Aqueous Extract of Gembili (Dioscorea esculenta) Tubers Exceeds Its Ethanol Fractions in Phenolic Content and Antioxidant Capacity

Ika Puspitaningrum (Department of Pharmacology and Clinical Pharmacy, Stifar Yayasan Pharmasi Semarang, Semarang 50193, Central Java, Indonesia)
Lia Kusmita (Department of Pharmaceutical Biology, Stifar Yayasan Pharmasi Semarang, Semarang 50193, Central Java, Indonesia)

Indonesian Journal of Jamu
Vol. 11 No. 6 (2026): November–December 2026

Gembili (Dioscorea esculenta) tubers are used in Indonesia mainly as a source of inulin, recovered from hot-water extracts by ethanol precipitation, but how antioxidants partition during this step is unknown. A hot-water extract (AE) was compared with its ethanol-insoluble (EIF) and ethanol-soluble (ESF) fractions for total phenolic (TPC) and flavonoid (TFC) contents and for 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) activities. AE had the highest TPC (214.9 ± 6.1 mg gallic acid equivalents/g) and TFC (159.7 ± 6.5 mg quercetin equivalents/g), the lowest IC50 values (DPPH 30.0 ± 0.8; ABTS 28.5 ± 1.9 µg/mL), and the highest FRAP (269 ± 42 mg ascorbic acid equivalents/g). EIF exceeded ESF in all assays except FRAP (p < 0.001), and antioxidant capacity followed TPC across nine determinations (DPPH IC50, r = −0.94). The inulin-rich precipitate therefore retains part of the antioxidant capacity of the tuber.