Bioassay-guided isolation and identification of antimicrobial compounds from thyme essential oil by means of overpressured layer chromatography, bioautography and GC-MS

A simple method is described for efficient isolation of compounds having an antibacterial effect. Two thyme (Thymus vulgaris) essential oils, obtained from the market, were chosen as prospective materials likely to feature several bioactive components when examined by thin layer chromatography coupled with direct bioautography as a screening method. The newly developed infusion overpressured layer chromatographic separation method coupled with direct bioautography assured that only the active components were isolated by means of overrun overpressured layer chromatography with online detection and fractionation. Each of the 5 collected fractions represented one of the five antimicrobial essential oil components designated at the screening. The purity and the activity of the fractions were confirmed with chromatography coupled various detection methods (UV, vanillin-sulphuric acid reagent, direct bioautography). The antibacterial components were identified with GC-MS as thymol, carvacrol, linalool, diethylphthalate, and alpha-terpineol. The oil component diethyl-phthalate is an artificial compound, used as plasticizer or detergent bases in the industry. Our results support that exploiting its flexibility and the possible hyphenations, overpressured layer chromatography is especially attractive for isolation of antimicrobial components from various matrixes

Three Drosophila Hox Complex microRNAs Do Not Have Major Effects on Expression of Evolutionarily Conserved Hox Gene Targets during Embryogenesis

The discovery of microRNAs has resulted in a major expansion of the number of molecules known to be involved in gene regulation. Elucidating the functions of animal microRNAs has posed a significant challenge as their target interactions with messenger RNAs do not adhere to simple rules. Of the thousands of known animal microRNAs, relatively few microRNA:messenger RNA regulatory interactions have been biologically validated in an normal organismal context. Here we present evidence that three microRNAs from the Hox complex in Drosophila (miR-10-5p, miR-10-3p, miR-iab-4-5p) do not have significant effects during embryogenesis on the expression of Hox genes that contain high confidence microRNAs target sites in the 3′ untranslated regions of their messenger RNAs. This is significant, in that it suggests that many predicted microRNA-target interactions may not be biologically relevant, or that the outcomes of these interactions may be so subtle that mutants may only show phenotypes in specific contexts, such as in environmental stress conditions, or in combinations with other microRNA mutations

In vitro effects of citral on Trypanosoma cruzi metacyclogenesis

Citral, the main constituent of lemongrass (Cymbopogon citratus) essential oil, was added to Trypanosoma cruzi cultures grown in TAU3AAG medium to observe the effect on the epimastigote-to-trypomastigote differentiation process (metacyclogenesis). Our results showed that citral (20 μg/mL) did not affect epimastigote viability or inhibit the differentiation process. Concentrations higher than 60 μg/mL, however, led to 100% cell death (both epimastigote and trypomastigote forms). Although epimastigotes incubated with 30 μg/mL citral were viable and able to adhere to the substrate, we observed around 50% inhibition in metacyclogenesis, with a calculated concentration that inhibited metacyclogenesis by 50% after 24 h (IC50/24 h) of about 31 μg/mL. Treatment with 30 μg/mL citral did not hinder epimastigote multiplication because epimastigote growth resumed when treated cells were transferred to a drug-free liver infusion tryptose culture medium. Metacyclogenesis was almost totally abolished at 40 μg/mL after 24 h of incubation. Furthermore, the metacyclic trypomastigotes obtained in vitro were similarly susceptible to citral, with an IC50/24 h, concentration that killed 50% of the cells after 24 h, of about 24.5 μg/mL. Therefore, citral appears to be a good candidate as an inhibitory drug for further studies analyzing the T. cruzi metacyclogenesis process