This study focused on the assessment of the vasorelaxant activity of the organic and aqueous extracts obtained from leaves and fruits of a Mexican hawthorn (Crataegus gracilior) on isolated rat aorta, and on the purification and identification of some of their secondary metabolites by the use of chromatographic and spectroscopic techniques. The results obtained showed that the methanol extract has a significantly more potent and effective vasorelaxant effect than the other tested extracts, with an EC50 = 8.69 ± 4.34 µg/mL and an Emax = 94.6% ± 11.30%, values that are close to that of acetylcholine, the positive control. From the same extract, two major triterpenes were isolated and identified as ursolic and corosolic acids by comparison of their experimental NMR spectroscopic data with those reported in the literature. Chlorogenic acid, rutin, quercetin, kaempferol and (+)-catechin were also identified using HPLC coupled with PDAD. All these compounds have already been proven to possess on their own antihypertensive effect and other benefits on cardiovascular diseases and they can support, at least in part, the traditional use of this plant species.

Cacti are the most representative vegetation of arid zones in Mexico where rainfall is scarce, evapotranspiration is high and soil fertility is low. Plants have developed physiological strategies such as the association with microorganisms in the rhizosphere zone to increase nutrient uptake. In the present work, four bacterial isolates from the rhizosphere of Mammillaria magnimamma and Coryphantha radians were obtained and named as QAP3, QAP19, QAP22 and QAP24, and were genetically identified as belonging to the genus Bacillus, exhibiting in vitro biochemical properties such as phosphate solubilization, indoleacetic acid production and ACC deaminase activity related to plant growth promotion, which was tested by inoculating M. magnimamma seeds. It was found that all isolates increased germination from 17 to 34.3% with respect to the uninoculated control seeds, being QAP24 the one having the greatest effect, accomplishing the germination of viable seeds (84.7%) three days before the control seeds. Subsequently, the inoculation of Mammillari zeilmanniana plants with this isolate showed a positive effect on bloom, registering during two months from a one year period, an increase of up to 31.0% in the number of flowering plants compared to control plants. The characterized Bacillus spp. isolates have potential to be used in conservation programs of plant species from arid zones.

Resumen: Se analizó la riqueza fl orística, el hábito y la forma de vida, la presencia de especies nativas e introducidas, la fl ora sinantrópica, los patrones de distribución y endemismo, el estado de conservación de las plantas vasculares y se caracterizó los tipos de vegetación presentes en la Sierra El Rincón, Querétaro y Michoacán, México. Se registraron 79 familias, 216 géneros, 333 especies y 23 taxa infraespecífi cos. Las familias con la mayor riqueza fl orística fueron Asteraceae (67), Poaceae (28) y Fabaceae (13). En cuanto a los géneros destacaron Quercus y Stevia. El hábito herbáceo está presente en el 84.1 % de las especies y las formas de vida predominantes fueron las hemicriptófi tas (45.1 %) y terófi tas (12.9 %). El 96 % de la fl ora es nativa a México y el 36.6 % son indicadoras de disturbio. Se registraron siete patrones de distribución geográfi ca, donde se destaca que el 35.4 % (118) de la fl ora es endémica de México. Así como dos patrones de endemismo, en los cuales 29 especies (8.7 %) limitan su distribución al centro del país y 89 (26.7 %) presentan una amplia distribución en el territorio nacional. De acuerdo con la NOM-059-SEMARNAT-2010 son Especies Sujetas a Protección Especial a Gentiana spathacea y Mammillaria rhodantha subsp. pringlei, y como Amenazada se encuentra Dasylirion acrotrichum. Se reconocieron siete tipos de vegetación, de los cuales el bosque de Quercus y de QuercusPinus son los tipos dominantes en el área de estudio. Además de contribuir signifi cativamente a la riqueza fl orística de la región, esta sierra brinda diversos servicios ambientales a la población como la recarga de acuíferos, fl ora útil y áreas de esparcimiento. Es necesario coordinar esfuerzos y desarrollar un plan de manejo integral dirigido a la conservación y al uso sustentable de la fl ora y vegetación de la Sierra El Rincón. Palabras Clave: Amealco, bosque de encino-pino, Epitacio Huerta, Flora del Bajío, Huimilpan. Abstract:In this work the taxonomic richness, habit and life form, presence of native and introduced species, sinantropic fl ora, distribution and endemism patterns, and species conservation status were analyzed, and the type of vegetation was characterized in Sierra El Rincón, Querétaro and Michoacán states, Mexico. Seventy nine families, 216 genera, 333 species, and 23 infraspecifi c taxa were recorded. Asteraceae (67), Poaceae (28) and Fabaceae (13) were the richest families. For genera, Quercus and Stevia were the richest. The herbaceous habit is present in 84.1 % of species and the main life forms were hemicryptophytes (45.1 %) and therophytes (12.9 %). From total fl ora, 96 % are native to Mexico and 36.6 % are disturbance indicators. Seven geographic distribution patterns were recorded, from total fl ora, 35.4 % (118) is endemic to Mexico. Two endemism patterns were recorded, in which 29 species (8.7 %) have their distribution limited to center of Mexico, and 89 species (26.7 %) show a wide distribution in Mexico. According to NOM-059-SEMARNAT-2010, Gentiana spathacea and Mammilla...

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