This thesis presents the isolation and structure elucidation of a range of secondary metabolites from four selected medicinal plants from Southeast Asia; Thailand and Bangladesh, namely, Cassia tora, Piper betel, Brugueira gymnorrhiza and Avicennia alba. A Variety of natural products belonging to several classes were isolated and investigated for their biological activity. The evaluation of Piper betel extracts for antimicrobial activity and some second metabolites isolated from Piper betel for Antimethicillin-Resistant Staphylococcus aureus activity (MRSA) were targeted in this thesis. A total of eightteen compounds were isolated from the selected plants, including mixtures of two steroids and two sesquiterpenes and two of the compounds were active against MRSA. Phytochemical investigation of Cassia tora leaves resulted in two anthraquinones (physcion and chrysophanol) and a mixture of steroids (β-sitosterol and stigmasterol). Physcion and chrysophanol are reported from the leaves of Cassia tora for the first time. Phytochemical investigation of Piper betel leaves led to the isolation of two phenolic compounds (eugenol and 4-allyl pyrocatechol), a mixture of sesquiterpenes (β- elemene and trans-calamenene), γ-muurolene and an unidentified cycloartane derivative. Eugenol and 4-allyl pyrocatechol were active against MRSA, β-elemene, trans-calamenene, γ-muurolene and the unidentified cycloartane derivative are being reported for the first time from the leaves of Piper betel. Phytochemical investigation of Bruguiera gymnorrhiza leaves led to six triterpenoids (careaborin and taraxerol, β-Z-p-coumaroyl taraxerol, taraxerone, β-lauryl-β-amyrin and, 3,4-seco-taraxerol) and one quinone (stenocarpoquinone B). These compounds are being isolated for the first time from the leaves of Bruguiera gymnorrhiza and the Rhizophoraceae family. Phytochemical investigation of Avicennia alba stems led to a triterpenoid (betulinic acid) and a steroid (β-sitosterol). Antibacterial activity of isolated compounds was investigated against Antimethicillin-Resistant Staphylococcus aureus activity (MRSA). Eugenol and 4- allyl pyrocatechol were active and gave MIC valves, 64 and 128 μg/mL.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:570591 |
| Date | January 2012 |
| Creators | Chawananorasest, Khanittha |
| Publisher | University of Strathclyde |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=17196 |
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