Gentisic acid (2,5-dihydroxybenzoic acid) is primarily found naturally in plants and has demonstrated a significant range of biological activities; however, its efficacy and safety as a topical application ingredient are not yet well established. Thus, the compound’s potential antioxidant and antimicrobial properties were evaluated for efficacy, while the cytotoxicity was evaluated for safety. The antioxidant activity, measured by the DPPH kinetic method, showed an Efficiency Concentration (EC₅₀) of 0.09 with an antioxidant reducing power (ARP) of 11.1. The minimum inhibitory concentration (MIC) against Staphylococcus aureus was 4.15 mg/mL, Escherichia coli was 4.00 mg/mL, Candida albicans was 3.00 mg/mL, and Cutibacterium acnes was 3.60 mg/mL, and the MIC for C. acnes has remained unpublished until now. The substance showed low cytotoxicity by the neutral red uptake (NRU) methodology against HaCat, HDFa, and HepG2 cells at concentrations of up to 10.0, 7.3, and 4.0 mM, respectively, also representing unpublished data. This evidence demonstrates gentisic acid as a promising active substance for skin topical application in the cosmetic or pharmaceutical industry.

SARS-CoV-2 caused a global pandemic with high transmission rates, even with widespread vaccination. In addition to isolation and prevention measures, it is important to find new solutions to inactivate the virus and prevent its viability on surfaces, such as clothing and face masks. Chitosan derivatives, with their antibacterial activity, biocompatibility, and non-toxicity, are a promising option for coating these components with virucidal materials. N-(2-hydroxypropryl)-3-trimethylammonium chloride, a quaternized chitosan derivative with degrees of substitution ranging from 59 to 93%, was synthesized. This derivative was used to coat cotton and polypropylene fabrics, such as face masks, without visibly affecting their morphology or filtering capacity. In vitro tests demonstrated that the coatings produced had high antiviral activity against coronavirus, with efficacy up to 99.99%, and were also bactericidal against E. coli and S. aureus. These results show that quaternized chitosan derivatives have great potential to be used as virucidal coatings, helping to prevent the spread of SARS-Cov-2 and other pathogens on surfaces, which can even be useful for the quick development of solutions for future pandemics.

Dermatophyte fungal infections are difficult to treat because they need long-term treatments. 4-Nerolidylcatechol (4-NC) is a compound found in Piper umbellatum that has been reported to demonstrate significant antifungal activity, but is easily oxidizable. Due to this characteristic, the incorporation in nanostructured systems represents a strategy to guarantee the compound’s stability compared to the isolated form and the possibility of improving antifungal activity. The objective of this study was to incorporate 4-NC into polymeric nanoparticles to evaluate, in vitro and in vivo, the growth inhibition of Microsporum canis. 4-NC was isolated from fresh leaves of P. umbellatum, and polymer nanoparticles of polycaprolactone were developed by nanoprecipitation using a 1:5 weight ratio (drug:polymer). Nanoparticles exhibited excellent encapsulation efficiency, and the antifungal activity was observed in nanoparticles with 4-NC incorporated. Polymeric nanoparticles can be a strategy employed for decreased cytotoxicity, increasing the stability and solubility of substances, as well as improving the efficacy of 4-NC.