(4-->6)-Coupled proteracacinidins and promelacacinidins from Acacia galpinii and Acacia caffra

The series of naturally occurring proanthocyanidins with 7,8-dihydroxylated A-rings is extended by identification of the proteracacinidins epioritin-(4beta-->6)-oritin-4alpha-ol, epioritin-(4beta-->6)-ent-oritin-4alpha-ol, ent-oritin-(4beta-->6)-epioritin-4alpha-ol, ent-oritin-(4beta-->6)-oritin-4alpha-ol, ent-oritin-(4alpha-->6)-epioritin-4alpha-ol, ent-oritin-(4alpha-->6)-oritin-4alpha-ol, ent-oritin-(4alpha-->6)-epioritin-4beta-ol, the 'mixed' pro-teracacinidins/-melacacinidins epioritin-(4beta-->6)-epimesquitol-4alpha-ol, epioritin-(4beta-->6)-epimesquitol-4beta-ol and epimesquitol-(4beta-->6)- epioritin-4alpha-ol, and the promelacacinidin epimesquitol-(4beta-->6)-epimesquitol-4beta-ol.     

Trimeric proteracacinidins and a (6-->6)-bis-leucoteracacinidin from Acacia galpinii and Acacia caffra

The rare series of trimeric proteracacinidins is extended by identification of the first analogs with exclusive C-C interflavanyl bonds, i.e. epioritin-(4beta-->6)-oritin-(4alpha-->6)-epioritin-4alpha-ol,oritin-(4beta-->6)-oritin-(4alpha-->6)-epioritin-4alpha-ol, and epioritin-(4beta-->6)-epioritin-(4beta-->6)-epioritin-4alpha-ol. These compounds are accompanied by the bis-leucoteracacinidin, epioritin-4alpha-ol-(6-->6)-epioritin-4beta-ol, the first naturally occurring bis-flavan-3,4-diol.     

Structure and stereochemistry of triflavanoids containing both ether and carbon-carbon interflavanyl bonds.

The first triflavanoids with both C-C and C-O-C interflavanyl bonds, epioritin-(4beta-->6)-epioritin-(4alpha-->4)-epioritin-4beta-ol, epioritin-(4beta-->3)-epioritin-(4beta-->6)-epioritin-4beta-ol and epioritin-(4beta-->3)-epioritin-(4beta-->6)-epimesquitol-4alpha-ol, were identified in the heartwood of Acacia caffra. The ethereal interflavanyl bond is readily susceptible to reductive cleavage with sodium cyanoborohydride in trifluoroacetic acid/dichloromethane which hence permits the unequivocal assignment of the absolute configuration of constituent flavanyl units.     

Structure and synthesis of ether-linked proteracacinidin and promelacacinidin proanthocyanidins from Acacia caffra

Two new ether-linked proanthocyanidins, epioritin-(4beta-->3)-epioritin-4beta-ol and epimesquitol-(4beta-->4)-epioritin-4beta-ol, were isolated from the heartwood of Acacia caffra. Their structures and absolute configurations were established by spectroscopic methods and syntheses.     

Polyphenols from peanut skins and their free radical-scavenging effects

Separation of the water-soluble fraction of peanut skins led to the isolation of five proanthocyanidins. Based on the spectroscopic investigation and partial acid catalyzed degradation, their structures were determined to be epicatechin-(2beta-->O -->7, 4beta -->6)-[epicatechin-(4beta-->8)]-catechin (1), epicatechin-(2beta-->O -->7, 4beta-->8) epicatechin-(4beta-->8)-catechin-(4alpha-->8)-epicatechin (2), and procyanidins B2 (3), B3 (4) and B4 (5). The absolute configuration of the new compounds was determined from their circular dichroism curves and the (1)H NMR spectra of analysis of flavan-3-ols formed by thiolytic degradation of 1 and 2 in the presence of a chiral dirhodium complex (dirhodium tetra-(R)-(trifluoromethyl) phenyl acetate).     

