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Abstract: Tagetes erecta, Cosmos sulphureus, Antigonon leptopus and Bougainvillea glabra are edible flowers frequently used by the ethnic population of northern Thailand for preparation of salads and flower teas. The main constituents of ethanolic extracts of these flowers, identified with the help of a high-performance liquid chromatography (HPLC) method, were phenolic acids and flavonoids. T. erecta flowers contained the highest level of phenolic compounds, 1107.5mg/100g dry weight (DW), which was 3- to 4-fold the level of phenolic compounds in three other flowers evaluated in this study. Lyophilised aqueous extract of T. erecta had the highest Folin–Ciocalteu value (212±9.0mgGAE/g DW) and exhibited the highest total reducing capacity (Ferric Reducing Antioxidant Power, FRAP assay; 329.4±21.8μmol Fe2+/g DW) and cellular antioxidant activity (CAA assay; EC50 =413μg/ml). However A. leptopus extract exhibited a superior oxygen free radical scavenging ability (oxygen radical absorbance capacity, ORAC-H assay). The extracts were evaluated for their abilities to suppress the proliferation of human cancer cells associated with the digestion system and to inhibit the activity of two enzymes, α-glucosidase and pancreatic lipase. A pronounced anti-proliferative activity against the colorectal adenocarcinoma (HT-29) cells exhibited T. erecta extract (IC50 =1.5mg/ml), while A. leptopus was most active against the gastric adenocarcinoma (AGS) (IC50 =0.2mg/ml) and bladder cancer cells (BL-13) (IC50 =0.9mg/ml). T. erecta extract was identified as an efficient inhibitor of α-glucosidase enzyme (IC50 =0.06mg/ml). T. erecta, C. sulphureus and B. glabra extracts equally inhibited the activity of pancreatic lipase (IC50: 4.82 and 4.60mg/ml, respectively). The results obtained in this study for the first time identified a number of potential health-enhancing properties of aqueous extracts obtained from edible flowers consumed by the indigenous people of Thailand. [Copyright &y& Elsevier]

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., (© 2021 Society of Chemical Industry.)