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Three acylated flavonol glycosides have been identified from leaves of Planchonia grandis Ridley. They possess kaempferol as aglycone and two triglycosidic chains substituting hydroxyl groups at the 3- and 7-positions. The first glycosidic unit of each chain is esterified by a cis or trans p-coumaric acid. Structural elucidation was achieved by means of UV, NMR and mass spectrometry.
Four acylated pelargonidin glycosides were isolated from the red-purple flowers of Ipomoea purpurea. The acylated anthocyanins were all based on pelargonidin 3-sophoroside-5-glucoside, acylated with caffeic acid and/or glucosylcaffeic acids. Three novel anthocyanins were elucidated to be pelargonidin 3-O-[2-O-(6-O-(trans-3-O-(beta-D-glucopyranosyl)-caffeyl)- beta-D-glucopyranosyl)-6-O-(trans-4-O-(6-O-(trans-caffeyl)-beta-D- glucopyranosyl)-caffeyl)-beta-D-glucopyranoside]-5-O- [beta-D-glucopyranoside], pelargonidin 3-O-[2-O-(6-O-(trans-caffeyl)-beta-D-glucopyranosyl)-6-O- (trans-4-O-(6-O-(trans-caffeyl)-beta-D-glucospyranosyl)-ceffeyl )-beta-D- glucopyranoside]-5-O-[beta-D-glucopyranoside] and pelargonidin 3-O[2-O-(2-O-(6-O-(trans-caffeyl)-beta-D-glucopyranosyl)-6-O- (trans-caffeyl)-beta-D-glucopyranoside]-5-O-[beta-D-glucopyoside]. Another anthocyanin was pelargonidin 3-O-[2-O-(glucosylcaffeylglucosyl)-6-O-(caffeyl)-glucoside]-5-gluc oside, which was reported to be present in the red-purple flowers of Pharbitis nil. Apart from the second pigment cited, these are analogous pigments of the violet-blue Ipomoea anthocyanins which are composed of acylated cyanidin glycosides, instead of pelargonidin.
A trisaccharide and four new glycosidic acids, named cuscutic acids A-D, along with known organic acids, acetic acid, propionic acid, (2S)-2-methylbutyric acid, tiglic acid, (2R, 3 R)-nilic acid, (11S) convolvulinolic acid and (11S)-jalapinolic acid have been isolated from the alkaline hydrolysate of the ether-insoluble resin glycoside-like fraction of the seeds of Cuscuta chinensis. The compounds were characterized on the basis of chemical and physical data.
The ethanolic extract from the stem bark of Dimocarpus fumatus, showed in vitro cytotoxic activity against KB cells. Fractionation of the extract gave compounds belonging to different classes. The two major components have been identified as a benzoquinone, sargaquinone, and a chromene, sargaol. One sphingolipid, soyacerebroside I, two glycosides of sitosterol, and fatty acids were also identified. Besides these known compounds, two new glycosides of long-chain fatty alcohols have been identified as 1-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D- glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->6)-beta-D- glucopyranosyl]hexadecanol and 1-O-[[alpha-L-arabinopyranosyl-(1-->3)]-alpha-L-rhamnopyranosyl-(1 -->2)- beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->6)-beta-D- glucopyranosyl] hexadecanol, and a mixture of three new diacylglycerylglucosides has been isolated. These structures were elucidated by analysis of 2D-NMR and mass spectra.
From the flower extracts of Crocus speciosus and C. antalyensis nine flavonol glycosides have been isolated. One of these products is a new flavonol glycoside identified as kaempferol 3-O-alpha-(2,3-di-O-beta-D-glucopyranosyl)rhamnopyranoside by UV, mass and NMR spectroscopy.
Two new oleanene glycosides (1-2) possessing hederagenin as the aglycone were isolated from the methanolic extract of the aerial parts of Caltha polypetala together with four known glycosides. The saccharide portion linked to C-3 of the aglycone is made up of alpha-L-arabinopyranose, alpha-L-rhamnopyranose and galactopyranose in the new compounds; while compound 1 possesses linked to C-28 a trisaccharide moiety made up of two beta-D-glucopyranose and one alpha-L-rhamnopyranose unit, in compound 2 the 28-COOH group is free. The structures were elucidated by 1D and 2D NMR experiments including 1H-1H (DQF-COSY, 1D-TOCSY, 2D-ROESY) and 1H-13C (HSQC, HMBC) spectroscopy.
Six novel rearranged cholestane glycosides with a six-membered hemiacetal ring system, designated as saundersiosides C-H, were isolated from the bulbs of Ornithogalum saundersiae. Their structures were determined on the basis of spectroscopic analysis and the result of hydrolysis. The conformation of the six-membered hemiacetal ring of the rearranged cholestanes was shown to be almost a boat-form by molecular mechanics and molecular dynamics calculation studies. Among the isolated compounds, saundersioside E, F, G and H with an aromatic acid ester group at the glycoside moiety were found to be highly cytostatic to human leukemia HL-60 cells, showing IC50 values of 0.021, 0.019, 0.063 and 0.052 microM, respectively, which are as potent as those of the clinically applied anticancer agents, etoposide and methotrexate.
