Di- and sesquiterpenoids from Cystoseira genus: structure, intra-molecular transformations and biological activity.

Natural products have been the single most productive source of leads for the development of drugs, because of the great variety of their chemical structures. Previous chemical investigation of members of the genus Cystoseira resulted in the discovery of various bioactive secondary metabolites. The secondary metabolites isolated and characterized are very interesting, both from the biological activity and structural complexity points of view, which make this genus an attractive target for further investigations. The present review covers the research progress on natural products isolated from this genus since January 1995 until now, concerning the isolation and structural elucidation of the secondary metabolites from Cystoseira species. In this contribution significant biological properties are briefly discussed. Simultaneously, we gradually construct an intra-molecular pathway that logically interrelates the isolated compounds.

A new natural spiro heterocyclic compound and the cytotoxic activity of the secondary metabolites from Juniperus brevifolia leaves.

A new natural spiro compound 3,4-dehydrotheaspirone and the known arctiol [1ß,6α-dihydroxy-4(14)-eudesmene] were isolated from Juniperus brevifolia. Arctiol is reported for the first time in the Juniperus genus. Their structures were established by 1D, and 2D NMR and MS spectra. Antimicrobial and cytotoxic activities of 1 and several secondary metabolites 3,4,5,6,7,8,9,10,11,12 previously isolated by our group from J. brevifolia were evaluated and some SAR has been established. The 18-hydroxydehydroabietane (4) displayed great antiproliferative activity against cancer cell lines tested, namely HeLa, A-549 and MCF-7. Compound 4 also presented a significant bactericidal effect against Bacillus cereus at different concentrations tested.

Cytotoxic activity of diterpenes and extracts of Juniperus brevifolia.

The hexane, dichloromethane, acetone and ethanol extracts of the leaves, bark and wood of Juniperus brevifolia were subjected to screening against human tumour cells lines from the cervix (HeLa) and larynx (Hep-2) in two different stages of the cell cycle. The dichloromethane and the chloroform-soluble portions of the acetone extracts of the leaves were active against both tumour cell lines. Chemical investigation of one of the most active extracts (dichloromethane extract from leaves) by preparative chromatography afforded compounds 1-10. Among these, compounds 1-3 were isolated for the first time from the Juniperus genus (18-hydroxyferruginol, 6,7-dehydrototarol and 7alpha-hydroxytotarol) while 4 and 5 are rare as natural products corresponding to (E)- and (Z)-isomers of 8alpha-hydroxy-labda-13(16),14-dien-19-yl-coumarate, respectively. The structures of all compounds were established based on various spectral data. The cytotoxic activity was evaluated for the first time for compounds 1-5 against HeLa and Vero cell lines in lag and log phases of growth. Compound 5 was shown to be active and selective to HeLa in the log phase.

Diagnosis of enzyme inhibition based on the degree of inhibition.

In this work, a method for the diagnosis of kinetic inhibition, based on the dependence of the degree of inhibition (epsilon(i)) on the inhibitor concentration [I] and on the substrate concentration [S], is presented. Because the degree of inhibition is a ratio between rates, kinetic data are normalized by the introduction of an internal control-the rate of the uninhibited reaction. Therefore, the error associated with the kinetic measurements decreases and less experimental measurements are necessary to achieve the diagnosis. The process described, which uses graphical and/or non-linear fitting procedures, allows distinguishing between 20 different kinds of inhibition, including not only linear and hyperbolic, but also parabolic and rational 2,2 inhibitions. Rational 2,2 indicates a new type of inhibition corresponding to an incomplete parabolic inhibition, i.e. mechanistically it corresponds to an inhibitor that binds to two inhibition sites producing enzymatic complexes that are still active. In spite of its comprehensiveness, the diagnosis process is greatly facilitated by the division of the diagnosis of the inhibition in a step-by-step procedure, where only two rival models are evaluated in each step. In the non-linear fittings, the choice between rival models uses a test based on information statistics theory, the Akaike information criterion test, in order to penalize complex models that tend to be favoured in fittings. Finally, equations that allow the determination of inhibition kinetic constants were also deduced. The formalism presented was tested by examining inhibition of acid phosphatase by phosphate (a linear competitive inhibitor).

Inhibition of mouse liver respiration by Chelidonium majus isoquinoline alkaloids.

The alkaloids from Chelidonium majus L. which had a significant inhibitory effect in mitochondrial respiration were those which contain a positive charge due to a quaternary nitrogen atom, i.e., chelerythrine, sanguinarine, berberine and coptisine, both with malate+glutamate or with succinate as substrates. When malate+glutamate was used as substrate, chelerythrine and berberine, which contain methoxy groups, were particularly more active, since they had a strong effect even at low concentrations. In submitochondrial particles, berberine and coptisine had a marked inhibitory effect on NADH dehydrogenase activity but practically no effect on succinate dehydrogenase activity, whereas chelerythrine and sanguinarine inhibited more strongly succinate dehydrogenase than NADH dehydrogenase, which is in agreement with the results found for mitochondrial respiration. Protopine and allocryptopine, which did not inhibit mitochondrial respiration, strongly inhibited NADH dehydrogenase in submitochondrial particles, but had no effect on succinate dehydrogenase activity.