Improving in the antibacterial activity and the antioxidant properties of chemically modified extracts of Zinnia peruviana

Abstract

In the present work we investigate the changes in the antibacterial activity and the antioxidant properties of modified extracts of Zinnia peruviana (L.) L. campesterol, stigmasterol and β-sitosterol were identified as majortriterpenoids in the natural extract, by CG-EIMS and NIST Mass Spectrometry Data Center. The acetonic extract was chemically modified by reactions of acid hydrolysis, sulfonylation, acetylation, methylation and silylation. The in-vitro antibacterial activity was evaluated against Gram-positive and Gram-negative bacteria. The acetonic extract showed significant activity only against Gram-positive bacteria (MIC/MBC = 2/9 mg/mL). The hydrolyzed extract improve the bioactivity to both, Gram-positive and Gram-negative (MIC/MBC = 2/8 mg/mL). Selectively, the acetylated extract was only effective toward Staphylococcus (MIC/MBC = 7/7 mg/mL). The tosylated extract was active against Gram-positive and P. aeruginosa (MIC/MBC = 24/24 mg/mL) and the silylated against Grampositiveand E. coli. (MIC/MBC = 15/15 mg/mL). The antioxidant activity was determining by DPPH and ABTS assays. Hydrolyzed extract increased the antioxidant properties (DPPH, IC50,(mg/mL) = 0.077 ± 0.007; ABTS IC50,(mg/mL) = 0.032 ± 0.005). The acylated and alkylated extracts reduce the bioactivity and silylated derivative eliminated the bioactivity. These results could be considered as a possible strategy to obtain antimicrobial agents from herbal medicines.