Incorporation of 5α-furostan-3β,26-diol into tigogenin by digitalis lanata

2,2′,4,4′-³H₄-dihydrotigogenin was converted by Digitalis lanata plants into tigogenin.     

Biosynthesis of Grayanotoxins in Leucothoe grayana Max.Incorporation of Mevalonic Acid and (—)-Kaurene into Grayanotoxin-III

The main subunits of glutenin were separated by preparative SDS-PAGE with a Laemmli system (U. K. Laemmli, Nature, 227, 680 (1970)) and their cysteine (Cys) contents were determined by amino acid analysis. Amino acid compositions of glutenin subunits, determined in the present study, were different from those determined by Danno et al. [G. Danno, K. Kanazawa and M. Natake, Agric. Biol. Chem., 40, 739 (1976)]. We found that these differences were due to the different methods of hydrolysis of subunit polypeptides. That is, hydrolysis of subunit polypeptides extracted from gel and hydrolysis of polypeptides in gel without extraction. Cys contents of glutenin subunits were determined as S-pyridylethyl cysteine (PE-Cys). Although no PE-Cys was detected in B-4 or B-4′, all other subunits were shown to have 4mol Cys per mol protein, respectively.     

The stereochemistry of the hydrogen elimination in the biological conversion of cholest-7-en-3β-ol into cholesterol

1. The syntheses of Δ⁷-[4-¹⁴C]cholestenol (XVI, Scheme 3) and Δ⁷-[6α-³H]-cholestenol (XII, Scheme 2) are described. 2. The metabolism of doubly labelled Δ⁷-cholestenol (II, Scheme 1) by rat-liver homogenates was studied. 3. During the enzymic conversion of Δ⁷-cholestenol into cholesterol (IV, Scheme 1) the 6α-hydrogen atom of the former is lost and the overall reaction corresponds to a cis-elimination. 4. In the light of these results various mechanisms for the conversion of Δ⁷-cholestenol into cholesterol are discussed.     

Biotransformation of 5-en-3β-ol steroids by Mucor circinelloides lusitanicus

In this work, we report the mode of biotransformation of 5-en-3β-ol steroids using Mucor circinelloides lusitanicus for the first time. Here, we selected seven 5-en-3β-ol steroids as substrates. The main characteristic of the fungus was to introduce a 7α-hydroxyl group into substrates 1--5. With substrate 2, 3β, 7α, 11α-trihydroxypregna-5-en-20-one (2b) was obtained as the final product in good yield (46.4%). All the metabolites were determined by infrared spectra, high-resolution mass spectrometry, proton nuclear magnetic resonance, and carbon-13 nuclear magnetic resonance.     

Stereoselectivity of raney nickel catalyst in hydrogenolysis of a steroidal α,β-unsaturated epoxide. Chemical synthesis of 3β-benzoyloxy-5α-cholest-8(14)-en-15α-ol

Hydrogenation of 3β-benzoyloxy-14α, 15α-epoxy-5α-cholest-7-ene in benzene over a Raney nickel catalyst gave 3β-benzoyloxy-5α-cholest-8(14)-en-15α-ol and 3β-benzoyloxy-5α-cholest-8(14)-ene in 39% and 46% yields, respectively. Hydrogenation of the same α,β-unsaturated epoxy steryl ester under the same conditions except with the inclusion of triethylamine (4%) gave 3β-benzoyloxy-5α-cholest-8(14)-en-15α-ol in 89% yield.     

Identification of 5α-stanols in patients with sitosterolemia and xanthomatosis: stereochemistry of the protonolysis of steroidal organoboranes.

Plasma and fecal sterols of patients who exhibited tendon xanthomas with normal plasma cholesterol levels were studied. Plasma levels were mg/dl mean ± SD) : cholesterol 232 ± 36; cholestanol 5.9 ± 2.1 (normal <0.6); sitosterol 18 ± 5.6 (normal <1.0); campesterol 11 ± 3.3 (normal <1.0). Other sterols such as sitostanol and campestanol (the 5α-dihydro derivatives of sitosterol and campesterol) were also present in large amounts. Examination of the feces from these subjects showed cholesterol, sitosterol, campesterol and their 5β-saturated derivatives. Presence of 5α-stanols in the plasma, and their absence in the feces indicates that the 5α-stanols are synthesized endogenously within the body rather than in the intestine by colonic bacteria. The absolute identification of the structures of these 5α-stanols was elucidated via hydroboration of their corresponding unsaturated sterols coupled with protonolysis of the resultant organoboranes.     

