Identification of antioxidant compounds from the stem bark fraction of Strychnos innocua Del.

Strychnos innocua is a shrub that is native to the tropic region of the world. It is used locally as food, medicine, fuel, and as an insect repellent. Extracts of this plant are used as an aphrodisiac and in the treatment of gonorrhoea, snakebite and dysentery. It has been proven to possess antioxidant and antimicrobial activities. There is little or no information on the identification and pharmacological activities of the chemical composition of the stem bark of this plant. The aim of this work is to identify the chemical compounds present in this plant and determine their antioxidant activities. The ethyl acetate extract of this plant was subjected to purification techniques which lead to the isolation of fraction SI1. The chemical composition of the fraction SI1 was then determined using gas chromatography-mass spectrometry (GCMS). Fractions SI1 was then analysed for its free radical scavenging potential using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Ferric ion reducing antioxidant property (FRAP) assay. A total of thirty compounds were identified with the major compounds being Cyclohex-2-enone,3-)2H-tetrazol-5-yl amino) (15.83 %), N-hexadecanoic acid (38.21%), N-hexadecanoic acid (38.21%), Octadecanoic acid (13.41%), Cis-vaccenic acid (13.41 %). The DPPH radical scavenging potential of the fraction SI1 compares well with the standard, ascorbic acid with IC50 of 3.71 +/- 0.31 mu g/mL and 1.68 +/- 1.27 mu g/mL, respectively. At 500 mu g/mL, the antioxidant potential of the standard ascorbic acid was 96.9% whereas the fraction SI1 had 62.1% free DPPH radical scavenging activity. The half-maximal inhibitory concentration (IC50) of SI1 observed is 0.0488 +/- 0.01 nm, and 0.5375 +/- 0.01 nm and for ascorbic acid. In conclusion, fraction SI1 can act as an antioxidant supplement for various applications in diverse fields of food, cosmetics, and medicine. Several compounds contained in the fraction SI1 may have contributed to the antioxidant properties of the fraction. The compounds identified could be useful precursors for the synthesis of therapeutic drugs associated with the treatment of human and animal diseases.