Antioxidant galloylated flavonol glycosides from Calliandra haematocephala

Abstract

Three new acylated quercetin rhamnosides have been isolated from the leaves and stem of Calliandra haematocephala Hassk. (Fabaceae) and their structures were established as quercitrin 2′′-O-caffeate (1), quercitrin 3′′-O-gallate (2) and quercitrin 2′′,3′′-di-O-gallate (3). Also, 17 known compounds were identified as gallic acid (4), methyl gallate (5), caffeic acid (6), myricitrin (7), quercitrin (8), myricetin 3-O-β-D-⁴C₁-glucopyranoside (9), afzelin (10), isoquercitrin (11), myricetin 3-O-(6′′-O-galloyl)-β-D-glucopyranoside (12), myricitrin 2′′-O-gallate (13), quercitrin 2′′-O-gallate (14), afzelin 2′′-O-gallate (15), myricitrin 3′′-O-gallate (16), afzelin 3′′-O-gallate (17), 1,2,3,4,6-penta-O-galloyl-β-D-⁴C₁-glucopyranose (18), myricitrin 2′′,3′′-di-O-gallate (19), quercetin 3-O-methyl ether (20), for the first time from the genus Calliandra except for 6. Compounds 7, 8, 13, 14, 16 and 19 exhibited moderate to strong radical scavenging properties on lipid peroxidation, hydroxyl radical, superoxide anion generation and DPPH radical in comparison with that of quercetin as a positive control in vitro. Compounds 7 and 8 exhibited lethal effect towards brine shrimp Artemia salina.

Keywords:

• Calliandra haematocephala
• Fabaceae
• Leaves and stem
• Galloylated flavonol rhamnosides
• ESI-MS
• Antioxidant activity

Acknowledgement

This study was supported by the Robert A. Welch Foundation (Grant F-130) to T.J.M. at the University of Texas at Austin, USA.