Synthesis and cytotoxic activity evaluation of dihydrocucurbitacin B and cucurbitacin B derivatives.

Two cucurbitacins, dihydrocucurbitacin B (1) and cucurbitacin B (2), which can be obtained in large amounts from the roots of Wilbrandia ebracteata and from the fruits of Luffa operculata, respectively, were used as starting materials for the preparation of a library of 29 semi-synthetic derivatives. The structural changes that were performed include the removal, modification or permutation of functional groups in rings A and B as well as in the side chain. All new semisynthetic compounds, as well as 1 and 2, were tested in vitro for their cytotoxic effects on non-small-cell lung cancer cells (A549 cells). Some of these compound displayed potent to moderate activity against A549 tumor cells, especially those cucurbitacin B derivatives which were modified at ring A.

Anti-leukemic activity of semisynthetic derivatives of lupeol.

In our previous work, lupeol was isolated from aerial parts of V. scorpioides and modified by semisynthetic approach. The purpose of this study was to investigate the cytotoxicity of lupeol and its derivatives previously prepared on the human K562 acute myeloid leukemia cell and human Jurkat acute lymphoid leukemia cell in vitro. Compounds 3ß-hydroxylup-20(29)-en-30-al (2), lup-20(30)-en-3ß,29-diol (3), 3ß-acetoxylup-20(29)-en-30-al (5) and 3ß-acetoxy-30-hydroxylup-20(29)-ene (6) presented cytotoxicity with IC50 ranging from 11.72 to 56.15 µM at 24 h of incubation for both cell lines. Most of the active compounds (3, 5 and 6) were selective to leukemia cells, in compare with healthy cells. The hemolysis assay showed high blood compatibility of the cytotoxic lupeol derivatives which makes possible an intravenous administration of these compounds aiming to the potential to development of anti-leukemic drugs.

Chemical modification produces species-specific changes in cucurbitacin antifeedant effect.

Cucurbitacins are secondary metabolites that mediate insect plant interactions not only as allomones against generalists but also as kairomones for specialist herbivores. This study was undertaken to identify the potential of cucurbitacin derivatives as insect antifeedant agents. The antifeedant capacity against a Cucurbitaceae specialist [ Epilachna paenulata (Coleoptera: Coccinellidae)] and a polyphagous insect [ Pseudaletia adultera (Lepidoptera: Noctuidae)] was evaluated in preference tests in which the insects were given a choice between food plants either treated with the cucurbitacin derivatives or treated with the solvent. The activity was found not to be related to the basic cucurbitacin skeleton, as only 15 of the 28 tested cucurbitacin derivatives were active. Only one of the tested compounds was phagostimulant to the specialist insect (the hemissuccinate of 16-oxo-dihydrocucurbitacin B derivative), while all other active derivatives were deterrent against one of the insects (13 compounds) or both of them (3 compounds). Changes in ring A of the cucurbitacins, as well as in the side chain, modified the activity. As a general trend, when chemical modifications of the basic structure produced a change in activity, the response was opposite in both insects used as biodetectors, indicating that a selective variation in the activity may be achieved by chemical modifications of the cucurbitacin skeleton.