Antioxidant activity and total phenolic content of methanol extracts of Ixora coccinea

Objective:To investigate the in vitro antioxidant activity of methanol extracts of Ixora coccinea L. (Rubiaceae) flower, leaf and stem. Materials and methods:The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, total antioxidant capacity (TAC) and xanthine oxidase inhibition assay were carried out to evaluate the antioxidant potential of the extract. The IC50 values were calculated for the DPPH and xanthine oxidase assays in order to evaluate the antioxidant efficiency of each of the I. coccinea extracts. The phenol contents were also determined. Results: I. coccinea flowers revealed the best antioxidant property, presenting much lower IC50 value (6.6 mg/mL for DPPH assay). The flower extract showed a significantly higher antioxidant capacity compared to the other extracts. Furthermore, the highest phenolic content (polyphenols) was found in the flower extract (210.55 +/- 6.31 mu g GAE/mg extract). Moreover, I. coccinea extracts scavenged the superoxide radical generated by the xanthine/xanthine oxidase system. The xanthine oxidase inhibition activity was in the order of allopurinol > leaf > flower > stem with the percentage of inhibition ranged from 39.7% to 77.3% for the plant parts investigated. The highest phenolic contents (polyphenols) were found in the flower extracts (210.55 6.31 mu g GAE/nng extract). Conclusions:I. coccinea could be considered as a potential source of natural antioxidant.