Biological Activity of Pumpkin Byproducts: Antimicrobial and Antioxidant Properties

Abstract

Pumpkin fruits are widely appreciated and consumed worldwide. In addition to their balanced nutritional profile, pumpkin species also present valuable bioactive compounds that confer biological and pharmacological properties to them. However, the seeds, peels, and fibrous strands resulting from pumpkin processing are still poorly explored by the food industry. The current study used those fruit components from the genotypes of pumpkin that are economically significant in Portugal and Algeria to produce bioactive extracts. In order to support their usage as preservatives, their phenolic content (HPLC-DAD-ESI/MS) and antioxidant (OxHLIA and TBARS) and antimicrobial properties (against eight bacterial and two fungal strains) were assessed. In terms of phenolic profile, the peel of the Portuguese ‘Common Pumpkin’ showed the most diversified profile and also the highest concentration of total phenolic compounds, with considerable concentrations of (-)-epicatechin. Regarding the antioxidant capacity, the seeds of ‘Butternut Squash’ from both countries stood out, while the fibrous strands of Portuguese ‘Butternut Squash’ and the seeds of Algerian ‘Gold Nugget Pumpkin’ revealed the strongest antimicrobial activity. The bioactive compounds identified in the pumpkin byproducts may validate their enormous potential as a source of bio-based preservatives that may enhance consumers’ health and promote a circular economy.

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

“…P3 was the sample presenting the lowest antioxidant potential, in accordance with its lower phenolic compounds content. The IC 50 values obtained in the present study were comparable or better than those reported for Portuguese and Algerian pumpkins [ 3 ], which presented IC 50 values ranging from 88 to 209 µg/mL and 335 to 588 µg/mL for the OxHLIA assay and from 3921 to 7765 µg/mL and 2123 and 4569 µg/mL for the TBARS assay, respectively. These findings indicate the high antioxidant capacity of pumpkin fruit waste and highlight the potential of its further valorization in the food industry, since a significant correlation between the polyphenol extraction efficiency and the antiradical potential of the extracts has been well-confirmed [ 28 ].…”

“…(-)-Epicatechin (peak 1) was the least representative compound in samples P1 and P2, contrarily to the results reported for the Portuguese pumpkin extracts, in which this was the most abundant compound [ 3 ]. The extracts from P1 and P2 showed higher contents of total phenolic compounds, approximately 3 mg/g each, while P3 presented almost half of the total concentration found in P1.…”

“…Peaks 1, 4, 5, 6, and 7 were tentatively identified considering the previous characterization of the extracts obtained from Portuguese and Algerian pumpkin peels [ 3 ]. (-)-Epicatechin ([M-H] − at m / z 289, peak 1) was tentatively identified by comparison with the available standard, while the flavonoid compounds (peaks 4, 5, 6, and 7) were compared with the literature [ 24 ].…”

“…For example, pumpkin peel is a rich source of these compounds and, beyond its antioxidant properties, it could also act as a natural preservative due to its high content of bioactive molecules. Recent research has shown that pumpkin peel extracts can inhibit the growth of bacteria and fungi, making them a natural alternative to chemical preservatives [ 3 , 4 ]. In fact, one study on the evaluation of the antimicrobial activity of pumpkin peel extract using the agar disc method demonstrated a remarkable broad-spectrum antimicrobial potential against the Gram-positive bacterium Streptomyces viridochromogenes [ 5 ], whereas Asif et al reported the satisfactory antibacterial activity of pumpkin peel extracts against four bacterial strains ( Escherichia coli , Pasteurella multocida , Staphylococcus aureus , and Bacillus subtilis ) [ 6 ].…”

“…Despite the abovementioned bioactivity of these bioresidues and the high volume generated by the food industry, to the best of our knowledge, few studies have been conducted on the extraction of bioactive compounds from pumpkin peels [ 3 , 15 ]. Therefore, this study was carried out with the aim of optimizing the extraction of preservative compounds from the peel of three pumpkin genotypes cultivated in Greece.…”