Antioxidant activity-guided isolation of constituents from Euphorbia gaditana Coss. and their antioxidant and tyrosinase inhibitory activities

Abstract Two previously unreported compounds, 4-O-(2′′-O-galloyl-β- d -glucopyranosyl)-3,5-dihydroxyacetophenone (1) and 5-isopropyl-2-oxo-3,6-dihydropyran-4-carboxylic acid (2), along with twenty-nine known compounds (3−31) were isolated from the aerial parts of Euphorbia gaditana Coss. Their structures were elucidated based on extensive spectroscopic analysis 1D and 2D-NMR, mass spectrometry HR-ESI-MS, optical rotation [α]D, acid hydrolysis and the comparison of NMR data with those described in literature. The antioxidant activity-guided study was conducted using DPPH and CUPRAC methods started from the extracts to bioactive isolated molecules. Most of the isolates (1-31) showed a good to excellent antioxidant activity compared to the standards BHT and ascorbic acid. Furthermore, 1 and 2 exhibited a moderate tyrosinase inhibitory activity (IC50 89.78 ± 0.93 and 52.39 ± 0.69 μg/mL, respectively) compared to the standard kojic acid (IC50 25.23 ± 0.78 μg/mL).