Synthesis and bioactivity of natural and C-3 fluorinated biosynthetic precursors of 28-homobrassinolide.

In this paper we describe the synthesis of two new fluorinated brassinosteroids: (22R,23R)-22,23-dihydroxy-3alpha-fluorostigmastan-6-one and (22R,23R)-22,23-dihydroxy-3beta-fluorostigmastan-6-one. Their bioactivities were evaluated in the rice lamina inclination test and compared with that of 28-homocastasterone, 28-homotyphasterol and 28-homoteasterone, possible biosynthetic precursors of 28-homobrassinolide. Results confirmed expected similarities between the biosynthesis of 24-ethylbrassinosteroids (named as the 28-homo series) and that described for 24-methylbrassinosteroids, and also indicated that these precursors might exhibit per se activities.

Synthesis and bioactivity evaluation of brassinosteroid analogs.

Four new analogs of 28-homocastasterone have been synthesized and completely characterized for the first time from stigmasterol. (22R, 23R,24S)-3beta-acetoxy-22,23-dihydroxy-5alpha-stigmastan+ ++-6-one (17), (22R,23R,24S)-3beta-bromo-22,23-dihydroxy-5alpha-stigmast an-6-one (18), (22R,23R,24S)-3beta-acetoxy-5,22, 23-trihydroxy-5alpha-stigmastan-6-one (20), and (22R,23R, 24S)-3beta-bromo-5,22,23-trihydroxy-5alpha-stigmastan-6-one (21), were obtained through a synthetic route based on regioselective Delta(5) epoxidation. Compounds 17 and 18, bearing a 5alphaH moiety, were prepared through a reductive opening of the 5beta,6beta epoxy precursor, and compounds 20 and 21, analogs with a 5alphaOH moiety were obtained by hydrolytic opening of a mixture of 5alpha,6alpha and 5beta,6beta epoxy precursors. Known compounds 19 and 22 were also obtained following the described synthetic routes, respectively. The new compounds were tested with the traditional auxin-like bioassay for brassinosteroids with 19 and 22 as standards. All compounds were comparatively evaluated for their inhibitory effect on the replication of DNA (HSV-1) virus.

Sulphur-containing derivatives structurally related to fenoxycarb are potent growth inhibitors against the intracellular form of Trypanosoma cruzi.

Sulphur-containing derivatives structurally related to the insect growth regulator fenoxycarb were shown to be extremely active antiproliferative agents against the amastigote form of Trypanosoma cruzi in in vitro assays. All of these drugs had previously been proved to be remarkably potent growth inhibitors against the epimastigote form of the parasite.

Mechanistic studies of the rearrangements of steroidal 16,17-ketols and syntheses of 20-->16-cis-gamma-carbolactones.

Utilization of 17-keto-androstanes as starting materials for the synthesis of alpha- or beta-oriented steroidal 20-->16-gamma-carbolactones has been explored following two different strategies. A highly efficient, stereospecific protocol has been developed for the beta-oriented cis-gamma-lactone. A different approach, involving prior attachment of a 3-carbon side chain on C-17 of a 17-oxo-16beta-acetoxyandrostane led to the epimeric, alpha-oriented lactone. The mechanism of the rearrangement of epimeric 16beta- or 16alpha-hydroxy-17-keto-androstanes to 17beta-hydroxy-16-keto-androstanes was studied by 13C NMR spectroscopy. The former occurs through a 1,2-sigmatropic H-shift, while the latter is likely to take place by simple enolization-reprotonation.

Structure-activity relationship of new growth inhibitors of Trypanosoma cruzi.

