Comparative study of the alkaloids in tribe Datureae and their chemosystematic significance

Sixty-six tropane alkaloids from crude leaf and root alkaloid mixtures of 12 different species and their varieties and subspecies from tribe Datureae were determined by GC–MS. The alkaloids 3β-hydroxy-6β-acetoxytropane, 3-propionyloxy-6-hyroxytropane, 3β-hydroxy-6β-tigloyloxytropane, 3β-tigloyloxy-6β-acetoxytropane and 3-tigloyloxy-7-isobutyryloxytropane are new reported tropane alkaloids.     

Alkaloid spectrum in diploid and tetraploid hairy root cultures of Datura stramonium

Hairy root cultures were obtained from diploid and induced tetraploid plants of Datura stramonium and analyzed by gas chromatography/mass spectrometry. Twenty alkaloids (19 for diploid and 9 for tetraploid hairy root cultures) were identified. A new tropane ester 3-tigloyloxy-6-propionyloxy-7-hydroxytropane was identified on the basis of mass spectral data. Hyoscyamine was the main alkaloid in both diploid and tetraploid cultures. In contrast to diploid hairy roots, the percentage contributions of the alkaloids, with exceptions for hyoscyamine and apoatropine, were higher in the total alkaloid mixture of tetraploid hairy roots.     

Tropane alkaloids of Datura innoxia from Morocco

Fifty three alkaloids were identified in the organs (roots, stems, leaves, flowers, and seeds) of Datura innoxia by GC/MS. Seventeen of them are reported for the first time for this species and one nor-derivative, 3-phenylacetoxynortropane (28), for the genus Datura. Furthermore, four new tropane esters were tentatively identified as 3-acetoxy-6,7-epoxytropane (acetylscopine) (10), 3-acetoxy-6-propionyloxy-7-hydroxytropane (15), 6,7-dehydro-3-phenylacetoxytropane (25), and 3-(2'-phenylpropionyloxy)-6,7-epoxynortropane (dihydroaponorscopolamine) (37) on the basis of their mass spectral data. Hyoscyamine (44) and scopolamine (48) figure as main alkaloids in the roots and aerial parts, respectively.     

Alkaloids of Erythroxylum zambesiacum root-bark

Six new alkaloids characterized from the root-bark ofErythroxylum zambesiacum were: 3α-(3,4,5-trimethoxybenzoyloxy)nortropane, 3α-(3,4,5-trimethoxybenzoyloxy)tropan-6β-ol, 3α-(3,4,5-trimethoxybenzoyloxy)-nortropan-6β-ol, 6β-benzoyloxytropan-3α,-diol, 6β-benzoyloxy-3α-(3,4,5-trimethoxycinnamoyloxy)tropan-7β-ol, and 7β-acetoxy-6β-benzoyloxy-3a-(3,4,5-trimethoxycinnamoyloxy)tropane. Other bases identified included 3α-(3,4,5-trimethoxybenzoyloxy)tropane, 3α-(3,4,5-trimethoxycinnamoyloxy)tropane, 3a-phenylacetoxytropan-6β-ol, 3α-(3,4,5-trimethoxybenzoyloxy)tropan-6β,7β-diol, 6β-benzoyloxytropan-3α-ol, and 6β-benzoyloxy-3α-(3,4,5-trimethoxycinnamoyloxy)tropane; other bases could not be fully characterized. The chemotaxonomic implications of the esterifying acids are discussed.     

Stereochemistry of tropane alkaloid formation in Datura

Five-month-old Datura innoxia plants were fed via the roots with either d(+)-hygrine-[2′-¹⁴C] or l(?)-hygrine-[2′-¹⁴C]. After 7 days the root alkaloids 3α,6β-ditigloyloxytropane, 3α,6β-ditigloyloxytropan-7β-ol, hyoscine, hyoscyamine and cuscohygrine were isolated from both groups of plants. d(+) but not l(?)-hygrine acts as a precursor for the tropane alkaloids whereas both enantiomers appeared to serve equally well in the biosynthesis of cuscohygrine.     

