RESUMO
Triatoma infestans is the principal vector of Trypanosoma cruzi, parasite responsible of Chagas's Disease transmission in Argentina. Pyrethroids have become common pesticides for the control of T. infestans but increasing resistance encourages the search of new alternatives and the use of natural products for biological control arises as a new strategy. Melia azedarach L. is originated from the Himalaya's region and several compounds are part of its rich phytochemistry. Folk medicine of the plant is due to its repellent and insecticidal activities. Aims of this work were to evaluate the repellent activity of methanolic and acetonic extracts from fruits of M. azedarach by means of the area preference method of fifth and first nymph stages as well as to test the acute lethal effect of the more repellent extract by means of direct application on cuticle on both stages. For repellence, qualitative filter papers were divided into two halves, one treated with methanolic (ME) or acetonic (AC) extract and the other without treatment. Controls were impregnated half with methanol or acetone and half without the solvents. One nymph was located in each Petri or well and repellence percentage was determined. For the lethal effect, fasted and fed to repletion 5th stage nymphs were topically administered with different concentrations of AC and deaths were registered after 24, 48, 72, 96, and 120 h. Phytochemical analysis of extracts was performed as well. AC demonstrated high repellent activity (100%, both stages), whereas ME extract activity was slight (10-21%). AC extract was selected for lethal assays due to early repellent activity. Fed to repletion nymphs were more sensitive to the lethal activity of the extract when compared to fasted nymphs (LD50: 11.5 vs. 23.1 µg/insect, respectively). Phytochemistry assays of extracts showed a higher concentration of flavonoids, alkaloids and triterpenes for AC. Considering these results, next assays will include the test of Melia azedarach extract on T. infestans that are resistant to pyrethroids for a possible synergism between AC and the pesticides.
RESUMO
The aim of this study was to evaluate the bioequivalence of two commercial long-acting formulations based on oxytetracycline (OTC) hydrochloride between the reference formulation (Terramycin LA, Pfizer) and a test formulation (Cyamicin LA, Fort Dodge Saude Animal). Both formulations were administered in a single intramuscular route at a dose of 20 mg OTC/kg of body weight in clinically healthy bovines. The study was carried out according to a one-period parallel design. Plasma samples were analyzed by high-pressure liquid chromatography. The limit of quantitation was 0.050 µg/mL with an accuracy of 101.67% with a coefficient of variation of 13.15%. Analysis of variance and 90% confidence interval tests were used to compare the bioavailability parameters (maximum plasma concentration, C max, and the area under the concentration-versus-time curve extrapolated to infinity, AUC0-∞) of both products. In the case of the time to maximum concentration (T max), non-parametric tests based on Wilcoxon's signed rank test were preferred. The comparison of the mean AUC0-∞ values did not reveal any significant differences (311.40 ± 93.05 µg h/mL and 287.71 ± 45.31 µg h/mL, respectively). The results were similar for the T max (3.58 ± 0.90 h versus 3.42 ± 0.51 h). However, when comparing the mean C max some significant differences were found (8.73 ± 3.66 µg/mL and 10.43 ± 3.84 µg/mL, respectively). The 90% confidence intervals for the ratio of AUC0-∞ and T max values for the reference and test product are within the interval 80-125%, but the 90% confidence intervals for the ratio of C max falls outside the proposed interval. It was concluded that C max of test product are not within the 20% of those of the reference, thus suggesting that test OTC is not bioequivalent to the reference formulation.