Phytochemistry (v.53, #7)
Biosynthesis of riboflavin in plants. The ribA gene of Arabidopsis thaliana specifies a bifunctional GTP cyclohydrolase II/3,4-dihydroxy-2-butanone 4-phosphate synthase by Stefan Herz; Sabine Eberhardt; Adelbert Bacher (723-731).
A cDNA segment from Arabidopsis thaliana with similarity to the ribA gene of Bacillus subtilis was sequenced. A similar gene was cloned from tomato. The open reading frame of A. thaliana was fused to the malE gene of Escherichia coli and was expressed in a recombinant E. coli strain. The recombinant fusion protein was purified and shown to have GTP cyclohydrolase II activity as well as 3,4-dihydroxy-2-butanone 4-phosphate synthase activity. The cognate gene was amplified by polymerase chain reaction from chromosomal Arabidopsis DNA and was shown to contain six introns. Intron 4 is located in the region connecting the GTP cyclohydrolase II and 3,4-dihydroxy-2-butanone 4-phosphate synthase domain of the putative domains catalyzing the two reaction steps. By comparison with the bacterial ribA gene, the Arabidopsis gene contains an additional 5′ element specifying about 120 amino acid residues. This segment contains numerous serine and threonine residues and does not show similarity with other known sequences. The N-terminal segment is not required for catalytic activity and is likely to serve as signal sequence for import into chloroplasts.
Keywords: Arabidopsis thaliana; Lycopersicon esculentum; Brassicaceae; Solanaceae; Riboflavin biosynthesis; GTP cyclohydrolase II; 3,4-dihydroxy-2-butanon 4-phosphate synthase;
Biosynthesis of 20-hydroxyecdysone in Ajuga hairy roots: the possibility of 7-ene introduction at a late stage by Ryo Hyodo; Yoshinori Fujimoto (733-737).
Administration of [3α- 2 H ]-3β-hydroxy-5β-cholestan-6-one to hairy roots of Ajuga reptans var. atropurpurea followed by 2 H -NMR spectroscopic analysis of the resulting 20-hydroxyecdysone so formed revealed that the substrate was efficiently incorporated into the latter. Additionally, [5β,7α,7β- 2 H 3 ]-2β,3β-dihydroxy-5β-cholestan-6-one was converted into 20-hydroxyecdysone. These findings clearly indicate that Ajuga hairy roots are capable of introducing a double bond at the 7-position at a late stage of 20-hydroxyecdysone biosynthesis, suggesting the possibility of an alternative biosynthetic pathway which does not involve 7-dehydrocholesterol as an obligatory intermediate.
Keywords: 20-Hydroxyecdysone; Ecdysteroid; Biosynthesis; 3β-Hydroxy-5β-cholestan-6-one; Ajuga reptans var. atropurpurea; Labiatae;
Photo-induced synthesis of tomatidenol-based glycoalkaloids in Solanum phureja tubers by D.Wynne Griffiths; Henry Bain; Nigel Deighton; Graeme W Robertson; M.Finlay B Dale (739-745).
The effect of light exposure on the steroidal glycoalkaloid content of Solanum phureja tubers has been investigated and compared with that in domesticated potato (Solanum tuberosum) tubers. The results indicated that the increase in the concentration of solanidine-based glycoalkaloids, ᾱ-solanine and ᾱ-chaconine was broadly similar in both species. However, in the S. phureja tubers, light exposure also induced the synthesis of tomatidenol-based glycoalkaloids. These have been identified as α- and β-solamarine. These glycoalkaloids were not detected in tubers continually stored in darkness.
Keywords: Glycoalkaloids; ᾱ-Solanine; ᾱ-Chaconine; ᾱ-Solamarine; Light exposure; S. phureja; S. tuberosum;
Fungicidal activity of natural and synthetic sesquiterpene lactone analogs by D.E. Wedge; J.C.G. Galindo; F.A. Macı́as (747-757).
