A study of compounds having antibacterial activity isolated from Rubus pinfaensis Levl. et Vant.

A study was undertaken into the isolation and evaluation of the antibacterial activity of the constituents Rubus pinfaensis Levl.et Vant, a herb used in Traditional Chinese Medicine to promote wound healing. An extract of plant material collected in China, has been subjected to chromatography, guided by biological monitoring. Four known triterpenoids, gallic acid, beta-sitosterol and three novel triterpene glycosides have been isolated and characterised. One new compound after enzymatic hydrolysis yielded a new aglycone, which has been named pinfaensic acid. Acylation and methylation yielded the methyl diacetoxy derivative, which was purified to allow its structural elucidation and hence identify the parent as glucosyl 23- formyl-2alpha,3beta,19alpha-trihydroxyurs-12-en-28-oate. The other new glucosides could be differentiated by their UV spectra, with one showing absorbance due to the presence of a conjugated diene. These glucosides were converted to methyl triacetoxy derivatives, from which the parent structures were established as glucosyl 2alpha,3beta,23-tri-hydroxyurs-12,18-dien-28-oate and its 12,19-diene isomer by 13C and 1H NMR studies. The aglycone acids have been given the names 18 and 19-pinfaenoic acid and hence the glycosides were named as 18 and 19-pinfaenoside. Of the known triterpenes, two have been identified as ursolic and euscaphic acids, while the others have been characterised as glucosides of tormentic and 19alpha-hydroxyasiatic acids. Enzymatic hydrolysis of the latter yielded the parent acid, which was further derivatised to methyl 2alpha,3beta,23-triacetoxy-19alpha-hydroxyurs-12-en-28-oate. The stereochemistry of this compound and that of 2alpha,3alpha-diacetoxyeuscaphic acid, also prepared by acylation, were unambiguously established by X-ray crystallography studies. Microbiological studies in vitro have shown that 19alpha-hydroxyasiatic, ursolic and gallic acids exhibit antibacterial activities. A synergistic effect was observed by the use of a combination of 19alpha-hydroxyasiatic acid with gallic acid.

Grantor dc:publisher.institution

Robert Gordon University

Year dc:date.issued

1994

Author dc:creator

• Liu, Iain Xiaojun

Advisor dc:contributor.advisor

• R.M.E. Richards, D.G. Durham and P.J. Cox

• Rubus pinfaensis Levl.et Vant
• Traditional Chinese medicine
• Wound healing
• Antibacterial
• Chromatography
• Pinfaensic acid
• 18 and 19-pinfaenoside
• 19alpha-hydroxyasiatic acid
• Ursolic and Gallic acids

Language dc:language

en

Identifier

oai:rgu-repository.worktribe.com:2807455
https://doi.org/10.48526/rgu-wt-2807455

OAI identifier oai:identifier

oai:rgu-repository.worktribe.com:2807455