Effect of Extraction and Drying Method on Chemical Composition, and Evaluation of Antioxidant and Antimicrobial Activities of Essential Oils from Salvia officinalis L.

The present study was carried out to determine, for the first time, the chemical composition, antioxidant and antimicrobial activities of essential oils from leaves of Salvia officinalis L. cultivated in Algeria. The essential oils (EOs) obtained by different extraction techniques: the microwave-assisted hydrodistillation (MAHD), the conventional hydrodistillation (HD) technique and the steam distillation (SD). The volatile compounds were analyzed by gas chromatography flame ionization detector (GC-FID) and by gas chromatography-mass spectrometry (GC-MS). The results were compared in terms of extraction time, yield extraction and chemical composition. The effect of drying method on the chemical composition of the essential oil generated by air or by oven drying. The results obtained showed that dried plant material yielded more essential oils than the fresh one. The highest EO yields were obtained for the oven-dried at 60 degrees C (2.5 %) for one day, followed by the air-dried plant material for twenty one days (2.25 %). The chemical analysis of EO led to the identification of 28, 30 and 25 compounds in HD, MAHD and SD oils, respectively. The main components of EO resulting from the different extraction techniques were 1,8-cineole (11.00-12.16 %), alpha-thujone (15.80-17.92 %), camphor (10.70-23.95 %), alpha-humulene (4.50-9.61 %) and viridiflorol (9.49-13.10 %). The method of drying induced very significant variations for some compounds, especially for main compounds such as camphor (21.78-25.36 %), alpha-thujone (16.84-17.40 %) 1,8-cineole (15.15-17.92 %), caryopyllene oxide (5.46-8.42 %). The antioxidant activity evaluated by DPPH (1,1 diphenyl-2picryl-hydrazyl) radical scavenging assay showed an appreciable efficiency. The antimicrobial activity tested on seven microorganisms showed that the EO obtained by SD was remarkably more active, and that Pseudomonas aeruginosa and Candida albicans were resistant to all tested oils.