Concentraciones de alcaloides, glucósidos cianogénicos, polifenolesy saponinas en plantas medicinales seleccionadas en Ecuador y su relación con la toxicidad aguda contra Artemia salina Alcoholic and aqueous extracts from leaves of these selected plants were prepared at different concentrations. To assess cytotoxicity of these extracts, different bioassays with A. salina were undertaken, and the mortality rates and LC 50 were obtained. Besides, concentrations of alkaloids, cyanogenic glycosides, phenols, tannins and saponins were determined by spectrophotometric methods; this constituted the first report of quantification of secondary metabolites in the selected plants from Ecuador. T. officinale had the highest concentration of total phenols (22.30 ± 0.23 mg/g) and tannins (11.70 ± 0.10 mg/g), C. aconitifolius of cyanogenic glycosides (5.02 ± 0.37 µg/g) and P. hysterophorus of saponins (6.12 ± 0.02 mg/g). Tannins values obtained were not adverse to their consumption. Alcoholic and aqueous extracts of selected plants had hemolytic activity depending on the concentration of saponins. Although the values of cyanogenic glycosides were permissible, it was necessary to monitor the presence of this metabolite in plants to minimize health problems. LC 50 values ranged from extremely toxic (3.37 µg/mL) to highly toxic (274.34 μg/mL), in P. carpunya and T. officinale, respectively. From correlation analysis, it was observed that increase values of alkaloids concentrations had highly significant (p<0.001) acute toxicity against A. salina, while at a higher polyphenol concentration the level of plants cytotoxicity decreased significantly (p<0.001). The results of principal component analysis showed that saponins apparently were in synergy with polyphenols to decrease cytotoxicity, but antagonize with alkaloids and cyanogenic glycosides, indicating that these secondary metabolites present variability in the mechanisms of action against A. salina, as cytotoxic compounds. These results also demonstrate that polyphenols and saponins can be lethal at low concentrations, demonstrating the potential of brine shrimp bioassay as a model to evaluate plant extracts containing low concentrations of chemical compounds with high polarities. The significant positive correlation between cytotoxicity and concentration of alkaloids confirmed by the bioassay of brine shrimp can be useful to identify promising sources of antitumor compounds, and to evaluate tolerable limits not affecting other benign cells. Contents of secondary metabolites found in the selected plants confer them great pharmacologic values. Rev. Biol. Trop. 64 (3):
Los ejemplares de las especies vegetales Cymbopogon citratus (hierba luisa) y Melissa officinalis (toronjil), se recolectaron al azar en la localidad de Machala, Ecuador. Las hojas fueron lavadas, secadas, molidas y extraídas por maceración con metanol; los filtrados concentrados por evaporación a presión reducida. A cada extracto, se le realizaron pruebas fitoquímicas y ensayos biológicos como: actividad antimicrobiana (antibiograma: difusión en agar) y letalidad con Artemia salina. Los extractos de C. citratus y M. officinalis revelaron la presencia de esteroles insaturados, triterpenos pentacíclicos, fenilpropanoides y catequinas. Mientras que en el de M. officinalis se detectaron, además, cumarinas y metilencetonas. Los extractos de ambas especies (soluciones de 20 y 40 mg/L) mostraron actividad antibacteriana contra las cepas Escherichia coli, Pseudomonas aeruginosa y Staphylococcus aureus, a excepción de los extractos metanólicos de M. officinalis (20 mg/L) y C. citratus (40 mg/L) que no exhibieron actividad frente a E. coli. La especie C. citratus mostró el mayor efecto antibacteriano contra las bacterias P. aeruginosa y S. aureus (halos de inhibición > 15mm). Se observó una actividad antifúngica alta del extracto de C. citratus, y una actividad moderada del extracto de M. officinalis, contra la cepa del hongo Candida albicans. C. citratus y M. officinalis mostraron una actividad letal significativa (CL50 <1000 μg/ml) frente a nauplios de A. salina a las 24 h de exposición: 358,03 y 72,25 μg/ml respectivamente. La especie M. officinalis presentó la mayor letalidad, considerado altamente tóxico según CYTED. A partir de los resultados obtenidos, se puede inferir que las plantas C. citratus y M. officinalis cultivadas en Ecuador son una fuente promisoria de metabolitos secundarios bioactivos con actividad farmacológica (antimicrobianos y citotóxicos).
Se realizó un estudio fitoquímico de metabolitos secundarios, actividad antimicrobiana y letal del extracto metanólico de las partes botánicas de Lippia citriodora K (cedrón). Se detectó la presencia taninos, polifenoles, triterpenos y esteroles insaturados para las hojas, flores y tallo; fenilpropanoides y catequinas para tallos y flores; alcaloides para hojas y flores; saponinas para hojas y tallos. Además, las flores exhibieron la presencia de cumarinas y metilencetonas. Todos los extractos metanólicos mostraron una acción bactericida alta contra cepas de Escherichia coli, Staphylococcus aureus y Pseudomonas aeruginosa, a excepción del extracto de las flores que exhibió una actividad antibacteriana moderada o mediana contra cepas de S. aureus. Además, se observó un efecto antifúngico moderado del extracto de las hojas, y una actividad alta de los extractos del tallo y flores, contra la cepa del hongo Candida albicans. Todos los extractos mostraron letalidad significativa (<1000 µg/ml) frente a nauplios de Artemia salina a las 24 h de exposición (168,77, 82,19 y 172,76 µg/ml para las hojas, tallo y flores, respectivamente); donde el extracto del tallo presentó mayor letalidad con CL50 de 82,19 µg/ml, considerado altamente tóxico según CYTED. Se puede inferir que la especie L. citriodora es una fuente promisoria de metabolitos secundarios bioactivos con actividad farmacológica.AbstractThis research was based on a phytochemical study of secondary metabolites, lethal and antimicrobial activity of methanolic extract of botanical organs Lippia citriodora K (lemon verbena). It was detected the presence of tannins, polyphenols, triterpenes and unsaturated sterols for leaves, flowers and stem; phenylpropanoids and catechins for stems and flowers; alkaloids for leaves and flowers; saponins for leaves and stems. In addition, the flowers exhibited the presence of coumarins and methylenketones. Methanolic extracts showed high bactericidal action against strains of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, in the antimicrobial bioassay, except for the flowers which exhibited moderate activity against S. aureus strains. Furthermore, moderate antifungal effect was observed for leaves extract and high activity for stem and flowers extracts against the strain of Candida albicans fungus. All extracts showed significant lethality (<1000 μg/ml) against A. salina nauplii at 24 h of exposure (168.77, 82.19 and 172.76 μg/mL for leaves, stems and flowers, respectively); where the methanolic extract of the stem showed the highest lethality with LC50 value of 82.19 μg/ml, considered highly toxic according to CYTED. It can be inferred that L. citriodora is a promising source of bioactive secondary metabolites with pharmacological activity.
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