Feeding and arrestment responses of Diabrotica speciosa to cucurbitacin-content formulations

The objective of this work was to evaluate arrestant and stimulant feeding effects on Diabrotica speciosa (Ger.), using cucurbitacin-content starch-based formulations prepared with varying starch sources, and adding potassium lignate. In a glass slide assay, the wash off resistance of formulations was compared. Potassium lignate did not improve wash off resistance. Lagenaria vulgaris L. powder, in which cucurbitacin B concentration was determined as 0.28%, was added to the most adhesive formulation. The resultant material was used in a two-choice assay in which leaves of common bean, Phaseolus vulgaris L., treated with concentrations of 2.5%, 5%, 10%, 15% and 20% were offered to insects together with untreated control leaves. Greater number of insects and leaves consumed were found on leaves treated with cucurbitacin-content formulation (2.5%, 5% - greatest response -, 10% and 15% concentrations) than on untreated control leaves. The concentration, in which responses were higher, was sprayed in a bean field at 1,000, 1,900 and 3,000 g ha-1. Greater number of beetles was found in plots treated with the highest dosage, 3 and 6 days after spraying. Ten days after spraying, no significant differences were found among dosages, probably due to washoff of the bait.

Investigating the Affects of Cucurbitacin-I on Cellular Motility

Cellular migration is an integral component of many biological processes including immune function, wound healing and cancer cell metastasis. A complete model illustrating the mechanism by which cells accomplish movement is still lacking. Exploring the affects of various drugs on cell motility may be instrumental in discovering new proteins which mediate cell movement. This project aims ultimately to characterize the molecular target of the drug Cucurbitacin-I, a natural plant product. This drug has been shown to inhibit migration of epithelial sheets and may have anti-tumor activity. In this paper, we show that Cucurbitacin-I inhibits the migration of MDCK and B16F1 cells. The drug also affects the integrity of the actin cytoskeleton of these cells by indirectly stabilizing filamentous actin. Cucurbitacin-I does not, however, have an effect on the motility or cytoskeletal morphology of the soil amoeba, Dictyostelium discoidium.

Cucurbitacinas e suas principais características estruturais

The cucurbitacins are highly oxygenated triterpenoid compounds found in several botanical families that show high toxicity and varied biological activities. This review presents the main cucurbitacins so far isolated and their key structural characteristics. It complements and updates the existing reviews on this subject.

DI-HIDROCUCURBITACINA B: SEMI-SÍNTESE DE NOVOS DERIVADOS GLICOSILADOS

In the last ten years, the interest in natural and semi-synthetic cucurbitacin derivatives has increased, primarily due their cytotoxic and anti-tumoral activities. However, the isolation of glycosylated cucurbitacins has been difficult due the presence of β-glucosidase enzyme. With the aim of obtaining new glycosylated derivatives, the glycosylation of dihydrocucurbitacin B under Köenigs-Knorr and imidate reaction conditions was studied. Novel glycoside derivatives 16-(1,2-orthoacetate-3,4,6-tri-O-acetyl-α-D-glucopyranosyl)-dihydrocucurbitacin B (2), 2-O-β-D-2,3,4,6-tetra-O-acetyl-galactopyranosyl dihydrocucurbitacin B (3) and 2-O-β-D-galactopyranosyl dihydrocucurbitacin B (4) were synthesized for the first time in 17% (2 and 3) and 48% (4) yields.