Flavonoids and phenylethanoids from the flowers and leaves of Aeschynanthus species and cultivars (Gesneriaceae)

Abstract

Forty-one flavones, each one of flavonol, chalcone and dihydroflavonol, two flavanones, and four phenylethanoids were isolated from corollas, calyces and leaves of two Aeschynanthus species, A. fulgens and A. pulcher, and six cultivars, 'Mahligai', 'Mona Lisa', SoeKa', 'Redona', 'Freshya' and 'Bravera'. Flavonoids were mainly the glucuronides and/or methylglucuronides based on hispidulin, nepetin, pectolinarigenin, 6-hydroxyluteolin, scutellarein, apigenin and luteolin, and identified by UV spectra, HR-MS, LC-MS, acid hydrolysis, NMR, and/or HPLC and TLC comparisons with authentic samples. Of these flavonoids, twelve, i.e. hispidulin 7,4'-di-O-glucuronide, 7,4'-di-O-methylglucuronide, 7-O-methylglucuronide-4'-O-glucuronide, 7-O-glucuronide-4'-O-methylglucuronide, 7-O-glucosyl-(1 → 2)-glucuronide and 8-C-glucoside, nepetin 7,4'-di-O-glucuronide, 7-O-glucuronide-4'-O-methylglucuronide and 7-O-methylglucuronide-4'-O-glucuronide, pectolinarigenin 7-O-glucosyl-(1 → 2)-glucuronide and 7-O-xylosyl-(1 → 2)-(6″-malonylglucoside), and 6-hydroxyluteolin 7,4'-di-O-glucuronide, were previously undescribed.

Keywords: Aeschynanthus; Flavone glucuronides; Flavone methylglucuronides; Gesneriaceae; Hispidulin; Nepetin; Pectolinarigenin.