New inhibitors of homoserine dehydrogenase from Paracoccidioides brasiliensis presenting antifungal activity.

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by fungi of the genus Paracoccidioides spp., which mainly affects workers in rural regions of Latin America. Although the antifungal agents currently available for the treatment of PCM are effective in controlling the disease, many months are needed for healing, making the side effects and drug interactions relevant. In addition, conventional treatments are not able to control the sequelae left by PCM, even after the cure, justifying the search for new therapeutic options against PCM. In this context, the enzyme homoserine dehydrogenase of P. brasiliensis (PbHSD) was used to screen a library of natural products from the Zinc database using three different docking programs, i.e. Autodock, Molegro, and CLC Drugdiscovery Workbench. Three molecules (Zinc codes 2123137, 15967722, and 20611644) were better ranked than the homoserine substrate (HSE) and were used for in vitro trials of the minimum inhibitory concentration (MIC) and minimal fungicidal concentration (MCF). All three molecules presented a fungicidal profile with MICs/MCFs of 8, 32, and 128 µg mL-1, respectively. The two most promising molecules presented satisfactory results with wide therapeutic ranges in the cytotoxicity assays. Molecular dynamics simulations of PbHSD indicated that the ligands remained bound to the protein by a common mechanism throughout the simulation. The molecule with the lowest MIC value presented the highest number of contacts with the protein. The results presented in this work suggest that the molecule Zinc2123137 may be considered as a hit in the development of new therapeutic options for PCM.

Psychotria leiocarpa Extract and Vincosamide Reduce Chemically-Induced Inflammation in Mice and Inhibit the Acetylcholinesterase Activity.

Species from Psychotria are used in folk medicine against inflammatory diseases, respiratory disturbances, and anti-hallucinogenic. In the present study, the compound vincosamide (PL-1) was identified for the first time in methanolic extract of the Psychotria leiocarpa (ME-PL) leaves, as well as the anti-inflammatory and anticholinesteric effects in rodents and molecular docking simulations. The fractionation of the chloroform fraction (CF-PL) through chromatographic methods afforded the known compound PL-1. The anti-inflammatory activity of the ME-PL (30, 100, and 300 mg/kg) and PL-1 (3, 30, and 100 mg/kg) was analyzed using experimental models: paw edema, pleurisy, and mechanical and thermal hyperalgesia induced by carrageenan. The anticholinesterase activity of the ME-PL (30 and 100 mg/kg) and PL-1 (30 mg/kg) was showed by acetylcholinesterase (AChE) inhibitory in brain structures. The molecular docking simulations were performed using Molegro Virtual Docker v6.0. Overall, the results indicated that ME-PL and PL-1 demonstrated an anti-edematogenic effect in Cg-induced paw edema, leukocyte migration in the pleurisy model, and significantly reduced mechanical hyperalgesia, cold response to acetone in mice. The samples exhibited maximal inhibition of enzyme acetylcholinesterase (AChE) in the frontal cortex. The molecular coupling of PL-1 with the AChE showed significant interactions with the catalytic and peripheral site, corroborating the activity presented in the inhibition assay. The acute administration of ME-PL did not cause signs of toxicity in the treated animals. The results showed that P. leiocarpa inhibited AChE and anti-inflammatory activity, and alkaloid vincosamide could be responsible, at least in part, for the observed effects, supporting the popular use of this genus.