As demonstrated in our previous paper, the crude extract of S. trilobata has antioxidant activity. The current investigation aims to identify the bioactive compound responsible for S. trilobata's antioxidant effect. The results shown that the ethyl acetate extract has the lowest EC50 values, indicating the highest DPPH scavenging (EC50 values for F- hexane, F- chloroform, F- ethyl acetate, and F-aqueous were > 800.00 µg/ml, 625.64 ± 43.05 µg/ml, 19.67 ± 0.98 µg/ml, 478.17 ± 34.67 µg/ml, respectively). Semi-polar compounds can be antioxidant bioactive compounds. Furthermore, there appeared to be a good correlation between phenolic content and antioxidant activity of the extracts, with higher phenolic content ethyl acetate fractions demonstrating higher antioxidant activity.