Structure and synthesis of the first procassinidin dimers based on epicatechin, and gallo- and epigallo-catechin

The range of natural dimeric procassinidins is extended by identification of cassiaflavan-(4alpha-->8)-epicatechin, cassiaflavan-(4alpha 8)-epigallocatechin, cassiaflavan-(4beta-->8)-epicatechin, cassiaflavan-(4beta-->8)-epigallocatechin, cassiaflavan-(4beta-->8)-gallocatechin, ent-cassiaflavan-(4beta-->8)-epicatechin and cassiaflavan-(4alpha-->6)-epicatechin in the bark of Cassia petersiana. Their structures and absolute configuration were confirmed by synthesis.     

Heterogeneity of the interflavanyl bond in proanthocyanidins from natural sources lacking C-4 (C-ring) deoxy flavonoid nucleophiles

The proanthocyanidin pool in the floral kingdom usually involves the presence of carbon-carbon bonds linking predominantly flavan-3-ol constituent moieties. Such an ensemble of flavan-3-ol units originates via electrophilic aromatic substitution of flavan-4-yl carbocations (or their equivalents) derived from flavan-4-ols and/or flavan-3,4-diols and the nucleophilic centers of the m-oxygenated A-rings of flavan-3-ol nucleophiles. In the absence of these potent flavan-3-ol nucleophiles with their aptitude for the formation of carbon-carbon bonds, alternative centers emerge as participants in interflavanyl bond formation. Such a phenomenon is demonstrated for the distribution of various profisetinidin-, prorobinetinidin-, proguibourtinidin-, promelacacinidin- and proteracacinidin-type pro- and leuco-anthocyanidins in several southern hemisphere heartwood species.     

Phenolic glycosides from Kaempferia parviflora

Three phenolic glycosides were isolated together with two known flavonol glycosides from the H2O-soluble fraction of rhizomes of Kaempferia parviflora. Their structures were determined to be rel-(5aS,10bS)-5a,10b-dihydro-1,3,5a,9-tetrahydroxy-8-methoxy-6H-benz[b]indeno[1,2-d]furan-6-one 5a-O-[alpha-L-rhamnopyranosyl-(1-->6)-beta-d-glucopyranoside] (1), its rel-5aS,10bR isomer (2), and (2R,3S,4S)-3-O-[alpha-L-rhamnopyranosyl-(1-->6)-beta-d-glucopyranosyl]-3'-O-methyl-ent-epicatechin-(2alpha-->O-->3,4alpha-->4)-(5aS,10bS)-5a,10b-dihydro-1,3,5a,9-tetrahydroxy-8-methoxy-6H-benz[b]indeno[1,2-d]furan-6-one 5a-O-[alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside] (3). The structures were elucidated on the basis of analyses of chemical and spectroscopic evidence.     

4alpha-methyl-24beta-ethyl-5alpha-cholesta-14,25-dien-3beta-ol and 24beta-ethylcholesta-5, 9(11), 22E-trien-3beta-ol,sterols from Clerodendrum inerme

From the aerial parts of Clerodendrum inerme, two new sterols (4alpha-methyl-24beta-ethyl-5alpha-cholesta-14, 25-dien-3beta-ol and 24beta-ethylcholesta-5, 9(11), 22E-trien-3beta-ol) and a new aliphatic ketone (11-pentacosanone) were isolated together with another known aliphatic ketone (6-nonacosanone) and a diterpene (clerodermic acid). The structure elucidations were based on analyses of physical and spectroscopic data.     

Stereoselective halogenation of the 16-hydroxymethyl-3-methoxy-13alpha-estra-1,3,5(10)-trien-17-ols and their solvolytic investigation

The primary hydroxy functions of 16alpha-hydroxymethyl-3-methoxy-13alpha-estra-1,3,5(10)-trien-17beta-ol (3a) and 16beta-hydroxymethyl-3-methoxy-13alpha-estra-1,3,5(10)-trien-17alpha-ol (4a) were stereoselectively transformed into good leaving groups. On alkaline methanolysis of the 16-halomethyl or 16-tolylsulfonyloxymethyl derivatives, a new D-seco-13alpha-estrone derivative was obtained in high yield.     

