Computational Structural Revision of Elaeophorbate and Other Triterpenoids with the Help of NAPROC-13. A New Strategy for Structural Revision of Natural Products.

A considerable number of natural products have been published in recent years with misassigned structure, even though they had been correctly elucidated in the past. The availability of databases containing revised structures can prevent the amplification of errors in structural elucidation. NAPROC-13, a dereplication tool based on the 13C chemical shift, has been used to search for substances that, possessing the same chemical shifts, have been described with different structures. The correct structure of these different structural proposals is verified by computational chemistry. This paper reports the structural revision of nine triterpenoids following this methodology.

Caracterización química y actividad biológica de las hojas y semillas de Chrysobalanus icaco L. (Icaco) / Chemical characterization and biological activity of leaves and seeds of Chrysobalanus icaco L. (icaco)

Introducción: Chrysobalanus icaco L. (Chrysobalanaceae) es un arbusto utilizado en la fitoterapia tradicional latinoamericana, pero en la provincia de Chiriquí se ha registrado el uso de su fruto para hacer conservas, no de forma medicinal. Objetivo: Caracterizar los metabolitos secundarios presentes en las hojas y semillas de Chrysobalanus icaco y evaluar su actividad biológica in vitro. Métodos: Los metabolitos secundarios presentes en los extractos de las hojas, semilla inmadura y madura de Chrysobalanus icaco, se detectaron a través de tamizaje fitoquímico y purificación por técnicas cromatográficas. Posteriormente se evaluó el contenido de polifenoles totales y la actividad antioxidante total de la infusión de las hojas, semillas y pulpa de esta especie, así como la actividad antibacteriana in vitro. Resultados: En las hojas se identificaron por tamizaje fitoquímico, flavonoides, glucósidos cardiotónicos, triterpenos y esteroides. Para la semilla inmadura se encontró presencia mayoritaria de mezclas de azucares, mientras que para la semilla madura se detectaron ácidos grasos en el endocarpio (almendra). Los datos de polifenoles totales en extractos de Icaco mostraron alto contenido de estos metabolitos en la infusión de hojas secas, y la inhibición del radical DPPH fue mayor también para las hojas secas de icaco, seguido de la infusión de semilla inmadura. Por otro lado, la infusión de hojas secas y el licuado de la pulpa fueron los que mostraron una mayor inhibición contra la cepa de Staphylococcus spp. en el ensayo de actividad antibacteriana. Conclusión: Las hojas secas de Chrysobalanus icaco mostraron alto contenido de polifenoles, asociado a su potencial actividad antioxidante y antibacteriana. Además, se aportaron nuevos datos de composición química de la semilla, se observó que los azúcares detectados inicialmente en la semilla inmadura se pierden considerablemente con la maduración del fruto.

Introduction: Chrysobalanus icaco L. (Chrysobalanaceae) is a shrub used in Latin American traditional phytotherapy, but in the province of Chiriquí its fruit has been reported to be used in food preserves, not for medicinal purposes. Objective: Characterize the secondary metabolites present in Chrysobalanus icaco leaves and seeds and evaluate their in vitro biological activity. Methods: The secondary metabolites present in extracts from leaves and immature and mature seeds of icaco were detected by phytochemical screening and purification with chromatographic techniques. Evaluation was then conducted of total polyphenolic content and total antioxidant activity of the leaf, seed and pulp infusion as well as its antibacterial activity in vitro. Results: Phytochemical screening of the leaves found flavonoids, cardiotonic glycosides, triterpenes and steroids. Sugar mixtures were the most abundant components in immature seeds, whereas fatty acids were found in the endocarp (almond) of mature seeds. Total polyphenolic data about icaco extracts showed high contents of these metabolites in the dry leaf infusion. DPPH radical inhibition was also greater for icaco dry leaves, followed by immature leaf infusion. The dry leaf infusion and the pulp shake displayed the greatest inhibition against the Staphylococcus spp. strain in the antibacterial activity test. Conclusion: Icaco dry leaves exhibited a high polyphenolic content, associated to their antioxidant and antibacterial activity. Fresh data were also contributed about the chemical composition of the seed. It was observed that the sugars initially detected in immature seeds are considerably lost as the fruit ripens.

Germacrone Derivatives as new Insecticidal and Acaricidal Compounds: A Structure-Activity Relationship.

Currently, the use of synthetic pesticides is the main method of plant protection applied in agri- and horticulture. However, its excessive use leads to the development of pesticide resistance, a contamination of the environment, toxicity to non-target organisms, and risks for human health. With the ultimate aim of contributing to the develop of a more sustainable pest management, we used the natural product germacrone (compound 1), reported to possess significant insecticidal activity, as starting material for the generation of molecular diversity (2-24). Some of the generated derivatives are natural compounds, such as 1,10-epoxygermacrone (2), 4,5-epoxygermacrone (3), gajutsulactone A (7), germacrol (11), isogermacrone (14), 9-hydroxyeudesma-3,7(11)dien-6-one (19), eudesma-4,7(11),dien-8-one (20), eudesma-3,7(11)-dien-8-one (21) and eudesma-4(15),7(11)-dien-8-one (22). Compounds, 7,11-9,10-diepoxigermacr-4,5-en-8-ol (17), 7,11-epoxieudesma-4,7(11)-dien-8-one (23) and 7,11-epoxieudesma-3,7(11)-dien-8-one (24) are described for the first time. The biocidal activity of most of these compounds was assayed against the tick Hyalomma lusitanicum. The acaricidal effects of compound 24 were four times higher than that of germacrone (1). Compound 2 is an insect antifeedant a thousand times more potent than germacrone against Rhopalosiphum padi, which makes this substance a promising selective antifeedant against this cereal pest.