RESUMO
The objective of this work was to conduct an activity-guided isolation of antibacterial compounds from Rabdosia serra. The ethanol extracts of R. serra leaf and stem were partitioned sequentially into petroleum ether, ethyl acetate, butanol and water fractions, respectively. The ethanol extract of leaf evidenced broad-spectrum antibacterial activity against gram-positive bacterial, including Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes. The ethyl acetate fractions of leaf and stem exhibited strong inhibition against gram-positive bacteria, and were then purified further. On the basis of antibacterial assay-guided purification, three phenolic compounds (rosmarinic acid, methyl rosmarinate and pedalitin) and four C-20 oxygenated ent-kauranes (effusanin E, lasiodin, rabdosichuanin D and a new compound namely effusanin F) were obtained, whose contents were determined by HPLC analysis. The broth microdilution method confirmed the important inhibition potential of C-20 oxygenated ent-kauranes with low minimum inhibitory concentration (MIC) values. Effusanin E, lasiodin and effusanin F could be useful for the development of new antibacterial agents.
Assuntos
Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Diterpenos do Tipo Caurano/isolamento & purificação , Diterpenos do Tipo Caurano/farmacologia , Isodon/química , Fenóis/farmacologia , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/farmacologia , Antibacterianos/química , Bacillus subtilis/efeitos dos fármacos , Diterpenos do Tipo Caurano/química , Testes de Sensibilidade Microbiana , Estrutura Molecular , Fenóis/química , Fenóis/isolamento & purificação , Extratos Vegetais/química , Staphylococcus aureus/efeitos dos fármacosRESUMO
Water-soluble polysaccharides of Rabdosia serra leaf and stem were fractionated by ultrafiltration and DEAE-Sepharose fast flow chromatogram to obtain water (RSLP-I and RSSP-I), 0.1M NaCl (RSLP-II and RSSP-II) and 0.2M NaCl (RSLP-III and RSSP-III) eluates. Their molecular weights were determined by high performance gel permeation chromatography. Monosaccharide composition analysis indicated that the water eluates comprised of rhamnose, arabinose, xylose, mannose, glucose and galactose. The ascending percentage of galactose and descending percentage of glucose in the eluates were observed with the increase of NaCl concentration. The branched RSLP-I and RSSP-I were composed mainly of â6)-Glcp-(1â, â6)-Galp-(1â, and â5)-Araf-(1â residues with the ratio of 15.0:4.2:3.8 and 5.5:6.4:3.5, respectively. However, a low level of 1,6-linked glucosyl was observed in RSLP-II, RSSP-II, RSLP-III and RSSP-III. The structural characteristics were further analysed by infrared spectrophotometry. The purified leaf and stem polysaccharides possessed moderate antioxidant capacities.