Antioxidant Activity of Usnic Acid Compound from Methanol Extract of Lichen <i>Usnea</i> sp.

Lichen Usnea sp. is one of the sources of natural bioactive compounds which are currently being developed as medicinal ingredients. The purpose of this study was the isolation and identification of secondary metabolites from methanol extract, toxicity test and antioxidant activity of Usnea sp. Lichen was isolated by maceration using methanol solvent, then separated by liquid-liquid partition and separation using vacuum chromatography. Based on the results of the study, NMR-1D spectral data and FTIR spectrum is the presence of functional groups showed the presence of F15 compound is usnic acid consisting of 18 carbons with 3 carbons from the C=O carbonyl group. The results of the toxicity test showed that all of them were active against Artemia salina L. shrimp larvae with LC50 values of 0.820 µg/mL (Usnea sp.), 1.030 µg/mL (n-hexane), 1.056 µg/mL (ethyl acetate), and 1.236 µg/mL (methanol extract). The results of the antioxidant activity test showed that the inhibitory activity of usnic acid isolate was very active with an IC50 value of 11.696 µg/mL. Meanwhile, methanol extracts and ethyl acetate showed antioxidant activity with IC50 values of 18.098 and 26.917 µg/mL, respectively.