Bioactive compounds from Glyptopetalum sclerocarpum stem bark

Abstract

From the stem bark of Glyptopetalum sclerocarpum Laws., nine new quinone-methide triterpenes, 20-hydroxy-tingenone, 20,22beta-dihydroxy-tingenone, 20,22beta-dihydroxy-20-epi-tingenone, 20-hydroxy-22-oxo-tingenone, 20-hydroxy-22-oxo-20-epi-tingenone, 20,21alpha-dihydroxy-22-oxo-21-desoxotingenone, 21alpha-hydroxy-20,22-dioxo-30(20-->21)abeo-21-desoxo-tingenone, 20-oxo-20,21-seco-tingen-21-oic acid and 20-oxo-21-nor-20,21-seco-tingen-22-al, were isolated with three known compounds, tingenone, 22beta-hydroxy-tingenone and 20-hydroxy-20-epi-tingenone. Elucidation of their structures was based on detailed spectroscopic examination. All compounds were toxic to brine shrimp and exhibited antimicrobial activities against gram-positive bacteria and fungi. These activities were influenced by functional groups on ring E of their pentacyclic tritepene structure and their lipophilic nature. Tingenone, 22beta-hydroxy-tingenone and 20-hydroxy-20-epi-tingenone rapidly rearranged under acid condition to isotingenone III, 20beta-hydroxy-isotingenone III and 20-hydroxy-20eip-isotingenone III, respectively. These acid-rearranged compounds were less toxic to brine shrimp and lost their antimicrobial activities.