ABSTRACT
In carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a formidable challenge. This complexity is comparable to the synthesis of 1,2-cis-β-D-mannosides, primarily due to the adverse anomeric and Δ-2 effects. Over the past decades, to attain β-stereoselectivity in D-rhamnosylation, researchers have devised numerous direct and indirect methodologies, including the hydrogen-bond-mediated aglycone delivery (HAD) method, the synthesis of β-D-mannoside paired with C6 deoxygenation, and the combined approach of 1,2-trans-glycosylation and C2 epimerization. This review elaborates on the advancements in β-D-rhamnosylation and its implications for the total synthesis of tiacumicin B and other physiologically relevant glycans.
Subject(s)
Glycosides , Mannosides , Glycosylation , StereoisomerismABSTRACT
Chrysophyllum albidum G. is a tropical plant and commonly found in Nigeria. It belongs to the sapotaceae family and used in folklore in the treatment of yellow fever, malaria, diarrhea, vaginal and dermatological infections. The study was aimed at investigating the antioxidant properties of this plant by employing the in vitro and in vivo experimental models. The effect of DPPH free radical scavenging activity on the fractions of petroleum ether, ethanol, butanol, ethylacetate, and water of C. albidum was determined. The ethyl acetate fraction was purified in column chromatography to obtain myricetin rhamnoside. Structure elucidation was done by NMR and mass spectroscopic techniques. Furthermore, ethanol extract was administered to five groups of eight rats per group. The animals in the normal group were administered with vehicle alone for 7 days. The positive control animals were given vehicle on the first four days, and with the vehicle and hepatotoxin [CC1[4]] on the fifth, sixth and seventh day. The animals in the treatment category were respectively administered with 500, 1000 and 1500 mg/kg b.w. of extract and distilled water for the first four days, and with distilled water, extract and CC1[4] on the last three days. Animals were subsequently anaesthetized and blood samples were collected for catalase [CAT], malondialdehyde [MDA], reduced gluthathione [GSH] and superoxide dismutase [SOD] assays. The petroleum ether fraction showed the least antiradical activity [4057.5 +/- 809.6 g/kg] while ethyl ether exhibited the highest activity [414.4 +/- 92.0 g/kg]. Myricetin rhamnoside also exhibited an excellent radical scavenging activity [314.1 +/- 60.2] which was comparable to the positive control. Result from animal study showed that C. albidum exhibited significant [p < 0.05] differences on the activity of CAT, MDA and GSH. The plant could therefore be employed as sources of natural antioxidant boosters and for the treatment of some oxidative stress disorders in which free radicals are implicated
Subject(s)
Animals, Laboratory , Male , Antioxidants/chemistry , Superoxide Dismutase/blood , Biphenyl Compounds/chemistry , Chemical and Drug Induced Liver Injury/prevention & control , Free Radical Scavengers/chemistry , Carbon Tetrachloride/pharmacology , Catalase/blood , Malondialdehyde , Mannosides , Plant Extracts/chemistry , Plant Leaves/chemistry , Rats, WistarABSTRACT
<p><b>AIM</b>To study the biotransformation of kaempferitrin, a major chemical principle of the fruits of Siraitia grosvenori (Swingle) C. Jeffery, with human intestinal flora.</p><p><b>METHODS</b>The kaempferitrin was incubated with human intestinal flora. The biotransformation products were isolated and purified by chromatographic methods and the structures were determined by spectroscopic techniques.</p><p><b>RESULTS</b>Kaempferitrin was converted into kaempferol 3-O-alpha-L-rhamnoside (afzelin, I) , kaempferol 7-O-alpha-L-rhamnoside (II), kaempferol (III) and p-hydroxybenzoic acid (IV) by human intestinal flora. rhamnoside (II), kaempferol (III) and p-hydroxybenzoic acid (IV) by human intestinal flora.</p><p><b>CONCLUSION</b>The structure of kaempferitrin can be biotransformatedly converted by human intestinal flora.</p>
