Senecio polyanthemoides Sch. Bip. (Asteraceae) Essential Oils: Chemical Composition, Interpopulation Variability Study and In Vitro Biological Activities of Eight Wild Populations

The in vitro antibacterial, antioxidant, cytotoxic and larvicidal activities of essential oils isolated by hydrodistillation from the aerial parts (above the ground organs consisting of the leaves, stems and flowers) of Senecio polyanthemoides growing in three district municipalities of KwaZulu-Natal Province, South Africa were investigated. The water-distilled oils were analyzed by GC and GC/MS. Sixty-three constituents were characterized in all the samples analyzed representing 86.0–99.2% of the total oil compositions. The major components of the oils were monoterpenoid compounds with β-pinene, myrcene, α-phellandrene, cis-β-ocimene, trans-β-ocimene, β-caryophyllene, α-humulene and germacrene D found in all samples. Numerical cluster and principal component analyses of the major constituents revealed four well-defined chemotypes and a high variability within the oil samples. The essential oils show significant multi-methods activities on antioxidant, cytotoxic, and larvicidal, alongside effective antibacterial action against some key pathogens (Staphylococcus aureus, Escherichia coli, Bacillus pumilus and Enterococcus faecalis), with inhibition zone ranging from (8.3 ± 0.6–27.3 ± 0.9) mm and MIC values of ≤5.0 mg/mL. Documenting the inaugural, in-depth analysis of S. polyanthemoides growing in South Africa, this study provides novel findings on its antioxidant, larvicidal, brine shrimp lethality, and antibacterial activities.