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Application of directly coupled HPLC-NMR-MS to the identification and confirmation of quercetin glycosides and phloretin glycosides in apple peel.

Directly coupled HPLC-NMR-MS was used to identify and confirm the presence of quercetin O-glycosides and phloretin O-glycosides in an extract of apple peel. From the MS and MS/MS data, the molecular weights of the intact molecules as well as those of quercetin and phloretin and their sugar moieties were deduced. The NMR data provided information on the identity of the compounds as well as the alpha and beta conformations and the position of the glycosides on quercetin and phloretin. The following O-glycosides of quercetin could be identified: quercetin-3-alpha-L-rhamnosyl-(1-->6)-beta-D-glucoside (rutin), quercetin-3-beta-D-galactoside (hyperin), quercetin-3-beta-D-glucoside (isoquercitrin), quercetin-3-beta-D-xyloside (reynoutrin), quercetin-3-alpha-L-arabinofuranoside (avicularin), and quercetin-3-alpha-L-rhamnoside (quercitrin). Phloretin was present as phloretin-2'-beta-D-glucoside (phloridzin) and the 2'-beta-D-xylosyl-(1-->6)-beta-D-glucoside. Concentrations were between 0.2 and 5 mg/g of apple peel.

Chromatography, High Pressure Liquid↗

Cardiac glycosides. 7. Sugar stereochemistry and cardiac glycoside activity.

Digitoxigenin alpha-L-, beta-L-, alpha-D-, and beta-D-glucosides; alpha-L-, beta-L-, alpha-D-, and beta-D-mannosides; and alpha-L- and beta-L-rhamnosides were stereoselectively synthesized from the corresponding sugar tetrabenzyl trichloroacetimidates. The Na+,K+-ATPase receptor inhibitory activities of these glycosides (as a measure of receptor binding) were compared with those of digitoxigenin, digitoxigenin 6'-hydroxy-beta-D-digitoxoside, digitoxigenin beta-D-galactoside, and digitoxigenin beta-D-digitoxoside. The observed activities reveal that a given sugar substituent may have a role in binding of some glycoside stereoisomers, but not others. With alpha-L- and possibly beta-L-rhamnosides, the 5'-CH3 and 4'-OH appear to have a predominant role in binding to the Na+,K+-ATPase receptor. Addition of a 6'-OH to form the corresponding mannosides dramatically disrupts the effect of both the 5'-CH3 and 4'-OH in prompting receptor binding of the alpha-L isomer. However, with the beta-L isomer, some influence of 4'-OH, 3'-OH, and 2'-OH binding remains. With beta-D-glycosides, binding via the "5'-CH3 site" appears to be of little importance and addition of a 6'-OH diminishes activity only slightly. With these beta-D-glycosides, an equatorial 4'-OH, axial 3'-OH, and equatorial 2'-OH groups appear to contribute to binding.

Cardiac Glycosides↗

Stereoselective synthesis of 2-deoxy-2-iodo-glycosides from furanoses. A new route to 2-deoxy-glycosides and 2-deoxy-oligosaccharides of ribo and xylo configuration.

[reaction: see text] A general procedure for the stereoselective synthesis of 2-deoxy-2-iodo-hexo- and -hepto-pyranosyl glycosides from furanoses is reported. The proposed methodology provides a new route for accessing 2-deoxy-oligosaccharides. The procedure involves three reactions: Wittig-Horner olefination to give alkenyl sulfanyl derivatives, electrophilic iodine-induced cyclization to give phenyl 2-deoxy-2-iodo-1-thio-hexo-glycosides, and glycosylation. Protected furanoses 1, 3, and 6-11, which include examples of the four possible isomeric configurations of furanoses, were reacted with diphenyl phenylsulfanylmethyl phosphine oxide to give the alkenyl sulfanyl derivatives 2, 4, and 12-16. The iodine-induced cyclization of these compounds afforded the phenyl 2-deoxy-2-iodo-1-thio-glycosides 18, 20, and 22-27 with practically complete regio- and stereoselectivity. Products of 6-endo cyclization, in which the iodine at C-2 was in a cis relationship with the alkoxy at C-3, were almost exclusively produced. Better yields were obtained for compounds with a ribo or xylo configuration than for compounds with other configurations. Compounds 18, 20, and 22-27 were found to be efficient glycosyl donors in the glycosylation of cholesterol and glucopyranoside 29a, affording the corresponding 2-deoxy-2-iodo-glycosides and 2-deoxy-2-iodo-oligosaccharides with good yields and stereoselectivities. The glycosydic bond in the major isomers was always trans to the iodine at C-2.

Deoxy Sugars↗

Triterpene glycosides from the far eastern sea cucumber Pentamera calcigera II: disulfated glycosides.