Subject(s)
Humans , Bacteria , Metabolism , Biotransformation , Fruit , Chemistry , Intestines , Microbiology , Kaempferols , Metabolism , Pharmacokinetics , Mannosides , Metabolism , Momordica , Chemistry , Parabens , Metabolism , Plants, Medicinal , Chemistry , Proanthocyanidins , MetabolismABSTRACT
<p><b>AIM</b>To study the bioactive constituents from the flower of Castanea mollissima Blume.</p><p><b>METHODS</b>Compounds were isolated and purified by column chromatography on silica gel and polyamide. Structures were determined by various spectroscopic data,including UV, IR, 1H and 13CNMR, EIMS and FABMS, 1H-13C-COSY and HMBC.</p><p><b>RESULTS</b>Two compounds were isolated from the ethyl acetate fraction of 95% ethanol extract and the structures were elucidated as kaempferol-3-O-[6"-(E)-p-coumaroyl]-alpha-D-mannopyranoside (1) and kaempferol-3-O-[6", 4"-di-(E)-p-coumaroyl]-alpha-D-mannopyranoside (2).</p><p><b>CONCLUSION</b>Compounds 1 and 2 are new compounds, named castanoside A and B respectirely.</p>
Subject(s)
Fagaceae , Chemistry , Flowers , Chemistry , Glucosides , Chemistry , Kaempferols , Chemistry , Mannosides , Chemistry , Molecular Conformation , Molecular Structure , Plants, Medicinal , ChemistryABSTRACT
<p><b>OBJECTIVE</b>To study the chemical constituents in the Galeobdolon chinense.</p><p><b>METHOD</b>The chemical constituents were separated by means of chromatogrophy, and their structures were identified by spectra of FAB-MS, IR, UV, 1H-NMR, 13C-NMR, DEPT, HMQC and HMBC.</p><p><b>RESULT</b>Two compounds were obtained and identified as galeobdoside (I) whose structure was apigenin-7-O-beta-D-(6'-p-hydoxy-cinnamoyloxy)-mannoside and verbascoside (II).</p><p><b>CONCLUSION</b>Compound I was a new compound and compound II was obtained from this plant for the first time.</p>
Subject(s)
Flavonoids , Chemistry , Glucosides , Chemistry , Lamiaceae , Chemistry , Mannosides , Chemistry , Molecular Conformation , Molecular Structure , Phenols , Chemistry , Plants, Medicinal , ChemistryABSTRACT
Two flavonoid compounds, viz. 5,7-dimethyl ether of leucopelargonidin 3-0-alpha-L rhamnoside and 5,3'-dimethyl ether of leucocyanidin 3-0-alpha-D galactosyl cellobioside obtained from the bark of F. bengalensis were evaluated for their antioxidant action in hyperlipidemic rats. The results were compared with the activity of a structurally similar flavonoid, quercetin, a known antioxidant. The Ficus compounds showed significant antioxidant effects which may be attributed to their polyphenolic nature. The methylation of two hydrozyl groups in the Ficus flavonoids might have slowed down their antioxidant action as compared to quercetin.
Subject(s)
Animals , Anthocyanins , Antioxidants/isolation & purification , Cellobiose/analogs & derivatives , Chromans/isolation & purification , Flavonoids/isolation & purification , Hyperlipidemias/drug therapy , Lipid Peroxidation/drug effects , Male , Mannosides/isolation & purification , Quercetin/pharmacology , Rats , Rats, Sprague-Dawley , Rosales/chemistry , Trees/chemistryABSTRACT
Dimethoxy ether of Leucopelargonidin-3-0-alpha-L rhamnoside isolated from the bark of the Indian Banyan tree Ficus bengalensis Linn. was tested for antidiabetic effect. At a medium effective dose (100 mg/kg) on oral administration, the compound showed significant hypoglycemic and serum insulin raising action in normal as also moderately diabetic dogs (induced by alloxan) during a period of two hours. The mechanism of action of the glycoside compound seems to be similar to that of drugs which stimulate insulin secretion. On acute and chronic administration in single doses of 0.2-1.8 g/kg to different groups of mice and daily administration of 100, 250 and 500 mg/kg to rats for a period of one month respectively did not show any toxic effect and the compound was not lethal even at the high dose of 1.8 g/kg in experimental animals.