From drug repurposing studies, this work aimed to evaluate the activity of different pyrazinoic acid (POA) derivatives against Sporothrix brasiliensis. The POA esters were prepared and characterized as previously reported by classical esterification reactions, with good to excellent yields. Sporothrix brasiliensis isolates from cats (n=6) and standard strains of S. brasiliensis and S. schenckii were used to assess the antifungal activity of the POA derivatives through broth microdilution assay (CLSI M38-A2). Among the tested compounds, molecules 3 and 4 showed fungistatic and fungicidal activities against all Sporothrix spp. strains, and the obtained MIC and MFC values ranged from 2.12 to 4.24 mg/mL and from 1.29 to 5.15 mg/mL, respectively. Compound 2 and 5 were active as in vitro inhibitors of fungal growth, but showed weak fungicidal activity, while molecules 1 and POA itself were inactive. The results suggest the activity of POA derivatives against Sporothrix spp. may be dependent on the lipophilicity. In addition, the antifungal susceptibility of the isolates to itraconazole was performed, showing that two Sporothrix isolates from cats were itraconazole-resistant. Compounds 3 and 4 were also active against these itraconazole-resistant isolates, indicating a possible alternative route to the standard mode of action of itraconazole.

Parabens are p-hydroxybenzoic acid esters widely used as preservatives. With the aim of teaching the structure-activity relationships (SAR) knowledge in a practical form, this paper proposed a practical class to view the SAR of parabens as antimicrobial agents. Methyl, ethyl, n-propyl, isopropyl and isopentyl paraben compounds were synthesized and their respective antimicrobial activities were assessed through determination of minimum inhibitory concentrations (MIC) against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 stains. With the MIC values, it was possible to verify theircorrelation with calculated lipophilicity (ClogP). This method can be applied in practical Medicinal Chemistry classes.

Pyrazinoic acid esters have been synthesized as prodrugs of pyrazinoic acid. In the literature, its preparation is reported through the reaction of pyrazinoyl chloride with alcohols and the reaction with DCC/DMAP. In this work, it is reported a 2² factorial design to evaluate the preparation of these esters through the substitution of alkyl bromides with carboxylate anion. The controlled factors were alkyl chain length of bromides (ethyl and hexyl) and the used base (triethylamine and DBU). Results revealed that the used base used has significant effect on yield, and alkyl bromide used has neither significant influence, nor its interaction effect with base.