Three New Pentacyclic Triterpenes and Some Flavonoids from the Fruits of an Indian Ayurvedic Plant Dendrophthoe falcata and Their Estrogen Receptor Binding Activity

Extensive chromatographic screening of extracts of the fruits of the Indian Ayurvedic plant, Dendrophthoe falcata, resulted in the isolation of three new triterpenes, 3β-acetoxy-1β-(2-hydroxy-2-propoxy)-11α-hydroxy-olean-12-ene (1), 3β-acetoxy-11α-ethoxy-lp-hydroxy-olean-12-ene (2) and 3β-acetoxy-1β-hydroxy-11α-methoxy-olean-12-ene (3) along with nine known compounds, 3β-acetoxy-1β, 11α-dihydroxy-olean-12-ene (4), 3β-acetoxy-1β, 11α-dihydroxy-urs-12-ene (5), 3β-acetoxy-urs-12-ene-11-one (6), 3β-acetoxy-lup-20(29)-ene (7), 30-nor-lup-3β-acetoxy-20-one (8), (20S)-3β-acetoxy-lupan-29-oic acid (9), kaempferol-3-Ο-α-L-rhamnopyranoside (10), quercetin-3-Ο-α-L-rhamnopyranoside (11), and gallic acid (12). The structures of these compounds were determined using 1D and 2D NMR and high resolution electrospray mass spectrometry. These compounds were assayed for binding to estrogen receptors-α and β and kaempferol-3-Ο-α-L-rhamnopyranoside (10) was found to be a ligand for both receptors with greater affinity for β. The triterpenes (1-9) are reported for the first time in the genus Dendrophthoe and assumes taxonomic significance.