Fungicidal activity of 36 natural and synthetic sesquiterpene lactones with guaianolide, trans, trans-germacranolide, cis, cis-germacranolide, melampolide, and eudesmanolide carbon skeletons was evaluated against the phytopathogenic fungi Colletotrichum acutatum, C. fragariae, C. gloeosporioides, Fusarium oxysporum, Botrytis cinerea, and Phomopsis sp. Dose-response data for the active compounds dehydrozaluzanin C, dehydrocostuslactone, 5α-hydroxydehydrocostuslacone, costunolide, and zaluzanin C are presented. A new 96-well microbioassay procedure for fast and easy evaluation of antifungal activity was used to compare these compounds with commercial fungicide standards. Some structure-activity conclusions are also presented.
Keywords: Fungicides; Dehydrozaluzanin C; Zaluzanin C; Dehydrocostuslactone; Costunolide; 5α-Hydroxydehydrocostuslactone; Sesquiterpene lactones; Colletotrichum acutatum; Colletotrichum fragariae; Colletotrichum gloeosporioides; Fusarium oxysporum; Botrytis cinerea; Phomopsis sp;
Prenylflavonoid variation in Humulus lupulus: distribution and taxonomic significance of xanthogalenol and 4′-O-methylxanthohumol by Jan F. Stevens; Alan W. Taylor; Gail B. Nickerson; Monika Ivancic; John Henning; Alfred Haunold; Max L. Deinzer (759-775).
The resins produced by either lupulin or leaf glands of over 120 plants of Humulus lupulus and one plant of H. japonicus (Cannabinaceae) were analyzed for the presence of prenylated flavonoids. The H. lupulus taxa investigated were H. lupulus var. lupulus from Europe, H. lupulus var. cordifolius from Japan, and H. lupulus from North America. Fifty-two of the plants examined were cultivars of European, American, and Japanese origin. Twenty-two flavonoids were detected in the glandular exudates of H. lupulus by HPLC-MS–MS. Xanthohumol (3′-prenyl-6′-O-methylchalconaringenin) was the principal prenylflavonoid in all H. lupulus plants and was accompanied by 11 structurally similar chalcones. Ten flavonoids were identified as the flavanone isomers of these chalcones. Three other prenylchalcones were isolated from H. lupulus cv. ‘Galena’, one of which was identified as 3′-prenyl-4′-O-methylchalconaringenin (named ‘xanthogalenol’). The distribution of three 4′-O-methylchalcones, i.e. xanthogalenol, 4′-O-methylxanthohumol, and 4′,6′-di-O-methylchalconaringenin, was found to be limited to wild American plants from the Missouri–Mississippi river basin, H. lupulus var. cordifolius, and most of their descendents. These 4′-O-methylchalcones were absent from cultivars of European origin, and from wild hops from Europe and southwestern USA. The flavonoid dichotomy (presence versus absence of 4′-O-methylchalcones) indicates that there are at least two evolutionary lineages within H. lupulus (European and Japanese–American), which is in agreement with morphological, molecular, and phytogeographical evidence. Leaf glands of H. japonicus from eastern Asia did not produce the H. lupulus prenylflavonoids.
Keywords: Humulus lupulus; H. japonicus; Cannabinaceae; Hops; Prenylated flavonoids; Xanthohumol; Xanthogalenol; Mass spectrometry; Chemotaxonomy;
Biosynthetic studies on the tropane ring system of the tropane alkaloids from Datura stramonium by Rosa Duran-Patron; David O’Hagan; John T.G. Hamilton; Chi W. Wong (777-784).
Isotopic labelling experiments have been carried out in Datura stramonium root cultures with the following isotopically labelled precursors; [ 2 H 3 ]-, [2- 13 C , 2 H 3 ]-, [1- 13 C , 18O2]-acetates, 2 H 2 O , [ 2 H 3 -methyl]-methionine, [2- 13 C ]-phenyllactate, [3- 2 H ]-tropine and [2′- 13 C , 3- 2 H ]-littorine. The study explored the incorporation of isotope into the tropane ring system of littorine 1 and hyoscyamine 2 and revealed that deuterium from acetate is incorporated only into C-6 and C-7, and not into C-2 and C-4 as previously reported. Oxygen-18 was not retained at a detectable level into the C(3)–O bond from [1- 13 C , 18 O 2 ]-acetate. The intramolecular nature of the rearrangement of littorine 1 to hyoscyamine 2 is revealed again by a labelling study using [2′- 13 C , 3- 2 H ]-littorine, [2- 13 C ]-phenyllactate and [3- 2 H ]-tropine.
