Investigation with the crude methanol extract of leaves and flowers of Gmelina philippensischem. as well as petroleum ether, carbon tetrachloride and dichloromethane soluble partitionates were carried out to evaluate antioxidant activity. It was evaluated by analyzing the bleaching rate of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and phosphomolybdenum total antioxidant assay using, butylated hydroxytoluene (BHT) and ascorbic acid (ASA) as standard antioxidants. The total phenolic content was also determined and expressed in gallic acid equivalent (mg of GAE/g of sample). A great variance was observed for polyphenol content as well as antioxidant activity (1.354 to 10.179 mg GAE/g and DPPH IC50 9.75 to 35.25 μg/ml) depending on the nature of the solvent used to fractionate the crude extracts. The result demonstrated that carbon tetrachloride soluble fraction of leaves extract revealed the highest amount of phenolic compounds (10.179 mg GAE/g) and also had significant antioxidant activity (IC50 9.75 μg/ml). A positive correlation was seen between total phenolic content and total antioxidant activity of leaves and flowers of G. philippensis chem. having correlation coefficient (R2) values of 0.9878 and 0.9385, respectively. The general toxicity of the extractive was studied by brine shrimp lethality bioassay and from the results (LC50 0.902 to 0.487 μg/ml).
Key words: Antioxidant, brine shrimp lethality bioassay, Gmelina philippensis chem., phenolic content, verbenaceae.
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