Antimicrobial and antioxidant activities of Mexican oregano essential oils (Lippia graveolens H. B. K.) with different composition when microencapsulated inβ-cyclodextrin

Abstract

To study how the antimicrobial and antioxidant activities of Lippia graveolens essential oils with different composition are affected after the microencapsulation process with beta-cyclodextrin (beta CD). Three Mexican oregano essential oils (EOs) with different carvacrol/thymol/p-cymene ratios (38 : 3 : 32, 23 : 2 : 42, 7 : 19 : 35) were used in this study. Microencapsulation was carried out by spray-drying. Antimicrobial activities were measured as MBC (minimal bactericidal concentration) using 0.05%/0.10%/0.20% (w/v) dilutions of EOs against Escherichia coli ATCC 11229, Pseudomonas aeruginosa ATCC 9027 and Staphylococcus aureus ATCC 6538. Antioxidant activities were determined by the 2,2'-diphenyl-1-picrylhydrazil (DPPH) method. EOs showed antimicrobial and antioxidant activity, but microencapsulation preserved the antimicrobial activity in all cases and increased the antioxidant activity from four- to eightfold. Although the Lippia essential oils were from the same species, their composition affects the biological activities before and after the microencapsulation process, as well as encapsulation efficiency. Our study supports the fact that microencapsulation of EOs in beta-cyclodextrin preserves the antimicrobial activity, improves the antioxidant activity and acts as a protection for EOs main compounds. Microencapsulation affects positively EOs main compounds, improves antioxidant activity and retains antimicrobial activity, enhancing the quality of the oils.