Solvent Free Microwave-Assisted Extraction of Antioxidants from Sea Buckthorn (Hippophae rhamnoides) Food By-Products

After processing, every extraction process generates huge amount of unintended wastes, especially from fruits and vegetables which represent a major disposal problem for the food industry. They are promising sources of bioactive compounds that could be used for their favourable nutritional properties. Sea buckthorn juice production results in generation of large amount of by-products, which are suggested to contain substantial amounts of valuable natural antioxidants. Extracts obtained by solvent-free microwave hydrodiffusion and gravity (MHG) technique and conventional solvent extraction (CSE) method were analysed with HPLC for quantification of flavonoids along with evaluating their phenolic contents by Folin-Ciocalteu method and reducing power by the reduction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. MHG is a green extraction method which offers important advantages like shorter extraction time (15 min), cleaner feature (no solvent or water used) and extraction of valuable flavonoids (Isorhamnetin, isorhamnetin 3-O-glucoside, isorhamnetin 3-O-rutinoside and quercetin 3-O-glucoside) at optimised power (400 W). Along with extracting similar flavonols in enough concentratioin, MHG extract has shown much higher phenolic contents (1,147 milligram gallic acid equivalents (GAE) per gram) against CSE extract (741 mg GAE/g) with greater antioxidant activity determined by DPPH assay.