Four new pregnane glycosides, stelmatocryptonoside A, B, C, and D (1-4), were isolated from the stems of Stelmatocrypton khasianum. On the basis of chemical and spectral data, the structures of 1-4 were established as 3beta, 16alpha-dihydroxy-pregn-5-en-20-one-16-O-beta-D-glucopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside; 3beta, 20-dihydroxy-pregn-5-en-20-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl-(1-->2)-beta-D-digitalopyranoside; 3beta, 16alpha-dihydroxy-pregn-5-en-20-one-16-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside; and 3beta, 16alpha-dihydroxy-pregn-5-en-20-one-16-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside. This is the first report of pregnane glycosides with sugar chains linked at C-16 of the aglycone.
The cyanogenic glycosides belong to the products of secondary metabolism, to the natural products of plants. These compounds are composed of an alpha-hydroxynitrile type aglycone and of a sugar moiety (mostly D-glucose). The distribution of the cyanogenic glycosides (CGs) in the plant kingdom is relatively wide, the number of CG-containing taxa is at least 2500, and a lot of such taxa belong to families Fabaceae, Rosaceae, Linaceae, Compositae and others. Different methods of determination are discussed (including the indirect classical photometrical and the new direct chromatographic ones). The genetic control of cyanogenesis has no unique mechanism, the plants show variation in the amount of the produced HCN. The production of HCN depends on both the biosynthesis of CGs and on the existence (or absence) of its degrading enzymes. The biosynthetic precursors of the CGs are different L-amino acids, these are hydroxylated then the N-hydroxylamino acids are converted to aldoximes, these are turned into nitriles. The last ones are hydroxylated to alpha-hydroxynitriles and then they are glycosilated to CGs. The generation of HCN from CGs is a two step process involving a deglycosilation and a cleavage of the molecule (regulated by beta-glucosidase and alpha-hydroxynitrilase). The tissue level compartmentalisation of CGs and their hydrolysing enzymes prevents large-scale hydrolysis in intact plant tissue. The actual level of CGs is determined by various factors both developmental and ecological ones, which are reviewed too. The last part of the present work demonstrates the biological roles of CGs in plant physiological processes and in plant defence mechanisms as well. The effect of CGs (HCN) on different animals, the symptoms of poisonings are discussed to cows, sheep, donkeys, horses and chicks. Finally, the poisonous effects of cassava (Manihot esculenta) roots are summarised on experimental animals and on the human organism.
The hydroxylysine-glycosides in bovine and mouse C1q are directly quantified in parallel with those in human C1q after the alkaline hydrolysis of these molecules. Human, bovine and mouse C1q contain 68.3, 66.3 and 64.0 hydroxylysine-galactosylglucose residues in each of these molecules respectively. Only human C1q contains 2.5 residues of hydroxylysine-galactose per molecule, and both of bovine and mouse C1q contain no detectable hydroxylysine-monosaccharides in their molecules. The percentage of hydroxylysine residues glycosylated to total hydroxylysine residues in each of these molecules is calculated to be 86.4, 92.0 and 95.1% for human, bovine and mouse C1q respectively and is comparable with each other. The percentages of hydroxylysine residues resistant to periodate oxidation to total hydroxylysine residues in these molecules were 61.1, 65.3 and 74.3% for human, bovine and mouse C1q respectively and were significantly lower than those estimated by the direct quantification of hydroxylysine-glycosides after the alkaline hydrolysis of these molecules.
DNA damaged by oxygen radicals has been implicated as a causative event in a number of degenerative diseases, including cancer and aging. So it is very significant to look for ways in which either oxygen radicals are scavenged prior to DNA damage or damaged DNA is repaired to supplement the cells' inadequate repair capacity. The repair activities and reaction mechanism of phenylpropanoid glycosides (PPGs) and their derivatives, isolated from Chinese folk medicinal herbs, towards both dGMP-OH* adducts and dAMP-OH* adducts were studied with the pulse radiolytic technique. On pulse irradiation of nitrous oxide saturated 2 mM dGMP or dAMP aqueous solution containing one of the PPGs or their derivatives, the transient absorption spectra of the hydroxyl adduct of dGMP or dAMP decayed with the formation of that of phenoxyl radicals of PPGs or their derivatives within several decades of microseconds after electron pulse irradiation. The result indicated that dGMP or dAMP hydroxyl adducts can be repaired by PPGs or their derivatives. The rate constants of the repair reactions were deduced to be 0.641-1.28 x 10(9) M(-1) s(-1) for dGMP-OH* and 0.2-0.491 x 10(9) M(-1) s(-1) for dAMP-OH*, which positively correlated to the number of phenolic hydroxyl groups in the glycoside structure. A deeper understanding of this new repair mechanism may help researchers to design strategies to prevent and/or intervene more effectively in free radical related diseases.
