Kien Giang has a diverse ecosystem with many species of plants used as medicine. Ethanol extracts from
14 plant species collected in Kien Giang were evaluated for total polyphenols, flavonoids and total
antioxidant activity. Total phenolic content was determined spectrophotometrically according to Folin–
Ciocalteu colorimetric method. Total flavonoid content of ethanolic extracts was determined using
aluminum chloride colorimetric method. The total antioxidant capacity was evaluated by the
phosphomolybdenum method. The results showed that total phenolic content of ethanolic extracts of the
investigated plant species ranged from 82.88 to 671.83 mg GAE/g extract, while the total flavonoid content
ranged from 139.90 to 563.93 mg QE/g extract. The highest antioxidant activity was shown in the leaf and
fruit extracts of Sphaerocoryne affinis (with Abs0.5 value of 36.15 µg/mL; 44.65 µg/mL) that contained the
highest concentrations of polyphenols and flavonoids. These plants exhibited strong antioxidant activity
and will be potential sources for isolating antioxidants.