Optimization of polyphenol extraction from Hippophae salicifolia D. Don leaf using supercritical CO2 by response surface methodology

In this study, an eco-friendly supercritical carbon dioxide (SC-CO2) extraction of polyphenolic compounds from Hippophae salicifolia leaf was optimized to achieve the highest extraction yield with maximum total phenolic content (TPC) and minimum IC50. The central composite design was used to establish an experimental design for RSM. The effect of the pressure, temperature, carbon dioxide flow rate, and co-solvent amount was scrutinized using variance analysis (ANOVA). Under optimized condition (25.13 MPa, 47.53 °C, 14.47 g/min, and 2.43%), the experimental data (yield of extraction: 4.38%, TPC: 84.31 mg GAE/g, and IC50: 41.94 µg/mL) showed good agreement with the predicted values (yield of extraction: 4.53%, TPC: 83.37 mg GAE/g, and IC50: 40.2 µg/mL). Nine polyphenolic compounds: gallic acid, caffeic acid, ferulic acid, vanillic acid, p-coumaric acid, quercetin, myricetin, kaempferol, and rutin were analyzed in SC-CO2 extract using HPLC. SC-CO2 extraction was more selective for ferulic acid, myricetin, and quercetin extraction. The study results revealed that SC-CO2 extract had significant antibacterial activity against eight bacterial strains.