Antibacterial activity of thymol/carvacrol and clinoptilolite composites prepared by supercritical solvent impregnation

A green approach to develop zeolite-thymol antimicrobial composites: analytical characterization and antimicrobial activity evaluation

“…The peak at 555 cm −1 could be assigned to the external vibration of double four-rings [ 39 ]. As far as the hybrid composites are concerned, no significant variations in the thymol and zeolite IR spectra were detected, indicating that the inorganic support hosted the active principle without establishing chemical interactions with it, as already observed in the composites of Dikić et al., obtained by SSI [ 27 ]. Semi-dry and dry preparations revealed a much higher thymol loading than in the wet formulation.…”

“…Recently, palygorskite loaded with thymol showed antibacterial activity against E. coli and S. aureus higher than pure compound, probably due to enhanced hydrophilia and dispersion of these antimicrobials conveyed through clays [ 55 ]. These results were confirmed in clinoptinolite-zeolite loaded with thymol or carvacrol composites obtained by SSI, which showed that the bactericidal activity against E. coli and S. aureus in water media could not be ascribed only to the release of monoterpene compounds, but also properties of the composite material [ 27 ]. Monoterpene compounds such as thymol and carvacrol can be adsorbed on the external Na + -montmorillonite surface through hydrogen bonds between OH- groups of the essential oil compounds and OH- groups of the clay [ 56 ].…”

“…Indeed, Dikić et al. (2021) [ 27 ] found a fast release of carvacrol and a slow release of thymol from clinoptinolite-zeolite based composites.

Figure 6 Percentage of thymol released in physiological solution over time (a); Residual thymol percentage with respect to the loading content, monitored at 25°C; for each sampling time, asterisks indicate a statistically significant difference (p<0.05) (b).

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“…Zeolites have been also used in combination with Ag, Cu or Zn ions [ 25 ], or subjected to organic functionalization via adsorption of quaternary ammonium compounds (QACs) [ 26 ], to produce antimicrobial systems. Recently, Dikić and coworkers [ 27 ] prepared a composite based on a natural zeolite (clinoptilolite) and carvacrol or thymol by supercritical solvent impregnation (SSI) in supercritical carbon dioxide (scCO 2 ). The composites showed antibacterial activity toward Escherichia coli and Staphylococcus aureus strains.…”

Zeolite/Chitosan/Gelatin Films: Preparation, Supercritical CO2 Processing, Characterization, and Bioactivity

“…[ 32 ] The reason for this can be found in the high porosity of zeolite and relatively high affinity of zeolite toward thymol and carvacrol in scCO 2 ‐assisted process. [ 47 ]…”