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Identification of secondary metabolites and evaluation of the antimicrobial activity of the ethanol extract of callistemon speciosus (Red swab)

Abstract:

Introduction: Callistemon speciosus, widely distributed in the Andes region, is a medicinal plant commonly used for its antiseptic, expectorant and bronchodilator properties. Objectives: To identify possible secondary metabolites present in Callistemon speciosus and evaluate the in vitro antimi-crobial activity against bacteria and fungus strains. Method: From all parts of the dried plant, except the root, a main ethanolic extract (CSEE) was prepared. Subsequently, from the main extract, a subextraction was carried out using ethanol (A) and chloroform (B) (1:1). Then the secondary metabolites present in the subextracts were separated by thin layer and column chromatography. Afterward, using UV-Vis spectroscopy the absorption of each purified fraction was determined. The microbiological activity of CSEE was performed using the Mitscher method. Results: Following the rules of Woodward and Fisher, 3 structures were identified: 7-methoxy-flavone, 7-hydroxy-flavone and myricetin. CSEE inhibited bacterial growth in a concen-tration-dependent manner. Thus, at a concentration of 10000 µg/mL showed activity against S. aureus and C. albicans, and partial activity for E. coli, K. pneumoniae, and P. aeruginosa. While at a concentration of 1000 µg/mL it only shows activity against C. albicans and S. aureus. Finally, at a concentration of 100 µg/mL, it is partially active against S. aureus. Conclusions: These results provide data on the phytochemi-cal composition and antimicrobial activity of CSEE. However, complementary studies should be carried out with more specific techniques to have a complete phytochemical profile of the plant and confirm its antimicrobial activity.