Distribution of alkaloids in Anthocercis littorea and A. viscosa

The distribution of tropane alkaloids in organs of Anthocercis littorea and A. viscosa is reported. The following alkaloids have been isolated: atropine (hyoscyamine), apoatropine, noratropine (norhyoscyamine), littorine, hyoscine, norhyoscine, meteloidine, 3α, 6β-ditigloyloxytropan-7β-ol, 6β-tigloyloxytropan-3α-ol, 3α-tigloyloxytropane, tigloidine, tropine, ψ-tropine, (?)-tropan-3α-6β-diol, cuscohygrine and unknown bases.     

Two Tropinone Reductases with Distinct Stereospecificities from Cultured Roots of Hyoscyamus niger

Tropinone is an alkamine intermediate at the branch point of biosynthetic pathways leading to various tropane alkaloids. Two stereospecifically distinct NADPH-dependent oxidoreductases, TR-I and TR-II, which, respectively, reduce tropinone to 3α-hydroxytropane (tropine) and 3β-hydroxytropane (ψ-tropine), were detected mainly in the root of tropane alkaloid-producing plants but not in nonproducing cultured root. Both reductases were purified to near homogeneity from cultured root of Hyoscyamus niger and characterized. The TR-I reaction was reversible, whereas the TR-II reaction was essentially irreversible, reduction of the ketone being highly favored over oxidation of the alcohol ψ-tropine. Marked differences were found between the two reductase in their affinities for tropinone substrate and in the effects of amino acid modification reagents. Some differences in substrate specificity were apparent. For example, N-propyl-4-piperidone was reduced by TR-II but not by TR-I. Conversely, 3-quinuclidinone and 8-thiabicyclo[3,2,1]octane-3-one were accepted as substrates by TR-I but hardly at all by TR-II. Both enzymes were shown to be class B oxidoreductases, which transfer the pro-S hydrogen of NAD(P)H to their substrates. Possible roles of these tropinone reductases in alkaloid biosynthesis are discussed.     

Tropane alkaloids from Erythroxylum caatingae Plowman

Three tropane alkaloids, 1-3, were isolated from Erythroxylum caatingae, i.e., 6β-benzoyloxy-3α-[(4-hydroxy-3,5-dimethoxybenzoyl)oxy]tropane (1), a new tropane alkaloid, along with the known alkaloids 3α,6β-dibenzoyloxytropane (2) and 6β-benzoyloxy-3α-[(3,4,5-trimethoxybenzoyl)oxy]tropane (catuabine B; 3). Their structures were determined by 2D- ((1) H and (13) C) NMR. By LC/ESI-MS/MS analysis of the fractions of alkaloids 1-3, it was possible to detect five more alkaloids, 4-8, two of these, 4 and 8, possibly being new natural products. X-Ray crystallography of the chloride derivate of 1, i.e., 6β-benzoyloxy-3α-(4-hydroxy-3,5-dimethoxybenzoyloxy)tropane hydrochloride (1a) confirmed the structure of 1. Cytotoxicity was tested against the cell lines HEp-2, NCI-H292, and KB for the MeOH extract and alkaloid 3, and antitumor activity was tested against Sarcoma 180 only for the MeOH extract.     

