentration were determined by High performance liquid chromatography and Fourier transform infrared (FTIR) spectroscopy. Results and conclusions: The major flavonols were quercetin, myricetin and kaempferol, which were found to be significantly higher (p < 0.05) in all sprouted powders. Quercetin gylcosides also increased with sprouting, while non-significant decrease was found in Punjab Naroya and Commercial onion powders. FTIR analysis revealed the presence of functional groups with O–H and C–H bonds and the structural similarities and differences between onion powders was found following sprouting which were evident by the presence of certain sharp bands in sprouted samples. Quantitative analysis of flavonoids by HPLC showed that sprouted onion powders contained more phytochemicals than raw onion powder. This research suggests the potential of sprouting in onion for product development with enhanced bioactive compounds.

Keywords

• Onion cultivar
• Quercetin glycosides
• Sprouting
• High performance liquid chromatography
• FTIR
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