Vermiculitas modificadas com carvacrol aplicadas como material antibacteriano

Abstract

Incorporating essential oils or their components into inorganic matrices is a strategy to reduce the rapid volatility of the oils and allow a slow release by oil-loaded solids. Carvacrol (Carv) is the essential oil component of oregano and thyme that have diverse bioactivities including antimicrobial activity. In the present study the incorporation of carvacrol in pristine (Ver) and two acid-activated vermiculites was evaluated. Activated samples were obtained by reaction of the Ver sample with 1 and 2 mol L-1 HNO3 and activated matrixes were named V1M and V2M respectively. Samples containing 100 mg of solid reacted with 20 mL of 50% v/v aqueous ethanolic carvacrol solutions, in which the amounts of oil in solution were 0.5 mL and 1.0 mL The solids before and after oil incorporation were characterized by short- and long-range structural, morphological, and thermal techniques. The agar diffusion test evaluated the antibacterial activity of the materials against Escherichia coli (ATCC-25922) e Staphylococcus aureus (ATCC 25923). X-ray diffraction (XRD) patterns indicated that oil was incorporated on the surface of the matrices, and Fourier transform infrared spectroscopy (FTIR) spectra suggested the contribution of hydrogen bonding between the species. The maximum incorporation of the compound occurred in the acid-activated samples and amounts were 0.08, 0.51 and 0.67 mmol of oil per gram of Ver1M/1Carv, V1M/ 1Carv and V2M/1Carv, respectively. The release amounts were 0.5 (5%) and mg (7.5%) of oil per gram of Ver/0.5carv and Ver/1.0carv in 12 h. For V1M/Carv and V2M/Carv, values in 12 h were 2.50, 5.43, 4.03 and 8.18 mg g-1 and corresponded to 4.0, 7.0, 5.2, and 8.1%, respectively. The antibacterial action was better than the positive control. The inhibition diameter values were 13, 27 and 32 mm against S. aureus and 12, 25 and 28 mm against E. coli, for the Verm/1Carv, V1M/1Carv and V2M/1Carv samples, respectively, indicating that the Gran positive strain was more sensitive. The promising data are associated with the controlled oil release, and the antibacterial action of the hybrids indicated the possible use of these solids in pharmaceutical or cosmetic products.