The Influence of Ripeness on the Phenolic Content, Antioxidant and Antimicrobial Activities of Pumpkins ( Cucurbita moschata Duchesne)

Abstract

Cucurbita moschata Duchesne ( Cucurbitaceae) is a plant food highly appreciated for the content of nutrients and bioactive compounds, including polyphenols and carotenoids, which contribute to its antioxidant and antimicrobial capacities. The purpose of this study was to identify phenolic acids and flavonoids of Cucurbita moschata Duchesne using high-performance liquid chromatography–diode array detection–electrospray ionization tandem mass spectrometry (HPLC–DAD–ESI-MS) at different ripening stages (young, mature, ripened) and determine its antioxidant and antimicrobial activities. According to the results, phenolic acids and flavonoids were dependent on the maturity stage. The mature fruits contain the highest total phenolic and flavonoids contents (97.4 mg GAE. 100 g ⁻¹ and 28.6 mg QE. 100 g ⁻¹).A total of 33 compounds were identified. Syringic acid was the most abundant compound (37%), followed by cinnamic acid (12%) and protocatechuic acid (11%). Polyphenol extract of the mature fruits showed the highest antioxidant activity when measured by DPPH (0.065 μmol TE/g) and ABTS (0.074 μmol TE/g) assays. In the antimicrobial assay, the second stage of ripening had the highest antibacterial activity. Staphylococcus aureus was the most sensitive strain with an inhibition zone of 12 mm and a MIC of 0.75 mg L ⁻¹. The lowest inhibition zone was obtained with Salmonella typhimurium (5 mm), and the MIC value was 10 mg L ⁻¹.