Alkaloids from the leaves of Strychnos wallichiana

The leaves of Strychnos wallichiana Steud. ex. DC. from Bangladesh contain icajine and novacine as their major alkaloids. Smaller amounts of strychnine, brucine, pseudostrychnine, pseudobrucine, N-methyl-sec.-pseudo-β-colubrine, 14-hydroxyicajine, strychnine N-oxide, and brucine N-oxide are also present. The new bases 14 hydroxynovacine and icajine N-oxide have been isolated.     

Influence of the ion-balance in the growth medium on the yield and alkaloid content ofDatura stramonium L.

Plants ofDatura stramonium var.tatula L. Torr. were grown for 24 weeks on vermiculite and provided with mineral solutions where the relative proportions of the major anions (N, S, P) and cations (K, Ca, Mg) were varied within a constant total.With all treatments a cyclic transport of alkaloids (hyoscyamine) from the roots to the upper plant parts appeared. The fluctuations in alkaloid content in the leaves followed those in the roots with a delay of 4 weeks.The interionic ratios seemed to influence growth and alkaloid content rather than to affect the ontogenic variations. In general, the response to the different treatments could be divided into two types. The nitrogen treatments which gave at the same time a higher crop yield and an increased hyoscyamine content, and the other treatments where a much lower yield and content was obtained.The scopolamine content on the other hand seemed to be more affected by the developmental stage. Also, the time of maximal yield was not influenced by the ion-balance but rather the climatic conditions.     

大花翠雀的新二萜生物碱

从大花翠雀(Delphinium grandiflorum L.)的地上部分分离到两个微量的新二萜生物碱——大花翠雀辛(grandifloricine,Ⅰ)和大花翠雀亭(grandifloritine,Ⅱ)。通过分析光谱信息测定了它们的化学结构,并通过化学反应转变为 takaosamine 而得到确证。     

Stoichiometry of interaction between soluble (—)-dopa melanin and enantiomers of ephedrine by NMR spectroscopy

Synthetic soluble (—)-dopa melanin was prepared in deuteriated buffer, pH 8, by autooxidation of the precursor. At 6 mM of the precursor, the incorporation was over 90%. The changes in the line width measurements of N-CH₃ protons of enantiomers of ephedrine in the soluble melanin were quantified by NMR spectroscopy. The dissociation constants of (—)-1R,2S-ephedrine, (+)-1S,2R-ephedrine, (—)-1R,2R-ψ-ephedrine, and (+)-1S,2S-ψ-ephedrine were 11.7, 4.20, 3.60, and 4.80 mM, respectively. Since the concentration of (—)-dopa was known and since the conversion of (—)-dopa to indole units of melanin was considered as 1:1, the stoichiometry of the interaction between the drug and the indole unit was calculated. Based on the dissociation constants of the enantiomers, it appears that up to four molecules of (—)-ephedrine can interact with one indole unit of the melanin, while such a ratio for other isomers appear to be 2:1. The preference by indole units of melanin is stereoselective. © 1992 Wiley-Liss, Inc.     

Studies on the biosynthesis of tropane alkaloids in Datura stramonium L. transformed root cultures

The relative contributions made by the l-arginine/agmatine/N-carbamoylputrescine/putrescine and the l-ornithine/putrescine pathways to hyoscyamine formation have been investigated in a transformed root culture of Datura stramonium. The activity of either arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17) was suppressed in vivo by using the specific irreversible inhibitors of these activities, dl--difluoromethylarginine or dl--difluoromethylornithine, respectively. It was found that suppression of arginine decarboxylase resulted in a severe decrease in free and conjugated putrescine and in the putrescine-derived intermediates of hyoscyamine biosynthesis. In contrast, the suppression of ornithine decarboxylase activity stimulated an elevation of arginine decarboxylase and minimal loss of metabolites from the amine and alkaloid pools. The stimulation of arginine decarboxylase was not, however, sufficient to maintain the same potential rate of putrescine biosynthesis as in control tissue. It is concluded that (i) in Datura the two routes by which putrescine may be formed do not act in isolation from one another, (ii) arginine decarboxylase is the more important activity for hyoscyamine formation, and (iii) the formation of polyamines is favoured over the biosynthesis of tropane alkaloids. An interaction between putrescine metabolism and other amines is also indicated from a stimulation of tyramine accumulation seen at high levels of dl--difluoromethylornithine.Abbreviations ADC arginine decarboxylase - DFMA dl--dif-luoromethylarginine - DFMO dl--difluoromethylornithine - MPO N-methylputrescine oxidase - ODC ornithine decarboxylase - PMT putrescine N-methyltransferase We are indebted to Dr. E.W.H. Bohme of Merrell Dow Research Laboratories (Cincinnati, Ohio, USA) for kind gifts of DFMO and DFMA and to Dr. M.J.C. Rhodes for helpful advice and discussion.     

