Natural deep eutectic solvents-based concurrent approach for qualitative and quantitative enhancement of Rosa damascena essential oil and recovery of phenolics from distilled rose petals

Abstract

In pursuit of adopting environment friendly methodologies to amplify essential oil (EO) yield of industrially important aromatic plants, enrichment of bioactive content in distillation waste, and to establish the recovery process for the enriched product; this study employed natural deep eutectic solvents (NADESs) as cosolvent in the conventional hydro distillation method using Rosa damascena Mill L (Damask rose) petals as biomass. R. damascena is one of the most important species of Rosaceae family known for producing high-valued rose EO [often termed as “liquid gold”] but with very low yield. Herein, nine NADESs were used as cosolvent along with conventional hydro distillation method which led to 1.7 times EO yield enhancement (retention of EO quality as per ISO guidelines) using NADES-4 [choline chloride: glycerol (1:1)] as cosolvent. Further, to sustainably utilize the residue (otherwise waste) left after hydro distillation, hydrolate (aqueous part left in the flask) and spent (dried solid waste) were analyzed with UHPLC to determine targeted phenolics compounds. All the samples (EO, dried hydrolate, and spent) were also evaluated for in-vitro antioxidant activity using DPPH-radical scavenging assay, which revealed that hydrolate obtained by using NADES-5 [choline chloride: glucose (5:1)] showed the highest activity (IC50 0.85 µg/mL) as compared to ascorbic acid (IC50 5.40 µg/mL). Hence, the present study provides a green protocol for enhancing rose EO yield with phenolics-enriched antioxidant byproducts.