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Biomedical subjects

T J Mabry

Publications and source records attributed to T J Mabry.

At least 37 records · Page 2Linked to original sources
PubMed1995

Enzymes of B-ring-deoxy flavonoid biosynthesis in elicited cell cultures of "old man" cactus (Cephalocereus senilis).

Elicited cell cultures of the cactus Cephalocereus senilis produce a group of flavonoids with unsubstituted B-rings, including an aurone which represents a new class of phytoalexin. Preliminary enzymological studies indicated that the chalcone synthase (CHS) and chalcone isomerase (CHI) from cultures of C. senilis were active with cinnamoyl-CoA and 2',4',6'-trihydroxychalcone, respectively, probable intermediates for synthesis of flavonoids with unsubstituted B-rings. We now demonstrate that the cultures contain two isoforms of CHI, both of which are induced by elicitor treatment and are active with both 2',4,4',6'-tetrahydroxy- and 2',4',6'-trihydroxychalcone. (Hydroxy)-cinnamate:CoA ligase in the cactus cultures was active with cinnamic, 4-coumaric, caffeic, ferulic, and 4-methoxycinnamic acids, but not sinapic acid. A single form of CoA ligase, as resolved by chromatofocusing analysis, was active against both cinnamate and 4-coumarate. Cinnamic acid 4-hydroxylase (CA4H) activity was induced by elicitor treatment. Thus, elicited cultures contain the necessary enzymatic activities for synthesis of B-ring-hydroxy and -deoxy flavonoids. Synthesis of only the deoxy class in response to elicitation may result from some form of metabolic compartmentation through which the CA4H reaction is bypassed, leading to formation of cinnamoyl CoA which may then be incorporated into B-ring deoxy flavonoids via nondiscriminating CHS and CHI activities.

Acyltransferases↗
PubMed1995

Rapid gas chromatographic screening of edible seeds, nuts and beans for non-protein and protein amino acids.

Water extraction with subsequent picric acid treatment and solvent washing (ethyl acetate and diethyl ether) was employed for the rapid isolation of free amino acids from non-aqueous food samples. The isolated amino acids were subjected to N(O,S)-isobutyloxycarbonylation followed by solid-phase extraction and tert.-butyldimethylsilylation for direct analysis by gas chromatography and gas chromatography-mass spectrometry. When the present method was applied to nineteen food samples (common beans, seeds, and nuts), seventeen protein amino acids and fifteen non-protein amino acids were simultaneously screened. Eleven non-protein amino acids including gamma-aminobutyric acid, pipecolic acid, pyroglutamic acid, alpha-aminobutyric acid, alpha-aminoadipic acid, and beta-alanine were tentatively identified, and four compounds assumed to be non-protein amino acids remained unidentified.

Amino Acids↗
PubMed1995

Screening for non-protein amino acids in seeds of the Guam cycad, Cycas circinalis, by an improved GC-MS method.

The non-protein amino acid, beta-N-methyl-amino-L-alanine (L-BMAA) from Cycas circinalis seeds, has been implicated as a causative agent of amyotrophic lateral sclerosis-Parkinsonism dementia complex (ALS-PDC), a disease known from Guam and other areas in the western Pacific. We analyzed C. circinalis seeds for additional free non-protein amino acids by a recently developed GC-MS method. The samples were prepared by water extraction of seed flour. The amino acids present in the extract were derivatized by N(O,S)-isobutyloxycarbonylation of the amine functional groups and then tert-butyldimethylsilylation of the carboxyl functional groups. Peaks for a total of seventeen derivatives of non-protein amino acids were detected by GC-MS. In addition to L-BMAA, four other non-protein amino acids were identified as beta-alanine, gamma-amino-butyric acid, pyroglutamic acid, and alpha-aminoadipic acid.

Amino Acids↗
PubMed1995

GC-MS analysis of nonprotein amino acids in Gymnocladus dioicus as N(O,S)-isobutyloxycarbonyl silyl derivatives.

