Highly efficient pumpkin-seed extraction with the simultaneous recovery of lipophilic and hydrophilic compounds

Abstract

Enabling technologies have led to the design of new extraction protocols for naturally occurring compounds that are fast, sustainable and have low energy demands. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) have been used, in this study, for the recovery of valuable nutraceuticals and primary metabolites from pumpkin seeds (Curcubita sp.) and have been compared with conventional methods. In order to optimise extraction parameters and conditions, we have compared yields, total phenolic content, antioxidant activity, as well as fatty-acid and lipid profiles. The best yield, in both lipophilic and hydrophilic compounds, was achieved under UAE with a ternary solvent mixture (hexane/ethanol/water - 30:49:21). However, the highest phenolic content and antioxidant capacity were obtained using MAE under subcritical conditions with good extraction yields. The oil composition, as obtained using GC-FID analyses, showed a prevalence for unsaturated fatty acids; mainly linoleic and oleic acids. The use of UAE with ternary mixtures presented the highest lipid content and a slightly higher percentage of unsaturated compounds. Preliminary tests to verify the scalability of UAE with a ternary mixture showed that the extraction performance was maintained when using larger volumes (factor 10). This study will pave the road for the potential exploitation of UAE as a fast and efficient procedure for the simultaneous recovery of lipophilic and hydrophilic compounds from pumpkin seeds.