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At least 19 recordsLinked to original sources
PubMed2005

Pro-erectile effects of an alkaloidal rich fraction from Aspidosperma ulei root bark in mice.

In recent years, there has been a renewed interest in the search for novel natural substances active against erectile dysfunction. Plants that belong to the genus Aspidosperma (Apocyanaceae) are known to be very rich in indole alkaloids and have an ethnomedical history of use as traditional remedies for erectile dysfunction. This study examined whether the indole alkaloidal rich fraction (F(3-5)) from Aspidosperma ulei Markgr. root bark could manifest penile erection-related behavioral responses (penile erection, erection-like and genital grooming) in mice. Intraperitoneal injection of F(3-5) (25 and 50mg/kg) elicited all the three different behavioral responses in a manner similar to yohimbine (2mg/kg, i.p.), a known indole alkaloid. Seventy-five percent of mice treated with yohimbine or F(3-5) showed penile erections, which were completely blocked by clonidine, an alpha-2-adrenoceptor agonist and haloperidol, a dopaminergic antagonist and as well as by l-NAME, a nitric oxide synthase inhibitor. These results point out that F(3-5) facilitates penile erection in mice possibly through the activation of central dopamine and blockade of presynaptic alpha-2 adrenoceptors with a subsequent enhancement in nitric oxide release from the penile nerves and arteries. This study further supports the traditional use of extracts from Aspidosperma species in erectile dysfunction.

Animals↗
PubMed2002

An efficient approach to Aspidosperma alkaloids via [4 + 2] cycloadditions of aminosiloxydienes: stereocontrolled total synthesis of (+/-)-tabersonine. Gram-scale catalytic asymmetric syntheses of (+)-tabersonine and (+)-16-methoxytabersonine. Asymmetric syntheses of (+)-aspidospermidine and (-)-quebrachamine.

Described is a concise, highly stereocontrolled strategy to the Aspidosperma family of indole alkaloids, one that is readily adapted to the asymmetric synthesis of these compounds. The strategy is demonstrated by the total synthesis of (+/-)-tabersonine (rac-1), proceeding through a 12-step sequence. The basis for this approach was provided by a highly regio- and stereoselective [4 + 2] cycloaddition of 2-ethylacrolein with 1-amino-3-siloxydiene developed in our laboratory. Subsequent elaboration of the initial adduct into the hexahydroquinoline DE ring system was accomplished efficiently by a ring-closing olefin metathesis reaction. A novel ortho nitrophenylation of an enol silyl ether with (o-nitrophenyl)phenyliodonium fluoride was developed to achieve an efficient, regioselective introduction of the requisite indole moiety. The final high-yielding conversion of the ABDE tetracycle into pentacyclic target rac-1 relied on intramolecular indole alkylation and regioselective C-carbomethoxylation. Our approach differs strategically from previous routes and contains built-in flexibility necessary to access many other members of the Aspidosperma family of indole alkaloids. The versatility of the synthetic strategy was illustrated through the asymmetric syntheses of the following Aspidosperma alkaloids: (+)-aspidospermidine, (-)-quebrachamine, (-)-dehydroquebrachamine, (+)-tabersonine, and (+)-16-methoxytabersonine. Of these, (+)-tabersonine and (+)-16-methoxytabersonine were synthesized in greater than 1-g quantities and in enantiomerically enriched form ( approximately 95% ee). The pivotal asymmetry-introducing step was a catalyzed enantioselective Diels-Alder reaction, which proceeded to afford the cycloadducts in up to 95% ee. Significantly, the synthetic sequence was easy to execute and required only four purifications over the 12-step synthetic route.

Alkaloids↗
PubMed2002

An extract from the bark of Aspidosperma quebracho blanco binds to human penile alpha-adrenoceptors.