In vitro organogenesis and alkaloid accumulation in Datura innoxia

The kinetics of tropane alkaloids accumulation in different organs such as roots, leaves, stems, flowers and seeds of Datura innoxia was investigated by GC-MS. Twenty-six tropane alkaloids were detected. The ester derivatives of tropine (3alpha-tigloyloxytropine and 3-tigloyloxy-6-hydroxytropine) are the major compounds. Undifferentiated callus were established from the stem explants of Datura innoxia using Murashige and Skoog (MS) medium supplied with 6-benzylaminopurine (BA, 1 mg l(-10) and indole-3-acetic acid (IAA, 0.5 mg l(-1)) in combination for 6 weeks. Callus differentiation was initiated by subculture onto solid MS medium, free from hormones, for more than 10 months. Initially, shoots were formed after four weeks from subculture. Further subculturing in basal MS medium without growth regulators initiated the rooting of a shooty callus after 6 weeks. Investigation of the alkaloid content of the unorganized and organized callus revealed that callus (either green or brown) yielded only trace amounts of alkaloids. On the other hand, re-differentiated shoots contained mainly scopolamine while re-differentiated roots biosynthesized hyoscyamine as the main alkaloid.     

Simultaneous determination of scopolamine, hyoscyamine and littorine in plants and different hairy root clones of Hyoscyamus muticus by micellar electrokinetic chromatography

Hyoscyamus muticus hairy root clones were established following infection with Agrobacterium rhizogenes strains A4, LBA-9402 and 15834 and with A. tumefaciens strain C58C1pRTGus104. The accumulation of tropane alkaloids hyoscyamine, littorine and scopolamine was evaluated by micellar electrokinetic capillary electrophoresis. Littorine was reported for the first time in these clones as well as in the roots of the intact plant and confirmed by collision induced dissociation-mass spectrometry. Tropane alkaloid content in hairy roots was compared with leaves and roots of normal plants at two vegetative stages. Significant differences appeared between the alkaloid contents of the different clones. In particular, all the hairy root clones and the roots of the intact plant produced 1.5-3 and 4.5-9 times more littorine than scopolamine, respectively. The only exception was clone KB7, carrying the h6h gene, which overproduced scopolamine. The aerial parts of H. muticus plants did not contain any littorine, thus indicating different transportation or translocation mechanisms of the various tropane alkaloids.     

Tropane alkaloids from Schizanthus hookeri

Tropine, a pair of diastereoisomeric hygrolines and two new tropane alkaloids; 3α-senecioyloxytropan-6β-ol and 6β-angeloyloxytropan-3α-ol, were isolated from roots of Schizanthus hookeri.     

Weed control ability of Egyptian Natural Products against annual,perennial and parasitic weeds

The research and application of natural product herbicides have received considerable attention recently over the world as alternative tools against chemical herbicides for weed control due to many unique properties. A wide variety of compounds shows the broadest spectrum of herbicidal activity were found in Egyptian plant resources including; [6,3′-dihydroxy-3,5,7,4′-tetra methoxy flavone, dihydro-quercetin, 3,6,7,3`,4`-pentamethoxyflavone, quercetagetin 3, 5, 6, 7, 3′, 4′-hexamethyl ether, 6,-4′-dihydroxy-3,7-dimethoxyflavone, 6,4⁻-dihydroxy-3,5,7-trimethoxyflavone, sesquiterpene (Eudesm-4(15), 11(13)-diene-12,5β-oIide) and 3, 5-dicaffeoyl quinic acid] from Jasonia montana, [15-hydroxyisocostic acid, methyl 15- oxo-eudesome-4, 11(13)-diene 12-oate as well as 1α, 9α-dihydroxy-α-cyclocostunolide, isorhamnetin 3-sulfate, isorhamnetin 3-O-rutinoside rhamanetin and epicatechin] from Conyza dioscoridis, [chlorogenic acid, hydroxyl-3-methoxyflavone, quercetin, kaempferol 3β-D-6”-O-cis-cinnamoyl glucoside, kaempferol, mangiferin, coumaroyl glucoside, coumaroyl quince acid, dicaffeoyl quinic acids] from Silverleaf nightshade Solanum elaeagnifolium Cav, [apigenin, matricolone, herniarin and coumarin, apigenin-7-O-4″, 6″-diacetyl glycoside and apigenin 7-O-4–acetyl glycoside] from Matricaria chamomilla, and [kaempferol 3-O-β-(6″-p-coumaroyl glucopyranoside] from Abutilon theophrasti respectively. These constituents are isolated by chromatographic techniques and identified by spectroscopic methods and tested in both pre and post emergence stages of weeds to determine the effective dose and time for use. The natural herbicide isolated from plant or microorganisms are potentially useful as selective, biodegradable, safe to the environment which will provide an alternative natural solution for combating crop weeds. This review focuses on the characteristics of natural product herbicides from Egyptian plants and evaluates against weeds.     