Three new triterpene glycosides, calcigerosides D(1) (1), D(2) (2), and E (3), have been isolated from the sea cucumber Pentamera calcigera. Their structures have been deduced from extensive spectral analysis (NMR and MS) and chemical evidence. All the compounds are disulfated pentaosides differing in aglycon structure and position of sulfate group, which were determined by the measurement of NT(1) values in the cases of glycosides 1 and 2. Glycoside 1 is a nonholostane derivative, that is, it lacks an 18(20)-lactone, which is very rare among the sea cucumber glycosides.

Animals↗

Natural glycosides containing allopyranose from the passion fruit plant and circular dichroism of benzaldehyde cyanohydrin glycosides.

[structure: see text] Leaves of the edible passion fruit plant, Passiflora edulis, contain benzylic beta-D-allopyranosides 1 and 2, representatives of a rare class of natural glycosides with D-allose as the only sugar constituent. The glycoside 1 is the first known cyanogenic glycoside containing a sugar different from D-glucose attached directly to the cyanohydrin center. Asymmetric perturbation of the (1)L(b) transition of the benzene chromophore was shown to be useful for determination of absolute configuration of the cyanohydrin center of aromatic cyanogenic glycosides.

Benzaldehydes↗

Synthesis of silylallene glycosides and diene diglycosides by C-glycosidation of D-glucal with 1,4-bis(trimethylsilyl)-2-butyne.

[reaction: see text] Silylmethylallenyl glycosides, symmetrical and unsymmetrical diene glycosides, were synthesized by C-glycosidation with 1,4-bis(trimethylsilyl)-2-butyne in good yield. The nature of the product is controlled by the choice of Lewis acid, BF(3).OEt(2), or SnCl(4). The efficient construction of unsymmetrical diene glycosides was achieved in one pot on the basis of the order of addition of sugar starting materials.

Glycosides↗

New 6-O-acyl isoflavone glycosides from soybeans fermented with Bacillus subtilis (natto). I. 6-O-succinylated isoflavone glycosides and their preventive effects on bone loss in ovariectomized rats fed a calcium-deficient diet.

Three new 6-O-acylated isoflavone glycosides were isolated from soybeans fermented with Bacillus subtilis (natto) and identified as daidzein 7-O-beta-(6''-O-succinyl)-D-glucoside (1), genistein 7-O-beta-(6''-O-succinyl)-D-glucoside (2), and glycitein 7-O-beta-(6''-O-succinyl)-D-glucoside (3) on the basis of spectral data and chemical transformations. During fermentation, the content of the isoflavone glycosides first decreased and then increased, whereas the corresponding 6''-O-succinyl derivatives first accumulated and then decreased, in either soybeans or soybean cooking solution. These changes suggest that enzymatic interconversion of isoflavone glycosides and the corresponding 6''-O-succinylated derivatives occurs in these media during fermentation. The 6-O-succinylated isoflavone glycosides 1, 2 and 3 accounted for 4.8, 7.2 and 0.6%, respectively, of the total isoflavones in commercial fermented soybeans (Japanese natto). Oral administration of 1 or 2 alone for 4 weeks at a dose of 50 mg/kg/d prevented bone loss in ovariectomized (ovx) rats fed a calcium-deficient diet, being as effective as the positive controls, daidzin and genistin, respectively. Compound 1 seems to be proestrogenic, like daidzin, which suppresses bone resorption to prevent bone loss after ovariectomy by directly acting on bone sites, while 2 appears to have a different mechanism of action, like that of genistin.

Animals↗

Development of highly potent D-glucosamine-based chiral fluorescent labeling reagents and a microwave-assisted beta-selective glycosidation of a methyl glycoside reagent.

We synthesized new chiral fluorescence labeling reagents having a 2,3-anthracenedicarboximide group from D-glucosamine, and it was possible to introduce target alcohols at the anomeric positions of the reagents with beta-selectivity by glycosidations. Especially, it was possible to use methyl glycoside reagent as a glycosyl donor with a Lewis acid and microwave irradiation, and it gave selectively beta-glycoside while the reaction without microwave irradiation gave alpha- and beta-mixed glycosides. Those reagents showed very high chiral discrimination ability, and they made it possible to separate the eight stereoisomers of 4,8,12,16-tetramethylheptadecanol by HPLC after derivatizations.

Carbohydrate Conformation↗

2-(Trimethylsilyl)ethyl glycosides. Synthesis of the asialo-GM1-tetrasaccharide, spacer glycoside, and BSA and Sepharose glycoconjugates.