Several drugs bearing the 4-phenoxyphenoxy skeleton and other closely related structures were designed, synthesized, and evaluated as antiproliferative agents against Trypanosoma cruzi, the etiologic agent of Chagas' disease. The new class of drugs was envisioned by modifying the nonpolar 4-phenoxyphenoxy moiety replacing selected aromatic protons by different groups via electrophilic aromatic substitution reactions as well as introducing a sulfur atom at the polar extreme. Of the designed compounds, sulfur-containing derivatives were shown to be potent antireplicative agents against T. cruzi. Among these drugs, 4-phenoxyphenoxyethyl thiocyanate (compound 56) proved to be an extremely active growth inhibitor of the epimastigote forms of T. cruzi and displayed an IC50 of 2.2 microM. Under the same assay conditions, this drug was much more active than Nifurtimox, one of the drugs currently in clinical use to control this disease. This thiocyanate derivative was also a very active inhibitor against the intracellular form of the parasite at the nanomolar level. Other sulfur derivatives prepared also exhibited very potent antiproliferative action against T. cruzi. The presence of a sulfur atom at the polar extreme for this family of compounds seems to be very important for biological action because this atom was always associated with high inhibition values. 4-Phenoxyphenoxyethyl thiocyanate presents very good prospective not only as a lead drug but also as a potential chemotherapeutic agent.

Growth inhibitory effect of juvenile hormone analogues on epimastigotes of Trypanosoma cruzi.

Several compounds, structurally related to the insect growth regulator Fenoxycarb, exhibited interesting inhibition action to control proliferation of Trypanosoma cruzi, the parasite responsible for Chagas' disease. Some of these drugs were shown to be potent growth inhibitors of this parasite. All of these drugs had previously presented juvenoid activity on several non-related bug species such as Tenebrio molitor, Galleria mellonella, Dysdercus cingulatos, and Pyrrhocoris apterus.

Design, synthesis, and biological evaluation of new growth inhibitors of Trypanosoma cruzi (epimastigotes).

As a continuation of our project aimed at the search for new chemotherapeutic agents against Chagas' disease, several drugs structurally related to the insect growth regulator Fenoxycarb and the naturally occurring juvenile hormone of insects were designed, synthesized, and evaluated as antiproliferative agents against the parasite responsible of this disease. Isoprenoid derivatives (compounds 33, 34, 36, and 37) were potent growth inhibitors of Trypanosoma cruzi epimastigotes. In addition, taking into account the high activity observed for compound 30 and the inhibitory action of related compounds, the allyl ether moiety bonded at the polar extreme of these inhibitors proved to be a promising group for the design of new drugs.

The sterols of Cucurbita moschata ("calabacita") seed oil.

From the sterol fraction of seed oil from commercial Cucurbita moschata Dutch ("calabacita") delta 5 and delta 7 sterols having saturated and unsaturated side chain were isolated by chromatographic procedures and characterized by spectroscopic (1H and 13C-nuclear magnetic resonance, mass spectrometry) methods. The main components were identified as 24S-ethyl 5 alpha-cholesta-7,22E-dien-3 beta-ol (alpha-spinasterol); 24S-ethyl 5 alpha-cholesta-7,22E,25-trien-3 beta-ol (25-dehydrochondrillasterol); 24S-ethyl 5 alpha-cholesta-7,25-dien-3 beta-ol; 24R-ethyl-cholesta-7-en-3 beta-ol (delta 7-stigmastenol) and 24-ethyl-cholesta-7, 24(28)-dien-3 beta-ol (delta 7,24(28)-stigmastadienol).

Cyclopiazonic acid and aflatoxins production byAspergillus flavus isolated from Argentinian corn.

Thirty-four isolates ofAspergillus flavus obtained from the main Argentinian corn production area were tested for their ability to produce both cyclopiazonic acid (CPA) on corn and on liquid media and aflatoxins on corn.Aflatoxins and CPA were quantified by comparison with standards. The last one was confirmed by mass spectrometry.All but one of the isolates produced CPA on liquid medium in a range between 3120 to 62500 µg/kg, 27/34 isolates produced CPA on corn at levels ranging from 833 to 10000 µg/kg and 5/34 isolates produced aflatoxin B1 in a range between 29 to 115 µg/kg. According to these findings, the percentage ofAspergillus flavus isolates with CPA production ability and their levels of CPA production were higher than the observed elsewhere.It was observed significant differences (p<0,01) between CPA production on corn (median: 1761 µg/Kg) and in liquid medium (median: 27950 µg/Kg). These data represent the first report of the co-production of CPA and aflatoxin B1 by isolates ofAspergillus flavus obtained from corn in Argentina.

