Green microwave-assisted extraction of Euphorbia guyoniana: Optimization, metabolite profile and in vivo anti-inflammatory potential

This study aimed to optimize microwave-assisted extraction of phenolic compounds from undervalued traditional plant Euphorbia guyoniana (Boiss. & Reut.) using central composite design of response surface methodology. The independent variables were extraction time (x1: 5 - 25 min), ethanol concentration in the extractive solvent (x2: 30 - 70%), microwave power (x3: 180 - 800 Watt) and feed-to-solvent ratio (x4: 1:7.5 - 1:17.5) while dependent variables were total phenolic content (TPC) and total flavonoid content (TFC). Extract obtained by using the optimal extraction parameters was evaluated for its in vivo anti-inflammatory activity by the carrageenan-induced paw edema model and was subjected to RP-HPLC-PDA-ESI-MS analysis to investigate the presence of phenolic compounds. The optimal conditions for highest TPC (377.22 {+/-} 5.42 mg GAE/100g) and TFC (184.40 {+/-} 1.18 mg QE/100g) were obtained at extraction time of 25 min, ethanol concentration of 40.57%, microwave power of 450 Watt and feed-to-solvent ratio of 1:17.5. The quadratic models significantly (p < 0.0001) fitted the experimental data with R2 values of 0.984 and 0.970 for TPC and TFC, respectively. Optimal extract of Euphorbia guyoniana significantly higher inhibited carrageenan induced inflammation with a concentration of 50 mg/kg (75,98%) when compared with reference anti-inflammatory drug ibuprofen (43,77%). Finally, above the previously reported phenolic constituents, i.e, quercetin and kaempferol derivatives, hydroxycinnamates have been identified for the first time in Euphorbia guyoniana plant extract.