Characterization and Antimicrobial Activity of Volatile Constituents from Fresh Fruits of Alchornea cordifolia and Canthium subcordatum

Bacterial resistance has been increasingly reported worldwide and is one of the major causes of failure in the treatment of infectious diseases. Natural-based products, including plant secondary metabolites (phytochemicals), can be exploited to ameliorate the problem of microbial resistance. The fruit essential oils of Alchornea cordifolia and Canthium subcordatum were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The essential oils were subjected to in vitro antibacterial, antifungal and cytotoxic activity screening. Thirty-eight compounds comprising 97.7% of A. cordifolia oil and forty-six constituents representing 98.2% of C. subcordatum oil were identified. The major components in A. cordifolia oil were methyl salicylate (25.3%), citronellol (21.4%), α-phellandrene (7.4%), terpinolene (5.7%) and 1,8-cineole (5.5%). Benzaldehyde (28.0%), β-caryophyllene (15.5%), (E,E)-α-farnesene (5.3%) and methyl salicylate (4.5%) were the quantitatively significant constituents in C. subcordatum fruit essential oil. A. cordifolia essential oil demonstrated potent in vitro antibacterial activity against Staphylococcus aureus (MIC = 78 μg/mL) and marginal antifungal activity against Aspergillus niger (MIC = 156 μg/mL). C. subcordatum showed antibacterial activity against Bacillus cereus and S. aureus (MIC = 156 μg/mL) and notable antifungal activity against A. niger (MIC = 39 μg/mL). However, no appreciable cytotoxic effects on human breast carcinoma cells (Hs 578T) and human prostate carcinoma cells (PC-3) were observed for either essential oil. The antimicrobial activities of A. cordifolia and C. subcordatum fruit essential oils are a function of their distinct chemical profiles; their volatiles and biological activities are reported for the first time.