Biosynthesis of bakuchiol,a meroterpene from Psoralea corylifolia

Biosynthesis of bakuchiol was examined using phenylalanine and mevalonic acid as substrates. It has been demonstrated that bakuchiol is derived from one phenylpropane (with the loss of one carbon atom) and two isoprenoid (C₅) units.     

Biosynthesis of Se-Methylselenocysteine in lima beans

It has been shown that maturing seeds of lima beans synthesize Se-methylselenocysteine, the selenium analogue of S-methyleysteine. The latter amino acid is a natural constituent of these seeds. The leaves of lima beans do not contain detectable amounts of S-methylcysteine, and in this tissue Se-methionine appears to be the principal product of selenate assimilation.     

Biosynthesis of p-hydroxybenzoic acid in poplar lignin

Biosynthetic pathways to p-hydroxybenzoic acid in polar lignin were examined by tracer experiments. High incorporation of radioactivity to the acid was observed when shikimic acid-[1-¹⁴C], phenylalanine-[3-¹⁴C], trans-cinnamic acid-[3-¹⁴C], p-coumaric acid-[3-¹⁴C] and p-hydroxybenzoic acid-[COOH-¹⁴C] were administered, while incorporation was low from shikimic acid-[COOH-¹⁴C], phenylalanine-[1-¹⁴C], phenylalanine-[2-¹⁴C], tyrosine-[3-¹⁴C], benzoic acid-[COOH-¹⁴C], sodium acetate-[1-¹⁴C] and d-glucose-[U-¹⁴C]. Thus p-hydroxybenzoic acid in poplar lignin is formed mainly via the pathway: shikimic acid → phenylalanine → trans-cinnamic acid → p-coumaric acid → p-hydroxybenzoic acid.     

Biosynthesis of radiolabelled alkaloids from 14C-tyrosine in Erythrina crista-galli

Alkaloid biosynthesis has been demonstrated in the young expanding tissues of Erythrina crista-galli shoots, the stem part of which elaborated, from [2-^14C]-tyrosine, alkaloid of specific radioactivity 2μuCi mmol^?1, 10-fold greater than previously reported.     

Resin acids from two amazonian species of Hymenaea

The major diterpene acid constituents of two Amazonian species of Hymenaea have been isolated and identified. A new resin acid, guamáic acid, is described.     

Biosynthesis of lathyrine in lathyrus tingitanus

Possible mechanisms in the biosynthesis of lathyrine are discussed. An in vitro system for the specffic 4-hydroxylation of diamino acids is reporte     

Biosynthesis of triterpenoid sapogenols in soybean and alfalfa seedlings

By incubation of germinating soybeans with mevalonate-[2-¹⁴C] (MVA), radioactivity was incorporated into four sapogenols which were identified by TLC. Unequivocal evidence for the identity of three of the four sapogenols was provided by co-crystallization to constant specific radioactivity. The partition of incorporated radioactivity into lipid- and water-soluble fractions and the pattern of radioactivity of individual sapogenols varied with the mode of administering labeled substrates to soybean seedlings, such as incubation of germinating soybeans with MVA-[2-¹⁴C], immersion of roots into MVA-[2-¹⁴C] or foliar application of squalene-[¹⁴C]. When alfalfa seedlings were incubated with MVA-[2-¹⁴C], about two-thirds of the radioactivity incorporated into the sapogenols was associated with medicagenic acid.     

Synthesis of α- and β-N-oxalyl-l-α,β-diaminopropionic acids and their isolation from seeds of Lathyrus sativus

The α- and β-N-oxalyl derivatives of l-α,β-diaminopropionic acid have been chemically synthesized and also isolated from seed extracts of Lathyrus sativus. Chemical and physical properties of the natural and synthetic isomers were in good agreement. The toxicity of the α-isomer to chicks was evaluated and compared with that of the β-isomer.     

Biosynthesis of eugenol and cinnamic aldehyde in Cinnamomum zeylanicum

Incorporation of [¹⁴C]-phenylalanine and [¹⁴C]-methionine into cinnamon cuttings suggests that synthesis of eugenol from phenylalanine involves exchange of the terminal carbon in the side chain with that from a donor molecule such as methionine whereas synthesis of cinnamic aldehyde incorporates phenylalanine in toto.     

Biosynthesis of triterpenoids from amino acids in Pisum sativum. The distribution of the radioactivity in squalene biosynthesized from radioisotopically labelled l-leucine and l-valine

Radioisotopically labelled l-leucine and l-valine were fed to Pisum sativum and incorporated into squalene and β-amyrin. Chemical degradation of the radioactive squalene revealed an equal distribution of the radioactivity in the isopentenyl pyrophosphate(IPP)-derived and the 3,3-dimethylallyl pyrophosphate(DMAPP)-derived moieties of the squalene molecule, unlike the unbalanced distribution in favour of the DMAPP-derived moiety of a monoterpenoid molecule biosynthesized from these amino acids by higher plants.     

Biosynthesis of the phytoalexin wyerone in Vicia faba

In contrast to earlier results [1-¹⁴C] acetate, [2-¹⁴C] malonate and [n 9,10-³H] oleate show significant incorporations into wyerone and related Vicia faba phytoalexins, following infection by Botrytis cinerea.     

Biosynthesis of the 6-oxygenated isoflavone afrormosin in Onobrychis viciifolia

dl-Phenylalanine-[2-¹⁴C], 2′,4′,4-trihydroxychalcone-[carbonyl-¹⁴C] and formononetin-[Me-¹⁴C] were all good precursors of afrormosin (7-hydroxy-6,4′-dimethoxyisoflavone) in Onobrychis viciifolia seedlings. This demonstrates that 6-oxygenation may be a late process in the biosynthesis of isoflavones.     

