Green Extraction of Carotenoids from Sea Buckthorn Pomace – the Effect of Solvent and Extraction Method
Sea buckthorn pomace (SBP) is produced in large amounts during the processing of berries for the production of oil and juice. Although it is rarely used, the pomace still contains valuable bioactive compounds, such as carotenoids, tocopherols and phenolic compounds. The aim of our study was to evaluate the efficiency of carotenoid extraction from SBP, using green solvents (ethyl acetate - ETA, ethyl lactate - ETL, cyclopentyl methyl ether - CPME, methyl tetrahydrofuran - MeTHF and cold pressed sunflower oil - SFL), compared with a mix of organic solvents. Moreover, two extraction methods were applied: conventional solid-liquid extraction (maceration) and ultrasound assisted extraction. Total and individual carotenoids in the extracts were determined by HPLC-PDA and the antioxidant activity by DPPH assay. The total carotenoid extracted ranged from 45.32 mg/100 g powder (ETA) to 64.31 mg/100 g powder for OS mixture, when maceration was applied. When UAE method was used, the total carotenoids ranged between 45.75-65.82 mg/100 g powder, with the highest value being obtained for CPME, closely followed by MeTHF. CPME was the most efficient in extracting zeaxanthin esters and carotenes, while ETL was the most efficient for extracting free zeaxanthin. Except for sunflower oil, for all the tested solvents UAE gave better yields than conventional solid-liquid extraction. The extracts obtained with green solvents displayed antioxidant activity and there was a positive correlation between the amount of carotenoids in the extract and the inhibition of DPPH radical.