Chemical composition and in vitro biological studies of volatile oils from Nigerian bee propolis

Abstract

Volatile oils of propolis obtained from Ondo (Ondo town) and Osun (Ile-Ife) States in Rain forest region of southwest Nigeria were extracted using the hydrodistillation method. The oils were analysed on GC/MS and investigated for DPPH scavenging activities, antibacterial potentials, and inhibitory activities on lipase and alpha glucosidase enzymes. Spectrophotometric methods were used for the DPPH scavenging and enzyme’ inhibitions assays while the agar well diffusion method was employed for the antibacterial test. GC/MS analysis of essential oils obtained from Ondo (BPO) and Ile-Ife (BPI) indicated 80 (97.82%) and 66 (99.31%) compounds respectively. Upon classification, both oils were rich in monoterpenes, sequisterpenes and non-isoprenoid hydrocarbons. Principal chemical components of BPO included trans-α-bergamotene (9.08%), α-copaene (5.83%), cadina-1,4-diene (4.04%), 2-methyl-5-propionylfuran (3.43%), 1,5,9,9-tetramethyl-1,4,7-cycloundecatriene (3.52%), benzaldehyde (2.98%), sulcatone (2.95%), γ-muurolene (2.51%), caryophyllene (2.40%), α-bisabolol (2.09%), α-eudesmol (2.07) and α-curcumene (2.06%) while those of BPI were trans-α-bergamotene (10.14%), citral (5.44%), α-copaene (5.25%), cadina-1,4-diene (5.09%), melonal (3.69%), sulcatone (3.56%), farnesol (2.71%), 3,5,9-trimethyl-deca-2,4,8-trien-1-ol (2.66%), α-curcumene (2.64%), 1,5,9,9-tetramethyl-1,4,7-cycloundecatriene (2.20%), and α-muurolene (2.20%). Both oils inhibited α-glucosidase and had DPPH scavenging activities better than the standards, however, anti-lipase activity was observed for BPI only. The oils also demonstrated broad spectrum of antibacterial activities. The volatile components of Nigerian bee propolis are being investigated for the first time, and the plethora of biological activities resulting from their diverse chemical composition showed that bee propolis could be a potential source for drug discovery.