Aldo Manzin

Drug resistance represents one of the great plagues of our time worldwide. This largely limits the treatment of common infections and requires the development of new antibiotics or other alternative approaches. Noteworthy, the indiscriminate use of antibiotics is mostly responsible for the selection of mutations that confer drug resistance to microbes. In this regard, recently, ozone has been raising interest for its unique biological properties when dissolved in natural oils. Ozonated oils have been reported to act in a non-specific way on microorganisms hindering the acquisition of advantageous mutations that result in resistance. Here, we focused on the antimicrobial effect of two commercial olive (OOO) and sunflower seeds (OSO) oils. Nuclear magnetic resonance spectroscopy and thermal analysis showed the change in the chemical composition of the oils after ozonation treatment. Different ozonated oil concentrations were then used to evaluate their antimicrobial profile against Candida albicans, Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli by agar diffusion and broth dilution methods. Cytotoxicity was also evaluated in keratinocytes and epithelial cells. Overall, our results revealed that both OOO and OSO showed a potent microbicidal effect, especially against C. albicans (IC50 = OOO: 0.3 mg/mL and OSO: 0.2 mg/mL) and E. faecalis (IC50 = OOO: 0.4 mg/mL and OSO: 2.8 mg/mL) albeit exerting a certain effect also against S. aureus and E. coli. Moreover, both OOO and OSO do not yield any relevant cytotoxic effect at the active concentrations in both cell lines. This indicates that the ozonated oils studied are not toxic for mammalian cells despite exerting a potent antimicrobial effect on specific microorganisms. Therefore, OOO and OSO may be considered to integrate standard therapies in the treatment of common infections, likely overcoming drug resistance issues.

Severe acute respiratory syndrome-related Coronavirus 2 (SARS-CoV-2) has infected more than 762 million people to date and has caused approximately 7 million deaths all around the world, involving more than 187 countries. Although currently available vaccines show high efficacy in preventing severe respiratory complications in infected patients, the high number of mutations in the S proteins of the current variants is responsible for the high level of immune evasion and transmissibility of the virus and the reduced effectiveness of acquired immunity. In this scenario, the development of safe and effective drugs of synthetic or natural origin to suppress viral replication and treat acute forms of COVID-19 remains a valid therapeutic challenge. Given the successful history of flavonoids-based drug discovery, we developed esters of substituted cinnamic acids with quercetin to evaluate their in vitro activity against a broad spectrum of Coronaviruses. Interestingly, two derivatives, the 3,4-methylenedioxy 6 and the ester of acid 7, have proved to be effective in reducing OC43-induced cytopathogenicity, showing interesting EC50s profiles. The ester of synaptic acid 7 in particular, which is not endowed with relevant cytotoxicity under any of the tested conditions, turned out to be active against OC43 and SARS-CoV-2, showing a promising EC50. Therefore, said compound was selected as the lead object of further analysis. When tested in a yield reduction, assay 7 produced a significant dose-dependent reduction in viral titer. However, the compound was not virucidal, as exposure to high concentrations of it did not affect viral infectivity, nor did it affect hCoV-OC43 penetration into pre-treated host cells. Additional studies on the action mechanism have suggested that our derivative may inhibit viral endocytosis by reducing viral attachment to host cells.