Valorization of Pumpkin Peel as a Source of Bioactive Compounds: Optimization of Heat- and Ultrasound-Assisted Extraction

Abstract

The peels from three pumpkin genotypes cultivated in Greece were assessed for their phenolic content and bioactive properties to obtain extracts with a high preservative capacity. The optimization of the extraction was performed through response surface methodology (RSM) based on a Box–Behnken experimental design after applying two extraction techniques: heat-assisted (HAE) and ultrasound-assisted (UAE) extraction. The implemented independent variables were time, solvent concentration, and temperature/power (for HAE/UAE), while as dependent variables the dry residue (DR), reducing power (RP), and total phenolic content (TP) were considered. In general, HAE was the most effective technique for ‘TL’ (75 min; 30 °C; 24% ethanol) and ‘Voutirato’ (15 min; 30 °C; 10% ethanol), while UAE was more effective for ‘Leuka Melitis’ (5 min; 400 W; 0% ethanol). The extracts obtained in the global optimum conditions for each genotype peel were then assessed for their phenolic profile, by HPLC-DAD-ESI/MS, and bioactive potential. Seven phenolic compounds were detected, including four flavonoids, two phenolic acids, and one flavan-3-ol. The extracts presented high antioxidant, antibacterial, and antifungal potential, with no cytotoxicity for non-tumor cells. The optimized conditions for the extraction of preservative compounds from bioresidues were defined, allowing the acquisition of antioxidant and antimicrobial extracts and proving their potential for food application.

Cistus, Acacia, and Lemon verbena Valorization through Response Surface Methodology: Optimization Studies and Potential Application in the Pharmaceutical and Nutraceutical Industries

“…In this context, it becomes evident that gallic acid is not conjugated with punicalagin through the carboxyl group, as indicated by the m/z 1083 fragment, which corresponds to the independent loss of gallic acid itself. (11), 315 (15), 179 (5), 161 (100) Forsythiaside 6 15.51 491 315 (100), 300 (23) Isorhamnetin-3-O-glucuronide 7 16.34 623 461 (21), 315 (5), 179 (15), 161 (100) Verbascoside 8 16.59 623 461 (18), 315 (8), 179 (11), 161 (100) Isoverbascoside 9 18.51 637 461 (18), 315 (13), 193 (31), 175 (100), 161 (25) Eukovoside…”

“…Mathematical tools such as RSM have helped reduce the number of experimental runs in order to optimize processes. Using these tools, the operational costs are lower, and the efficiency of resources is higher [13].…”

“…The heat-assisted extraction (dynamic maceration) was carried out according to the modified methodology described by Leichtweis et al [13]. For this purpose, a thermostatic bath was used with stirring performed with submersible magnetic stirrers (Micro Stirrers, Thermo Scientific Cimarec, Thermo Fisher Scientific, Waltham, MA, USA).…”

“…With the aim of exploiting natural resources through the valorization of species, science has invested in the use of more environmentally friendly techniques with green solvents that allow for high profitability and quality of extraction at the lowest possible cost. Thus, the new technologies (e.g., extraction assisted by ultrasound and microwaves) have been used to the detriment of conventional technologies (e.g., extraction using heat-maceration, Soxhlet), as they are sustainable methods that can be easily implemented by the industry [13,14].…”

Valorization of Pumpkin Byproducts: Antioxidant Activity and Carotenoid Characterization of Extracts from Peel and Filaments

“…The literature around spectrophotometric and chromatographic data of carotenoids from pumpkin waste is very lacking, especially when it concerns filaments, and generally focuses on the phenol fraction or other bioactive compounds [5,21,22]. In addition, it must be highlighted that the composition of pumpkin waste can change based on pumpkin variety, harvesting time, conditions, and methods of extraction [23][24][25].…”