Browsing by Autor "Antonio Morales"

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Actividad insecticida de extractos liquénicos de Physcia sp. en larvas de Tecia solanivara Insecticidal activity of lichen extracts from Physcia sp.in Tecia solanivara larvae
(2018) Patricia Pérez; Janne Rojas; Antonio Morales; Mariet Vizcaya; Claudio Lugo
Los extractos obtenidos con solventes de diferente polaridad (eter de petroleo (EEP), acetona (EA) y metanol (EM)) de Physcia aipolia, fueron evaluados como posibles sustancias insecticidas frente a larvas de Tecia solanivara, la mayor plaga que enfrenta el cultivo de la papa. Para realizar el estudio, se utilizo la tecnica de exposicion a superficies tratadas con insecticidas formulados. Se prepararon ocho diferentes concentraciones de las sustancias a ensayar comprendidas entre 5,0x104 y 5,0x10-10 μg/mL, la mortalidad de las larvas se registro transcurridas 24 horas de la aplicacion de los mismos. Los resultados revelaron actividad insecticida en EA a partir de 5,0x10-6 μg/mL, en EEP a 5,0 x10-2 μg /mL, y EM a 5,0 x102 μg/mL. El analisis de los datos detecto diferencias estadisticamente significativas entre los tratamientos evaluados con el testigo por debajo de 5,0 μg /mL. Los datos obtenidos representan una contribucion en el campo de los productos naturales puesto que hasta la fecha no se han encontrado estudios que reporten actividad larvicida en Tecia solanivora utilizando extractos del genero ni de la especie. Palabras claves: Insecticida, liquen, Physcia, Tecia solanivora. Abstract The extracts obtained with solvents of different polarity (petroleum ether (EEP), acetone (EA) and methanol (EM)) of Physcia aipolia, were evaluated as possible insecticidal substances against larvae of Tecia solanivara, the largest pest facing the crop of the potato. To carry out the study, the technique of exposure to surfaces treated with formulated insecticides was used. The substances to be tested were prepared at eight different concentrations ranging from 5.0x10-4 to 5.0x10-10 μg / mL, larval mortality was recorded 24 hours after application of the substances. The results showed insecticidal activity in EA from 5.0 x 10-6 μg / mL, in EEP at 5.0 x 10-2 μg / mL, and EM at 5.0 x 10 2 μg / mL. The analysis of the data detected statistically significant differences between the treatments evaluated in relation to the control. The data obtained represent a contribution in the field of natural products since to date no studies have been found that report larvicidal activity in Tecia solanivora using extracts of the genus or of the species. Keywords: Insecticide, lichen, Physcia, Tecia solanivara.
Antimicrobial activity of four Valeriana L. (Caprifoliaceae) crude extracts, endemic species of the Venezuelan Andes
(Vicerractoría Investigación, 2018) María Rondón; Judith Josefina Velasco; Janne Del Carmen Rojas; Luis E. Gámez; Antonio Morales
Valeriana L. genus is represented in Venezuela by 16 species, 9 of these are endemic of Venezuelan Andes growing in high mountains at 2800 masl. In this investigation, four species were analyzed in order to determine the main secondary metabolites and antimicrobial activity of extracts obtained from aerial parts of Valeriana parviflora, V. rosaliana, V. triplinervis and V. phylicoides. Alkaloids, flavonoids, tannins, sterols, triterpenoids and saponins were qualitatively observed in all methanolic extracts tested. The color intensity or a precipitate formation was used as analytical response to these tests. Antimicrobial activity was evaluated against Gram positive, Gram negative bacterial strains and yeast, using disc diffusion method. N-hexane extracts of V. triplinervis and V. rosaliana showed the highest efficiency against Staphylococcus aureus, exhibiting inhibition zones of 16 mm and 15 mm; MIC (Minimal Inhibition Concentration) values were observed at 116 mg/mL and 150 mg/mL, respectively. Dichloromethane and methanolic extracts of V. triplinervis and methanolic extract of V. rosaliana showed a rather moderate activity (MIC between 200 to 316 mg/ml) but a very weak antibacterial activity was observed in V. phylicoides and V. parviflora extracts (MIC > 420 mg/mL). None of the extracts assayed in this investigation showed any activity against Candida albicans and Candida krusei. Statistical analysis showed no significant differences on the different polarity extracts assayed with respect to antimicrobial activity against S. aureus (P > 0.10), however it was observed significant differences between the Valeriana species analyzed (P < 0.10) in relation to the minimal inhibitory concentration (MIC).