Distribution and roles of p-hydroxycinnamate: CoA ligase in lignin biosynthesis

p-Hydroxycinnamate:CoA ligases were extracted from the xylems of angiosperms and gymnosperms, and the substrate specificities toward ferulate and sinapate were examined. Most of angiosperm and gymnosperm CoA ligases examined were active with ferulate but not with sinapate; however, the enzymes of Erythrina crista-galli, Robinia pseudoacacia and bamboo showed considerable activity with sinapate. The other enzymes, although inactive with sinapate, showed no inhibitory effect on the Erythrina CoA ligase reaction with sinapate. The K_ms for sinapate and ferulate of the Erythrina enzyme were 1.0 and 2.1 μM, respectively, and p-hydroxycinnamate was the best substrate among cinnamates examined. The MW of the CoA ligase was 40 000 and the pH optimum was between 7.2 and 7.6. The possible roles of p-hydroxycinnamate:CoA ligase in lignin biosynthesis are discussed.     

Caffeic acid, tyrosol and p-coumaric acid are potent inhibitors of 5-S-cysteinyl-dopamine induced neurotoxicity

Parkinson’s disease is characterized by a progressive and selective loss of dopaminergic neurons in the substantia nigra. Recent investigations have shown that conjugates such as the 5-S-cysteinyl-dopamine, possess strong neurotoxicity and may contribute to the underlying progression of the disease pathology. Although the neuroprotective actions of flavonoids are well reported, that of hydroxycinnamates and other phenolic acids is less established. We show that the hydroxycinnamates caffeic acid and p-coumaric acid, the hydroxyphenethyl alcohol, tyrosol, and a Champagne wine extract rich in these components protect neurons against injury induced by 5-S-cysteinyl-dopamine in vitro. The protection induced by these polyphenols was equal to or greater than that observed for the flavonoids, (+)-catechin, (−)-epicatechin and quercetin. For example, p-coumaric acid evoked significantly more protection at 1 μM (64.0 ± 3.1%) than both (−)-epicatechin (46.0 ± 4.1%, p < 0.05) and (+)-catechin (13.1 ± 3.0%, p < 0.001) at the same concentration. These data indicate that hydroxycinnamates, phenolic acids and phenolic alcohol are also capable of inducing neuroprotective effects to a similar extent to that seen with flavonoids.     

Sugar-related hydroxy acids from Phaseolus and trifolium species

-Hydroxy acids isolated from leaves of French bean (Phaseolus vulgaris) and clover (Trifolium incarnatum) were analysed by GLC as trimethylsilyl derivatives and identified by MS. Large amounts of a 2-C-methyltetronic acid and appreciable amounts of gluconic acid and of a 2-C-(hydroxymethyl)pentonic acid were found from French bean. Glyceric acid was the predominant acid from clover but the presence of several other acids, e.g. threonic and malic acids, was also demonstrated.     

Biosynthesis of the phytoalexin phaseollin in Phaseolus vulgaris

Feeding experiments in CuCl₂-treated French bean (Phaseolus vulgaris) seedlings have demonstrated that labelled 2′,4′,4-trihydroxychalcone, daidzein, 7,2′,4′-trihydroxyisoflavone, 3,9-dihydroxypterocarpan and phaseollidin are all good precursors of the pterocarpan phytoalexin phaseollin. These compounds represent a logical sequence in the biosynthetic pathway to phaseollin.     

Biosynthesis of sesquiterpenes in Hymenaea inferred from their quantitative co-occurrence

Leaf pocket resins of 11 species of the tropical arborescent genus Hymenaea are virtually identical qualitatively, but of widely varying quantitative proportions. Within this large range of variability, several strong positive quantitative correlations between resin constituents were found, especially between caryophyllene and β-humulene and between γ-muurolene and δ-cadinene. These data lead to clarification of sesquiterpene biosynthetic routes in Hymenaea. In addition, quantitative relationships found among caryophyllene, α- and β-selinene, γ-muurolene and δ-cadinene are explained only with difficulty by long accepted biosynthetic pathways, and the intermediacy of germacrenes is suggested.     

Biosynthesis of the 6a-hydroxypterocarpan phytoalexin pisatin in Pisum sativum

Comparative feeding experiments in cupric chloride-treated Pisum sativum pods and seedlings have demonstrated excellent incorporation into the 6a-h     

Two isoflavones from Piscidia erythrina

Two new prenylated isoflavones were isolated from the root bark of Piscidia erythrina. The first compound was identified as 2′-deoxypiscerythrone. The second compound, the most abundant component of the extract, was identified as 3′-6′-di-Δ²-isopentenyl-5,7,2′,4′-tetrahydroxy-5′-methoxyisoflavone.     

Antimicrobial agents from higher plants: Activity and structural revision of flemiflavanone-D from Flemingia stricta

Flemiflavanone-D from Flemingia stricta is active in vitro against Staphylococcus aureus and Mycobacterium smegmatis. Reexamination and interpretation of its spectral properties required revision of its molecular formula to C₂₅H₂₈O₆ and its structure to 2S-5,7,4′-trihydroxy-6-γ,γ-dimethylallyl-3′-γ,γ-dimethylallyl-oxidoflavan-4-one. The new structure was confirmed when reaction with chlorotrimethylsilane sodium iodide in acetonitrile deoxygenated and cyclized flemiflavanone-D to the known dicycloeuchrestaflavanone A. The absolute stereochemistry of flemiflavanone-D was established to be 2S by circular dichroism measurements.