Evaluation of phytochemical composition and antioxidant properties of ethanol extract of bark of Dialium ovoideum thwaites

Abstract

Antioxidants have been discovered to play an important function in protecting the body from damage caused by reactive free radicals via interacting with free radicals, chelating, and serving as oxygen scavengers. Dialium ovoideum thwaites, an endemic plant in Sri Lanka, which is locally identified as Gal Siyambala. Leaves of D. ovoideum thwaites have been reported to possess antioxidant properties. Hence, this study aimed to investigate the phytochemical profile and evaluate the antioxidant properties of the ethanol extract of the bark of D. ovoideum thwaites. The extract was prepared using the Soxhlet extraction method and it was subjected to phytochemical screening using standard procedures. The gravimetric method was utilized to conduct the quantitative analysis of flavonoids, tannins, and saponins. Folin-Ciocalteau assay was used to determine the total phenolic content. DPPH radical scavenging and ferric-reducing power assays were used to determine the antioxidant properties. The results of qualitative phytochemical screening showed the presence of phenols, flavonoids, saponins, steroids and tannins. In quantitative analysis, the phytochemical constituents indicated 10.7% (w/w) of flavonoids, 1.1% (w/w) of tannins and 0.9% (w/w) of saponins. The total phenolic content was 233.4±22.7 mg gallic acid equivalent/g extract while the IC50 value for the DPPH assay was 68.5±6.3 μg/mL which is comparable to ascorbic acid (32.0±2.1 μg/mL). The reducing potential of the extract showed that it possesses a significant (p<0.05) reductive potential as compared with the ascorbic acid standard. Results revealed that the ethanol extract of the bark of D. ovoideum thwaites exhibits antioxidant properties which are positively correlated with its total phenolic content.