Screening of Chemical Composition, Antimicrobial and Antioxidant Activities in Pomegranate, Quince, and Persimmon Leaf, Peel, and Seed: Valorization of Autumn Fruits By-Products for a One Health Perspective
Antimicrobial resistance is increasing globally and is now one of the major public health
problems. Therefore, there is a need to search for new antimicrobial agents. The food industry
generates large amounts of by-products that are rich in bioactive compounds, such as phenolic
compounds, which are known to have several health benefits, including antioxidant and antimicrobial
properties. Thus, we aimed to characterize the phenolic compounds present in pomegranate, quince,
and persimmon by-products, as well as their antioxidant and antimicrobial activities. Phenolic
compounds were extracted from pomegranate, quince, and persimmon leaves, seeds, and peels
using a mixture of ethanol/water (80/20). The polyphenol profile of the extracts was determined by
high-performance liquid chromatography. The antioxidant activity of the extracts was determined by
the 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and cupric
reducing antioxidant capacity (CUPRAC) methods. Antimicrobial susceptibility was evaluated using
the Kirby–Bauer disk diffusion method. In general, leaves showed higher concentrations of phenolics
than the peel and seeds of fruits. In total, 23 phenolic compounds were identified and quantified,
with sanguiin and apigenin-3-O-galactoside being present in the highest concentrations. Leaf extracts
of pomegranate showed higher antioxidant activities than the other components in all methods used.
In general, all extracts had a greater antimicrobial activity against Gram-positive bacteria. Persimmon
leaf and seed extracts inhibited a greater number of bacteria, both Gram-positive and -negative.
The lowest minimum inhibitory concentration (MIC) detected among Gram-positive and -negative
bacteria was 10 mg/mL for pomegranate peel and leaf extracts against Staphylococcus aureus and
S. pseudintermedius and for pomegranate leaf extract against Escherichia coli. Our results reinforce
the need to value food industry by-products that could be used as food preservatives and antibiotic
adjuvants against multiresistant bacteria.
This work was supported by projects UIDP/00772/2020 and LA/P/0059/2020, funded by
the Portuguese Foundation for Science and Technology (FCT), and by LAQV-REQUIMTE, which is
financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020). This work
was also supported by National Funds from the FCT–Portuguese Foundation for Science and Technology,
under project UIDB/04033/2020, as also to CIMO (UIDB/00690/2020 and UIDP/00690/2020),
SusTEC (LA/P/0007/2020), and for L. Barros institutional contract; to FEDER through the Regional
Operational Program North 2020, under the Project GreenHealth, Norte-01-0145-FEDER-000042.