Functional characterization of recombinant hyoscyamine 6β-hydroxylase from Atropa belladonna

(-)-Hyoscyamine, the enantiomerically pure form of atropine, and its derivative scopolamine are tropane alkaloids that are extensively used in medicine. Hyoscyamine 6β-hydroxylase (H6H, EC 1.14.11.11), a monomeric α-ketoglutarate dependent dioxygenase, converts (-)-hyoscyamine to its 6,7-epoxy derivative, scopolamine, in two sequential steps. In this study, H6H of Atropa belladonna (AbH6H) was cloned, heterologously expressed in Escherichia coli, purified and characterized. The catalytic efficiency of AbH6H, especially for the second oxidation, was found to be low, and this may be one of the reasons why Atropa belladonna produces less scopolamine than other species in the same family. 6,7-Dehydrohyoscyamine, a potential precursor for the last step of epoxidation, was shown not to be an obligatory intermediate in the biosynthesis of scopolamine using purified AbH6H with an in vitro (18)O labeling experiment. Moreover, the nitrogen atom in the tropane ring of (-)-hyoscyamine was found to play an important role in substrate recognition.     

Changes in the Total Alkaloid Content of Datura innoxia Mill. Subjected to Salt Stress

Datura plants were grown on a clayed support and subjected tosalinity stress (153.8 mol m^–3 NaCl) at the 6-leaf stage.Salt treatment increased total alkaloid content in young leaves.The results indicated that at the organ level tropane alkaloidaccumulation was related to plant growth. Key words: Datura innoxia, salt stress, tropane alkaloids     

Radioimmunoassay for the quantitative determination of scopolamine

A radioimmunoassay for the determination of pmol amounts of the tropane alkaloid scopolamine has been developed. The assay uses tritiated [N-C³H₃]scopolamine of high specific activity (0.67 Ci/mmol) as tracer. The measuring range of the assay extends from 0.5 to 50 ng of scopolamine, and as little as 200 pg may be detected. The antiserum raised against a conjugate of scopolamine-N-β-propionic acid-human serum albumin is highly specific, and neither hyoscyamine, 6-hydroxyhyoscyamine, scopine, tropic acid nor other related alkaloids interfere in the scopolamine determination in crude plant extracts. This assay allows for the first time the rapid, sensitive and precise (CV = 2.5 %) determination of this alkaloid in unpurified extracts of scopolamine-containing plants. The distribution of scopolamine in Datura plants, as well as its diurnal changes in leaf concentrations, has been investigated in detail and a preliminary survey on the variability of scopolamine leaf concentrations in a population of Datura sanguinea plants is given.     

Flavonoids and coumarins from Platymiscium praecox

The wood of Platymiscium praecox Mart. (Leguminosae-Lotoideae) contains sitosterol, 4,2′,4′-trihydroxychalcone, (2R)-7-hydroxyflavanone, (±)-7,4′-dihydroxyflavanone, (2S, 3S)-3,7-dihydroxyflavanone, 3,7-dihydroxyflavone, 3,7,4′-trihydroxyflavone, 6,7-dihydroxy-4′-methoxyisoflavone and 6,7-dimethoxycoumarin. It also contains three novel compounds: 7-hydroxy-4-methoxy-5-methylcoumarin, 7-O-glucosyloxy-4-methoxy-5-methylcoumarin and 7-hydroxy-4,8-dimethoxy-5-methylcoumarin.     