Two different derivatives of novel nonprotein amino acids in Gymnocladus dioicus seeds are prepared for gas chromatographic (GC) and mass spectrometric (MS) analysis. The interfering components in a water extract of the seeds are removed by picric acid treatment and multistep washing with organic solvents followed by N(O,S)-isobutyloxycarbonylation combined with solid-phase extraction. The resulting N(O,S)-isobutyloxycarbonyl (isoBOC) amino acids are then converted to either tert-butyldimethylsilyl (TBDMS) or trimethylsilyl (TMS) derivatives, which are analyzed by dual capillary column GC and GC-MS. The characteristic ions in the mass spectra of N(O,S)-isoBOC TBDMS and N(O,S)-isoBOC TMS derivatives enable confirmation of molecular weight and existence of functional groups containing active protons. Temperature programmed retention index sets measured on DB-5 and DB-17 capillary columns (J&W Scientific; Folsom, CA) are useful for distinguishing among structural isomers. gamma-Methylglutamic acid, diastereoisomers of 3-hydroxy-4-methylglutamic acid, cis and trans isomers of 5-hydroxypipecolic acid, and some free protein amino acids are identified in Gymnocladus dioicus seeds.

Amino Acids↗
PubMed1994

The magical and medicinal usage of Stangeria eriopus in South Africa.

The underground caudex of the cycad Stangeria eriopus is used extensively by several ethnic groups in South Africa, mainly as an ingredient in magical potions but also as an emetic. An assessment of two main outlets showed that 3410 plants were sold in the month of July 1992; continued usage of this material now threatens the remaining plant populations. A proximate analysis of the caudex material gives high carbohydrate content with only small percentages of fat, protein, fibre and ash. An unusually high content of sodium sulphate may explain the efficacy of Stangeria-containing preparations as an emetic. The phytosterols sitosterol and stigmasterol are present in a 4:1 ratio while the fatty acid component comprises palmitic, oleic, stearic and arachidic acids. Twelve amino acids were identified in the material, including the non-protein amino acids beta-alanine, gamma-aminobutyric acid and pyroglutamic acid. The candidate neurotoxin beta-N-methylamino-L-alanine could not be detected but cycasin is present at the levels of 0.17% and 0.21% in fresh and dry caudex material, respectively and appears to be accompanied by the related toxin, macrozamin.

Attitude to Health↗
PubMed1994

Simultaneous gas chromatographic analysis of non-protein and protein amino acids as N(O,S)-isobutyloxycarbonyl tert.-butyldimethylsilyl derivatives.

A unique derivatization procedure is described for the simultaneous determination of protein and non-protein amino acids present in aqueous samples. This procedure involves N(O,S)-isobutyloxycarbonylation combined with solid-phase extraction with subsequent tert.-butyldimethylsilylation for gas chromatographic analysis. Using this combined procedure, linear responses were obtained in the range of 10-100 ppm, with correlation coefficients varying from 0.991 to 0.999, for the free amino acids studied except for homocysteine (0.922) and homoserine (0.982). The relative standard deviations ranged from 0.7 to 5% for most amino acids with a few exceptions. Temperature-programmed retention index (I) sets as measured on DB-5 and DB-17 dual-capillary columns were characteristic of each amino acid and thus useful for the screening of amino acids by computer I matching. The mass spectral patterns of amino acid derivatives, exhibiting characteristic [M-57]+, [M-113]+, [M-131]+, [M-159]+, [M-174]+ and other ions, permitted rapid structural confirmation. The present method allowed simultaneous screening of free protein and non-protein amino acids when applied to seed samples such as almond, walnut, and sunflower seeds.

Amino Acids↗
PubMed1994

An acylated flavone C-glycoside from Glycyrrhiza eurycarpa.

A new acylated flavone C-glycoside, apigenin 6-C-alpha-L-rhamnopyranoside-8-C-[6"-(3-hydroxy-3-methyl-glutaroyl )-beta-D-glucopyranoside], was isolated from rhizomes of Glycyrrhiza eurycarpa and its structure was established on the basis of spectroscopic data.

Apigenin↗
PubMed1994

Flavonol glycosides from Cephalocereus senilis.

