Highly-Oxygenated Isopimarane-Type Diterpenes from Orthosiphon stamineus of Indonesia and Their Nitric Oxide Inhibitory Activity.

Abstract

From the methanolic extract of Indonesian Orthosiphon stamineus, nine new highly-oxygenated isopimarane-type diterpenes [7-O-deacetylorthosiphol B (1), 6-hydroxyorthosiphol B (2), 3-O-deacetylorthosiphol I (3), 2-O-deacetylorthosiphol J (4), siphonols A—E (5—9)] have been isolated together with nine known diterpenes [orthosiphols H (10), K (11), M (12) and N (13); staminols A (14) and B (15); neoorthosiphols A (16) and B (17); norstaminol A (18)]. Their structures were determined based on the spectroscopic data. The isolated diterpenes inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-activated macrophage-like J774.1 cells. Compounds 4—7, 9, 10, 14, and 17 showed inhibitory activities more potent (IC₅₀, 10.8—25.5 μM) than a positive control N^G-monomethyl-L-arginine (L-NMMA; IC₅₀, 26.0 μM).