β-Cyclodextrin inclusion complexes containing clove (Eugenia caryophyllata) and Mexican oregano (Lippia berlandieri) essential oils: Preparation, physicochemical and antimicrobial characterization

Mexican oregano and clove essential oils are widely used as antimicrobial, insecticidal, antifungal and antioxidant compounds. To reduce their volatility and their hydrophobicity, they were encapsulated in beta-cyclodextrin (beta-CD) complexes by co-precipitation method, and the physicochemical and microbiological properties of these inclusion complexes were characterized. Different essential oil (EO) to beta-CD weight ratios were tested (4: 96, 8: 92, 12: 88, and 16: 84 w/w) and encapsulation efficiency and rate were determined. GC-MS and GC-FID analysis were also performed to determine the main oil constituents, which were eugenol and carvacrol in clove and Mexican oregano essential oils respectively and to quantify their ratio in inclusion complexes. H-1 NMR spectroscopy confirmed essential oil inclusion. The 4: 96 ratio (clove essential oil: beta-CD) gave the highest eugenol content and greatest microencapsulation efficiency; and the 8: 92 and 12: 88 ratios (Mexican oregano essential oil: beta-CD) the highest carvacrol content. Complexes antimicrobial activity was tested against two food-related microorganisms: Listeria monocytogenes ATCC 19114 and Escherichia coli ATCC 25922 by means of agar disk diffusion assay. The results demonstrated the inclusion of the majority of biologically active clove and Mexican oregano essential oil molecules, providing increased stability by reducing their volatility and preserving their biological properties.