Cleavage reaction of 5 beta, 6 beta steroidal epoxides carrying different groups at C-3.

The particular behavior of 5 beta, 6 beta steroidal epoxides carrying different groups at C-3 was studied. These epoxides may exhibit different cleavage behavior according to the nature of the solvent, the acid-base state of the medium, and the leaving abilities of the C-3 substituent. Results and alternative mechanisms are presented.

Effects of juvenile hormone analogues (JHA) on the development of Trypanosoma cruzi.

Juvenile hormone analogues were tested for their lytic activity on Trypanosoma cruzi Chagas, 1909 blood tripomastigotes cultivated in vitro. The results indicated that the carbamate 4 and the phenoxyphenol derivative 1 are considered good candidates for blood sterilization. The compounds were also assayed for inhibition of development of parasites in infected mice showing a moderated degree of activity.

Effects of juvenile hormone on mammalian steroidogenesis.

The effects of juvenile hormone-III (JH-III) and the JH analogue 2-(4-phenoxyphenoxy)-ethoxyte-trahydropiran on testicular steroidogenesis were studied. By using cultured MA-10 Leydig tumor cells as a model, these compounds were found to be potent inhibitors of LH/hCG steroidogenic action in a dose-dependent manner. Scatchard plot analysis of the binding data indicated that the JH analogue did not significantly alter the affinity nor the number of hCG binding sites, as well as GTP binding to plasma membranes. JH analogue inhibited the stimulatory action of both cholera toxin and forskolin on cAMP production and the concomitant steroidogenic response. JH analogue inhibited (Bu)2cAMP-stimulated progesterone synthesis, indicating that a process downstream to the adenylyl cyclase in the steroidogenic pathway is also affected.

Corticosteroidogenesis in the toad Bufo arenarum H: evidence for a precursor role for an aldosterone 3 beta-hydroxy-5-ene analogue (3 beta, 11 beta, 21-trihydroxy-20-oxo-5-pregnen-18-al).

A material isolated following pregnenolone incubations with toad (Bufo arenarum) inter-renal tissue at 28 degrees C has been identified as a 3 beta-hydroxy-5-ene analogue of aldosterone (3 beta, 11 beta, 21-trihydroxy-20-oxo-5-pregnen-18-al). The initial identification was made by enzymic and m.s. methods, and structural confirmation was achieved through comparison with chemically synthesized authentic material. The relative efficacy of corticosterone, 18-hydroxycorticosterone and the 3 beta-hydroxy-5-ene aldosterone analogue as aldosterone precursors was evaluated. In the in vitro situation studied, the 3 beta-hydroxy-5-ene steroid was by far the best precursor.

Alkaloids from bufonid toads (Melanophryniscus): decahydroquinolines, pumiliotoxins and homopumiliotoxins, indolizidines, pyrrolizidines, and quinolizidines.

Skins of bufonid toads of the genus Melanophryniscus contain several classes of alkaloids: decahydroquinolines, pumiliotoxins, allopumiliotoxins, homopumiliotoxins, both 3,5- and 5,8-disubstituted indolizidines, 3,5-disubstituted pyrrolizidines, and a 1,4-disubstituted quinolizidine. Tricyclic alkaloids, including precoccinelline [193A] and alkaloid 236, an oxime methyl ether, are present in one population of Melanophryniscus stelzneri.

A pregnane glycoside from the roots of Mandevilla pentlandiana.