Pyridine alkaloid distribution in the hoplonemertines

Hoplonemertines possess a family of pyridine compounds affecting the nervous system (Kem, 1985). Anabaseine, the first pyridine to be isolated, stimulates nicotinic receptors. Two other substances, 2,3-bipyridyl and nemertelline (a tetrapyridyl) were isolated from Amphiporus angulatus. In this study samples of 19 species of hoplonemertines were surveyed for the presence of stable pyridines using thin layer chromatography. Pyridines were selectively detected with the Konig reagent.Pyridines were found to be nearly ubiquitous constituents of this taxonomic group. Nevertheless, individual species often differed in the pyridines present as well as the variety of compounds present. A new Konig-reactive pyridine was found in 11 hoplonemertine species. Only Zygonemertes virescens and Amphiporus lactifloreus contained anabasine. Only A. angulatus contained 2,3-bipyridyl and nemertelline. This initial survey suggests that differences in pyridine compositions between hoplonemertines may be a useful taxonomic character.     

An alkaloid from Haplophyllum tuberculatum

A new alkaloid (+)-tuberine was isolated from Haplophyllum tuberculatum. Physicochemical and spectral evidence established its structure and stereochemistry as N- benzoyl-4′-[(2″S,3″S,6″S)-(+)-7″-acetoxy-2″-hydroxy-3″,7″-dimethyl-3″,6″-epoxyoctyloxy]phenethylamine.     

Hormonal changes associated with leaf senescence in cotton (Gossypium barbadense)

To study the hormonal regulation of foliar senescence in cotton ( Gossypium barbadense L. cv. Giza 68, long staple), the sequential changes in gibberellins (GAs), indoleacetic acid (IAA) and abscisic acid (ABA) were examined in the cotyledons from the completion of expansion through senescence (days 12-24 after sowing). The onset of senescence could be detected on day 20, the stage of maximum accumulation of leaf metabolites. At this stage, free GAs quickly lost more than 40% of their initial activity. Further decrease of free GAs was then characteristically observed in the senescent leaves. A remarkable increase in free IAA and free ABA between days 18 and 20 immediately followed by nutrient depletion, suggests the contribution by both hormones to the senescence system. The definite drop in free IAA below its initial level occurred on day 24, when most of the leaf protein and chlorophyll were already broken down.     

Purification and properties of indole 2,3-dioxygenase from maize leaves

An indole 2,3-dioxygenase was purified ca 38-fold from maize leaves. The enzyme had an MW of about 98000, an optimum pH of 5.0 and the energy of activation was 9.1 kcal/mol. The K_max for indole was 1.4 × 10^?4 M. The enzyme was inhibited by diethyldithiocarbamate, salicylaldoxime and sodium dithionite. The inhibition by diethyldithiocarbamate was specifically reversed by Cu²⁺. The dialysed enzyme was stimulated by Cu²⁺. Four atoms of oxygen were utilized in the disappearance of 1 mole of indole. Inhibition of the enzyme by -SH compounds and -SH group inhibitors, and their partial removal by Cu²⁺ only, suggested the involvement of -SH groups in binding of Cu²⁺ at the catalytic site.