1 H‐NMR analysis, antioxidant activity, and α‐amylase and α‐glucosidase inhibitory potential of ten common Thai edible flowers

BACKGROUND Edible flowers have been used in cooking as foods as well as medicine alternatives. The objectives were to identify a major class of organic compounds in edible flowers by applying proton nuclear magnetic resonance ( 1 H‐NMR) metabolite fingerprinting and to evaluate bioactivity including antioxidant and α‐amylase and α‐glucosidase inhibitory activities. RESULTS A total of 32 metabolites including five organic acids, eight sugars, 11 amino acids and eight phenolic compounds were identified by using 1 H‐NMR at 600 MHz. The aromatic proton of phenolic compounds was observed at the low‐field region ranged between δ 5.5 ppm and 10.0 ppm. Total phenolic content (TPC) of the extracts of edible flowers ranged from 6.0 mg GAE g −1 dry weight (DW) to 47.97 mg GAE g −1 DW. Antioxidant activity varied from 140.5 mmol L −1 TE g −1 DW to 985.2 mmol L −1 TE g −1 DW. The extracts from edible flowers showed dose‐dependent inhibition against enzyme. The extract of African marigold ( Tagetes erecta L.) had the highest half maximal inhibitory concentration (IC 50 ) against α‐amylase at 0.13 mg mL −1 while the extract of flower of Sesban agasta ( Sesbania grandiflora Desv.) had the lowest IC 50 against α‐amylase at 0.63 mg mL −1 . Moderate correlation was found between IC 50 values against α‐glucosidase and antioxidant activity values ( R 2  = 0.66) ( P  < 0.05). CONCLUSION 1 H‐NMR application provided metabolomic fingerprinting of edible flowers and the in vitro inhibitory potential activity against key enzymes related to diabetes indicated that specific edible flowers have a potential use for dietary management during the early stages of hyperglycaemia. © 2021 Society of Chemical Industry