SKRINING FITOKIMIA DAN UJI AKTIVITAS ANTIOKSIDAN PADA EKSTRAK DAUN KEPEL (Stelechocarpus burahol (Blume) Hook.f. & Thomson) DENGAN PELARUT BERBEDA KEPOLARANNIM.: 22106040061Eva Mar’atus SolihahauthorOxidative stress triggers degenerative diseases, requiring safer exogenous antioxidants to replace synthetic ones. Kepel (Stelechocarpus burahol (Blume) Hook.f. & Thomson) leaves, rich in secondary metabolites, offer a potential natural antioxidant source. This study determined the effect of solvent polarities on the phytochemical profile, total phenolic-flavonoid contents, and antioxidant activity of kepel leaves. The extraction was carried out using n-hexane (non-polar), ethyl acetate (semi-polar), and ethanol (polar) solvents, yielding five types of extracts: n-hexane, ethyl acetate, ethanol, ethyl acetate II, and ethanol II. Analyses included qualitative screening, LC-HRMS, antioxidant assays (DPPH, ABTS), and total phenolic (Folin-Ciocalteu, 732 nm) and flavonoid (AlCl3, 398 nm) quantification via UV-Vis spectrophotometry. LC-HRMS showed n-hexane selectively extracted lipids. Ethyl acetate extracted terpenoids, phenolics, alkaloids, lipids, and steroids. Ethanol dominantly extracted alkaloids, quaternary ammoniums, steroids, amino acids, phenolics, terpenoids, and flavonoids. Ethanol II exhibited the highest antioxidant activity (IC50 6.64 ± 1.00 μg/mL; ABTS 2,929.34 ± 69.43 μM TE/mg), while n-hexane showed the lowest (IC50 42.15 ± 4.01 μg/mL; ABTS 576.99 ± 7.17 μM TE/mg). This aligns with the highest phenolics in ethanol II (311.65 ± 13.90 mg GAE/g), whereas single ethyl acetate yielded the highest flavonoids (141.70 ± 9.87 mg QE/g). Conclusively, solvent polarity significantly affects the phytochemical profile, phenolic-flavonoid contents, and antioxidant activity of kepel leaves.570 Biologi, Ilmu Hayat2026-03-06UIN SUNAN KALIJAGA YOGYAKARTA;FAKULTAS SAINS DAN TEKNOLOGIThesis