The tri and tetra-saccharide glycosides beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OTMSEt and beta-D-Gal-(1-3)-beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OT MSEt (asialo-GM1) have been synthesized by sequential glycosylations of a suitably protected 2-(trimethylsilyl)ethyl (TMSEt) lactoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl chloride and 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl bromide. The tetrasaccharide glycoside was transformed into the corresponding hemiacetal sugar as well as the 1-chloro sugar. The latter was used for glycosylation of 2-bromoethanol. The resulting glycoside was used to alkylate methyl 3-mercaptopropionate and the resulting spacer glycoside was used for the preparation of the title glycoconjugates.

Carbohydrate Sequence↗

[Isolation and identification of flavon(ol)-O-glycosides in caraway (Carum carvi L.), fennel (Foeniculum vulgare Mill.), anise (Pimpinella anisum L.), and coriander (Coriandrum sativum L.), and of flavon-C-glycosides in anise. I. Phenolics of spices (author's transl)].

The flavonoid constituents of various spices were separated by means of chromatography on cellulose colums, and the following compounds were obtained crystalline: Quercetin 3-glucuronide from caraway, fennel, anise, and coriander; isoquercitrin from caraway and fennel; rutin from fennel and anise; quercetin 3-O-caffeylglucoside and kaempferol 3-glucoside from caraway; quercetin 3-arabinoside from fennel, and luteolin 7-glucoside, isoorientin and isovitexin from anise. Other constitutents which were however not obtained crystalline, but which could be identified by the usual procedures were kaempferol 3-glucuronide and kaempferol 3-arabinoside in fennel, apigenin 7-glucoside and a luteolin glycoside in anise, and isoquercitrin and rutin in coriander. The glycosides contained in the fruit of the four spices also occur in the leaves. Leaves of caraway and fennel in addition contain isorhammetin glycosides in low concentration.

Condiments↗

Analytical methods for monoterpene glycosides in grape and wine. II. Qualitative and quantitative determination of monoterpene glycosides in grape.

Free and glycosidically bound terpenes of five Vitis vinifera grape cultivars (muscat of Alexandria, muscat of Frontignan, muscat of Hamburg, muscat Ottonel and Gewürztraminer) were investigated. The free and bound fractions were separated by selective retention on Amberlite XAD-2 resin. The glycosidic fractions were analysed by gas chromatography and gas chromatography-mass spectrometry using either enzymic hydrolysis and subsequent analysis of the released aglycones or trimethylsilyl (TMS) and trifluoroacetyl derivatives. The known monoterpenyl, benzyl and 2-phenylethyl beta-D-glucopyranosides, beta-rutinosides, 6-O-alpha-L-arabinofuranosyl-beta-D-glucopyranosides and 6-O-beta-D-apiofuranosyl-beta-D-glucopyranosides were determined. A number of other glycosides were detected and the structures of some of them, mainly apiosylglucosides and glucosides with aglycones in higher oxidation state than linalol, were tentatively identified using the mass spectra of their TMS and TFA derivatives and the results obtained from the analysis of their aglycones.

Chromatography, Gas↗

The preparation of carbohydrate-protein conjugates: cyanuric trichloride coupling of 2-aminoethyl glycosides, and mixed-anhydride coupling of 8-carboxyoctyl glycosides to bovine serum albumin.

Preparation of the following glycosides is described: 2-aminoethyl beta-D-glycosides of (A) 2-acetamido-3,4,6-trio-O-acetyl-2-deoxy-D-glucopyranose, (B) 2-acetamido-4-O-(2-acetamido-3,4,6-trio-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-3,6-di-O-acetyl-2-deoxy-beta-D-glucopyranose (N,N'-diacetylchitobiose pentaacetate), (C) 4-O-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)-2,3,6-trio-O-acetyl-beta-D-glucopyranose (cellobiose heptaacetate); 8-carboxyoctyl glycosides of (D) cellobiose, and (E) N,N'-diacetylchitobiose. Conjugates were prepared from (A), (B), and (C) by coupling to bovine serum albumin by cyanuric trichloride and subsequent deacetylation; (D) and (E) were coupled to bovine serum albumin by the mixed-anhydride reaction. Conjugates (A) and (B) were insoluble; conjugates (C), (D), and (E) functioned as artificial antigens and gave rise to precipitating antibodies in rabbits. Specificities of the antisera were determined by inhibition studies.

Antibodies↗

Conversion of p-methoxyphenyl glycosides into the corresponding glycosyl chlorides and bromides, and into thiophenyl glycosides.

p-Methoxyphenyl (pMP) beta-D-glycopyranosides (Glc, Gal, GlcNPhth, GalNPhth, GlcNTroc, Gal beta 4Glc, Gal alpha 4Gal) were prepared from the corresponding 1-O-acetyl sugars in 79-90% yield, using boron trifluoride etherate as promoter. Treatment of the pMP glycosides with acyl chlorides or bromides in the presence of various Lewis acids gave the corresponding glycosyl chlorides and bromides in 81-98% yield. Treatment of the acyl-protected pMP glycosides with thiophenol and boron trifluoride etherate gave the corresponding thioglycosides in 80-100% yield and high (> 20:1) beta/alpha selectivity. The stability of pMP glycosides was investigated against a series of reagents.

