## 3 Results and Discussion
### In Vitro Antifungal Assays
citratus_ EO was the best performing of the tested oils, showing complete fungal growth inhibition in all tests, with this effect being observed at even the lowest tested concentrations in most fungi. _P. brevicompactum_ proved to be the most resilient of the tested fungi, with only _C. citratus_ at 1.5 and 2 \(\mu\)L cm\({}^{-3}\) being able to prevent colony inception and growth. With previously described antibacterial, antifungal, antibioofilm and antioxidant properties [34; 90; 91; 92; 93; 94; 95], the main constituents of this EO are in accordance with previous reports of _C. citratus_ EO volatile profiles, even if some variations on the relative abundance of these compounds are observed [34; 90; 92; 93; 95]. These variations are present in all plant EOs, and depend on several factors, such as the methods used for drying the leaves before EO extraction, plant origin, time and place of harvest and cultivar [95; 96], but nevertheless, citral remains the most abundant component. Our results are in line with previous research that showed strong antifungal activity for this EO, including in _Aspergillus_ and _Penicillium_ species [34; 90; 91; 92; 93], with the proposed mechanisms of action encompassing cell integrity disruption, leading to cell death, as well as inhibition of ergosterol biosynthesis, a principal constituent of fungal cell membrane, with these effects being mainly attributed to citral [34]. _Lavandula angustifolia_ EO also showed promising results, even if not to the degree of efficacy displayed by _C. citratus_. Its main constituents include linalool, lavanduly acetate, linalyl acetate and borneol in varying concentrations [97], and its antifungal activity is already well described, including in the context of cultural heritage preservation [27; 32; 96]. Of the remaining EOs, _T. villosa, T. summifera, T. mastichina_ and _A. feniculum_ had no visible effect on the fungal isolates tested. _Thapsia villosa_'s previously reported fungicidal and fungistatic activities on _Aspergillus_ spp. [87] were not observed in our study, suggesting that these activities are not present in its vapors. While _T. summifera_ EO has been reported as possessing antibacterial activity [98; 99] and was confirmed to be rich in both \(\alpha\)-Pinene and \(\beta\)-Pinene (Table 3), which has known antifungal activity [99; 100], this activity is strongly dependent on the racemic mixture of its enantiomers, which is dependent on plant origin, among other factors [99; 100], thus potentially explaining the results obtained. _Thymus masticltina_ and _A. feniculum_ were also unable to visibly inhibit fungal growth, despite previous reports of antimicrobial activity against both bacteria and fungi [101; 102]. Both _Menttha_ EOs had variable and differing degrees of success during our assays, depending on the fungal species tested. Previous reports indicate that _M. suaveolens_ is mostly composed of Piperitone oxide and Piperitone oxide [103; 104], while _M. pulgeium_ EO typically contains large quantities of Pulegone, alongside Menthol, Menthone and Isopulegol [105; 106]. And while both of our _Menttha_ EOs were rich in Pulegone (Table 2), a high concentration of L-Menthone was observed only in _M. pulgeium_, with no further major constituents being identified for _M. suaveolens_. These differences potentially explain the difference in effectiveness across the tested fungal species between these two EOs. Overall, these are promising results and establish the potential for volatilized EOs, in particular those from _C. citratus_ and _L. angustifolia_, to be used as a tool for the mitigation of fungal contamination in museums and other cultural heritage repositories, as an alternative to commercial biocides, which are usually harmful for both humans and the environment. The application of untested substances in cultural heritage always comes with the latent concern of the potential alterations they can induce.