Exploring wild Thymus sp. (L.) chemotypes across Pistoia Mountains provides thyme essential oil and hydrolate inhibiting fungal growth on paper.

Abstract

Thymus sp. (L.) encompasses over 500 aromatic species distributed in the Mediterranean area, in dry, rocky environments up to 1800 m above sea level. Plants of Thymus sp. (L.) from the Serpyllum group, growing in five areas of the Pistoia Mountains, were georeferenced and sampled for a chemical characterization of the terpene content. Fresh biomass was collected to distill thyme essential oil, and the derived hydrolate was recovered as byproduct of the process. The antifungal efficacy of the chemically characterized thyme essential oil and hydrolate was evaluated on two fungal biodeteriogens typically affecting paper objects, Alternaria alternata and Cladosporium cladosporioides. High thymol content thyme essential oil (about 75 %) and hydrolate (about 62 %) were obtained from steam distillation and used to perform in vitro tests on paper samples following a non-invasive approach. For both fungi, a significant growth reduction on inoculated Whatman paper was observed with both hydrolate and thyme essential oil. The GC-MS analysis of 94 thyme samples led to the characterization of seven chemotype classes, and a PCA was carried out to investigate the potential impact of different collection sites on the chemotypes variability. These findings highlight the necessity of an accurate selection of the plant material for an optimized production of thyme essential oil and hydrolate with improved antifungal efficacy.