Atividade antimicrobiana e antioxidante de terpenoides

Abstract

Terpenes are the main constituents of plant essential oils. These compounds are formed by the condensation of isoprene units, and when contain oxygen are named terpenoids. The present work aimed to evaluate the antimicrobial and antioxidant activity of terpenoids citral, citronellal, citronellol, 1,8-cineole, geraniol, α- terpineole and sesquiterpene β-caryophyllene. Thus for, the minimal inhibitory concentrations (MIC), and the inhibitory dosage 50% (ID50) were determined using the microplate serial dilution method (0 to 10 μL/mL v/v). Cell viability at the MIC concentration was evaluated by plating and counting. The effect of terpenoids on bacterial and yeast respiration was evaluated. Moreover, the following specific tests were developed on Saccharomyces cerevisiae and Candida albicans using citral, citronellal, citronellol and geraniol: cell viability, cellular lysis, and loss of cellular components. The in vitro antioxidant activity of the terpenoids was determined by the DPPH (1,1-difenil 2-picrilhidrazil)essay. In vivo antioxidant activity of citral and citronellal was evaluated using S. cerevisiae as model organism. The results showed that all the six terpenoids and one sesquiterpene have antimicrobial activity, with variation among terpenoids and microrganisms. In general, citral exhibited the highest antimicrobial activity, where β-cariophyllene affects a restricted number of organisms. The presence of citral and citronellal at their MICs reduced respiration of Salmonella typhimurium and Staphylococcus aureus. Respiration inhibitory activity of citral, citronellol, citronellal and geraniol was also evidenced on C. albicans and S. cerevisiae. Geraniol was the terpenoid with the highest microcide activity on C. albicans and S. cerevisiae, as determined by the methylene blue staining method. Citronellal and citronellol exhibited low lytic activity on S. cerevisiae, but not on C. albicans. Citral, citronellol, citronellal and geraniol induced the loss of cellular components in both C. albicans and S. cerevisiae. All the compounds showed in vitro antioxidant activity, particularly citral. Conversely, citronellal was the only terpenoid with in vivo antioxidant activity on eukaryotic cells. In general, the present work showed that citral has an important antioxidant and antimicrobial activity, inducing the loss of cellular components and inhibiting cell respiration. These informations are important for the pharmacological application of this compound or essential oils with high concentration of citral.