Antioxidant Activity, Total Phenolic and Total Flavonoid Content of Etlingera maingayi (Baker) R.M.Sm.

บทคัดย่อ

Etlingera maingayi (Baker) R.M.Sm. is a rare plant species native to southern Thailand. It is infrequently utilized, with its primary use being for edible flowers. This study aimed to investigate and evaluate the antioxidant properties of the aerial parts of E. maingayi. Dried plant materials were extracted using ethanol, followed by solvent removal via rotary evaporation. Antioxidant activities were assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays, and the ferric reducing antioxidant power (FRAP) assay. The chemical constituents of the extract were quantified using the Folin–Ciocalteu method for total phenolic content and the aluminum chloride colorimetric method for total flavonoid content. The E. maingayi extract exhibited antioxidant activity with an IC_₅₀ value of 0.56 ± 0.01 mg/mL in the DPPH assay, compared with Trolox as a positive control (IC₅₀= 0.036 ± 0.003 mg/mL). In the ABTS assay, the extract showed an IC₅₀ value of 4.53 ± 0.59 mg/mL, compared with Trolox (IC₅₀= 0.28 ± 0.06 mg/mL). Furthermore, the extract demonstrated ferric reducing antioxidant power (FRAP) at 150.54 ± 1.79 mg FeSO₄/g extract. The total phenolic and flavonoid contents were 83.76 ± 3.36 mg gallic acid equivalents (GAE)/g extract and 65.11 ± 6.84 mg catechin equivalents (CE)/g extract, respectively. These results indicate that the ethanolic extract of the aerial parts of E. maingayi possesses significant antioxidant activity and is rich in polyphenolic compounds. Therefore, this species may serve as a potential natural source of antioxidants for future applications.