GC-MS Analysis and Antibacterial Activities of <i>Feretia apodanthera</i> Del. (Rubiaceae) and <i>Ozoroa insignis</i> Del. (Anacardiaceae)

Two medicinal plants, Feretia apodanthera and Ozoroa insignis, used in west African folk medicine to treat infectious diseases, were investigated for their antibacterial potential and their biocidal components. Two extractions were processed in water and aqueous-acetone (70%) and further fractionated by column-chromatography. Both extracts and fractions exhibited selective activity against human pathogenic bacteria as assayed by disc diffusion and microdilution methods. The aqueous-acetone extract of F. apodanthera was active against all the Gram-negative and Gram-positive bacteria (d ≥ 8 mm; MIC ≤ 2.5 mg/ml) while the same extract from O. insignis got markedly activity on Gram-negative bacteria E. coli and K. pneumonia (d ≥ 11 mm). However, the fractions (20µg) of both two plant species were selectively more active on Gram-negative bacteria (d ≥ 11 mm). Tetramethyl silicate, trifluoroamine oxide and neophytadiene were identified by GC-MS as the main volatile compounds present that enhance the antibacterial effects in synergy with others.