Effectiveness of ammonium-based deep eutectic solvents in extracting polyphenol from Chlorella vulgaris

Abstract

This study investigated the extraction of polyphenols from Chlorella vulgaris microalgae using environmentally friendly choline chloride-based deep eutectic solvents (DESs), specifically DES 1 (choline chloride: ethylene glycol, 1:2) and DES 2 (choline chloride: glycerol, 1:2). Thermal characterization of DESs through DSC analysis confirmed their formation as a glass former, while through density and viscosity analysis reveals their influence on extraction efficiency. Both DESs and methanol were employed in solid-liquid extraction combined with centrifugation. The Folin-Ciocalteu method quantified total phenolic content, showing DES 1 and DES 2 to outperform methanol (80.04, 68.63, and 60.15 mg GAE/g, respectively). High performance liquid chromatography (HPLC) was used in order to confirm these results. The HPLC result revealed that DES 1 exhibited the highest extraction efficiency at 198.00 ± 4.45 mg/L of Gallic acid yielded, followed by DES 2 at 189.83 ± 4.84 mg/L and the lowest is MeOH at 138.47 ± 5.36 mg/L. DPPH Radical Scavenging assay indicated both DES 1 and DES 2 extracts with significant radical scavenging activity (88.45 ± 0.17) % and (66.13 ± 1.62) %, respectively, compared to MeOH extracts that showed the lowest antioxidant activity at (30.41 ± 1.70) %. Overall, this study highlighted the potential of DESs in enchancing polyphenol extraction from Chlorella vulgaris, with room for further optimization and exploration of DES-polyphenol interactions.