Chemical composition, enantiomeric analysis, and bactericidal activities of sesquiterpene-rich essential oil of Acanthospermum hispidum DC. from northwestern Nigeria

InformationAcanthospermum hispidum (Asteraceae), a medicinal plant indigenous to Nigeria and known locally as "Dagunro" in Yoruba and "Kasihinyawo" in Hausa, has been a traditional remedy in local healthcare practices.This study explores the chemical composition, enantiomeric analysis, and bactericidal activities of the sesquiterpene-rich essential oil of A. hispidum from Nigeria.The essential oil of A. hispidum was obtained through hydrodistillation and chemical constituents and enantiomeric distributions were identified using gas chromatography-mass spectrometry (GC-MS) analysis.The antibacterial activity was assayed using the micro-dilution method against selected pathogenic bacterial strains.The essential oil was dominated by sesquiterpenes.The major constituents identified in the essential oil include (E)-β-caryophyllene (21.8%), α-bisabolol (20.7%), bicyclogermacrene (7.9%), caryophyllene oxide (6.6%), α-humulene (5.9%), and germacrene D (6.1%).Chiral GC-MS analysis further elucidated the enantiomeric distribution of chiral terpenoid components, which includes (+)-α-pinene 92.8% : (-)-αpinene 7.2%;(+)-sabinene 14.7%: (-)-sabinene 85.3%; (+)-β-pinene 52.4% : (-)-β-pinene 47.6%; (+)-limonene 17.3% : (-)-limonene 82.7%; and (+)-linalool 8.6% : (-)-linalool 91.4%.The antibacterial activity of A. hispidum essential oil revealed notable inhibitory activity with Minimum Inhibitory Concentrations (MIC) ranging from 125 µg/mL to 1250 µg/mL.The essential oil showed marked activity against Staphylococcus aureus (MIC = 125μg/mL), moderate activity against Salmonella typhi and Proteus vulgaris (MIC = 625μg/mL).The presence of bioactive compounds such as α-bisabolol and β-caryophyllene may have implications for the potential therapeutic application of A. hispidum essential oil.