Reactions of 4β,5-epoxy-5β-androstan-3-ones with hydrogen fluoride in pyridine

4β,5-Epoxy-5β-androstane-3,17-dione ($\text{1a}$), 17β-hydroxy-4β,5-epoxy-5β-androstan-3-one ($\text{1b}$) and 17β-acetoxy-4β,5-epoxy-5β-androstan-3-one ($\text{1c}$) were treated with anhydrous hydrogen fluoride in pyridine (70% solution) at 55° and yielded the corresponding 4-en-4-ols e.g. 4-hydroxy-4-androstene-3, 17-dione ($\text{2a}$).As the reaction temperature was lowered each epoxide formed a second product which, at ?75°, was the major component of the reaction mixture and was identified as the 5α-fluoro-4α-ol derivative of the parent enone, e.g. 4α-hydroxy-5-fluoro-5α-androstane-3,17-dione ($\text{3a}$). These fluorohydrins are thermally unstable, losing hydrogen fluoride.The acetates of the fluorohydrins were also prepared, characterized, and shown to be more stable than the parent alcohols.     

Incorporation of privileged structures into 3-O-β-chacotriosyl ursolic acid can enhance inhibiting the entry of the H5N1 virus

The glycoprotein hemagglutinin of influenza virus plays a key role in the initial stage of virus infection, making it a potential target for novel influenza viruses entry inhibitors. Two “privileged fragments”, 2-(piperidin-1-yl)ethan-1-amine and 2-(1,3-oxazinan-3-yl)ethan-1-amine were integrated into 3-O-β-chacotriosyl ursolic acid producing new derivatives 5 and 6 with improved activity against IAVs in vitro. Mechanistically, compound 6 was effective in inhibiting infection of H1-, H3-, and H5-typed influenza A viruses by interfering with the viral hemagglutinin. Furthermore, the docking studies were in agreement with the antiviral data. These results showed that the title compound 6 as a new lead compound was meriting further optimization and development.     

Mode of formation of cholesta-5,7-dien-3β-ol from cholest-5-en-3β-ol by larvae of Calliphora erythrocephala

1. The conversion of cholest-5-en-3beta-ol (cholesterol) into cholesta-5,7-dien-3beta-ol by axenic Calliphora erythrocephala larvae was demonstrated. 2. The transformation is probably direct (Delta(5)-->Delta(5,7)) and does not involve a Delta(0) intermediate (Delta(5)-->Delta(0)-->Delta(7)--> Delta(5,7)). 3. Delta(7)-bond formation involves the stereospecific elimination of the 7beta hydrogen atom. 4. The relative amounts of free and esterified sterols were determined in larvae grown on cholesterol as sole sterol source and on 5alpha-cholestan-3beta-ol supplemented with minimal amounts of cholesterol. 5. The significance of the results is assessed in relation to the probable role of cholesta-5,7-dien-3beta-ol as an intermediate in the biosynthesis of ecdysones.     

Biosynthesis of 3α,6β-ditigloyloxytropane and 3α,6β-ditigloyloxytropan-7β-ol in Datura

Datura meteloides; plants were fed with tiglic acid-[-¹⁴C] via the roots and after 2 days the percentage incorporation into the alkaloids 3α-tigloyloxytropane, 3α,6β-ditigloyloxytropane, meteloidine and 3α,6β-ditigloyloxytropan-7β-ol were 15·2, 1·82, 2·2 and 1·8 respectively. 3α,6β-Ditigloyloxytropane was partially hydrolysed to 6β-hydroxy-3α-tigloyloxytropane which contained 58·1% of the radioactivity of the original base, whereas 3α,6β-ditigloyloxytropan-7β-ol gave meteloidine containing only 9·2% of the original activity. The results suggest that the di- and tri-hydroxytropanes may be formed by different routes.     

The transformation of 10α-cucurbita-5,24-dien-3β-ol into cucurbitacin C by seedlings of Cucumis sativus

Labelled 10α-cucurbita-5,24-dien-3β-ol, the simplest tetracyclic triterpene with a cucurbitane skeleton, was transformed into cucurbitacin C in Cucumis sativus seedlings. This transformation has been previously postulated, but this is the first time it has been demonstrated to operate in plant tissues. Two other potential precursors of cucurbitacins, cycloartenol and parkeol, were incubated under the same conditions. Cycloartenol gave only the expected phytosterols whereas parkeol was recovered unchanged.     

Stereospecific Reduction of Keto Group in 3β-Triphenylmethoxy-5α-cholest-8(14)-en-15-one

The reduction of 3-triphenylmethoxy-5-cholest-8(14)-en-15-one with lithium aluminum hydride resulted in a quantitative yield of 3-triphenylmethoxy-5-cholest-8(14)-en-15-ol.     

