Solvent-Free Microwave Extraction of Thymus mastichina Essential Oil: Influence on Their Chemical Composition and on the Antioxidant and Antimicrobial Activities.

André R T S Araujo,Cassandra Cunha,Paula Coutinho,Lúcia A Silva,Márcio Rodrigues,Maximiano P Ribeiro,Farid Chemat,Luisa Jordao,Jesus Rodilla,Xavier Fernandez,Sandrine Périno

doi:10.3390/ph14080709

Abstract

Solvent-free microwave extraction (SFME) is a combination of microwave heating and dry distillation performed at atmospheric pressure without the addition of water or organic solvents that has been proposed as a green method for the extraction of essential oils from aromatic and medicinal herbs. In this work, SFME and the conventional techniques of steam distillation (SD) and hydrodistillation (HD) were compared with respect to the extraction and antioxidant and antimicrobial activities of Thymus mastichina essential oil. The main constituent of essential oils obtained using different methods was 1,8-cineole (eucalyptol). The results showed that the essential oils extracted by means of SFME in 30 min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained using conventional HD over 120 min. In addition, SFME generates less waste and less solvent, consumes less energy, and provides a higher yield for a shorter extraction time, which is advantageous for the extraction of the T. mastichina essential oil compared to SD. The antioxidant and antimicrobial activities of the T. mastichina essential oil obtained from either SFME or conventional extraction methods (SD or HD) showed a similar pattern. Large-scale experiments using this SFME procedure showed a potential industrial application.

Highlights

The Lamiaceae family is one of the largest and most distinctive families of lowering plants, with about 236 genera and almost 7200 species worldwide, and are best known for their unique essential oils [1]
The essential oil isolated from the aerial parts of T. mastichina has been described for its antibacterial [7,8,9], antifungal [6,7,10] antioxidant [6,11,12] antiinflammatory [6,11,13], and anti-Alzheimer activities [6,12], which are based on its specific chemical composition
The composition of the essential oils extracted by the different methods is similar

Summary

Introduction

The Lamiaceae family is one of the largest and most distinctive families of lowering plants, with about 236 genera and almost 7200 species worldwide, and are best known for their unique essential oils [1]. In this family, the genus Thymus includes 214 species and 36 subspecies and is widely disseminated throughout the Mediterranean region with several species endemic to the Iberian Peninsula [2]. In Portugal, white thyme can be found all over the country, except in calcareous regions [5] It is an aromatic plant characterized by leaves arranged in opposite pairs and by zygomorphic and bilabiate flowers [6]. The essential oil isolated from the aerial parts of T. mastichina has been described for its antibacterial [7,8,9], antifungal [6,7,10] antioxidant [6,11,12] antiinflammatory [6,11,13], and anti-Alzheimer activities [6,12], which are based on its specific chemical composition

Methods

Results

Conclusion