A pregnane triglycoside containing a new genin 3 beta,14 beta-dihydroxy-21-methoxy-5 beta-pregnan-20-one has been isolated from the dried roots of Mandevilla pentlandiana. Chemical and spectroscopic evidence for the glycoside are consistent with the structure 3 beta, 14 beta-dihydroxy-21-methoxy-5 beta-pregnan-20-one-3-O-beta-D- diginopyranosyl-(1----4)-O-beta-D-cymaropyranosyl-(1----4)-O -beta-D-cymaropyranoside. It is noteworthy that 3 beta,14 beta,21-trihydroxy 5 beta-pregnan-20-one, biosynthetically related to the genin of this glycoside, has been proved to be a precursor of cardenolides, also produced by this plant.

Carbon-13 nuclear magnetic resonance spectral data of steroidal vicinal ketols and related compounds.

Carbon-13 nuclear magnetic resonance spectra for 31 3 beta-hydroxy and acetoxy androstane derivatives bearing vicinal oxygenated functions at ring D with and without oxygenated functions at C-6 are reported. Relative substituent effects are discussed.

Síntesis, controles químicos y radioquímicos del "mebrofenin-Tc-99m": estudios radiofarmacológicos y usos en seres humanos / Synthesis, chemical and radiochemical cotrols of mebrofenin-Tc-99m: radiopharmacological studies and uses in humans

En este trabajo se presenta el estudio químico radiofarmacológico y el uso en seres humanos realizado con el "mebrofeini-Tc-99m". La finalidad del trabajo fue determinar el uso potencial de este radiofármaco en seres humanos portadores de distintas entidades clínico patológicas. Para esto, se sintetizó el producto mejorando el rendimiento de reacción, mediante una modificación en la segunda etapa del camino de síntesis, lo que condujo a elevarlo del 70 al 90%. Se determinó la cinética plasmática mediante la circulación extracorpórea realizada en ratas wistar, mientras que la hepática y renal se llevó a cabo en ratones endocriados. Todos los resultados fueron analizados mediante un procesador, obteniéndose las vidas medias plasmáticas y los máximos tiempos de captación (AU)

Síntesis, controles químicos y radioquímicos del "mebrofenin-Tc-99m": estudios radiofarmacológicos y usos en seres humanos / Synthesis, chemical and radiochemical cotrols of mebrofenin-Tc-99m: radiopharmacological studies and uses in humans

En este trabajo se presenta el estudio químico radiofarmacológico y el uso en seres humanos realizado con el "mebrofeini-Tc-99m". La finalidad del trabajo fue determinar el uso potencial de este radiofármaco en seres humanos portadores de distintas entidades clínico patológicas. Para esto, se sintetizó el producto mejorando el rendimiento de reacción, mediante una modificación en la segunda etapa del camino de síntesis, lo que condujo a elevarlo del 70 al 90%. Se determinó la cinética plasmática mediante la circulación extracorpórea realizada en ratas wistar, mientras que la hepática y renal se llevó a cabo en ratones endocriados. Todos los resultados fueron analizados mediante un procesador, obteniéndose las vidas medias plasmáticas y los máximos tiempos de captación

Cyclic biospecific affinity chromatographic method for the purification of the sex steroid binding protein (SBP): application to the purification of SBP from toad.

A novel biospecific affinity chromatographic procedure was developed for the purification of the sex steroid binding protein from Bufo arenarum. A charcoal column connected in series to the affinity column allows the removal of any ligand non-covalently bound to the matrix or released during its storage, thus avoiding the need for exhaustive and prolonged washing procedures. In addition, it is not necessary to remove the endogenous ligand from the starting material and the binding to the affinity column can be monitored to determine the time required to achieve the maximum yield. The advantages are the charcoal adsorption of the ligand "washed" from the affinity column by the protein to be purified and the amplification provided by the cyclic use of the system. The procedure improves the yield from less than 1% (by conventional procedures) to more than 50%. With minor modifications this procedure can be useful for the purification of binding proteins and receptors.