Antimicrobial activity of essential oil from Oregano (Lippia graveolens) encapsulated in cyclodextrins

Many biomolecules are substances with labile components and can be charged as a result of oxidation, chemical interactions etc. To minimize the harm of these negative processes, microencapsulation is used to entrap liquid substances as essential oils oleoresins in a protective layer of coating material. Different biopolymers have been used in developing microcapsules for the control-release of various core materials. Oregano is an important plant in semiarid zones and it is used traditionally as condiment in preparation of food. The principal compounds presents in Lippia are thymol and carvacrol and some studies reported that thymol and carvacrol are responsible of antimicrobial activity. This study was aimed to investigate activity antimicrobial of encapsulated essential oil and non-encapsulated essential oil.

Three oregano oils with different relation thymol/carvacrol/p-cymene were encapsulated in β-cyclodextrin using a spray dryer. Antimicrobial activity was evaluated using Escherichia coli, Pseudomonas sp, Staphylococcus aureus strains. The results showed that essential oils encapsulated have more antimicrobial activity than non- encapsulated essential oils. The minimum inhibitory concentrations (MICs) were 0.05% –0.1% w/v for the oil₁ microencapsulated containing thymol/carvacrol/p-cymene(3:41:27), 0.1% –0.2% w/v for the oil₂ microencapsulated with thymol/carvacrol/p-cymene (2:26:38) and oil₃ microencapsulated thymol/carvacrol/p-cymene (19:7:34). The MICs for non-encapsulated oils was 0.2% w/v, oil₁ (2:38:32), oil₂ (1:23:42) oil₃ (19:7:34).

In the microencapsulation process, temperature is near to 100^oC for a few seconds and relation thymol/carvacrol/p-cymene changed in the oil₁ and oil₂ encapsulated, increasing their antimicrobial activity.

1. Baranauskiene, R. et. al. (2006)J. Food Res. 39: 413–425