Two new saponins from tetraploid jiaogulan (Gynostemma pentaphyllum), and their anti-inflammatory and α-glucosidase inhibitory activities

Abstract

Jiaogulan tea has been commercialised globally. This study investigated the chemical components and health properties of a new jiaogulan genotype, tetraploid Gynostemma pentaphyllum. Two new saponins, (23S)-21β-O-methyl-3β,20ξ-dihydroxy-12-oxo-21,23-epoxydammar-24-ene-3-O-[α-L-rhamnopyranosyl(1→2)][β-D-glucopyranosyl(1→3)]-α-L-arabinopyranoside (4) and 23β-H-3β,20ξ-dihydroxy-19-oxo-21,23-epoxydammar-24-ene-3-O-[α-L-rhamnopyranosyl(1→2)][β-D-xylopyranosyl(1→3)]-α-L-arabinopyranoside (5), together with one lactone, 3,5-dihydroxyfuran-2(5H)-one (1), and two flavonoids, rutin (2) and kaempferol 3-O-rutinoside (3), were characterised in the aerial parts of tetraploid jiaogulan. The chemical structures of the five isolated compounds were elucidated by NMR, HR-MS spectra and chemical degradation. The five compounds were also examined and compared with the methanol extract and n-butanol soluble fraction of the jiaogulan for their inhibitory activities on lipopolysaccharide (LPS)-induced IL-1β, IL-6 and COX-2 mRNA expression in RAW 264.7 mouse macrophages, and their in vitro α-glucosidase suppressing capacities. The results from this study may be used to promote the potential application of jiaogulan in functional foods.

Keywords: Anti-inflammation; Gynostemma pentaphyllum; Jiaogulan; NMR; Saponin; α-Glucosidase inhibition.