Ultrasound-assisted extraction of carotenoids from pumpkin pulp

Pumpkin, a vegetable belonging to Cucurbitaceae family, is considered a functional food and a medicinal plant due to the presence of many phytochemicals with interesting health effects. The aim of the research was to select the best extraction technique for the recovery of carotenoids from Cucurbita moschata pulp. Unconventional methods, i.e. ultrasound-assisted extraction (UAE) and microvawe-assisted extraction (MAE), were employed and a comparison with a traditional method, i.e. maceration, was carried out. A binary (hexane:isopropanol, 60:40 v/v) and a ternary (hexane:acetone:ethanol, 50:25:25 v/v/v) mixtures were tested. The binary mixture, a temperature of 45 °C, a solid:liquid ratio of 1:20, and a time of 30 minutes were chosen as the best extraction conditions. The extraction yield (%), the antioxidant activity evaluated by different in vitro assays (ABTS, DPPH, and FRAP) and an analytical characterization by RP-HPLC-DAD of extracts were determined. HPLC-MS was also carried out for structure confirmation of bioactives. In addition to the two main peaks corresponding to β-carotene and α-carotene, the chromatographic profiles of extracts highlighted the presence of other interesting bioactive compounds (violaxanthin, neoxanthin, antheraxanthin, lutein, but also mono- and diesterified structures). All the obtained extracts showed interesting antioxidant properties. The obtained results suggest that UAE for 30 min at 45 °C was the most successfully extracting technique for carotenoids extraction from pumpkin pulp in respect to the other methods (MAE and MAC), taking into consideration all considered data and their correlation. A similar approach is in progress for the extraction and analysis of pumpkin waste (peel, seeds, filaments).