RESUMO
The tender green pods of the common bean (Phaseolus vulgaris L.) are marketed fresh, frozen or canned. The main bean accessions cultivated for green pods in central Chile are Arroz, Magnum, Peumo and the introduced Malibú. Little is known about the identity of phenolics in the processed pods or in the boiled bean leaves. Raw leaves from Chilean bean landraces showed a strong inhibition towards the enzyme α-glucosidase, associated with flavonoids and caffeoyl malic acid content. The aim of this work was to assess the phenolic composition, antioxidant capacity and activity towards α-glucosidase of boiled leaves and green pods from selected bean landraces. The study was performed with four green pods samples and six leaf accessions, respectively. The leaves included the continuous growth bean Ñuño (red seed and black seed). Antioxidant capacity and inhibition of α-glucosidase were measured. The main phenolics were identified by comparison with standards and were quantified using calibration curves. The extracts of most boiled green pods inhibited α-glucosidase while the leaves were inactive. The content of phenolics in the boiled pods is low, with rutin and quercetin 3-O-glucuronide as the main constituents. In boiled leaves, the main phenolics were quercetin 3-O-glucuronide and kaempferol 3-O-glucuronide. The main flavonoids and caffeoyl malic acid in leaves decreased after boiling. Boiling affected the phenolic profile, reducing antioxidant capacity and glucosidase inhibition, highlighting the importance of characterizing foods as they are ingested.
Assuntos
Antioxidantes , Phaseolus , Antioxidantes/farmacologia , alfa-Glucosidases , Chile , Fenóis/análise , Flavonoides , Folhas de Planta/químicaRESUMO
The MeOH:H2O (7:3) extracts of leaves from Chilean bean landraces were assessed for total phenolic (TP), total flavonoid (TF), total proanthocyanidin (TPA) content, antioxidant capacity (ORAC, FRAP, TEAC, CUPRAC, DPPH) and the inhibition of enzymes associated with metabolic syndrome (α-glucosidase, α-amylase, pancreatic lipase). The chemical profiles were analyzed by HPLC-DAD. Higher antioxidant activity in the ORAC and CUPRAC assay was found for the landrace Coscorrón, and the best effect in the TEAC for Sapito, respectively. The main phenolics were flavonol glycosides and caffeic acid derivatives. The extracts presented strong activity against α-glucosidase, but were inactive towards α-amylase and pancreatic lipase. The leaf extract from the Sapito landrace was fractionated to isolate the main α-glucosidase inhibitors, leading to caffeoylmalic acid with an IC50 of 0.21 µg/mL. The HPLC fingerprints of the leaves differentiate three groups of chemical profiles, according to the main phenolic content. A significant correlation was found between the α-glucosidase inhibition, the content of caffeoylmalic acid (r = -0.979) and kaempferol 3-O-ß-D-glucoside (r = 0.942) in the extracts. The presence of α-glucosidase inhibitors in the leaves of Chilean beans support their potential as a source of bioactive compounds.