Vitamin a appears as yellow crystals or orange solid. Practically water insoluble. (NTP, 1992)
颜色/状态:
Solvated crystals from polar solvents, such as methanol or ethyl formate
蒸汽压力:
7.5X10-8 mm Hg at 25 °C /Estimated/
稳定性/保质期:
存在于烟叶中。
折光率:
Index of refraction: 1.6410 at 20 °C/D (calculated form refractive indexes of 20-70% solutions in mineral oil); max absorption: 324-325 nm (E=1,835, 1%, 1 cm)
Hepatic. Retinol is conjugated with glucuronic acid; the B-glucuronide undergoes enterohepatic circulation and oxidation to retinol and retinoic acid. Retinoic acid undergoes decarboxylation and conjugation with glucuronic acid.
Retinol is converted to retinyl phosphate in epithelial tissues, and this intermediate is in turn metabolized to mannosylretinylphosphate in a reaction that is catalyzed by a microsomal enzyme and requires guanosine diphosphomannose as a glycosyl donor. ... /the vitamin A/ mediates transfer of mannose to specific glycoproteins.
来源:Hazardous Substances Data Bank (HSDB)
代谢
视黄醇部分转化为β-葡萄糖苷酸,后者经历肠肝循环并被氧化为视黄醛和视黄酸。
Retinol is in part conjugated to form a beta-glucuronide, which undergoes enterohepatic circulation and is oxidized to retinal and retinoic acid.
Within the retina, all-trans-retinol is oxidized to retinal by alcohol dehydrogenases, and is then Isomerized to the 11-cis-isomer which combines with opsin in the rod to yield rhodopsin, and with different opsins in human cones to yield three different iodopsin pigments.
Retinoic acid (RA) is the bioactive metabolite of vitamin A (retinol) which acts on cells to establish or change the pattern of gene activity. Retinol is converted to RA by the action of two types of enzyme, retinol dehydrogenases and retinal dehydrogenases. In the nucleus RA acts as a ligand to activate two families of transcription factors, the RA receptors (RAR) and the retinoid X receptors (RXR) which heterodimerize and bind to the upstream sequences of RA-responsive genes.
Vision:Vitamin A (all-<i>trans</i> retinol) is converted in the retina to the 11-<i>cis</i>-isomer of retinaldehyde or 11-<i>cis</i>-retinal. 11-<i>cis</i>-retinal functions in the retina in the transduction of light into the neural signals necessary for vision. 11-<i>cis</i>-retinal, while attached to opsin in rhodopsin is isomerized to all-<i>trans</i>-retinal by light. This is the event that triggers the nerve impulse to the brain which allows for the perception of light. All-<i>trans</i>-retinal is then released from opsin and reduced to all-<i>trans</i>-retinol. All-<i>trans</i>-retinol is isomerized to 11-<i>cis</i>-retinol in the dark, and then oxidized to 11-<i>cis</i>-retinal. 11-<i>cis</i>-retinal recombines with opsin to re-form rhodopsin. Night blindness or defective vision at low illumination results from a failure to re-synthesize 11-<i>cis</i> retinal rapidly. <br/>Epithelial differentiation: The role of Vitamin A in epithelial differentiation, as well as in other physiological processes, involves the binding of Vitamin A to two families of nuclear retinoid receptors (retinoic acid receptors, RARs; and retinoid-X receptors, RXRs). These receptors function as ligand-activated transcription factors that modulate gene transcription. When there is not enough Vitamin A to bind these receptors, natural cell differentiation and growth are interrupted.