Keywords: Datura stramonium; Biosynthesis; Tropane alkaloids; Hyoscyamine; Littorine;
Structure and synthesis of ether-linked proteracacinidin and promelacacinidin proanthocyanidins from Acacia caffra by Linette Bennie; Elfranco Malan; Johan Coetzee; Daneel Ferreira (785-793).
Two new ether-linked proanthocyanidins, epioritin-(4β → 3)-epioritin-4β-ol and epimesquitol-(4β → 4)-epioritin-4β-ol, were isolated from the heartwood of Acacia caffra. Their structures and absolute configurations were established by spectroscopic methods and syntheses.
Keywords: Acacia caffra; Leguminosae; Proteracacinidins; Promelacacinidins; Proanthocyanidins; Synthesis;
Structure and synthesis of the first procassinidin dimers based on epicatechin, and gallo- and epigallo-catechin by Johan Coetzee; Lulama Mciteka; Elfranco Malan; Daneel Ferreira (795-804).
The range of natural dimeric procassinidins is extended by identification of cassiaflavan-(4α → 8)-epicatechin, cassiaflavan-(4α → 8)-epigallocatechin, cassiaflavan-(4β → 8)-epicatechin, cassiaflavan-(4β → 8)-epigallocatechin, cassiaflavan-(4β → 8)-gallocatechin, ent-cassiaflavan-(4β → 8)-epicatechin and cassiaflavan-(4α → 6)-epicatechin in the bark of Cassia petersiana. Their structures and absolute configuration were confirmed by synthesis.
Keywords: Cassia petersiana; Leguminosae; Flavanoids; Proanthocyanidins; Procassinidins; Synthesis;
Triterpenoids from Tripterygium wilfordii by Hongquan Duan; Yoshihisa Takaishi; Hiroshi Momota; Yasukazu Ohmoto; Takao Taki; Yongfeng Jia; Duan Li (805-810).
The extract (TII) of Tripterygium wilfordii Hook f. afforded four triterpenoids: wilforic acid D (3β,24-epoxy-2α-hydroxy-24R∗-ethoxy-29-friedelanoic acid); (E) 3β,24-epoxy-2-oxo-3α-hydroxy-29-friedelanoic acid; (F) 2β-hydroxy-3-oxo-friedelan-29-oic acid; 29-hydroxy-3-oxo-olean-12-en-28-oic acid and 17 known triterpenoids. Their structures were established on the basis of spectroscopic studies. In a bioactivity analysis, only the known dulcioic acid compound showed a significant inhibitory effect on cytokine production.
Keywords: Tripterygium wilfordii; Triterpenoids; Immunosuppressive activity;
6-[ω-arylalkenyl]-5,6-dihydro-α-pyrones from Cryptocarya moschata (Lauraceae) by Alberto José Cavalheiro; Massayoshi Yoshida (811-819).
Eleven 6-[ω-arylalkenyl]-5,6-dihydro-α-pyrones, cryptomoscatones D2, E1, E2, E3 and F1 and cryptopyranmoscatones A1, A2, A3, B1, B2 and B4, in addition to goniothalamin and cryptofolione, were isolated from branch and stem bark of Cryptocarya moschata, Lauraceae. Their structures were established by spectroscopic methods.
Keywords: Cryptocarya moschata; Lauraceae; 6-[ω-arylalkenyl]-5,6-dihydro-α-pyrone; Cryptomoscatone; Cryptopyranmoscatone; Cryptofolione; Goniothalamin; Styryl-pyrone;
Regulation of Primary Metabolic Pathways in Plants by Jeffrey B Harborne (821-822).
Plant Secondary Metabolism by Jeffrey B Harborne (821).
Heavy Metal Stress in Plants: From Molecules to Ecosystems by D Neumann (822).
Corrigendum to “Highly oxygenated bisabolenes and an acetylene from Matricaria aurea” by Ahmed A Ahmed; Maha A.Abou Elela (825).
Erratum to “Epoxyconiferyl alcohol from Fraxinus oxycarpa bark” by I Kostova; D Dinchev; B Mikhova; T Iossifova (827).