Abstract:
Acne vulgaris (AV) or acne is characterised as a chronic inflammatory disorder affecting the pilosebaceous unit (sebaceous gland associated with hair follicle) where the causative microorganism Propionibacterium acnes has been identified. The present study was conducted to investigate the potential of 21 southern African plants against P. acnes based on antimicrobial, antioxidant and anti-inflammatory activity. Two species, namely, Clausena anisata and Helichryssum kraussii were able to inhibit P. acnes growth with MICs at 31.25 and 62.5 μg/ml, respectively. The antioxidant activity for the 21 extracts ranged from 1.10–109.10 μg/ml. Active antibacterial species C. anisata and H. kraussii also showed good antioxidant activity with IC50 of 34.46 and 4.24 μg/ml, respectively. These two lead extracts were further investigated for their cytotoxicity on human leukaemic monocyte lymphoma (U937) cells. Clausena anisata showed less toxicity with an IC50 of 74.46 μg/ml and a selectivity index of 2.38. Clausena anisata was hence further selected for investigation of anti-inflammatory activity and mechanism of action studies on the lipase and hyaluronidase enzyme. The concentration of Interleukin-8 (IL-8) in cells treated with heat-killed P. acnes alone was 840.52 pg/ml. Cells stimulated with P. acnes which were co-treated with 50, 25, 12.5 and 6.25 μg/ml of C. anisata extract, showed decreased IL-8 production with concentrations of 322.48 ± 0.07, 365.98 ± 0.24, 383.62 ± 0.08 and 409.52 ± 0.13 pg/ml, respectively. The statistical analysis was done using the Graph Pad Prism 4. These results indicated the potential of C. anisata for a treatment against AV. Lipase activity was inhibited by 21.93% at 500 μg/ml by the C. anisata extract which indicated the potential of this extract to reduce sebum production associated with AV progression. Hyaluronidase activity was inhibited by 49.02% at 500 μg/ml and could potentially deter the spread of P. acnes cells to neighbouring cells during pathogenesis. The compound trans-4-hydroxy-1-methyl-L-proline was isolated for the first time from C. anisata. Anti-acne treatments often require multiple activities to function efficiently. The antimicrobial activity, antioxidant activity and anti-inflammatory activity of C. anisata make it a great candidate for further investigation against AV.
