Rafael Estévez-Reyes

Isokaerophyllin, a butyrolactone from Bupleurum salicifolium

Abstract From the leaves of Bupleurum salicifolium two benzylidene-benzyl-γ-butyrolactone-type lignans were isolated. One was identified as kaerophyllin, the other as its cis-isomer, hitherto unreported. The latter was characterized as 2(3,4-dimethoxy)-benzylidene-3-(3,4-dioxymethyl)-phenylmethyl-3 S-γ-butyrolactone by spectroscopic chemical methods, and from a study of its derivatives.

Lignanolides from bupleurum salicifolium

Abstract Three new lignans isolated from the roots of Bupleurum salicifolium were characterised as guamarol, isoguamarol and guamarolin on the basis of chemical and spectral evidence. The known lignans, kaerophyllin, isokaerophyllin and matairesinol, were also obtained.

Macrocarpins A-D, new cytotoxic nor-triterpenes from Maytenus macrocarpa

Macrocarpins A (1), B (2), C (3) and D (4), four new nor-triterpenes, have been isolated from the roots of Maytenus macrocarpa. The structures were established by spectroscopic examinations. Natural compounds 1, 2, 4 and the acetyl derivative 1a are cytotoxic against four tumoral cell lines with IC50 values ranging between 0.4 and 5.2 microM.

Structural elucidation and conformational analysis of new lignan butenolides from the leaves of Bupleurum salicifolium

Abstract From the leaves of Bupleurum salicifolium two new benzylidene-benzyl-γ-butyrolactone-type lignans salicifoline ( 2 ) and isosalicifoline ( 3 ) were isolated. The dibenzyl-butyrolactone (-)-epinortrachelogenin ( 1 ) was also isolated and it is the first time than this lignan has been obtained from a natural source. Their structures were determined by means of 1 H and 13 C NMR spectroscopic studies, including 1 H- 13 C heteronuclear correlation (HETCOR), long range correlation spectra with inverse detection (HMBC), and chemical evidence. A study of the conformational analysis of these lignans using Molecular Mechanics Calculations is also included.

Inhibition of potato cyst nematode hatch by lignans fromBupleurum salicifolium (Unbelliferae)

A series of lignans fromBupleurum salicifolium Soland (Umbelliferae) were tested for nematostatic activity on the cysts and freed secondstage juveniles of the potato cyst nematodesGlobodera rostochiensis andG. pallida. None of the six lignans tested—bursehernin, matairesinol, syringaresinol, the novel product buplerol, guayarol, and a derivative, nortrachelogenin triacetate—showed nematicidal activity in an in vitro analysis with second-stage juveniles, but significant differences were noted when the lignans were assayed for nematostatic activity as cyst hatching inhibitors. Bursehernin and matairesinol showed the greatest activity, at concentrations of 50 ppm. This is the first known instance of a natural product inhibiting the hatch of the nematodeG. pallida. The HID (hatching inhibiting dose) of bursehernin was estimated, and some conclusions were drawn about the structure-activity relationships of the lignans under study.

13C NMR assignments of some dibenzyl-γ-butyrolactone lignans

Abstract 1 H 13 C heteronuclear correlation and long-range correlation spectra with inverse detection, allowed the unequivocal assignment of 13 C spectra of some dibenzyl-γ-butyrolactones isolated from Bupleurum salicifolium .

Oxidation of natural targets by dimethyl dioxirane: Regio and stereospecific reactions on enol double bond of bioactive nor quinone methide triterpenes

Abstract Nor quinone methide triterpenes, like pristimerin and tingenone, possess one enol double bond (C 3 –C 4 ). They also have an extended conjugation with an additional double bond (C 7 –C 8 ). When these compounds are treated with dimethyl dioxirane, regio and stereoespecific oxidation occurs only on the enol double bond.