Volatiles associated with different flower stages and leaves of Acacia cyclops and their potential role as host attractants for Dasineura dielsi (Diptera: Cecidomyiidae)

Acacia cyclops (Fabaceae) is an Australian species which was introduced into South Africa in the nineteenth century. Because of its invasive status in South Africa, a gall midge, Dasineura dielsi (Diptera: Cecidomyiidae), was released in 2001 in order to impact its reproduction by inducing galls on the flowers and thereby preventing seed set. Nothing is known about the cues used by D. dielsi for locating its host flowers. As part of an initial investigation into whether or not chemical cues might play a role in host finding, we analysed headspace samples of Acacia cyclops volatiles from leaves and reproductive parts at different stages (early bud, late bud, early flowering, and senescing flowering stages) using gas chromatography–mass spectrometry (GC–MS). In total, 72 different compounds were detected of which 62 were identified. The analyses showed that open flowers, the stage used by D. dielsi for oviposition, and yellow buds had similar odour compositions with (Z)-3-hexen-1-ol acetate, 4-oxoisophorone, (Z)-β-ocimene, an unknown aliphatic compound, heptadecane, and nonadecane dominating in open flowers. Leaf volatiles were distinct from those in the reproductive plant parts by their high relative amount of (Z)-β-ocimene. (Z)-3-Hexen-1-ol acetate had its maximum relative amount in the green bud samples and was much lower in the later floral stages. In contrast, 4-oxoisophorone peaked in yellow buds and open flowers with little or none of it found in younger or older stages. The volatile compounds of the different flower stages and leaves are discussed in relation to their potential role as attractants used by the biocontrol agent D. dielsi to locate its host plant.     

Structural determinants of monohydroxylated bile acids to activate beta 1 subunit-containing BK channels

Lithocholate (LC) (10-300 microM) in physiological solution is sensed by vascular myocyte large conductance, calcium- and voltage-gated potassium (BK) channel beta(1) accessory subunits, leading to channel activation and arterial dilation. However, the structural features in steroid and target that determine LC action are unknown. We tested LC and close analogs on BK channel (pore-forming cbv1+beta(1) subunits) activity using the product of the number of functional ion channels in the membrane patch (N) and the open channel probability (Po). LC (5beta-cholanic acid-3alpha-ol), 5alpha-cholanic acid-3alpha-ol, and 5beta-cholanic acid-3beta-ol increased NPo (EC(50) approximately 45 microM). At maximal increase in NPo, LC increased NPo by 180%, whereas 5alpha-cholanic acid-3alpha-ol and 5beta-cholanic acid-3beta-ol raised NPo by 40%. Thus, the alpha-hydroxyl and the cis A-B ring junction are both required for robust channel potentiation. Lacking both features, 5alpha-cholanic acid-3beta-ol and 5-cholenic acid-3beta-ol were inactive. Three-dimensional structures show that only LC displays a bean shape with clear-cut convex and concave hemispheres; 5alpha-cholanic acid-3alpha-ol and 5beta-cholanic acid-3beta-ol partially matched LC shape, and 5alpha-cholanic acid-3beta-ol and 5-cholenic acid-3beta-ol did not. Increasing polarity in steroid rings (5beta-cholanic acid-3alpha-sulfate) or reducing polarity in lateral chain (5beta-cholanic acid 3alpha-ol methyl ester) rendered poorly active compounds, consistent with steroid insertion between beta(1) and bilayer lipids, with the steroid-charged tail near the aqueous phase. Molecular dynamics identified two regions in beta(1) transmembrane domain 2 that meet unique requirements for bonding with the LC concave hemisphere, where the steroid functional groups are located.     

