Constituintes químicos de Ouratea semisserrata e transformações químicas da neolignana aureina

Abstract

This work reports the results from the chemical study of branches and leaves of a specimen from Ouratea semiserrata, familiy Ochnaceae, collected in Ouro Preto-MG-Brasil. The compounds were isolated from the hexane and methanol extracts by chromatographic techniques and the structures were established by analysis of spectral data including 2D NMR experiments. The hexane extract of the branches afforded sitosterol, stigmasterol, 7-oxo-stigma-5-en-3[3-ol, 7-oxo-stigma-5,22-dien-3[3-ol. The methanol extract of the branches gave eudesmine, epieudesmine, a biisoflavone derived from two units of geistein, 3',6,8-trichloro-4',5-dihydroxy- 7-methoxyflavone and 3',5',6,8-tetrachloro-4',5-dihydroxy-7-methoxyflavone. The hexane extract of the leaves afforded lupeol and friedelin. The methanol extract of the leaves afforded 3()-0-D-glucopyranosyl-[3-sitosterol, ent-16a, 17-dihydroxycauran-19-oic acid, 6, 9 ,dihydroxymegastigma-4, 7-dien-3-ona,rutin, amentoflavone, podocarpusflavone A, lanaraflavone, 7-0-methylanaraflavone, 7, 7"-di-0-methylanaraflavone, a-D-glucose, [3-Dglucose,1[3-0-( 4-hydroxyphenyl)-6-0-( 4-hydroxibenzoyl)-Dglucopyranoside, 1[3-0-( 4-hydroxyphenyl)-6-0-( 4-methoxycinammoyl )D-glucopyranoside and Hl-0-( 4-hydroxybenzoyl)-D-glucopyranoside. five new compounds were isolated and characterized. The extracts have been submited to a bioassay with Artemia salina. Treatment of the neolignan aurein with trifluoroacetic acid furnished the rearranged product 2-(2-allyl-4-hydroxy-3,5-dimethoxyphenyl)-1-(3,4,5-tri methoxy-phenyl)-propane prevíously descríbed ín the literature along with íts derívatives produced by addition of trifluoroacetic acid and water to the double bond of the allyl group. The products were characterized on the basis of spectroscopic data, including 20 NMR experiments and mass spectra. Mechanisms are proposed to account for the products obtained.