Total Phenolic and Flavonoid Content and Evaluation of Antioxidant Activity of Roselle (Hibiscus sabdariffa), Lemongrass (Cymbopogon citratus), and Ginger (Zingiber officinale) Combination Extract Based on FRAP Methods

Combinations of roselle, lemongrass, and ginger have potential as natural antioxidant sources. Previous studies have evaluated similar combinations using the DPPH method; therefore, evaluation with an alternative method is needed to obtain a more comprehensive picture of antioxidant activity. This study aimed to determine the total phenolic and flavonoid contents and to evaluate the antioxidant activity of a roselle:lemongrass:ginger (2:1:1) combination extract using the FRAP (Ferric Reducing Antioxidant Power) method as an electron-transfer-based approach. Extraction was carried out with 70% ethanol; total phenolic content was measured by the Folin-Ciocalteu method, total flavonoid content by the AlCl₃ method, and reducing capacity was determined by the FRAP method expressed as ascorbic acid equivalents (mg AAE/g). The results showed that the total phenolic content of Formulation was 107.60±7.39 mg GAE/g and the total flavonoid content was 6.90±0.24 mg QE/g, both higher than those of the single roselle extract (63.43±0.52 mg GAE/g; 4.69±0.80 mg QE/g). The FRAP capacity of Formulation reached 135.34±37.75 mg AAE/g (n=2), relatively higher than that of the formulation with added jasmine. The increase in phenolic and flavonoid contents in Formulation was consistent with better reducing capacity, supporting the contribution of phenolic compounds to electron-transfer-based antioxidant activity. These findings conclude that the 2:1:1 ratio has potential as a natural antioxidant source based on electron transfer, but still requires ratio optimization through a mixture design approach and fractionation before being developed as a functional food raw material.