The increasing relates about resistance of microorganisms to conventional synthetic chemicals has prompted scientists to search for novel sources of biocides based on natural products. Essential oils (EOs) and their components have activity against a variety of targets, including microrganisms. Although EOs have significant potential applications, their use is limited due to low solubility in water and poor stability in presence of light, heat and oxygen. To overcome these drawbacks, particles containing EOs can be prepared, for example, by complexation with cyclodextrins. In many areas, these complexes have been used to increase aqueous solubility of poorly soluble substances and to increase their stability. Therefore, the aim of this study was to obtain and to characterize an inclusion complex between Pimenta dioica essential oil (PDEO) and β-cyclodextrin (β-CD). Pimenta dioica leaves were collected in Vitória (ES), weighed and subjected to hydrodistillation using a Clevenger-type apparatus. The PDEO majoritary compound was identified and quantified by gas chromatography coupled with mass spectrometry (CG-MS) and gas chromatography-flame ionization detection (CG-FID), respectively. For antibacterial activity, the minimum inhibitory concentrations of PDEO against Escherichia coli (ATCC 11229) and Staphylococcus aureus (ATCC 6538) were determined using microbroth dilution method. The complexes were prepared by freeze-drying method using adapted technique1: β-CD was solubilized in hydroalcoholic solution (1:3) and the PDEO solubilized in ethanol was added to the solution. The mixture was kept under stirring in a reciprocating bath for 18 hours. The resultant suspension was frozen at -96º C by immersion in liquid nitrogen, and lyophilized protected from light. The inclusion complexes were obtained in the molar ratios of 1:1 and 2:1 (PDEO:β-CD) and characterized by combined techniques of Fourier-transform infraered spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Physical mixture (PM) of PDEO and β-CD was also prepared for comparison purposes. The main compound for PDEO was β-myrcene (67%). The MIC of the PDEO for E. coli was 2500 ppm, and 1250 ppm for S. aureus, what confirms the antimicrobial activity of the PDEO against the investigated microorganisms. SEM images showed drastic changes regarding the particles of the complexes when compared with pure β-CD morphology, which went from crystalline to amorphous state, suggesting the sucess of the process. In complex, contributions of the peaks of the β-CD and PDEO spectra were observed, however with dislocations and intensity alterations. DSC thermogram of the physical mixture showed endothermic peak around 100º C and degradation process around 200º C, indicating that no complexation occurred in this system. In contrast, the thermograms of the inclusion complexes showed endothermic peak above 100º C and absence of the degradation peak of PDEO suggesting that the β-CD was able to accomodate the guest molecule. These results of combined techniques indicated that the complexation was successfully achieved. The inclusion complexes antimicrobial activity is still under investigation, aiming a possible application in food preservation.

1BHANDARI, B.R.; D'ARCY, B.R.; BICH, L.L.T. Lemon oil to β-cyclodextrin ratio effect on the inclusion efficiency of β-cyclodextrin and the retention of oil volatiles in the complex. Journal of Agricultural and Food Chemistry, v.46, n.4, p.1494-1499, 1998.