Comparison of chemical composition and activities of essential oils from fresh leaves of Pelargonium graveolens L′Herit. extracted by hydrodistillation and enzymatic pretreatment combined with a solvent-free microwave extraction method

Abstract

In this study, enzymatic pretreatment combined with solvent-free microwave extraction (EP-SFME) was used to extract essential oils from fresh leaves of Pelargonium graveolens L′Herit. The effects of hydrodistillation and enzymatic pretreatment combined with solvent-free microwave extraction on the yield and quality of essential oils were compared. The essential oil yield from the EP-SFME method (0.29% ± 0.04%) was 26.09% higher than that from the conventional hydrodistillation method. The gas chromatography-mass spectrometry analysis results showed that the content of main components in the essential oil from the EP-SFME method was significantly increased, including citronellol (+8.60%), geraniol (+3.14%), citronellyl formate (+2.77%), and geranic acid (+1.54%). The content of oxygenated compounds was also far higher than that of the hydrodistillation method. The essential oil from the EP-SFME method showed stronger antidepressant potential, as determined by the inhibition rate of acetylcholinesterase (IC50 =73.3 µg/mL). In contrast, the essential oil from the EP-SFME method showed higher comprehensive antimicrobial activity, including Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Candida albicans, and antioxidant activity than that from the hydrodistillation method. Therefore, the EP-SFME method is a green and effective method for the extraction of high-quality essential oils from fresh leaves of Pelargonium graveolens L′Herit.