Flavonoids isolated from the fresh sweet fruit of Averrhoa carambola, commonly known as star fruit

Abstract

Thirteen flavonoids were isolated from the fresh sweet fruit of Averrhoa carambola L. (Oxalidaceae), commonly known as star fruit, and their structures were determined by spectroscopic and chemical methods. 8-Carboxymethyl-(+)-epicatechin methyl ester, pinobanksin 3-O-β-d-glucoside, and carambolasides M–Q were undescribed structures. (+)-Epicatechin, aromadendrin 3-O-β-d-glucoside, helicioside A, taxifolin 3′-O-β-d-glucoside, galangin 3-O-rutinoside, and isorhamnetin 3-O-rutinoside were reported from this species for the first time. Pinobanksin 3-O-β-d-glucoside and carambolasides M–Q showed more potent 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity (IC50 = 5.3–2.3 μM) than l-ascorbic acid (10.5 μM). Further, (+)-epicatechin, pinobanksin 3-O-β-d-glucoside, isorhamnetin 3-O-rutinoside, and carambolasides O–Q exhibited weak porcine pancreatic lipase inhibitory activity.