RESUMEN
Abstract: The antibacterial activities of three Croton species were compared using bioautography and the serial microdilution methods. The methanolic extracts of all the species had low activity against Escherichia coli. The highest activity was observed with Croton megalobotrys against Enterococcus faecalis with a minimal inhibitory concentration (MIC) value of 0.02 mg/ml. Croton steenkapianus extracts were the least active of the species investigated, only managing an MIC value of 0.625 mg/ml against Pseudomonas aeruginosa. Croton megalobotrys leaf powder was serially extracted using solvents of various polarities. The lowest MIC value (0.06mg/ml) of the serially extracted fractions was observed with acetone against Pseudomonas aeruginosa. The liquid-liquid fractions of the methanol extract of Croton megalobotrys were also tested. The lowest MIC value of 0.02 mg/ml was observed with n-hexane fraction against Enterococcus faecalis. The carbon tetrachloride fraction was further fractionated using column chromatography with silica as the immobile phase. The resulting seven fractions were tested for activity following the bioassay-guided practice, and it emerged that the first three fractions had active compounds against Staphylococcus aureus when the bioautography method was used
Asunto(s)
Antibacterianos , Croton , Escherichia coli , SudáfricaRESUMEN
The antibacterial activities of three Croton species were compared using bioautography and the serial microdilution methods. The methanolic extracts of all the species had low activity against Escherichia coli. The highest activity was observed with Croton megalobotrys against Enterococcus faecalis with a minimal inhibitory concentration (MIC) value of 0.02 mg/ml. Croton steenkapianus extracts were the least active of the species investigated, only managing an MIC value of 0.625 mg/ml against Pseudomonas aeruginosa. Croton megalobotrys leaf powder was serially extracted using solvents of various polarities. The lowest MIC value (0.06 mg/ml) of the serially extracted fractions was observed with acetone against Pseudomonas aeruginosa. The liquid-liquid fractions of the methanol extract of Croton megalobotrys were also tested. The lowest MIC value of 0.02 mg/ml was observed with n-hexane fraction against Enterococcus faecalis. The carbon tetrachloride fraction was further fractionated using column chromatography with silica as the immobile phase. The resulting seven fractions were tested for activity following the bioassay-guided practice, and it emerged that the first three fractions had active compounds against Staphylococcus aureus when the bioautography method was used.
Asunto(s)
Antibacterianos/farmacología , Croton/química , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Extractos Vegetales/farmacología , Antibacterianos/química , Croton/clasificación , Enterococcus faecalis/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Humanos , Metanol , Pruebas de Sensibilidad Microbiana , Extractos Vegetales/química , Hojas de la Planta/química , Pseudomonas aeruginosa/efectos de los fármacos , Sudáfrica , Staphylococcus aureus/efectos de los fármacos , Resultado del TratamientoRESUMEN
The repellent effects of the essential oil of Lavendula angustifolia on adults of Hyalomma marginatum rufipes was studied at concentrations of 5, 10 and 20% v/v. A suitable tick climbing bioassay based on the questing behaviour of ticks was used to test for repellency. High percentage repellency (range 70-100) was shown at all concentrations of the essential oil of L. angustifolia, although at 5% v/v it only persisted for the first 40 minutes compared with 120 minutes at other concentrations (10 and 20% v/v). The repellent strength of L. angustifolia compared well (P > 0.05) with that of DEET (N,N-diethyl-m-toluamide), a commercial reference repellent, for the 2-hour period of the study.