PURPOSE: We determined whether an extract from the bark of the tree Aspidosperma quebracho blanco, which is used as a prescription drug to treat erectile dysfunction in some countries, can bind to human penile alpha1 and alpha2-adrenoceptors, and cloned human alpha-adrenoceptor subtypes. MATERIALS AND METHODS: Competition binding studies were performed with alpha1 and alpha2-adrenoceptors with the extract and 4 subfractions prepared from it using [3H]prazosin (New England Nuclear, Dreieich, Germany) and [3H]RX 821002 (2-methoxy-idazoxam) (Amersham, Braunschweig, Germany) as the radioligands, respectively. RESULTS: In a concentration dependent manner the extract inhibited 2-methoxy-idazoxam binding to human penile alpha2-adrenoceptors. Somewhat less potently it inhibited [3H] prazosin binding to penile alpha1-adrenoceptors. The extract also inhibited binding to cloned alpha2-adrenoceptors more potently than to alpha1-adrenoceptors but did not discriminate among subtypes. Subfraction B was more potent than the others for all cloned alpha1-adrenoceptor subtypes and much more potent at all penile and all cloned alpha2-adrenoceptor subtypes. This fraction largely contained yohimbine, whereas the other fractions were devoid of yohimbine. Based on yohimbine competition binding experiments with penile and cloned alpha1 and alpha2-adrenoceptors, it appears that the inhibitory effects of the abstract and its subfractions can largely be explained by its yohimbine content. CONCLUSIONS: An alpha-adrenoceptor mediated component of the pro-erectile effects of Aspidosperma quebracho blanco bark extract may predominantly be caused by its yohimbine content. The alpha-adrenoceptor independent, pro-erectile effects of the extract could not be determined from this study.

Aspidosperma↗
PubMed2006

Antileishmanial activity of indole alkaloids from Aspidosperma ramiflorum.

The present study was designated to evaluate the antileishmanial activity of acid and basic fractions that were obtained after acid-basic extraction, from ethanolic 70% crude extract and pure compounds from the stem bark of Aspidosperma ramiflorum. The basic alkaloidal fraction presented a good activity against the extracellular form (promastigotes) of Leishmania (L.) amazonensis (LD(50) value<47 microg/ml). Based on these findings, the basic fraction was fractionated on silica gel column chromatography in a bioassay-guided fractionation affording individual purified ramiflorines A and B. Both ramiflorines A and B showed significant activity against Leishmania (L.) amazonensis (LD(50) values of 16.3+/-1.6 microg/ml and 4.9+/-0.9 microg/ml, respectively). Our results are promising, showing that these compounds are biologically active against Gram-positive bacteria.

Animals↗
PubMed2002

Total synthesis of (+)-aspidospermidine: a new strategy for the enantiospecific synthesis of aspidosperma alkaloids.

A new strategy was developed for the enantiospecific synthesis of aspidosperma alkaloids. The key steps involve a novel ketene-lactonization reaction of a chiral vinyl sulfoxide to efficiently set up the quaternary carbon center, and a tandem Michael addition-alkylation reaction sequence to form the polycyclic core structure. This new strategy was employed in the total synthesis of natural product (+)-aspidospermidine.

Alkaloids↗
PubMed2002

Subincanadines A-C, novel quaternary indole alkaloids from Aspidosperma subincanum.

Three novel quaternary indole alkaloids with an unprecedented 1-azoniatricyclo[4.3.3.0(1,5)]undecane moiety, subincanadines A-C (1-3), as well as two new indole alkaloids with a 1-azabicyclo[5.2.2]undecane moiety, subincanadines D (4) and E (5), and a new indole alkaloid with a 1-azabicyclo[4.3.1]decane moiety, subincanadine F (6), have been isolated from the barks of Aspidosperma subincanum Mart, and the structures of 1-6 and the stereochemistry of 1-3 were elucidated by spectroscopic data and chemical means.

Aspidosperma↗
PubMed2005

Revisiting a classic approach to the Aspidosperma alkaloids: an intramolecular Schmidt reaction mediated synthesis of (+)-aspidospermidine.

[reaction: see text] A total synthesis of (+)-aspidospermidine (1) is described. The key reactions used in the synthesis of this pentacyclic Aspidosperma alkaloid were a deracemizing imine alkylation/Robinson annulation sequence, a selective "redox ketalization", and an intramolecular Schmidt reaction. A Fischer indolization step carried out on a tricyclic ketone mirrored the sequence reported by Stork and Dolfini in their classic aspidospermine synthesis.

Alkaloids↗