Analytical characterization and antimicrobial activity of green zeolite-thymol composites

Bacterial resistance to multiple antibiotics is a huge health problem [1]. In this respect, many plant extracts have been tested worldwide as potential sources of novel antimicrobial compounds [2]. In this work, the development, analytical characterization and bioactivity of zeolite-thymol composites, obtained using wet, semi-dry and dry processes, were carried out in order to obtain sustainable and powerful antimicrobial additives [3]. Analytical characterization by means of FT-IR, XRD, DSC, TGA and SEM was carried out to gain comprehensive information on the chemical-physical, thermal, and morphological features of the composites. GC-MS analyses allowed quantifying the active molecule loaded in the zeolite, its release and stability over time. Among the three loading procedures, the dry (i.e., solvent-free) approach allowed to reach the highest thymol content and loading efficiency (49.8±1.6% and 99.6±1.2%, respectively). Therefore, the bioactive surface of composites obtained by this method was assayed for its antimicrobial activity against four microbial strains belonging to S. aureus, E. coli, P. aeruginosa and C. albicans species. The higher antimicrobial activity produced by the solvent-free composite in comparison with that of pure thymol, at the same thymol concentration, was ascribed to the large interfacial contact between the composite and the bacterial target. This feature, together with its enhanced storage stability, suggested that this composite could be employed as effective additives for the development of antimicrobial biointerfaces for food, home and personal care applications. [1] E. Jacopin, S. Lehtinen, F. Débarre, J.R. Blanquart, Journal of the Royal Society Interface 17 (2020) 1 [2] B. Salehi, A.P. Mishra, I. Shukla, M. Sharifi-Rad, M.D.M. Contreras, A. Segura Carretero, H. Fathi, N.N. Nasrabadi, F. Kobardard, J. Sharifi-Rad, Phytotherapy Reseach 32 (2018) 1688 [3] S. Cometa, M.A. Bonifacio, A. Bellissimo, L. Pinto, A. Petrella, N. De Vietro, G. Iannaccone, F. Baruzzi, E. De Giglio, Heliyon 8 (2022) e09551