Effect of Total Phenolic Content on Metal Chelation and Free Radical Scavenging Activity of Rhizophora apiculata

Abstract

The present study is aimed to study and determine the total phenolic content, the metal chelation and the antioxidant activity of the extracts of Rhizophora apiculata bark and leaf from the organic solvents which were hexane, ethyl acetate and methanol. The total phenolic contents of six extracts were analyzed by the Folin-ciocateu colorimetric method. Their antioxidant properties were determined by free radical scavenging and metal chelation. The R.apiculata leaf and bark extracted in ethyl acetate and methanol had more total phenolic content than those extracted in hexane, especially the bark extracts, for which total phenolic content was calculated at 1.620 ± 0.082 mg GAE/ g CE for ethyl acetate bark extract and 1.595 ± 0.033 mg GAE/ g CE for methanolic bark extract. The results of the free radical scavenging activity study showed that the antioxidant activity of R.apiculata was more pronounced in the bark than in the leaf. This was clearly demonstrated by the lower IC50 values, especially in the ethyl acetate and methanolic extracts (IC50 = 6.31 ± 0.23 and 6.80 ± 0.19 g/mL, respectively). These antioxidant activities were stronger than those of the BHT standard, which produced IC50 values of 10.13 ± 0.45 g/mL. Furthermore, these data for antioxidant activity were supported by the results of the metal chelation assay, in which ethyl acetate and methanolic extracts of R.apiculata bark showed the highest capacity of metal chelation by ferrous ion at 10.497 ± 0.051 and 10.234 ± 0.101 mg Fe2+/ g CE, respectively. It can be concluded that the R.apiculata bark extracts had interesting bioactive substances, and were effective in scavenging free radicals and chelating metal ions. Its extract has the potential to be a powerful antioxidant agent. Further research is required on the recognition and purification of the interesting bioactive and phenolic compounds from ethyl acetate and methanol extracts of this species.