The kinetic study of the solid-liquid extraction of caffeine in Ilex guayusa Loes addresses a critical stage in the isolation of alkaloids such as caffeine. Solid-liquid extraction, a widely used technique, plays a fundamental role in obtaining these compounds. The study aimed to evaluate the applicability of the Peleg equation to model the solid-liquid extraction of caffeine in Ilex guayusa Loes leaves. Caffeine content was determined by UV-visible absorption spectroscopy. Extraction kinetics were estimated using the two-parameter Peleg’s equation. The correspondence between the experimental results and those predicted by the model was established by calculating Pearson's correlation. The results indicated significant extraction temperature and time effects on caffeine content, with concentrations ranging from 0.24 to 1.52 g.100 g-1 at different extraction temperatures (30, 40, and 50 °C). The Peleg equation effectively modeled caffeine extraction kinetics, with high Pearson correlation coefficients (0.96895 to 0.99685) confirming its suitability for predicting caffeine concentration. These results highlight the importance of understanding extraction kinetics to optimize caffeine extraction processes, offering valuable insights for industries using Ilex guayusa Loes extracts. Keywords: kinetics; Peleg's equation; aqueous extract; mathematical model

Essential oils are investigated due to their biological activity, and the Amazon rainforest, with its rich biodiversity, is a promising source of therapeutic compounds. The aim of this study was to evaluate the essential oil from the leaves of Bixa orellana as an antifungal agent, thus contributing to the search for alternatives that can address the growing resistance to conventional antifungals. B. orellana leaves were collected in the Ecuadorian Amazon and their essential oil was obtained by steam distillation. Their chemical composition was analysed by Gas Chromatography-Mass Spectrometry (GC-MS) and their antifungal activity against Candida albicans was evaluated using the Kirby–Bauer disc diffusion method (ATCC 10231), with nystatin as a positive control. GC-MS analysis revealed the presence of 60 compounds, the main ones being dihydroedulan (27.5%), β-caryophyllene (10.3%), nerolidol (7.21%), trans-β-bergamotene (5.73%), α-santalene (4.94%) and trans-α-bergamotene (4.26%). The essential oil showed moderate antifungal activity against C. albicans, producing an inhibition halo of 13 mm in diameter, which is 48% of the inhibition observed with nystatin (27 mm). The presence of sesquiterpenes, such as β-caryophyllene, known for its membrane-disrupting properties, probably contributes to the observed antifungal effects. The study highlights the potential of B. orellana essential oil as a natural antifungal agent; however, further research is required to evaluate its efficacy against a wider range of pathogenic fungi, its possible synergistic effects with conventional antifungals and its safety and efficacy in vivo.

Este estudio investiga la composición fitoquímica y la actividad antimicrobiana de los extractos acuoso, alcohólico y etéreo de Simira cordifolia contra Candida albicans y Escherichia coli. El tamizaje fitoquímico reveló la presencia de saponinas, flavonoides, fenoles/taninos, aminoácidos y alcaloides, con resultados más amplios en el extracto acuso. El ensayo antimicrobiano mostró zonas de inhibición significativas para ambos microorganismos, siendo E. coli más sensible, exhibiendo zonas de hasta 20 mm, en comparación con C. albicans con zonas de hasta 18 mm. El análisis estadístico utilizando ANOVA confirmó la alta significancia del modelo, con la concentración, el tipo de microorganismo y su interacción como factores clave. La robustez del modelo fue validada por altos valores de R² y una precisión adecuada. Los hallazgos sugieren que el extracto acuoso de Simira cordifolia contiene compuestos bioactivos potentes, lo que lo convierte en un candidato prometedor para el desarrollo de nuevos agentes antimicrobianos.

Evaluación de las propiedades antioxidantes y físicas de una crema exfoliante desarrollada a partir de la cáscara de Mauritia flexuosa L. (morete)

Este estudio evalúa la actividad antifúngica del extracto liofilizado de hojas de Tectona grandis contra tres hongos fitopatógenos, Aspergillus oryzae, Rhizopus stolonifer y Aspergillus niger. Se realizó un tamizaje fitoquímico que reveló que el extracto acuoso contenía la mayor diversidad de metabolitos bioactivos, incluyendo saponinas, flavonoides y alcaloides. En el experimento en condiciones controladas, se midió el efecto de diferentes concentraciones del extracto acuoso sobre el crecimiento de los hongos, con concentraciones que variaron entre 30 y 75 mg/ml. Los resultados mostraron que Rhizopus stolonifer fue el más afectado a bajas dosis, mientras que Aspergillus niger presentó un crecimiento notable en concentraciones de 36,3 mg/ml y 52,5mg/ml. El análisis de varianza (ADEVA) del modelo cúbico indicó que todos los términos del modelo, incluidos la dosis y la interacción entre dosis y tipo de hongo, fueron significativos (p < 0.0001). Además, el modelo cúbico mostró un R² ajustado de 0,9983, lo que sugiere un excelente ajuste a los datos observados. Estos hallazgos sugieren que el extracto de Tectona grandis tiene un potencial significativo como agente antifúngico, variando su efectividad según el tipo de hongo y la concentración utilizada, lo que podría ser útil en el desarrollo de estrategias de control biológico en cultivos.

Introduction. The development of phytosanitary products from plant extracts requires the establishment of quality and stability criteria to guarantee their efficacy and safety. Objective. To determine the specifications for the physicochemical quality control of a phytosanitary product based on a lyophilized aqueous extract of Tectona grandis leaves and to evaluate the stability under temperature-accelerated conditions to establish its shelf life. Materials and methods. The research was conducted in the province of Pastaza, Ecuador, from January to May, 2024. Mature leaves of T. grandis were collected, dried, pulverized and subjected to ultrasound-assisted extraction. The aqueous extract was freeze-dried and evaluated for pH, electrical conductivity, moisture, total ash, total polyphenol content and antioxidant activity. Bowker’s method was applied to establish specification limits with seven replicates and 95 % confidence. Stability was evaluated by monitoring the loss of antioxidant activity in accelerated storage (30, 40 and 50 °C), using kinetic models (zero, first and second order) and the Arrhenius equation to project shelf life at 4, 15 and 20 °C. Results. The product showed a pH of 5.46-5.48; conductivity of 5.1-5.9 µS/cm; moisture of 13.4-14.9 %; total ash of 12.83-13.25 %; total polyphenols of 55.33-57.93 mg ET/100, and an antioxidant activity of 17895.4-16526.2 mg Eq. Trolox/100g. The three kinetic models allowed for an adequate prediction of the shelf life. Conclusions. The quality and stability specifications of the lyophilized extract of T. grandis were defined, confirming its potential as a natural phytosanitary product.