Chemical constituents, antimicrobial and antioxidant activities of essential oils from fresh and air-dried leaves of Icacina trichantha (OLIV.)

Abstract

We investigated and compared the constituents, antimicrobial, and antioxidant activities of the essential oils from the fresh and air- dried leaves of Icacina trichantha. The essential oils were extracted by hydrodistillation, antimicrobial activities were tested on Staphylococcus aureus, Salmonella typhi, Escherichia coli, Pleisomonas shigellosis, Bacillus cereus, Proteus vulgaris, Candida albicans, and Candida tropicalis by agar diffusion method, while 2,2- diphenyl-1-picrylhydrazyl (DPPH) was used for the antioxidant activities at 6.25-200 μg/mL of the oils compared with ascorbic acid as standard. The fresh and air-dried leaf oils gave 0.39% (w/w) and 0.33% (w/w) corresponding to 17 compounds representing 99.99%, and 10 compounds representing 100% respectively. Major compounds in the fresh leaf oil were 9-oxabicyclo [6.1.0] nonane (15.52%), Methyl isododecanoate(11.91%), Oleic acid (10.51%), 3-Cyclohexen-1-ol,3-methyl-(8.24%) and Phytol (7.70%), while Linoleic acid- (34.61%), Palmitic acid (20.74%), 9,17-Octadecadienal, (Z)- (12.98%), 9-Octadecenal (Z) (7.96%) and gamma-sitosterol (7.13%) were the major constituents of the air-dried oil. The fresh leaf oil 50 mg/mL, gave the highest zone of inhibition of 12 mm against Candida albicans while the air-dried oil had the highest zone of inhibition of 18 mm with a minimum inhibitory concentration of 0.20 mg/mL against C. tropicalis. The fresh leaf oil had the highest antioxidant activity of 73.85% at 100 μg/mL, while the air-dried and ascorbic acid had 70.25% and 69.23% respectively at 200 μg/mL. The fresh leaf oil comprised mainly oxygenated hydrocarbons (52.51%) while the air-dried oil had fatty acids (58.44%). Both oils were more antifungal than antibacterial and had a comparable antioxidant activity with ascorbic acid.