A new flavonol tetraglycoside, together with two known flavonol glycosides, kaempferol 7-rhamnoside and kaempferol 3-rhamnosyl(1-->6) galactoside-7-rhamnoside, were isolated from fresh plant material of Cephalocereus senilis. The structure of the new compound was established as kaempferol 3-O-beta-D-glucopyranosyl(1-->2)-O-[alpha-L-rhamnopyranosyl (1-->6)]-beta-D-galactopyranoside-7-O-alpha-L-rhamnopyranoside based on spectroscopic data. The whole plant flavonoid chemistry was strikingly different from that found previously in chitin-treated cell suspension cultures of the same plant.

Carbohydrate Sequence↗
PubMed1994

Pokeweed antiviral protein inactivates pokeweed ribosomes; implications for the antiviral mechanism.

Pokeweed antiviral protein (PAP) and other ribosome-inactivating proteins (RIPs) had previously been thought to be incapable of attacking conspecific ribosomes, thus having no effect on endogenous processes. This assertion conflicts with a model for PAP's in vivo antiviral mechanism in which PAP (a cell wall protein) selectively enters virus-infected cells and disrupts protein synthesis, thus causing local suicide and preventing virus replication. We show here that pokeweed (Phytolacca americana) ribosomes, as well as endod (Phytolacca dodecandra) ribosomes, are indeed highly sensitive to inactivation by conspecific RIPs. Ribosomes isolated from RIP-free pokeweed and endod suspension culture cells were found to be highly active in vitro, as measured by poly(U)-directed polyphenylalanine synthesis. Phytolacca ribosomes challenged with conspecific RIPs generated dose-response curves (IC50 of 1 nM PAP or dodecandrin) very similar to those from wheat germ ribosomes. To determine if Phytolacca cells produce a cytosolic 'anti-RIP' protective element, ribosomes were combined with Phytolacca postribosomal supernatant factors from culture cells, then challenged with conspecific RIPs. Resulting IC50 values of 3-7 nM PAP, PAP-II, PAP-S or dodecandrin indicate that supernatants from these Phytolacca cells lack a ribosomal protective element. This research demonstrates that PAP inactivates pokeweed ribosomes (and is therefore potentially toxic to pokeweed cells) and supports the local suicide model for PAP's in vivo antiviral mechanism. The importance of spatial separation between PAP and ribosomes of cells producing this RIP is emphasized, particularly if crop plants are transformed with the PAP gene to confer antiviral protection.

Antiviral Agents↗
PubMed1993

New sesquiterpene alpha-methylene lactones from the Egyptian plant Jasonia candicans.

Extracts of the plant Jasonia candicans possess antimicrobial activity. ET2O/MeOH extracts were subjected to liquid chromatography, and several sesquiterpenes were isolated and identified including the known compounds confertin [1], 4,11(13)-eudesmadien-12-oic acid [2], and 11-eudesmen-4-ol [3]. Two new diol alpha-methylene lactone antimicrobial agents were identified from nmr and mass spectral data and X-ray crystallography as (4 alpha, 5 alpha, 8 beta, 10 beta)-4,10-dihydroxy-1,11(13)-guaidien-12,8-olide [4] and (4 alpha, 5 alpha, 8 beta, 10 alpha)-4,10-dihydroxyl-1,11 (13)-guaidien-12,8-olide[5], which differ in stereochemistry at the C-10 tertiary alcohol center.

Lactones↗
PubMed1993

Sesquiterpene glycosides from Calendula arvensis.

The extract of the aerial parts of Calendula arvensis afforded four new sesquiterpene glycosides 1-4 in addition to three known compounds. The structures of the new compounds were established by high field 1H-nmr spectroscopy.

Magnetic Resonance Spectroscopy↗
PubMed1991

Absolute configurations of three ent-beyerene derivatives.