Tropane alkaloids from Erythroxylum zeylanicum O.E. Schulz (Erythroxylaceae)

Six tropane alkaloids were isolated from the Sri Lankan endemic plant Erythroxylum zeylanicum O.E. Schulz (Erythroxylaceae) and structurally elucidated by NMR and MS measurements. Three of them, erythrozeylanines A [1R,3R,5S,6R-6-acetoxy-3-(3',4',5'-trimethoxybenzoyloxy)tropane], B [cis-3 beta-(cinnamoyloxy)tropane], and C [cis-6 beta-acetoxy-3 alpha-(cinnamoyloxy)tropane] are new, whereas the others have already been found in other Erythroxylum species. For the first time, the absolute configuration of a tropane alkaloid (erythrozeylanine A) has been determined by quantum chemical CD calculations.     

Effects of Oxygen on Nicotine and Tropane Alkaloid Production in Cultured Roots Duboisia myoporoides

The effects of oxygen on nicotine and tropane alkaloid production in root cultures of Duboisia myoporoides were investigated. Duboisia roots cultured in air produced both nicotine and tropane alkaloids equally. However, when roots were cultured in pure oxygen, the metabolic flux to tropane alkaloids increased, and that to nicotine alkaloids decreased. Intermediate product analysis by GC-MS showed an increase in tropine, but decreases in acetyl derivatives of tropane alkaloids and tropine esters with low-class fatty acids. Furthermore, hyoscyamine 6β-hydroxylase (H6H, EC 1.14.11.11, the key enzyme in the pathway from hyosyamine to scopolamine) also increased. These results suggest that pure oxygen contributes to scopolamine production not only by activating the biosynthetic steps for scopolamine, but also by inactivating the biosynthetic steps for nicotine and other tropine derivatives.     

Hyoscyamine 6 beta-hydroxylase, an enzyme involved in tropane alkaloid biosynthesis, is localized at the pericycle of the root

Hyoscyamine 6 beta-hydroxylase (H6H; EC 1.14.11.11) catalyzes the first reaction in the biosynthetic pathway from hyoscyamine to scopolamine in several solanaceous plants. Four monoclonal antibodies were raised against H6H purified from cultured roots of Hyoscyamus niger. The IgG1 antibody mAb5 inhibited H6H activities present in cell-free extracts of H. niger roots and specifically recognized 38-40-kDa proteins from six different scopolamine-producing plant species in Western blot analysis after sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The other three monoclonal antibodies all recognized SDS-denatured H6H protein from Hyoscyamus species, but did not bind to native H6H. Western blot analysis of protein extracts from various tissues of H. niger using these antibodies showed that H6H is abundant in cultured roots, present in plant roots, but absent in leaf, stem, calyx, cultured cells, and cultured shoots. Immunohistochemical studies using monoclonal antibody and immunogold-silver enhancement detected H6H only in the pericycle cells of the young root in several scopolamine-producing plants. Mature roots that underwent secondary growth and lacked the pericycle did not react with the antibody. This pericycle-specific localization of scopolamine biosynthesis provides an anatomical explanation for the tissue-specific biosynthesis of tropane alkaloids and may be important for translocation of tropane alkaloids from the root to the aerial parts.     

Non-reversibility of the isoleucine-acetate pathway in Datura

Five-month-old Datura meteloides plants were fed via the roots with 3-hydroxy-2-methylbutanoic acid-[1-¹⁴C] and isoleucine-[U-¹⁴C] as a positive control. After 5 days the plants were collected and in each case the root alkaloids 3α,6β-ditigloyloxytropane, 3α,6β-ditigloyloxytropan-7β-ol, meteloidine, hyoscine and hyoscyamine were isolated. Whereas isoleucine served as a precursor for the tiglic acid moieties 3-hydroxy-2-methylbutanoic acid did not.