Essential oils from different Citrus species and evaluation of their in vitro antibacterial, antiacetylcholinesterase, anti-inflammatory and antifungal activities

Abstract

Essential oils (EOs) from Citrus are not only economic, eco-friendly and natural alternatives to chemical preservatives but also have other biological applications. This study aimed to investigate the chemical composition of Citrus species (EOs from C. limonia, C. latifolia, C. sinensis and C. deliciosa fruit peel) to evaluate their in vitro antibacterial activity against Listeria monocytogenes, Yersinia enterocolitica, Staphylococcus aureus, Clostridium botulinum and Bacillus cereus. The chemotaxis model, which was used for evaluating their anti-inflammatory activity, showed that EOs exhibited effective results when the dose was 100 µg/mL. Regarding all antimicrobial activities, minimum inhibitory concentration (MIC) values of EOs were calculated by the broth microdilution method on 96-well microplates. EOs showed satisfactory antifungal activity against Malassezia furfur (MIC values between 32.5 and 62.5 µg/mL). Citrus deliciosa, whose MIC = 95.8 µg/mL, inhibited acetylcholinesterase (AChE) more selectively. All EOs from Citrus spp. fruit peel showed good antibacterial activity against Yersinia enterocolitica (MIC = 62.5 µg/mL) and Staphylococcus aureus (MIC = 62.5 µg/mL), mainly the EO from C. deliciosa whose MIC values were 50 µg/mL for both. EOs were moderately active against Clostridium botulinum, Bacillus cereus and Listeria monocytogenes since MIC values ranged from 100 μg/mL to 400 μg/mL. Both GC-FID and GC-MS analyses revealed that the single major constituent determined in EOs is the terpene limonene. EOs from Citrus may be important active ingredients of several products to prevent bacterial growth in food, to attack the fungus that causes seborrheic dermatitis and to treat inflammatory processes. In short, the promising antiacetylcholinesterase activity of EOs under evaluation was attributed to the high concentration of the monoterpene limonene