Asunto(s)
Mordeduras y Picaduras de Insectos/veterinaria , Repelentes de Insectos/farmacología , Lavandula/química , Aceites Volátiles/farmacología , Garrapatas , Animales , Bioensayo/veterinaria , Relación Dosis-Respuesta a Droga , Mordeduras y Picaduras de Insectos/prevención & control , Control de Ácaros y Garrapatas/métodos , Enfermedades por Picaduras de Garrapatas/prevención & control , Enfermedades por Picaduras de Garrapatas/veterinaria , Garrapatas/efectos de los fármacos , Factores de TiempoRESUMEN
The toxic effects of the extracts of Allium sativum (Garlic) were evaluated against adults of Hyalomma marginatum rufipes and Rhipicephalus pulchellus using three types (Types A, B and C) of contact toxicity bioassays. A. sativum bulbs were extracted with acetone, ethanol and dichloromethane (DCM) solvents. Among these three solvents, it is the DCM extract of A. sativum that appears to have anti-tick activity. In the Type A contact toxicity bioassay, DCM extracts of A. sativum demonstrated a high acaricidal bioactivity against H. m. rufipes with 100% of ticks killed in less than an hour, and toxicity persisted to the second day. A weak acaricidal activity of aqueous extracts of A. sativum was observed in the Type B contact toxicity bioassay. In the Type C contact toxicity bioassay, a concentration of 24% w/v of DCM extracts of garlic in sunflower oil (Helianthus annuus) had killed 100% of H. m. rufipes (LC50 = 5.9% w/v) and R. pulchellus (LC50 = 10.3% w/v) by 24 hours post-treatment of ticks. The results obtained from this study suggest that DCM extract of A. sativum is a potential source of novel acaricidal agents.
Asunto(s)
Ajo/química , Extractos Vegetales/toxicidad , Control de Ácaros y Garrapatas/métodos , Garrapatas/efectos de los fármacos , Acetona/farmacología , Animales , Bioensayo , Relación Dosis-Respuesta a Droga , Etanol/farmacología , Dosificación Letal Mediana , Cloruro de Metileno/farmacología , Rhipicephalus/efectos de los fármacos , Rhipicephalus/crecimiento & desarrollo , Garrapatas/crecimiento & desarrollo , Factores de TiempoRESUMEN
In this study we examine the feeding patterns of immature stages of Hyalomma truncatum and Hyalomma marginatum rufipes ticks on different hosts. Larvae of H. truncatum developed through a three-host pattern on two species of field mice, Rhabdomys pumilio and Lemniscomys rosalia. On guinea-pigs, both Hyalomma species followed a mixed two-host and three-host pattern, with the latter route being preferred, since more than 70% of the fully fed larvae dropped off from their hosts. H. truncatum was a two-host tick on rabbits. Larvae of H. marginatum rufipes did not prefer R. pumilio and L. rosalia as hosts. On guinea-pigs, H. marginatum rufipes immatures showed a mixed two-host and three-host pattern with a bias towards the three-host life cycle, since approximately 58% of the fully fed larvae dropped off. On rabbits, H. marginatum rufipes was exclusively a two-host tick. Mean engorgement weights and blood quantities ingested by H. truncatum nymphs that developed through a three-host pattern on mice were significantly higher (p < 0.0001) than for those that developed through a two-host pattern on guinea-pigs and rabbits. For H. marginatum rufipes, there were no significant differences (p > 0.05) between engorgement weights of nymphs that developed through two-host and three-host patterns. However, there were significant differences (p < 0.0001) in blood quantities ingested by nymphs of this tick species following feeding on different hosts.
Asunto(s)
Infestaciones por Garrapatas/parasitología , Garrapatas/fisiología , Animales , Conducta Alimentaria , Cobayas , Metamorfosis Biológica , Ninfa/fisiología , Conejos , Factores de TiempoRESUMEN
Guinea-pigs were infested three times at short (1 week) intervals or long (10 week) intervals between successive infestations with low (1), medium (8) and high (15) numbers of adult Rhipicephalus evertsi evertsi. To compare the resistance developed by the hosts at short and long intervals between infestations, a challenge (fourth) infestation was performed with the high number of ticks. Resistance was assessed by comparing the mean weight of engorged female ticks that dropped from the hosts. Concentrations of beta globulins in the host sera were also monitored. Different tick loads (low, medium and high) and infestation intervals had a similar influence on the reduction in weight of the females which was between 60-70% after the final challenge. However, the concentration of beta globulins, was highest in the guinea-pigs exposed to medium and high numbers of ticks with long infestation intervals, probably because of an increase in the production of protective antibodies in response to more intensive antigenic challenge. The relationship between engorgement weight and beta globulin levels in host sera is discussed.