Molecular characterization of a first human 3(alpha-->beta)-hydroxysteroid epimerase

In this report, we describe the isolation and characterization of a cDNA encoding an enzyme that exhibits catalytic characteristics of a 3(alpha-->beta)-hydroxysteroid epimerase (3(alpha-->beta)-HSE). The enzyme overexpressed in human 293 embryonic kidney cells transforms androsterone into epi-androsterone in two steps: the oxidation of androsterone to 5 alpha-androstane-3,17-dione, followed by the reduction of the latter to epi-androsterone. The reverse reaction, 3(beta-->alpha)-hydroxysteroid epimeration, is approximately 10-fold weaker. These results are confirmed by V(max)/K(m) determination, which shows that the enzyme catalyzes the oxidation of androsterone to 5 alpha-androstane-3,17-dione and the reduction of 5 alpha-androstane-3,17-dione to epi-androsterone more efficiently than the reverse reactions. The selective catalysis of the reaction following the 3(alpha-->beta) direction is also observed in intact transfected cells in culture, which better reflect physiological conditions. In vitro assays reveal that the recombinant enzyme prefers NAD(+) and NADH as cofactors and could recognize both C-19 and C-21 3 alpha-hydroxysteroids as substrates. DNA sequence analysis predicts a protein of 317 amino acids. Tissue distribution analysis using RT-PCR reveals that the mRNA of the enzyme is expressed in various tissues, including liver, brain, prostate, adrenal, and uterus, with the most abundant expression in the liver. Because active hydroxysteroids generally exert their effect in a stereo-specific manner, 3(alpha-->beta)-HSE could thus potentially play an important role in regulating the biological activities of various steroids.     

Concurrent occurrence of 3 beta,12 alpha-dihydroxy-5-cholenoic acid associated with 3 beta-hydroxy-5-cholenoic acid and their preferential urinary excretion in liver diseases

3 beta-Hydroxy-(delta 5-3 beta-ol), 3 beta,12 alpha-dihydroxy-(delta 5-3 beta,12 alpha-ol), 3 beta,7 alpha-dihydroxy-(delta 5-3 beta,7 alpha-ol) and 3 beta,7 beta-dihydroxy-(delta 5-3 beta,7 beta-ol) 5-cholenoic acids were identified in patients with liver diseases by gas-liquid chromatography-mass spectrometry (GLC-MS). Of these unusual 3 beta-hydroxy-5-en-metabolites, delta 5-3 beta-ol and delta 5-3 beta,12 alpha-ol were found as major components in the urine of patients with liver diseases (cholestasis, liver cirrhosis, chronic hepatitis, acute hepatitis). Other 3 beta-dihydroxy-5-en-metabolites, delta 5-3 beta,7 alpha-ol and delta 5-3 beta,7 beta-ol, were found as minor components in the urine. The levels of delta 5-3 beta-ol and delta 5-3 beta,12 alpha-ol in urine were correlated with their levels in serum, with total bile acids in the urine, and with liver function, implying that the degree of their increment correlated well with the severity of liver diseases. The most abundant amounts of delta 5-3 beta-ol and delta 5-3 beta,12 alpha-ol were found in the urine as sulfate conjugates in comparison with bile, portal and hepatic venous sera, and liver tissue of the patients. The biliary excretion and hepatic extraction of these 3 beta-hydroxy-5-en-unsaturated bile acids were more impaired and inefficient than those of cholic and chenodeoxycholic acids.     

Antiplasmodial activity of naphthoquinones and one anthraquinone from Stereospermum kunthianum

Six new partheniol metabolites were isolated from the biotransformation reaction with Mucor circinelloides ATCC 15242. These metabolites are: humula-1(10), 4, 7-trien-6alpha-ol 2, maali-3-en-8alpha-ol 3, aromadendrane-4alpha, 8alpha, 10alpha-triol 4, maaliane-4alpha, 8alpha, 9alpha-triol 5, maaliane-5alpha, 8alpha, 9alpha-triol 6, 5(9), 6-tricyclohumulane-4alpha, 8alpha, 10alpha-triol 7. The structural assignments of these metabolites were made possible by different spectroscopic means.     