Anisoles↗

A chlorinated monoterpene ketone, acylated beta-sitosterol glycosides and a flavanone glycoside from Mentha longifolia (Lamiaceae).

Mentha longifolia (Lamiaceae), an aromatic herb yielded a new halogenated chloro-derivative of menthone (longifone), two new derivatives of beta-sitosterol glycoside (longiside-A and -B) and a new flavanone-glycoside (longitin). The beta-sitosterol and flavanone glycosides were purified as their acetate derivatives. Structures of all the isolated constituents were elucidated with the aid of HMBC techniques. However, the structure of longifone was also determined through X-ray crystallography.

Acylation↗

Analysis of glycosidically bound aroma precursors in tea leaves. 1. Qualitative and quantitative analyses of glycosides with aglycons as aroma compounds.

Twenty-six synthetic glycosides constituting aglycons of the main tea aroma compounds ((Z)-3-hexenol, benzyl alcohol, 2-phenylethanol, methyl salicylate, geraniol, linalool, and four isomers of linalool oxides) were synthesized in our laboratory as authentic compounds. Those compounds were used to carry out a direct qualitative and quantitative determination of the glycosides as aroma precursors in different tea cultivars by capillary gas chromatographic-mass spectrometric (GC-MS) analyses after trifluoroacetyl conversion of the tea glycosidic fractions. Eleven beta-D-glucopyranosides, 10 beta-primeverosides (6-O-beta-D-xylopyranosyl-beta-D-glucopyranoside) with aglycons as the above alcohols, and geranyl beta-vicianoside (6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside) were identified (tentatively identified in the case of methyl salicylate beta-primeveroside) in fresh tea leaves and quantified on the basis of calibration curves that had been established by using the synthetic compounds. Primeverosides were more abundant than glucosides in each cultivar we investigated for making green tea, oolong tea, and black tea. Separation of the diastereoisomers of linalool and four isomers of linalool oxides by GC analyses is also discussed.

Calibration↗

Isolation and characterization of stelladerol, a new antioxidant naphthalene glycoside, and other antioxidant glycosides from edible daylily (hemerocallis) flowers.

Daylily (Hemerocallis spp.) flowers are utilized as an important ingredient in traditional Asian cuisine and are also valued for their reputed medicinal effects. In studies of the bioactive methanol and aqueous methanol extracts of lyophilized Hemerocallis cv. Stella de Oro flowers, kaempferol, quercetin, and isorhamnetin 3-O-glycosides (1-9), phenethyl beta-D-glucopyranoside (10), orcinol beta-D-glucopyranoside (11), phloretin 2'-O-beta-D-glucopyranoside (12), phloretin 2'-O-beta-D-xylopyranosyl-(1-->6)-beta-D-glucopyranoside (13), a new naphthalene glycoside, stelladerol (14), and an amino acid (longitubanine A) (15) have been isolated. All of these compounds were tested for their antioxidant and cyclooxygenase inhibitory activities. Stelladerol was found to possess strong antioxidant properties, inhibiting lipid oxidation by 94.6% +/- 1.4 at 10 microM in an in vitro assay. Several of the flavonol 3-O-glycoside isolates also demonstrated modest antioxidant activities at 10 microM. None of the isolates inhibited cyclooxygenase activity at 100 microM.

Antioxidants↗

Cardiac glycosides. 1. A systematic study of digitoxigenin D-glycosides.

A series of digitoxigenin glycosides was studied: five with beta-D-sugars varying stepwise in sugar structure from beta-D-digitoxose to beta-D-galactose, including one beta-D/alpha-D pair. I50 values for these glycosides and digitoxigenin were determined with hog kidney Na+, K+-ATPase. These data suggest a major and unexpected role for 4'-OH conformation in the sugar. All the glycosides with an equatorial 4'-OH were more active than the two with the 4'-OH axial [digitoxigenin beta-D-galactoside (6) I50 = 6.45 X 10(-8) M; digitoxigenin 2'-deoxy-alpha-D-ribo-hexopyranoside (alpha-3a) I50 = 9.33 X 10(-8) M; digitoxigenin I50 = 1.17 X 10(-7) M]. Stereochemistry of the 3'-OH had much less of an activity role than that of the 4'-OH, in contrast to existing models of "sugar-site" binding.

Animals↗