Antioxidant activity and lipase enzyme inhibition of gynura procumbens (Lour.) merr and curcuma xanthorrhiza roxb and their correlation with chemometric methods

Gynura procumbens (G. procumbens) and Curcuma xanthorrhiza (C. xanthorrhiza) are herbal medicines used empirically in lipids reduction. The samples used in this study were herbal extracts of ethyl acetate fraction (EAF), G. procumbens, C. xanthorrhiza, and their combinations. This research aims to assay the lipase enzymes inhibition and their antioxidant activity using DPPH (2.2 diphenyl 1-picrylhydrazyl), CUPRAC (Cupric ion Reducing Antioxidant Capacity), and BCB (β-Carotene Bleaching) methods, as well as their relationship with flavonoids and phenolics levels. The measurement was conducted using UV spectrophotometer and microplate reader. The results showed that the EAF herbal extract had the highest phenolic and flavonoid levels, which were 2.30 ± 0.09 w/v quercetin equivalent (QE) and 0.98 ± 0.05 w/v gallic acid equivalent (GAE), respectively. The samples with the highest antioxidant activity using DPPH and CUPRAC methods, as well as the lipase enzyme inhibition were EAF herbal products with IC50 value of 255.36 ± 1.87 µg/mL, 150.42 ± 13.71 µmol QE quercetin/100 g, and 115.79 ±3.44 µg/mL. Those with the greatest antioxidant activity using BCB method were the G. procumbens extracts with IC50 value of 232.15 ± 1.99 µg/mL. The loading plot from chemometric method showed that antioxidant activity of DPPH, CUPRAC, and BCB methods, as well as the lipase enzyme inhibition positively correlated with the total phenolic and flavonoid levels. Meanwhile, all samples had weak antioxidant activity except the EAF herbal products with CUPRAC method. © 2025 Elsevier B.V., All rights reserved.