Most of the recently reported methods for the quantitation of cardiac glycosides have been for digoxin and its metabolites. Recent procedures using high-performance liquid chromatography-radioimmunoassay (HPLC-RIA) and HPLC following derivatization show appreciable improvements in accuracy and specificity for quantitating digoxin in the low nanogram range. Gas chromatographic procedures have been explored to a very limited extent and further advances in the quantitation of cardiac glycosides are anticipated to arise from the use of laser desorption-Fourier transform mass spectrometry. However, currently, HPLC with derivatization and HPLC-RIA techniques remain the techniques of choice for quantitation of digoxin and/or its metabolites based on considerations of ease of use, sensitivity, specificity, accuracy and reproducibility.
The leaves of Eremophila gilesii have been used traditionally to treat colds, headaches, sores, and chest pains. Our previous screening of Australian native plants showed that the methanol extract of the aerial parts of E. gilesii demonstrated notable inhibition of ADP-induced human platelet aggregation and serotonin release. Subsequent fractionation on the methanol extract led to the isolation of two phenylethanoid glycosides, verbascoside (1) and poliumoside (2). This is the first study reporting the presence of phenylethanoid glycosides in E. gilesii.
The stems of Clerodendron trichotomum have been traditionally used for treatment of hypertension in far East Asia including China, Korea, and Japan. Bioassay-guided fractionation and purification of the EtOAc-soluble extract of Clerodendron trichotomum afforded acteoside (1), leucosceptoside A (2), martynoside (3), acteoside isomer (4), and isomartynoside (5). The angiotensin converting enzyme (ACE) activities were significantly inhibited by the addition of these phenylpropanoid glycosides (1-5) in a dose-dependent manner of which IC(50) values were 373+/-9.3 microg/ml, 423+/-18.8 microg/ml, 524+/-28.1 microg/ml, 376+/-15.6 microg/ml, 505+/-26.7 microg/ml, respectively. These results suggest that the antihypertensive effect of Clerodendron trichotomum may be, at least in part, due to ACE inhibitory effect of phenylpropanoid glycosides.
Digoxin, the cardiac glycoside most frequently used in clinical practice in the United States, can be given orally or intravenously and has an excretory half-life of 36 to 48 hours in patients with serum creatinine and blood urea nitrogen values in the normal range. Since the drug is excreted predominantly by the kidney, the half-life is prolonged progressively with diminishing renal function, reaching about 5 days on average in patients who are essentially anephric. Serum protein binding of digoxin is only about 20%, and differs markedly in this regard from that of digitoxin, which is 97% bound by serum albumin at usual therapeutic levels. Digitoxin is nearly completely absorbed from the normal gastrointestinal tract and has a half-life averaging 5 to 6 days in patients receiving usual doses irrespective of renal function. The bioavailability of digoxin is appreciably less than that of digitoxin, averaging about two-thirds to three-fourths of the equivalent dose given intravenously in the case of currently available tablet formulations. Recent studies have shown that gut flora of about 10% of patients reduce digoxin to a less bioactive dihydro derivative. This process is sensitive to antibiotic administration, creating the potential for important interactions among drugs. Serum or plasma concentrations of digitalis glycosides can be measured by radioimmunoassay methods that are now widely available, but knowledge of serum levels does not substitute for a sound working knowledge of the clinical pharmacology of the preparation used and careful patient follow-up.
Exposure of rat pheochromocytoma PC12 cells to Cuscuta chinensis glycoside induced neuronal differentiation with resulting outgrowth of neurites and increase of acetylcholinesterase activity. A specific inhibitor of mitogen-activated protein kinase (MAPK) kinase, PD98059, prevented this effect of C. chinensis on PC12 cells. These results suggested that C. chinensis glycoside induced neuronal differentiation in PC12 cells linked to the mitogen-activated protein kinase signaling cascade.
The past year has witnessed the expected increase in the number of solved structures of glycoside hydrolases and glycosyltransferases, and their constitutive modules. These structures show that, while glycoside hydrolases display an extraordinary variety of folds, glycosyltransferases and carbohydrate-binding modules appear to belong to a much smaller number of folding families.
The diversity of oligo- and polysaccharides provides an abundance of biological roles for these carbohydrates. The enzymes hydrolysing these compounds, the glycoside hydrolases, therefore mediate a wealth of biological functions. Glycoside hydrolases fall into a number of sequence-based families. The recent analysis of these families, coupled with the burgeoning number of 3D structures, provides a detailed insight into the structure, function and catalytic mechanism of these enzymes.