Comparative study on the chemical composition of laurel (Laurus nobilis L.) leaves from Greece and Georgia and the antibacterial activity of their essential oil

Galina Stefanova,Tanya Girova,Velizar Gochev,Magdalena Stoyanova,Zhana Petkova,Albena Stoyanova,Valtcho D Zheljazkov

doi:10.1016/j.heliyon.2020.e05491

Galina Stefanova, Tanya Girova + Show 5 more

Open Access

https://doi.org/10.1016/j.heliyon.2020.e05491

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Abstract

Laurel (Laurus nobilis L.) is a plant species from Lauraceae family, and is native to the Mediterranean region. The goal of this study was to compare chemical composition of laurel leaves and antibacterial activity of its essential oil (EO) from wild-grown trees in Greece and Georgia. The laurel leaves from the two native habitats had dissimilar concentrations of phenolic acids. Of the conjugated flavonols and flavons, kaempferol (1981.3 μg/g) and apigenin (1433.6 μg/g) were the major representatives in the leaves from Greece, while luteolin (839.1 μg/g) and kaempferol (688.1 μg/g) were the major ones in the leaves from Georgia, respectively. The EO content was 1.42% and 4.54% in the leaves from Greece and Georgia, respectively. The main EO constituents of the Greek laurel plants were 1,8-cineole (30.8%), α-terpinyl acetate (14.9%), α-terpineol (8.0%), sabinene (7.9%), and terpinen-4-ol (6.0%). The main EO constituents of the Georgian laurel plants were 1,8-cineole (29.2%), α-terpinyl acetate (22.6%), sabinene (12.2%), and methyleugenol (8.1%). The EO antimicrobial activities against 20 microorganisms were determined. Among the Gram-positive bacteria, the Enterococcus faecalis strain was the most sensitive, followed by Staphylococcus aureus ATCC 6538. Among the Candida species, C. albicans ATCC 10231 was the most sensitive to the laurel leaf EOs.

Highlights

The essential oil (EO) content of laurel leaves has been reported to range between 0.2% and 4.3% depending on the location, harvesting time, and EO extraction type and conditions (Abu-Dahab et al, 2014; Bahmanzadegan et al, 2015; El et al, 2014; Fidan et al, 2019; Shokoohinna et al, 2014; Vasundhara et al, 2016)
In the laurel leaves from Georgia, p-coumaric acid (45.3 μg/g) was the major free phenolic acid in the group of the hydroxycinnamic acid derivates, while sinapic (1513.9 μg/g), caffeic (789.3 μg/g), and cinnamic (513.4 μg/g) acids were the major conjugated acids
This study found significant dissimilarities in the chemical profile of laurel leaf EOs from Greece and Georgia

Summary

Introduction

To other EO-containing plants, the composition of laurel leaf EO has been shown to vary significantly as a function of the environment, genotype, and the type and duration of the distillation process (Abu-Dahab et al, 2014; Bahmanzadegan et al, 2015; Chahal et al, 2017; El et al, 2014; Fidan et al, 2019; Goudjil et al, 2015; Shokoohinna et al, 2014; Vasundhara et al, 2016). Laurel leaf EO has exhibited antimicrobial and antioxidant activities (Bahmanzadegan et al, 2015; Caputo et al, 2017; Dias et al, 2014; El et al, 2014; Fidan et al, 2019)

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