Non-flavonoid phenolics from Averrhoa carambola fresh fruit

Abstract

The fruit of Averrhoa carambola L. (Oxalidaceae) is a commercially important fruit. Our study on the chemical constituents present in the fresh sweet fruit led to the isolation of eleven non-flavonoid phenolic compounds. Their structures were identified by analyses of spectroscopic data. They were two new alkyl phenol diglucosides, carambolasides K (1) and L (2), four phenylpropanoids, (+)-isolariciresinol 9-O-β-d-glucoside (3), (+)-lyoniresinol 9-O-β-d-glucoside (4), (−)-lyoniresinol 9-O-β-d-glucoside (5), and 1-O-feruloyl-β-d-glucose (6), three benzoic acids, protocatechuic acid (7), 1-O-vanilloyl-β-d-glucose (8), and tecomin (9), a simple phenol, koaburaside (10), and a naphthoquinone, (+)-cryptosporin (11). All of them were reported from A. carambola fruit for the first time. Compounds 1–8 and 10 showed 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity comparable to l-ascorbic acid, while compounds 3, 5, and 7 exhibited potent ferric reducing antioxidant power (FRAP). In addition, compounds 6 and 11 demonstrated weak porcine pancreatic lipase inhibitory activity.

Keywords

• Averrhoa carambola
• Fresh star fruit
• Alkyl phenol diglucoside
• Non-flavonoid phenol
• Antioxidant activity
• Pancreatic lipase inhibition