Natural products from Rhynchostylis retusa (Orchidaceae), their chemophenetic significance and bioactivity

Abstract

Rhynchostylis retusa (L.) Blume is traditionally used for the treatment of pain, inflammation, and skin diseases. The study aims the bioassay-guided isolation of chemical constituents from R. retusa using human breast cancer cell line MDA-MB-231 and murine RAW 264.7 macrophages. The cell viability assay revealed that crude extract, hexane, and chloroform fractions inhibited the viability of MDA-MB-231 and RAW 264.7 macrophages. The hexane fraction led to the isolation of four fatty acids; 1-octene (1), (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid (2), methyl oleate (3), methyl linolenate (4); and one steroid, stigmasterol (5). The isolation and purification of chemical constituents from the most potent chloroform fraction yielded two phenylpropanoids, dihydroconiferyl dihydro-p-coumarate (6) and retusiusine B (7); one bis-nor-lignan, 3,3′-dimethoxy-4,4′-dihydroxy-9,9′-bis-nor-lignan (8) and one bibenzyl, gigantol (9); and vanillin (10). This is the first report of compounds 1–10 from R. retusa (L.) Blume and the genus Rhynchostylis. 3,3′-dimethoxy-4,4′-dihydroxy-9,9′-bis-nor-lignan (8) is new from natural sources. Gigantol (9) is a bioactive compound of R. retusa as it showed an inhibitory effect on the viability of MDA-MB-231 cells and RAW 264.7 macrophages. The bioactivity of R. retusa is possibly due to the presence of gigantol (9) in the plant. Thus, the study corroborates the traditional uses of R. retusa for the treatment of pain and inflammation. The chemophenetic significance of the isolated compounds is also discussed in this study.