Ophthalmological pre-clinical research about essential oil from the Origanum vulgare L., Lamiaceae

Margareth De Fátima Formiga Melo Diniz,Adriano Francisco Alves,Luiza Toscano Dias Rodrigues,Jana Luiza Toscano Mendes De Oliveira,Maria Carmem Toscano Tavares De Araujo,Walter Mendes De Oliveira Junior

doi:10.5935/0034-7280.20160025

Abstract

Objective: To evaluate acute eye irritation in rabbits following topical administration of essential oil. Methods: animals were divided into three groups, each containing three rabbits, with a total of 6 eyes per group. The difference between them was the concentration used (1, 3 and 9%). A single dose of 0.1 ml of the product was applied into the conjunctival sac of one eye of the animal, and the contralateral eye was used as control. The effects caused by the essential oil in the conjunctiva, iris and cornea were analyzed after 1, 24, 48 and 72 hours and at the end of the seventh day after topical application. Ophthalmologic evaluations were performed with the aid of a binocular indirect ophthalmoscope fluorescein and with and without the observed responses, before being graded according to the Draize scale. Pathological examinations were performed on all eyes studied at the end of the experiment. Results: in the group of animals subjected to the ocular instillation of 1% essential oil, there was no change. For treatment with 3% oil, conjunctival changes were found to be decreasing during the examination after 1 hour. Administration of the 9%essential oil induced conjunctival injection, without any change in the other ophthalmologic evaluation times. Conclusion: the evaluation contributed to meet the clinical changes in the ocular surface. Thus, it was possible to classify the oil at 1% as non-irritating and the concentration of 3% and 9 as mildly irritating, making it possible for clinical studies to establish the oil as an alternative therapy in bacterial conjunctivitis.

Highlights

Acute bacterial conjunctivitis is a common and highly contagious disease caused by direct contact with secretions from the infected eye(1)
Upon primary eye irritation test with the essential oil of Origanum vulgare 3%, we observed a change in the conjunctiva in the ophthalmologic assessment performed to complete 1 instillation of the substance and only a mild hyperemia in one of the study animals in the examination performed after 24 hours of topical use of the essential oil (Figure 2)
The reason to study the effects of the oil of Origanum vulgare L.on the ocular surface lies on the fact that it has promising antibacterial activity on strains from patients with bacterial conjunctivitis, as well as on the use expectation of this product as a source of antibacterial compounds which can be used in the treatment of ocular infections(4,9)

Summary

Introduction

Acute bacterial conjunctivitis is a common and highly contagious disease caused by direct contact with secretions from the infected eye(1). Bacteria have a remarkable number of genetic mechanisms for the development of antimicrobial resistance, making indispensable the emergence of new drugs that can keep the therapy for infectious cases effective. In this context, some medicinal plants and their essential oils, due to their antimicrobial properties, have aroused the interest of researchers around the world to research new antibiotics. We highlight the oregano (Origanum vulgare), which belongs to the genus Origanum (Lamiaceae) whose essential oil has antimicrobial activity against gram-positive and gram-negative bacteria (Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Rhizobium leguminosarum, Bacillus subtilis)(3)

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Conclusion