Biosynthesis of pyridine alkaloids from Tripterygium wilfordii

Nicotinic acid-6-¹⁴C and nicotinamide adenine dinucleotide-carbonyl-¹⁴C were rapidly metabolized in T. wilfordii Hook. with formation of all compounds in the pyridine nucleotide cycle. Nicotinic acid-6-¹⁴C and the nicotinamide moiety of NAD were efficiently incorporated into wilfordic acid and hydroxywilfordic acid, the pyridinium moieties of the ester alkaloids. The structures of wilfordic acid and hydroxywilfordic acid were confirmed using GLC-MS. The molecular formulae of the four isolated alkaloids were determined by high resolution MS and agreed with earlier results based on elemental analysis.     

Biosynthesis of coumestrol in Phaseolus aureus

Feeding experiments with 4′,7-dihydroxyisoflavone-[4-¹⁴C] (daidzein), 2′,4′,7-trihydroxyisoflavone-[T] and (±)-4′,7-dihydroxyisoflavanone-[T] (dihydrodaidzein) in suspension cultures of mung bean (Phaseolus aureus Roxb.) roots have shown that daidzein is a better precursor of the coumestan coumestrol than is the trihydroxyisoflavone and that dihydrodaidzein can also be converted very efficiently. The results provide further evidence for the intermediacy of a pterocarp-6a-en in coumestrol biosynthesis, and also indicate the possible existence of a 'metabolic grid' of isoflavones and isoflavanones in P. aureus.     

Biosynthesis of meteloidine

Tropine-3β-³H, N-methyl-¹⁴C was fed to Datura meteloides plants. After 7 days radioactive meteloidine, scopolamine, hyoscyamine, and 7β-hydroxy-3α,6β-ditigloyloxytropane were isolated from the plants and found to have essentially the same ³H/¹⁴C ratio as in the administered tropine. Degradation of the meteloidine established that all its tritium was located at C-3 and all the ¹⁴C was on the N-methyl group, indicating that tropine is a direct precursor of teloidine.     

'Cholesterol side-chain cleaving enzyme' aktivität in keimlingen und in vitro kultivierten geweben von Digitalis purpurea

Experiments with cholesterol-26-¹⁴C gave evidence for the occurrence of cholesterol side-chain cleaving enzyme in seedlings of Digitalis purpurea. Tissue cultures of D. pupurea failed to show cholesterol side-chain cleaving activity, which may be the reason why tissue cultures are unable to biosynthesize cardenolide glycosides.     

Evidence for the formation of methoxyl groups of ferulic and sinapic acids in Bambusa by the same O-methyltransferase

The two methylation reactions, i.e. caffeate to ferulate (FA) and 5-hydroxyferulate to sinapate (SA), in the biosynthesis of guaiacyl and syringyl lignins in angiosperms were demonstrated to be catalyzed by the same enzyme in bamboo. This follows from the facts that: the ratio (SA/FA) obtained for O-methyltransferase remains constant during purification of the enzyme; chromatography on DEAE-cellulose, Sephadex G100 and G200, and analyses by polyacrylamide gel electrophoresis and isoelectric focusing in pH gradients showed that the two methylating activities belonged to a single enzyme protein; caffeate and 5-hydroxyferulate compete each other in the formation of the enzyme-substrate complex, the latter substrate showing greater affinity for the enzyme. Thus, feedback control may operate at the methylation step, caffeate to FA, in biosynthesis of angiosperm lignin.     

Biosynthesis of the tigloyl esters of Datura: Cis-trans isomerism

Datura innoxia plants were wick fed with angelic acid-[1-¹⁴C] and l-isoleucine-[U-¹⁴C] to act as a positive control. After 7 days the root alkaloids 3α-tigloyloxytropane, 3α,6β-ditigloyloxytropane, and 3α,6β-ditigloyloxytropan-7β-ol were isolated and it was determined that angelic acid is not a precursor for the tigloyl moiety of these alkaloids. Tiglic acid-[1-¹⁴C] which was fed via the roots to hydroponic cultures of Datura innoxia, was incorporated to a considerable degree after 8 days.     

Interconversion of gibberellin A5 to gibberellin 3 in seedlings of dwarf Pisum sativum

[³H]-Gibberellin A₅ ([³H]-GA₅) applied to seedlings of dark-grown dwarf pea (Pisum sativum L. cv. Meteor), was converted to two acidic compounds, GA₃ and a chromatographically similar unknown. Identification of GA₃ was made by gas-liquid radiochromatography using three stationary phases.     

Action spectra for C-glucosylflavone accumulation in Hordeum vulgare plumules

Five-day-old etiolated barley plumules contain the C-glucosylflavones saponarin, lutonarin, and lutonarin 3′-methyl ether. When harvested 24 hr after illumination, increased flavonoid levels were essentially linear with increased energies of monochromatic light at seven wavelengths between 450 and 750 nm. Action spectra for saponarin and for a mixture of lutonarin and its 3′-methyl ether were determined between 380 and 760 nm at 6.6 kerg·cm^?2. The saponarin action spectrum showed distinct peaks at 620 and at 660 nm. These two peaks were similar in their photoreversibility when followed by either 6·6 or 34 kerg·cm^?2 of far-red light. Phytochrome is apparently the photoreceptor for the saponarin action spectrum. Lutonarin and its 3′-methyl ether showed peaks at 520 580, 620 and near 660 nm. The 660 nm peak was not photoreversible by 6·6 kerg·cm^?1, but was by 34 kerg·cm_?2, of far-red light. Phytochrome and protochlorophyll are the likely photoreceptors for these 3′-substituted flavonoids.     

Biosynthesis of the tigloyl esters in Datura: The role of 2-methylbutyric acid

Datura innoxia plants were wick fed with (±)-2-methylbutyric acid-[1-¹⁴C] and harvested after 7 days. The root alkaloids 3α,6β-ditigloyloxytropane and 3α,6β-ditigloyloxytropan-7β-ol were isolated and degraded. In each case the radioactivity was located in the ester carbonyl group indicating that this acid is an intermediate in the biosynthesis of tiglic acid from l-isoleucine. On the other hand, (±)-2-hydroxy-2-methylbutyric acid-[1-¹⁴C], which was fed to hydroponic cultures of Datura innoxia alongside isoleucine[U-¹⁴C] positive control plants, is not an intermediate.     

Aldoximes and nitriles as intermediates in the biosynthesis of cyanogenic glucosides

Young sorghum shoots have been shown to convert tyrosine, p-hydroxyphenylacetaldoxime and p-hydroxyphenylacetonitrile to dhurrin, the cyanogenic glucoside characteristic of this plant. Evidence for the in vivo formation of p-hydroxyphenylacetaldoxime but not p-hydroxyphenylacetonitrile from tyrosine has been obtained from a 'trapping experiment.'