Abstract The growing increase in the fish farming sector has favored the establishment of bacterial outbreaks caused by Aeromonas hydrophila in several species. The hexane extract of Hesperozygis ringens (HEHR) (Lamiaceae) leaves increased the survival rate of silver catfish (Rhamdia quelen) experimentally infected by A. hydrophila. However, it is noteworthy that no reports have been found on the possible mechanisms of action of this extract in infected fish. This study aimed to evaluate the effect of the HEHR, administered through single immersion bath, on lipid peroxidation and antioxidant defenses in muscle and liver tissue of silver catfish challenged with A. hydrophila. The results showed that the oxidative status of silver catfish was altered, although oxidative stress was not triggered during the experiment. HEHR at 30 mg/L (HEHR30) was not characterized as a pro-oxidant agent in the presence of infection, unlike florfenicol and HEHR at 15 mg/L treatments in some cases. In short, HEHR30 provided an important increase in hepatic catalase activity, characterizing one of the possible mechanisms involved in the greater survival of fish experimentally infected by A. hydrophila. Additionally, HEHR30 did not induce lipid peroxidation, nor reduced antioxidant defenses of silver catfish infected or not by A. hydrophila. species (HEHR Lamiaceae (Lamiaceae Rhamdia quelen A However bath altered experiment 3 mgL mg L (HEHR30 prooxidant pro oxidant infection 1 cases short HEHR3 activity Additionally (HEHR3

RESUMO O ergosterol é responsável por importantes funções na membrana plasmática dos fungos. A influência de agentes fungitóxicos no conteúdo de ergosterol na membrana é um dos mecanismos mais importantes de ação antifúngica e seu conhecimento permite a geração de produtos que associam compostos ativos de diferentes mecanismos, consequentemente, melhorando a eficácia dos conservantes de madeira. Portanto, este estudo otimizou um método para quantificar ergosterol em fungos apodrecedores da madeira. As espécies de podridão-branca selecionadas foram Ganoderma applanatum e Trametes versicolor, enquanto que as de podridão-parda foram Gloeophyllum trabeum e Lentinus lepideus. Discos miceliais de cada espécie foram transferidos para placas de Petri contendo meio batata-dextrose-ágar coberto por celofane. O micélio de cada fungo foi coletado, pesado e transferido para tubos de ensaio com 5 mL de hidróxido de potássio alcoólico 25%. Os tubos foram agitados em vortex por 5 min, submetidos a ultrassom por 5 min, incubados a 85 °C por 4 h, seguido da adição de 2 mL de água destilada estéril e 5 mL de n-heptano e subsequente agitação em ultrassom por 2 min. A camada de n-heptano foi analisada por espectrofotometria no UV entre 230 e 300 ηm. O branco continha apenas n-heptano. A massa micelial úmida dos fungos variou de 0,061 a 0,296 g. O teor de ergosterol foi de 0,007% para Lentinus lepideus e 0,004% para as demais espécies. A absorbância foi maior que a observada no branco para todas as amostras. O método adaptado foi eficiente para extração de ergosterol.

ABSTRACT Ergosterol is responsible for important functions in the fungal plasma membrane. The influence of fungitoxic agents on membrane ergosterol content is one of the most important mechanisms of antifungal action and its knowledge allows the generation of products that associate active compounds of different mechanisms, consequently improving the effectiveness of wood preservatives. Therefore, this study optimized a method for quantifying ergosterol in wood-decay fungi. The white-rot species selected were Ganoderma applanatum and Trametes versicolor, while the brown-rot were Gloeophyllum trabeum and Lentinus lepideus. Mycelial discs of each species were transferred to Petri dishes containing a cellophane-covered potato-dextrose-agar medium. Mycelia of each fungus were collected, weighed, and transferred to test tubes with 5 mL of 25% alcoholic potassium hydroxide. The tubes were vortexed for 5 min, subjected to ultrasound for 5 min, incubated at 85 °C for 4 h, followed by the addition of 2 mL of sterile distilled water and 5 mL of n-heptane and subsequent ultrasound shaking for 2 min. The n-heptane layer was analyzed by UV spectrophotometry between 230 and 300 ηm. The blank sample only contained n-heptane. The mycelia wet weight of the fungi ranged from 0.061 to 0.296 g. Ergosterol content was 0.007% for Lentinus lepideus and 0.004% for the other species. The absorbance was higher than the ones observed in the blank for all samples. The adapted method was efficient for ergosterol extraction.