THE PHYTOCHEMISTRY AND BIOLOGICAL ACTIVITIES OF ATHRIXIA PHYLICOIDES

Herbal medicines are an important part of the African culture and tradition and about 80% of \nAfrica’s population relies on traditional remedies for their primary health care needs (WHO, \n2008). Athrixia phylicoides is widely used as a traditional remedy, but despite its substantial \nuse, literature on its chemical composition and biological activities is limited. In this study, \nthe chemical composition of the essential oil was determined using gas chromatography \ncombined with mass spectroscopy (GC/MS) and analysis resulted in the identification of 182 \ncompounds. The major compounds identified in selected samples were α-pinene, β-pinene, \ncaryophyllene oxide, β-caryophyllene, myrcene and spathulenol. Based on the traditional uses \nof A. phylicoides, various in vitro biological activities were investigated. The extensive use of \nA. phylicoides for the treatment of boils, sores, bad acne, infected wounds and cuts, prompted \nthe antimicrobial (bacterial and fungal) study using the minimum inhibitory concentration \n(MIC) assay. The methanol extract and essential oil were more selective for the Grampositive \nbacteria than the Gram-negative bacteria. The extract exhibited stronger activity \nagainst all micro-organisms tested compared to the essential oil, with the highest activity \nagainst S. aureus, B. cereus and B. subtilis (MIC = 1 mg/ml). The bioactive compound, \n(4-hydroxyphenyl) propyl coumaroate was isolated from the extract and proved to be most \nactive against S. aureus (MIC = 19.5 μg/ml). Using the DPPH• assay, a comparative antioxidant \nstudy was performed. The anti-oxidant activity of the aqueous extract of A. \nphylicoides (IC50 = 14.01 ± 2.68 μg/ml) was greater than rooibos and Ceylon (black) tea (IC50 \n> 25.00 μg/ml); comparable to green rooibos and honeybush tea (IC50 = 18.01 ± 4.06 μg/ml; \n18.02 ± 4.27 μg/ml, respectively), but less active than green tea (IC50 = 9.64 ± 0.96 μg/ml). \nThe antimalarial activity was determined using the [3H] hypoxanthine incorporation method. \nThe essential oil exhibited greater antimalarial activity against the chloroquine-resistant \nPlasmodium falciparum (FCR-3) strain (IC50 = 1.006 ± 0.06 μg/ml) than the methanol extract. \nThe 5-lipoxygenase assay was used to assess the anti-inflammatory activity of the methanol \nextract and essential oil. Only the essential oil displayed anti-inflammatory activity (IC50 = \n25.68 μg/ml). Low safety indices were reported for both the methanol extract (SI = 2.28) and \nessential oil (SI = 1.77). The in vitro biological activities may validate the use of A. \nphylicoides in traditional medicine.