Correlation between Total Phenolic Content and Total Flavonoid Content of Baeckea frutescens L. Fractions and ABTS Radical Inhibition Activity

Abstract

Baeckea frutescens L., locally known in Kalimantan as ujung atap, is a medicinal plant that grows in sandy areas of Central Kalimantan, Indonesia. It has been traditionally used and is currently recognized for its strong antioxidant potential, primarily due to its content of phenolic and flavonoid compounds. This study aimed to identify antioxidant-active fractions from B. frutescens leaf extract and evaluate the correlation between ABTS radical-scavenging activity, total phenolic content (TPC), and total flavonoid content (TFC). Its leaves were extracted by maceration with 70% ethanol, followed by successive fractionation with n-hexane, ethyl acetate, and methanol. This study showed that the methanol fraction has the highest TPC (224.532 ± 0.832 mg GAE/g) and TFC (45.452 ± 0.113 mg QE/g), along with ABTS radical-scavenging activity, with the lowest IC₅₀ value of 23.411 ± 0.394 µg/mL, indicating the strongest antioxidant activity. Ethyl acetate and n-hexane fractions followed in descending order. All fractions demonstrated very strong antioxidant activity (IC₅₀ < 50 µg/mL). Furthermore, this study reported a strong positive correlation between TPC and TFC (r = 0.926). In addition, the IC₅₀ from this herb has strong negative correlations with TPC and TFC, which have r = -0.914 and r = -0.887, respectively. These results highlight the significant role of phenolic and flavonoid compounds in contributing to the antioxidant properties of B. frutescens leaf extract fractions.