Evaluation on Antioxidant Properties of Ethanolic Leaves and Branches Extracts of Nerium indicum from Jeju Island in Korea

The objective of the present study was to estimate the total phenolic content as well as flavonoids in Nerium indicum growing in Jeju island, Korea, and also to evaluate the antioxidant activity of these test preparations on two different in vitro antioxidant activity models. Total phenolic content was determined colorimetrically using Folin–Ciocalteu reagent and was found 774 and 534 mg gallic acid equivalent in the leaves and branches extracts, respectively. Total flavonoid content was determined by aluminum chloride colormetric method and was found 162 and 116 mg rutin equivalent in the leaves and branches extracts, respectively. Free radicals (DPPH, O₂^-• and H₂O₂) scavenging, ferrous ion chelating and ferric reducing assays were carried out to evaluate the antioxidant potential of the leaves and branches extracts of Nerium indicum. Based on IC₅₀ values, the leaves of Nerium indicum possessed higher antioxidant activity than those of branches. Leaves extracts of Nerium indicum showed significant scavenging of DPPH, O₂^-• and H₂O₂ radicals and showed IC₅₀ 0.63, 0.77 and 0.10 mg/mL, respectively. Nerium indicum extracts also inhibited the ferrous ion chelating and ferric reducing abilities in dose dependent manner and showed inhibitory concentration (IC₅₀) 0.82 and 1.49 mg/mL in leaves extracts of Nerium indicum, respectively. Moreover, a correlation between the total phenolic content of the extract, and their antioxidant properties were reported. These results showed that leaves and branches of Nerium indicum can be a promising source of natural antioxidant and holds promise as a natural ingredient in pharmaceutical supplement.