Phytochemical constituents, total flavonoid and phenolic contents and antioxidant activity of leaves of Syzygium guineense

We evaluated the phytochemical constituents and the antioxidant activity of methanolic leaf extract of Syzygium guineense. The class of phytochemicals was determined using Harborne’s method. The phytochemicals present in the extract were identified using GC-MS. Twenty-seven compounds were separated and twenty were identified. The most abundant compound was carbamic acid phenyl ester with a percentage composition of 13.67%. Spectrophotometric assay was used to determine the total flavonoid and phenolic contents. The assay indicates that the methanolic leaf extract is rich in polyphenols and flavonoids. At the highest concentration of the extract (500ug/ml), the total phenolic and total flavonoid contents of the extract were 274.92mg gallic acid equivalent/g and 8.42 mg quercetin equivalent/g respectively compared to gallic acid and quercetin standard with total phenolic and total flavonoids contents of 385.12 and 12.46 respectively at the same concentration. The antioxidant activity was determined using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing power assays. DPPH radical scavenging activity and ferric reducing power of the extract increased in a dose dependent manner and these activities were compared with ascorbic acid, a standard antioxidant. The results indicate that the leaf extract possess significant antioxidant activity as evident in their DPPH radical scavenging activity and ferric reducing power and could serve as source of natural antioxidant.