No abstract

Con el fin de evaluar las principales propiedades antioxidantes y antibióticas del exocarpio del fruto de Santol (Sandoricum koetjape), se realizó una bioprospección sobre este, así como una caracterización del contenido de polifenoles totales y proantocianidinas. Para lo anterior, al material seco y molido del exocarpio se le realizaron diferentes pruebas cuantitativas y fraccionamientos cromatográficos con diversas resinas, con el propósito de obtener metabolitos puros o mezclas de ellos más concentrados. Las fracciones y extractos fueron analizados empleando el método de Folin-Ciocalteu (polifenoles totales), DMAC (proantocianidinas totales) y DPPH (actividad antioxidante), utilizando siempre un patrón tradicional y uno propio de la muestra. Los resultados obtenidos con este último fueron hasta un 80 % más alto en comparación con los patrones tradicionales; además, se determinó cómo las fracciones con un mayor contenido de proantocianidinas presentan una mayor actividad antibiótica, con un 73 ± 4 % sobre la batería S. Aureus y un 42 ± 2 % sobre Bacilus spp., ambos análisis realizados por el método de Kirby-Bauer.

Ber is an antioxidant‐rich fruit from Asia and has recently been cultured in Central America. The antioxidant capacity and antimicrobial activity of Z. mauritiana cultured of bers from Guanacaste, Costa Rica, were evaluated. Two farm locations and two cultivars were evaluated. Total polyphenolic compounds (TPC), proanthocyanidin compounds (PAC), and ascorbic acid were spectrophotometrically quantified. Antioxidant activity has been analyzed using the DPPH method. Antimicrobial susceptibility was determined using the Kirby‐Bauer disk diffusion method. Ber samples contained 11–44 mg GAE/g TPC. Green fruits and leaves had the highest concentrations. The ascorbic acid concentration in ber fruits was determined between 251 and 466 mg/100 g. Ber vitamin C content is higher than most common fruits. Proanthocyanidin compounds were determined between 1.8 and 9.9 mg 4‐MCG/g, and the highest concentration was observed in the leaves. Our samples showed the antioxidant activity of 90–387 μmol TE/g, which was moderate activity. The nutritional quality of ber fruits was related to maturity conditions. The ber fruits, a crop from Asia previously adapted to live in Costa Rica, are rich in vitamin C and TPC, and the concentration of those metabolites was even higher than the concentration reported in bers grown in other countries. The TPC and PACs had an interestingly wide antimicrobial spectrum. Cultivars and farm locations have a significant effect on metabolite production.

Vector-borne diseases, such as those transmitted by Aedes aegypti, are a constant threat to inhabitants of tropical regions of the planet. Synthetic chemicals are commonly used as a strategy to control them; however, these products are known to persist in ecosystems and drive the appearance of resistance genes in arthropod vectors. Thus, the use of natural products has emerged as an environmentally friendly alternative in integrated vector control strategies. The present bioguided study investigated the larvicidal potential of Ipomoea cairica extracts, fractionated using thin-layer and open-column chromatography, because this species has been shown to exert larvicidal effects on the genus Aedes. The objective of this study was to evaluate the nonvolatile components in ethanolic extract of I. cairica stems as a potential natural larvicidal, and coumarins, such as 7-hydroxy-6-methoxychromen-2-one (scopoletin) and 7-hydroxychromen-2-one (umbelliferone), were identified as major compounds; however, they were not shown to be responsible for the larvicidal activity. Based on the results of the larvicidal action tests, these coumarins are not directly responsible for the larvicidal activity, but this activity might be attributed to a synergistic effect of all the compounds present in the most active secondary fraction, called F.DCM, which had an LC50 value of 30.608 mg/L. This type of study has yet not been conducted in the region; therefore, it is an important contribution to recognizing a natural and easy-to-cultivate source of vector control, such I. cairica.

Experiencia de aprendizaje en la transmisión de conocimientos teóricos y prácticos con aplicación de una evaluación formativa en laboratorios de química 513 Experiencia de aprendizaje en la transmisión de conocimientos teóricos y prácticos con aplicación de una evaluación formativa en laboratorios de química 514 EXPERIENCIA DE APRENDIZAJE EN LA TRANSMISIÓN DE CONOCIMIENTOS TEÓRICOS Y PRÁCTICOS CON APLICACIÓN DE UNA EVALUACIÓN FORMATIVA EN LABORATORIOS DE QUÍMICAaccomplished by: earlier preparation of both, teachers and students for the laboratory lessons; the realization of short exams before the laboratory session; a discussion on the practice at the beginning and at the end of the laboratory session and the completion of a laboratory inform in which the students, supported by updated bibliography references, explain, on their own words, the results obtained during the laboratory session.Additionally, teachers regularly discuss their experiences during the laboratory session in order to improve the quality of the practice. Those previous actions have stimulated the interest of the students; showing an important student promotion at the end of the semester.