Senecio pterophorus DC. (Asteraceae) Essential Oils: Antibacterial, Antioxidant, Cytotoxic and Larvicidal Activities

The antibacterial, antioxidant, cytotoxic and larvicidal activities of essential oils obtained by hydrodistillation from the leaves of Senecio pterophorus DC were investigated in the present study. The oils were tested for the antibacterial effects against eleven reference microorganisms using agar-disc diffusion and microdilution-broth methods. The oils exhibited weak to moderate activity against the tested bacterial strains. The highest antibacterial activity was against Staphylococcus aureus (ATCC 6538 and ATCC 3983), Streptococcus faecalis (ATCC 29212), Escherichia coli (ATCC 4983) and Proteus vulgaris (ATCC 0030). The zones of inhibition ranged from 14.0 +/- 2.0 to 21.0 +/- 2.6 mm while the minimum inhibitory concentrations were found between 0.63 and 10.0 mg/mL. In the antioxidant assay, the oils displayed poor ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and chelate iron (II) metal, but showed significant scavenging activity comparable to the standard antioxidants (Butyl hydroxyl anisole, butyl hydroxyl toluene, ascorbic acid and alpha-tocopherol) towards nitric oxide and hydroxyl scavenging procedures. The percentage mortalities of the oils at 250 mg/ml against Artemia salina nauplii and fourth-instar larvae of Culex quinquefasciatus was 100%. However, the lethal concentrations (LC50) values ranged from 12.15 to 13.23 mu g/mL while and LC90 was found between 30.50 and 39.45 mu g/mL against Artemia salina nauplii. In addition, LC50 and LC90 values of 12.15-13.23 mu g/mL and 30.50-39.45 mu g/mL respectively were found against fourth-instar larvae of Culex quinquefasciatus. Aims: The aim of this study was to isolate essential oils from the leaves of Senecio pterophorus DC (Asteraceae) and investigate the antibacterial, antioxidant, cytotoxic and larvicidal activities using standard procedures. Study Design: The study involves the hydrodistillation of essential oils from the air-dried plant materials and investigation of the biological potentials of the oil. Place and Duration of Study: Fresh plant materials of Senecio pterophorus were collected at full flowering stage in September, 2007 from Tongaat, Mtunzini and Gingindlovu in KwaZulu-Natal Province, South Africa. Methodology: About 500 g of air-dried plant samples was shredded and their oils were obtained by separate hydrodistillation for 4 h at normal pressure, according to the British Pharmacopoeia. The antibacterial activity was determined by using agar-disc diffusion and microdilution-broth methods while the antioxidant assay was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and chelate iron (II) metal procedures as well by means of nitric oxide and hydroxyl scavenging assays. The cytotoxic and larvicidal activities were conducted by means of brine shrimps (Artemisia salina) and standard larvicidal procedures respectively. Results: The essential oils displayed potents activities to the tested organisms. Conclusion: The present study confirmed that the essential oils of S. pterophorus may serves as potential phytochemicals.