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. 2022 Aug 26;11(9):1656.
doi: 10.3390/antiox11091656.

Antioxidant and Antimicrobial Activity of Hydroethanolic Leaf Extracts from Six Mediterranean Olive Cultivars

Vida Šimat  1 , Danijela Skroza  2 , Giulia Tabanelli  3 , Martina Čagalj  1 , Federica Pasini  4 , Ana María Gómez-Caravaca  5 , Carmen Fernández-Fernández  5 , Meta Sterniša  6 , Sonja Smole Možina  6 , Yesim Ozogul  7 , Ivana Generalić Mekinić  2
Affiliations

Antioxidant and Antimicrobial Activity of Hydroethanolic Leaf Extracts from Six Mediterranean Olive Cultivars

Vida Šimat et al. Antioxidants (Basel). .

Abstract

Phenolic profiles, antioxidant, and antimicrobial activities of hydroethanolic olive leaf extracts from six Mediterranean olive cultivars (Croatian: Lastovka, Levantinka, Oblica; Italian: Moraiolo, Frantoio, Nostrana di Brisighella) were investigated. As expected, various distributions of phenolic levels were observed for each cultivar and the total phenolic content showed high variability (ranging from 4 to 22 mg GAE/g of dry extract), with the highest amount of phenolics found in the Oblica sample, which also provided the highest antiradical (ORAC) and reducing activity (FRAP). The screening of individual compounds was performed by HPLC-PDA-ESI-QTOF-MS and the main detected compounds were oleuropein, hydroxytyrosol, oleoside/secologanoside, verbascoside, rutin, luteolin glucoside, hydroxyoleuropein, and ligstroside. While the antioxidant activity of the samples was relatively high, they showed no bactericidal and bacteriostatic activity against E. coli and S. Typhimurium; weak activity against Staphylococcus aureus, Bacillus cereus, and Listeria innocua; and inhibitory effects against Campylobacter jejuni at 0.5 mg dry extract/mL. The obtained results support the fact that olive leaf extracts, and especially those from the Oblica cultivar, could potentially be applied in various industries as natural preservatives and effective and inexpensive sources of valuable antioxidants.

Keywords: antimicrobial activity; antioxidant activity; olive leaves; phenolic compounds.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
The content of total phenolics (TPCs) in olive leaf (in mg of gallic acid equivalents (GAEs) per g of dry extract (n = 4). Columns marked with different letters are statistically different (p < 0.05).
Figure 2
Figure 2
Antioxidant activity of olive leaf extracts detected by FRAP, DPPH, and ORAC method (n = 4). Columns marked with different letters are statistically different (p < 0.05).
See this image and copyright information in PMC

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