(1): 11 beta,17-Bis(4-bromobenzoyloxy)-9 beta-hydroxy-ent-beyerene, C34H38Br2O5, Mr = 686.5, orthorhombic, P2(1)2(1)2(1), a = 6.1686 (12), b = 14.613 (3), c = 32.935 (7) A, V = 2969 (1) A3, Z = 4, Dx = 1.536 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 27.43 cm-1, F(000) = 1408, T = 173 K, R = 0.0347 and wR = 0.0358 for 3064 reflections [Io greater than or equal to 3 sigma(Io)]. (2): 7 beta,17-Bis(4-bromobenzoyloxy)-9 beta-hydroxy-ent-beyerene, C34H38Br2O5, Mr = 686.5, monoclinic, P2(1), a = 12.6424 (15), b = 6.8353 (12), c = 18.496 (2) A, beta = 101.901 (9) degrees, V = 1564.0 (4) A3, Z = 2, D chi = 1.458 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 26.03 cm-1, F(000) = 704, T = 173 A, R = 0.0336 and wR = 0.0361 for 4610 reflections [Io greater than or equal to 3 sigma(Io)]. (3): 17-(4-Bromobenzoyloxy)-9 beta,11 beta-epoxy-7 beta-hydroxy-ent-beyerene, C27H33BrO4, Mr = 501.5, orthorhombic, P2(1)2(1)2(1), a = 6.1315 (7), b = 18.389 (3), c = 21.109 (3) A, V = 2380.0 (6) A3, Z = 4, D chi = 1.399 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 17.38 cm-1, F(000) = 1048, T = 198 K, R = 0.0325 and wR = 0.0344 for 2292 reflections [Io greater than or equal to 3 sigma(Io)].(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗
PubMed1991

Structure of the flavone hymenoxin.

2-(3,4-Dimethoxyphenyl)-5,7-dihydroxy-6,8-dimethoxy-4H-chromen-4-o ne, C19H18O8, Mr = 374.38, monoclinic, P2(1)/n, a = 9.026(4), b = 15.054(6), c = 12.829(6) A, beta = 100.98(4) degrees, V = 1711(1) A3, Z = 4, Dx = 1.450 g cm-3, lambda (Mo K alpha) = 0.71073 A, mu = 1.07 cm-1, F(000) = 784, T = 295 K, R = 0.0778 for 2280 independent reflections. The nearly planar AB ring system (0.04 A r.m.s.d.), O(1) to C(10), and the planar C ring (0.001 A r.m.s.d.) are almost coplanar with an interplanar angle of only 4.4(4) degrees. The methyl groups at C(6) and C(8) are rotated out of the molecular plane on opposite sides with torsion angles C(5)C(6)O(6)C(11) = -94.5(4) and C(7)C(8)O(8)C(12) = 109.0(4) degrees. The methyl groups of ring C are coplanar with the ring, C(3')C(4')O(4')"(13) = 0.2(5) and C(6')C(5')O(5')C(14) = 1.3(5) degrees. The carbonyl group forms an intramolecular hydrogen bond with O(5), O(5)...O(4) = 2.612(5), H(5O)...O(4) = 1.85(4) A, O(5)-H(5O)...O(4) = 151.9(8) degrees, and an intermolecular hydrogen bond with O(7) of an adjacent molecule, O(7)...O(4) (-0.5 + x, -0.5 - y, 0.5 + z) = 2.689(5), H(7O)...O(4) = 1.92(4) A, and O(7)-H(7O)...O(4) = 163.2(8) degrees.

Flavonoids↗
PubMed1989

Structure of a non-planar flavonol, 5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone.

C20H20O10, Mr = 420.37, triclinic, P1, a = 8.771 (3), b = 13.508 (3), c = 15.970 (4) A, alpha = 86.04 (2), beta = 81.77 (2), gamma = 84.17 (2) degrees, V = 1860.0 (8) A3, Z = 4 (two molecules per asymmetric unit), Dm (by flotation in ZnCl2/H2O solution at 298 K) = 1.491, Dx = 1.503 g cm-3, Mo K alpha radiation, lambda = 0.71069 A, mu = 1.14 cm-1, F(000) = 880, T = 163 K. Full-matrix least-squares refinement converged to R = 0.039 and wR = 0.037 using 5198 reflections with I greater than 3 sigma (I). The two molecules in the asymmetric unit differ in the torsion angles involving the methoxy groups and in the dihedral angle between the planes of rings B and C, 33.31 (7) and 40.83 (7) degrees in molecules (I) and (II), respectively. This compound belongs to a class of 3,2'-dioxygenated flavonoids whose ultraviolet (UV), mass spectroscopic (MS) and chromatographic properties indicate that in solution these compounds have reduced planarity (and thus reduced conjugation) of the B-ring chromophore with the A, C-ring chromophore.

Chemical Phenomena↗