This study employed the mixture design method to determine optimal solvent combinations,
aiming to obtain refined extracts from squash peels with enhanced antioxidant properties.
We optimized extraction solvents, focusing on recovering the total phenolic compounds (TPC) and
increased antioxidant properties using a second-order polynomial equation through the response
surface methodology (RSM). Six solvents (MeOH, Hexane, DCM, EtOAc, BuOH, and water) were
assessed for their effects on TPC and antioxidant activity in preliminary experiments. The refined
extracts underwent a HPLC analysis for a phenolic composition determination and were further
evaluated for their antibacterial activity and cytotoxicity. The results revealed a rich phenolic content
in the refined extract from peels of Bejaoui landrace, primarily catechin (8.06 mg/g dry extract (DE)),
followed by epicatechin and kaempferol (5 mg/g DE). Antibacterial tests against Enterococcus faecalis,
Pseudomonas aeruginosa, Salmonella typhimurium, and Staphylococcus aureus showed significant antimicrobial
activities, especially for Karkoubi and batati landraces, where the growth inhibitions were
99%, 96%, 97%, and 80% and 94%, 89%, 98%, and 96% for the respective bacteria. The peel extracts
exhibited a negligible cytotoxicity on the RAW264.7 cell line, even at high concentrations. Our findings
emphasize the potential antioxidant and antibacterial properties of peel extracts due to diverse
phenolic compounds, suggesting the potential use of squash peels in the food and nutraceuticals
industries as sources of natural antimicrobial agents.
This study was supported by the Tunisian Ministry of Higher Education and Scientific
Research and was funded under the scope of the Project PulpIng-H2020-PRIMA 2019—Section
2—Multi-topic 2019. To the Foundation for Science and Technology (FCT, Portugal) for financial support
by national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020)
and SusTEC (LA/P/0007/2020); to FCT for the contract of L. Barros (CEEC Institutional); to the
General Secretariat for Research and Technology of the Ministry of Development and Investments
under the PRIMA Program. PRIMA is an Art.185 initiative supported and co-funded under Horizon
2020, the European Union’s Program for Research and Plants 2022, 11, 800 16 of 18 Innovation
(Prima2019-08).