Two flavonoid glycosides and a miscellaneous flavan from the bark of Guibourtia coleosperma

Two flavonoid glycosides, 7-O-beta-D-xylopyranosyl-epicatechin and epicatechin-(4beta-->8)-7-O-beta-D-xylopyranosyl-epicatechin both as their acetate and methyl ether acetate derivatives and a miscellaneous flavan Epicatechin-(7,8-bc)-9beta-(3-methoxy-4-acethoxyphenyl)-dihydro-2(3H)-pyranone as its acetate derivative were isolated from the bark of Guibourtia coleosperma. Their structures were established by spectroscopic methods.     

Epoxidation and reduction of cholesterol, 1,4,6-cholestatrien-3-one and 4,6-cholestadien-3beta-ol

Many naturally occurring polyhydroxylated sterols and oxysterols exhibit potent biologic activities. This paper describes reagent and position selectivity of epoxidation and reduction of cholesterol derivatives. Cholesterol was reacted with m-chloroperoxybenzoic acid (m-CPBA) to form 5alpha,6alpha-epoxycholestan-3beta-ol, but in reaction with 30% H(2)O(2), it did not reacted. 1,4,6-cholestatrien-3-one was obtained from cholesterol and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in dioxane. 1,4,6-cholestatrien-3-one was reacted with 30% H(2)O(2) and 5% NaOH in methanol to give 1alpha,2alpha-epoxy-4,6-cholestadien-3-one, which was stereoselectively reduced with NaBH(4) to form 1alpha,2alpha-epoxy-4,6-cholestadien-3beta-ol and reduced with Li metal in absolute ethanol to give 2-ethoxy-1,4,6-cholestatrien-3-one. And 1,4,6-cholestatrien-3-one was epoxidized with m-CPBA in dichloromethane to afford 6alpha,7alpha-epoxy-1,4-cholestadien-3-one, which was reacted with NaBH(4) to synthesize 6alpha-hydroxy-4-cholesten-3-one and reduced Li metal in absolute ethanol to form 2-ethoxy-1,4,6-cholestatrien-3-one, respectively. 1,4,6-cholestatrien-3-one was reduced with NaBH(4) in absolute ethanol to form 4,6-cholestadien-3beta-ol, which was reacted with 30% H(2)O(2) to leave original compound, but was reacted with m-CPBA to give 4beta,5beta-epoxy-6-cholesten-3beta-ol as the major product and 4beta,5beta-epoxy-6alpha,7alpha-epoxycholestan-3beta-ol as the minor product.     

Terpenes from leaves of Guarea macrophylla (Meliaceae)

The dichloromethane extract from the leaves of Guarea macrophylla (Meliaceae) was submitted to adsorption chromatography. Guai-6-en-10beta-ol, isopimara-7,15-dien-2alpha-ol and cycloarta-23,25-dien-3-one were isolated and identified by spectroscopic data, mainly by 1H and 13C NMR analyses; eight other known terpenoids were also isolated.     

Cinnamoyl glucosides of catechin and dimeric procyanidins from young leaves of Inga umbellifera (Fabaceae)

The rapidly growing, nearly achlorophyllous, young leaves of Inga umbellifera express high concentrations of mono and dimeric 3-O-gluco-cinnamoyl catechin/epicatechin, rare forms of substituted flavan-3-ols. Here we present structures for five novel compounds in this class: three monomers [catechin-3-O-beta-D-gluco(2-cinnamoyl)pyranoside, catechin-3-O-beta-D-gluco(6-cinnamoyl) pyranoside, catechin-3-O-beta-D-gluco(2,6-biscinnamoyl)pyranoside] and two dimeric procyanidins [catechin-3-O-beta-D-glucopyrano-(4alpha-->8)-catechin-3-O-beta-D-gluco(2-cinnamoyl)pyranoside and catechin-3-O-beta-D-glucopyrano-(4alpha-->8)-epicatechin-3-O-beta-D-gluco(6-cinnamoyl)pyranoside]. The young leaves of Inga umbellifera express high concentrations of 3-O-(cinnamoyl)glucosides of catechin and epicatechin.