ABSTRACT
Endophytic microorganisms from the base and top leaves of Spermacoce verticillata were isolated and the antimicrobial potential was evaluated. A total of 56 strains were isolated in pure culture, 44 fungi and 12 actinobacteria. The isolation frequency was higher in the base leaves (12.5%), when compared to the top leaves (3.05%). Among all fungi and actionobacteria identified, the majority belonged to the genus Guignardia (25%) and Microbispora (41.66%), respectively. The antimicrobial screening was firstly evaluated by agar plug assay and showed that 28.57% of the isolates presented activity mainly against gram positive bacteria Staphylococus aureus (ATCC-6538) and Bacillus subtilis (UFPEDA-16). The microorganisms that presented the best activities were then selected, evaluated in different culture media broth, and tested by disk diffusion assay using their fermented broth. The microorganisms selected for this assay exhibited antimicrobial activity mainly for Bacillus subtilis (UFPEDA-16). Since many isolates showed inhibitory activity against pathogenic microorganisms, it is suggestive that endophytic microorganisms from S. verticillata could be an interesting source to explore for bioactive metabolites and new tools need to be employed to explore the real potential of these microorganisms.
ABSTRACT
The antifungal activity of essential oils of fennel (Foeniculum vulgare Mill., Apiaceae), ginger (Zingiber officinale Roscoe, Zingiberaceae), mint (Mentha piperita L., Lamiaceae) and thyme (Thymus vulgaris L., Lamiaceae) was evaluated against mycotoxin producers Aspergillus flavus and A. parasiticus. High Resolution Gas Chromatography was applied to analyze chemical constituents of essential oils. The effect of different concentrations of essential oils was determined by solid medium diffusion assay. Mycelial growth and sporulation were determined for each essential oil at the concentrations established by solid medium diffusion assay. At the fifth, seventh and ninth days the mycelial diameter (Ø mm) and spore production were also determined. FUN-1 staining was performed to assess cell viability after broth macrodilution assay. Trans-anethole, zingiberene, menthol and thymol are the major component of essential oils of fennel, ginger, mint and thyme, respectively. The effective concentrations for fennel, ginger, mint and thyme were 50, 80, 50 and 50% (oil/DMSO; v/v), respectively. The four essential oils analysed in this study showed antifungal effect. Additionally, FUN-1 staining showed to be a suitable method to evaluate cell viability of potential mycotoxigenic fungi A. flavus and A. parasiticus after treatment with essential oils.