Asymmetric synthesis and evaluation of epoxy-α-acyloxycarboxamides as selective inhibitors of cathepsin L.

Cathepsin L plays important roles in physiological processes as well as in the development of many pathologies. Recently the attentions were turned to its association with tumor progress what makes essential the development of more potent and selective inhibitors. In this work, epoxipeptidomimetics were investigated as new cathepsin inhibitors. This class of compounds is straightforward obtained by using a green one-pot asymmetric epoxidation/Passerini 3-MCR. A small library of 17 compounds was evaluated against cathepsin L, and among them LSPN423 showed to be the most potent. Investigations of the mechanism suggested a tight binding uncompetitive inhibition.

Identification of Meliatoxins in Melia azedarach Extracts Using Mass Spectrometry for Quality Control.

Indiscriminate use of synthetic pesticides can be hazardous to both humans and the environment, but the use of natural products as a source of bio-based products, such as Melia azedarach extracts, is an interesting approach to overcome these hazards. Unfortunately, the limonoids found in M. azedarach with desired insecticidal properties (e.g. azadirachtin) may also be present with limonoids toxic to mammals. The goal of this report was to develop a fast and reliable MS-based experiment to characterize meliatoxins in crude extracts of M. azedarach, in order to provide unequivocal assessment of the safety for extracts for application in the field. MS and MS/MS experiments using MALDI ionization were evaluated as tools for the assignment of characteristic ions produced by each meliatoxin in crude extracts.The use of different experiments in combination, such as the analysis of fragment m/z 557 and [M + Na]+ (adducts ions m/z 681 and m/z 667), MALDI-MS can be used for detection of meliatoxins A1/B1 or A2/B2 in a crude extract and may be used to discriminate meliatoxins A from B, respectively. Subsequent MS/MS experiments can distinguish between the presence of group 1 and/or 2 in each class of meliatoxins classifying the proposed approach as a quick and efficient quality control method of meliatoxins in real M. azedarach samples.

New approach for natural products screening by real-time monitoring of hemoglobin hydrolysis using quartz crystal microbalance.

The hemoglobin (Hb) released from erythrocytes is a primary nutritive component for many blood-feeding parasites. The aspartic protease cathepsin D is a hemoglobinase that is involved in the Hb degradation process and is considered an interesting target for chemotherapy intervention. However, traditional enzymatic assays for studying Hb degradation utilize spectrophotometric techniques, which do not allow real-time monitoring and can present serious interference problems. Herein, we describe a biosensor using simple approach for the real-time monitoring of Hb hydrolysis as well as an efficient screening method for natural products as enzymatic inhibitors using a quartz crystal microbalance (QCM) technique. Hemoglobin was anchored on the quartz crystal surface using mixed self-assembled monolayers. The addition of the enzyme caused a mass change (frequency shift) due to Hb hydrolysis, which was monitored in real time. From the frequency change patterns of the Hb-functionalized QCM, we evaluated the enzymatic reaction by determining the kinetic parameters of product formation (k(cat)). The QCM enzymatic assay using immobilized human Hb was shown to be an excellent approach for screening possible inhibitors in complex mixtures, opening up a new avenue for the discovery of novel inhibitors.