Dillapiole in Piper holtonii as an Inhibitor of the Symbiotic Fungus Leucoagaricus gongylophorus of Leaf-Cutting Ants.

Plants of the Piperaceae family are studied for their diverse secondary metabolism with a vast array of compounds that act as chemical defense agents against herbivores. Of all the agricultural pests, the management of insects is a highly significant challenge in the Neotropics, and ants of the Attini tribe pose a major problem. Due to their symbiotic association with the fungus Leucoagaricus gongylophorus (Möller) Singer (Agaricaceae), the species of Atta and Acromyrmex have exhaustive foraging activity which has intensified as deforestation and monoculture farming have increased. The control of leaf-cutting ants is still carried out with synthetic products with negative consequences to the environment and human health. In search for natural and sustainable alternatives to synthetic pesticides, Piper holtonii C. DC. was selected among other plant species after field observations of the foraging activity of Atta cephalotes, which revealed that P. holtonii was never chosen by ants. In vitro evaluation of an ethanol extract of the leaves of P. holtonii resulted in promising inhibitory activity (IC50 102 ppm) against L. gongylophorus. Subsequently, bioassay-guided fractionation led to the isolation of the phenylpropanoid dillapiole, which was also detected in the essential oil. This compound demonstrated inhibition of the fungus with an IC50 of 38 ppm. Considering the symbiotic relationship between the Attini ants and L. gongylophorus, the negative effect on the survival of one of the organisms will affect the survival of the other, so dillapiole or standardized essential oil extracts of P. holtonii containing this active principle could be a unique and useful source as a control agent for leaf cutting-ants.

Actividad antiplasmódica in vitro de Piper holtonii (cordoncillo) / In vitro antiplasmodial activity of Piper holtonii (cordoncillo)

Introducción: especies vegetales del género Piper (Piperaceae) han sido usadas en la medicina tradicional en diferentes regiones del mundo, incluida Latinoamérica para el tratamiento de enfermedades tropicales como la malaria. Objetivo: evaluar la actividad antiplasmódica del extracto etanólico y las fracciones de diferente polaridad de Piper holtonii C.DC. Métodos: la actividad antiplasmódica del extracto etanólico de las partes aéreas de Piper holtonii y de las fracciones hexánica, clorofórmica, metanólica, butanólica y acuosa, se evaluó sobre un cultivo de Plasmodium falciparum cepa FCB-2. Se determinó la actividad hemolítica y se caracterizaron fitoquímicamente cada una de las fracciones. Resultados: el extracto etanólico y las fracciones de baja polaridad presentaron actividad promisoria con valores de CI50 inferiores a 25 µg/mL. Conclusiones: los resultados de la actividad biológica de Piper holtonii permiten sugerir que los metabolitos de baja y media polaridad están relacionados con la actividad antiplasmódica de esta especie.

Introduction: plant species of the genus Piper (Piperaceae) have been used in traditional medicine in various regions of the world. In Latin America they have been used to treat tropical diseases such as malaria. Objective: evaluate the antiplasmodial activity of the ethanolic extract and fractions of varying polarity of Piper holtonii C. DC. Methods: evaluation was conducted of the antiplasmodial activity of ethanolic extract from aerial parts of Piper holtonii and of hexane, chloroform, methanol, buthanol and aqueous fractions on a Plasmodium falciparum strain FCB-2 culture. Hemolytic activity was determined and phytochemical characterization of each fraction was performed. Results: both the ethanolic extract and the low-polarity fractions displayed promising activity, with CI50 values below 25 µg/mL. Conclusions: results concerning the biological activity of Piper holtonii suggest that low- and medium-polarity metabolites are related to antiplasmodial activity in this species.