Alleviating salt stress in tomato seedlings using Arthrobacter and Bacillus megaterium isolated from the rhizosphere of wild plants grown on saline–alkaline lands

Salt-induced soil degradation is common in farmlands and limits the growth and development of numerous crop plants in the world. In this study, we isolated salt-tolerant bacteria from the rhizosphere of Tamarix chinensis, Suaeda salsa and Zoysia sinica, which are common wild plants grown on a saline–alkaline land, to test these bacteria's efficiency in alleviating salt stress in tomato plants. We screened out seven strains (TF1–7) that are efficient in reducing salt stress in tomato seedlings. The sequence data of 16S rRNA genes showed that these strains belong to Arthrobacter and Bacillus megaterium. All strains could hydrolyze casein and solubilize phosphate, and showed at least one plant growth promotion (PGP)-related gene, indicating their potential in promoting plant growth. The Arthrobacter strains TF1 and TF7 and the Bacillus megaterium strain TF2 and TF3 could produce indole acetic acid under salt stress, further demonstrating their PGP potential. Tomato seed germination, seedling length, vigor index, and plant fresh and dry weight were enhanced by inoculation of Arthrobacter and B. megaterium strains under salt stress. Our results demonstrated that salt-tolerant bacteria isolated from the rhizosphere of wild plants grown on saline–alkaline lands could be used for alleviating salt stress in crop plants.     

The formation of cholest-5-ene-3β,26-diol as an intermediate in the conversion of cholesterol into bile acids by liver mitochondria

1. When [(14)C]cholesterol was incubated with rat liver mitochondria, radioactive 26-hydroxycholesterol, 3beta-hydroxychol-5-enoic acid and other bile acids were isolated from the incubation mixture. 2. In the absence of added 26-hydroxycholesterol, the specific radioactivity of the 26-hydroxycholesterol formed from [(14)C]cholesterol during the incubation was higher than that of the 3beta-hydroxychol-5-enoic acid. Addition of increasing amounts of 26-hydroxycholesterol led to a progressive fall in the specific radioactivity, and to a progressive increase in the mass, of the 3beta-hydroxychol-5-enoic acid recovered at the end of the incubation. 3. It is concluded that 26-hydroxycholesterol is an intermediate in the formation of 3beta-hydroxychol-5-enoic acid from cholesterol. 4. Comparison of the specific radioactivity of the 26-hydroxycholesterol formed in the incubation mixture with that of the added [(14)C]cholesterol indicates that endogenous cholesterol in mitochondria is accessible to cholesterol 26-hydroxylase.     

The oxidized form of cholesterol 3β-hydroxy-5-oxo-5,6-secocholestan-6-al induces structural and thermotropic changes in phospholipid membranes

The effect of an oxidized form of cholesterol, 3β-hydroxy-5-oxo-5,6-secocholestan-6-al on the thermotropic and structural properties of phospholipid membranes was investigated by differential scanning calorimetry and X-ray diffraction and compared with that of cholesterol. The phospholipids studied included 1-palmitoyl-2-oleoylphosphatidylserine, dipalmitoleoylphosphatidylethanolamine, 1-palmitoyl-2-oleoylphosphatidylethanolamine, dipalmitoleoylphosphatidylcholine, 1-palmitoyl-2-oleoylphosphatidylcholine. Depending on the constituent phospholipids, the oxidized cholesterol is observed to shift phase transitions, disrupt stacking, modify interbilayer spacings and promote increased negative membrane curvature. We determined by absorption spectroscopy that the amino group of phosphatidylserine forms a Schiff base with the aldehyde group of the 3β-hydroxy-5-oxo-5,6-secocholestan-6-al as was previously found for the amino group of phosphatidylethanolamine. This result strengthens the biologically significant finding that not only amino groups of proteins but also amino groups of phospholipids are able to form a Schiff base with oxidized cholesterol. The marked triangular shape of the Schiff base complex with phosphatidylethanolamine may explain how 3β-hydroxy-5-oxo-5,6-secocholestan-6-al can promote increased negative curvature in the hexagonal phase, as compared to cholesterol, even though its increased polarity would favor a location closer to the interface with water.     

Preparation of 3β,16β-dihydroxyandrost-5-en-17-one: Stabilization of its α-ketolic group toward alkali by formation of a semicarbazone

Alkaline hydrolysis of a 16β-acetoxy-17-oxo steroid is accompanied by almost complete rearrangement of the product to a 16-oxo-17β-hydroxy steroid. Hydrolysis can be achieved without rearrangement by 1) formation of a C-17 semicarbazone, 2) alkaline removal of the acetate group, and 3) removal of the semicarbazone group in the presence of pyruvic acid-acetic acid. By employing this technique, the title compound was obtained from its diacetate in a yield of 65%.