Picramnia glazioviana and Picramnia bahiensis as source for new natural products. Insecticidal and fungicidal evaluations and High-Resolution Bioassay/HPLC-HRMS-SPE/NMR studies

Abstract

Leaf-cutting ants of the genus Atta and Acromyrmex are considered the most important pests in agriculture, pastures, and reforestation programs due to the defoliation caused by the uncontrolled herbivory that the plants undergo, causing damages to the plantations and serious economic losses. In this context, the chemistry of natural products corroborates to minimize this problem with respect to the development of products for the control of leaf-cutting ants with broad spectrum characteristics of biological activities, and low environmental impact. In this work, the insecticide and fungicide profile of the extracts from P. glazioviana and P. bahiensis were evaluated. P. glazioviana showed a promising insecticidal activity to its ethanol extract, and to the dichloromethane (PGD) and ethyl acetate (PGA) phases. P. bahiensis, on the other hand, presented excellent activities to its extracts and fractions in both bioassays analyzed. These results encouraged the phytochemical study and isolation of the constituents present in both these species of plants. Thus, the study with P. bahiensis yielded the isolation of five known anthraquinones (chrysophanol, aloe-emodin, islandicin, pulmatin and chrysophanein) and two new anthrones C,O-diglycosides. In relation to P. glazioviana, from the PGD phase it was isolated twenty two new highly oxygenated nortriterpenes, compounds that present new chemical skeleton, and the biogenesis for the formation of these compounds was proposed. This is the first report of isolation of nortriterpenes in plants of the Picramniaceae family. Once it was discovered a new chemical skeleton of natural products, an achievement that brings huge contribution to the chemosystematics of this plant and to the chemistry of natural products as a whole. The HPLC-HRMS-SPE/NMR technique was also performed to this phase, allowing us to isolate and acquire excellent NMR spectra in few days of experiment, and high degree of purity for each compound. The PGD phase was also analyzed by high-resolution PTP1B, α-glucosidase and antibacterial bioassay. Although the construction of the biochromatogram has not indicated the presence of antidiabetic constituents in this phase, some constituents with antibacterial potential could be pinpointed through the biochromatogram against Staphylococcus aureus. This result is very promising regarding the discovery of new natural products with important biological activities. The high-resolution bioassay was also evaluated to the methanol extract from roots of P. bahiensis with the enzymes PTP1B and α-glucosidase, and some constituents could be pinpointed after the construction of the biochromatogram. Thus, this is the first work presenting the evaluation of Picramnia species exhibiting an antidiabetic potential.