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Title: A phytochemical-bioactivity investigation of the South African traditional herbal medicine, Agathosma betulina (buchu)
Author: O'Brien, David
ISNI:       0000 0004 2720 2307
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2005
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The phytochemistry, antimicrobial and antioxidant activity of several extracts of the South African traditional herbal medicine Agathosma betulina (buchu) was investigated. Antifungal screening showed that the reputed active principle in buchu oil, diosphenol, is not the main active component in the herb whereas additional compounds such as hydroxycinnamic acids and lipids may be contributory. However antibacterial screening showed that all the extracts showed very low activity against micro organisms responsible for the pathogenesis of the urinary tract. At a concentration of 1" acetone, 80% MeOH and aqueous extracts exhibited 75% to >90% activity against the stable radical DPPHe whereas the essential oil was weakly active. Furthermore a poor correlation between the total phenolic content and radical scavenging activity of the extracts was observed. The only extract that suppressed the oxidation of linoleic acid was the acetone extract. Four lipophilic flavonoids were detected in the acetone extract and were tentatively identified as the 3 and 3,3'-dimethyl ethers of quercetin and the 3 and 3,4' dimethyl ethers of kaempferol. Three antiradical flavonol glycosides 3, 4 and 5 were detected in the 80% MeOH extract. Flavonoid 5 was identified as rutin and this compound was the main antiradical component in the aqueous extracts. Flavonoid 3 was hyperoside whereas flavonoid 4 was identified as a novel compound designated agathosin on the basis of spectroscopic evidence. Agathosin was shown to be quercetin-3-0-p-o-glucoside esterified with oleuropeic acid, a monoterpenoid carboxylic acid. A rational basis for its structure and the significance of agathosin in the light of the traditional medicinal use of buchu is discussed in addition to its potential biological activity. Furthermore the results of the antimicrobial, antioxidant activity and total phenolic content of the plant extracts are discussed in the light of their chemical composition. In summation this work showed that buchu does not have a direct antimicrobial action, highlighted the importance of using more than one type of assay when assigning antioxidant activity to herbs and their extracts and showed that by assessing extracts from the same plant for different typesof bioactivity novel compounds may be detected.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available