Latex constituents from Calotropis procera (R. Br.) display toxicity upon egg hatching and larvae of Aedes aegypti (Linn.)

Calotropis procera R. Br. (Asclepiadaceae) is a well-known medicinal plant with leaves, roots, and bark being exploited by popular medicine to fight many human and animal diseases. This work deals with the fractionation of the crude latex produced by the green parts of the plant and aims to evaluate its toxic effects upon egg hatching and larval development of Aedes aegypti. The whole latex was shown to cause 100% mortality of 3rd instars within 5 min. It was fractionated into water-soluble dialyzable (DF) and non-dialyzable (NDF) rubber-free materials. Both fractions were partially effective to prevent egg hatching and most of individuals growing under experimental conditions died before reaching 2nd instars or stayed in 1st instars. Besides, the fractions were very toxic to 3rd instars causing 100% mortality within 24 h. When both fractions were submitted to heat-treatment the toxic effects were diminished considerably suggesting low thermostability of the toxic compounds. Polyacrylamide gel electrophoresis of both fractions and their newly fractionated peaks obtained through ion exchange chromatography or desalting attested the presence of proteins in both materials. When submitted to protease digestion prior to larvicidal assays NDF lost most of its toxicity but DF was still strongly active. It may be possible that the highly toxic effects of the whole latex from C. procera upon egg hatching and larvae development should be at least in part due to its protein content found in NDF. However the toxicity seems also to involve non protein molecules present in DF

Antinociceptive activity and toxicology of the lectin from Canavalia boliviana seeds in mice

The aim of the present study was to evaluate the potential antinociceptive and toxicity of Canavalia boliviana lectin (CboL) using different methods in mice. The role of carbohydrate-binding sites was also investigated. CboL given to mice daily for 14 days at doses of 5 mg/kg did not cause any observable toxicity. CboL (1, 5, and 10 mg/kg) administered to mice intravenously inhibited abdominal constrictions induced by acetic acid and the two phases of the formalin test. In the hot plate and tail immersion tests, the same treatment of CboL induced significant increase in the latency period. In the hot plate test, the effect of CboL (5 mg/kg) was reversed by naloxone (1 mg/kg), indicating the involvement of the opioid system. In the open-field and rota-rod tests, the CboL treatment did not alter animals` motor function. These results show that CboL presents antinociceptive effects of both central and peripheral origin, involving the participation of the opioid system via lectin domain.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Fundacao Cearense de Amparo a Pesquis

Structural Studies of an Anti-Inflammatory Lectin from <i>Canavalia boliviana</i> Seeds in Complex with Dimannosides

<div><p>Plant lectins, especially those purified from species of the Leguminosae family, represent the best-studied group of carbohydrate-binding proteins. Lectins purified from seeds of the <i>Diocleinae</i> subtribe exhibit a high degree of sequence identity notwithstanding that they show very distinct biological activities. Two main factors have been related to this feature: variance in key residues influencing the carbohydrate-binding site geometry and differences in the pH-dependent oligomeric state profile. In this work, we have isolated a lectin from <i>Canavalia boliviana</i> (Cbol) and solved its x-ray crystal structure in the unbound form and in complex with the carbohydrates Man(α1-3)Man(α1-O)Me, Man(α1-4)Man(α1-O)Me and 5-bromo-4-chloro-3-indolyl-α-D-mannose. We evaluated its oligomerization profile at different pH values using Small Angle X-ray Scattering and compared it to that of Concanavalin A. Based on predicted pKa-shifts of amino acids in the subunit interfaces we devised a model for the dimer-tetramer equilibrium phenomena of these proteins. Additionally, we demonstrated Cbol anti-inflammatory properties and further characterized them using <i>in vivo</i> and <i>in vitro</i> models.</p></div

The pH-dependent oligomerization of ConA and Cbol determined with SAXS.

<p>The pH-dependent oligomerization of ConA and Cbol determined with SAXS.</p

2F_obs - F_calc electron density maps from the carbohydrates contoured at 1.0 σ.

<p>(<b>A</b>) Xman. (<b>B</b>) Man(α1-3)Man(α1-O)Me, (<b>C</b>) Man(α1-4)Man(α1-O)Me.</p

Chemotaxis assay of human neutrophils incubated in the presence of Cbol.

<p>Cells were allowed to migrate in the Boyden chamber toward the medium alone or IL-8. Cells were pre incubated with different concentrations of CboL. Data show means ± SD from three independent experiments performed in triplicate.</p

Hydrophobic subsite of Cbol.

<p>M14M (shown as yellow sticks) performs one more hydrogen bond with Tyr12 (shown as blue sticks) when compared to M13M (shown as green sticks).</p