Normal doses of vitamin A are not associated with liver injury or liver test abnormalities, but higher doses (generally more than 40,000 IU daily, ~12,000 μg) can be toxic. Acute toxicity is caused by a single or a few repeated very high doses (generally >100 times the RDA), arising within days to weeks with a typical symptom complex of severe headache, nausea, vertigo, blurred vision, muscle aches and lack of coordination, followed by skin desquamation and alopecia. Severe overdose can cause increased cerebral spinal fluid pressure, progressive drowsiness and coma. Chronic hypervitaminosis A usually arises 3 months to many years after starting moderately high levels of vitamin A (generally 10 times the RDA) and is marked by dry skin, cheilosis, gingivitis, muscle and joint pains, fatigue, mental dullness, depression and liver test abnormalities. Serum bilirubin is typically only mildly elevated. Serum aminotransferase and alkaline phosphatase levels are variably increased, but usually only 1 to 4 times the upper limit of normal. Serum vitamin A levels are typically, but not invariably elevated. Liver biopsy is diagnostic and shows enlarged, lipid-laden stellate cells with variable degrees of sinusoidal fibrosis. The liver may be hypoechogenic on ultrasound examination and suggest the diagnosis of nonalcoholic fatty liver disease, but the lipid-laden cells found on liver biopsy are not hepatocytes, but rather stellate cells (formerly known as Ito cells or hepatic lipocytes) which contain excess vitamin A. Chronic, moderately high doses of vitamin A (generally over 1 to 8 years) can lead to portal hypertension with ascites and esophageal varices, even before frank cirrhosis can be shown to be present. While high doses of vitamin A are usually achieved by vitamin A supplements, hypervitaminosis A can also occur with excessive dietary intake of liver, particularly that of carnivores (bears, seals, dogs) or salt-water fish (cod liver oil).
Less than 5% of circulating vitamin A is bound to lipoproteins in blood (normal), but may be up to 65% when hepatic stores are saturated because of excessive intake. The amount of vitamin A bound to lipoproteins may be increased in hyperlipoproteinemia. When released from liver, vitamin A is bound to retinol-binding protein (RBP). Most vitamin A circulates in the form of retinol bound to RBP.
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
储存:肝脏(大约2年的成人需求量),肾脏和肺组织中储存少量。锌是动员肝脏中维生素A储备所必需的。
Storage: Hepatic (approximately 2 years' adult requirements), with small amounts stored in kidney and lung tissues. Zinc is required for mobilization of vitamin A reserves in the liver.
More than 90% of the intake of preformed vitamin A is in the form of retinol esters, usually as retinyl palmitate. ... When a large excess is ingested, some of the vitamin escapes in the feces. ... Absorption ... is related to that of lipid and is enhanced by bile. ... Aqueous dispersions ... are absorbed more rapidly than are oily solution.
Selective isomerization of retinal upon two-photon excitation
摘要:
The products of photo-isomerization when excited directly up to the two-photon-allowed (1)A(g)(-) excited state of alltrans and five cis isomers of retinal were determined. The composition of the isomers at the photo-stationary state was drastically changed as compared to one-photon excitation. The production of the 13-cis isomer was selectively increased, and the production of the dicis isomers was observed in the case of a direct excitation upon the 3(1)A(g)(-) state, although they were hard to be produced by one-photon excitation in n-hexane solution. These results clearly evidenced that there exist isomerization pathways via two-photon-allowed excited states. (C) 2003 Elsevier Science B.V. All rights reserved.
[EN] ACC INHIBITORS AND USES THEREOF<br/>[FR] INHIBITEURS DE L'ACC ET UTILISATIONS ASSOCIÉES
申请人:GILEAD APOLLO LLC
公开号:WO2017075056A1
公开(公告)日:2017-05-04
The present invention provides compounds I and II useful as inhibitors of Acetyl CoA Carboxylase (ACC), compositions thereof, and methods of using the same.
The present invention relates to oligoesters and their use or the creation of additives. Oligoester containing additives and/or oligoesters themselves may be used for formulating pharmaceutical preparations, cosmetics or personal care products such as shampoos and conditioners. These oligoesters are particularly useful for the creation of multi-purpose additives that can impart conditioning, long substantivity and/or UV protection. Individual oligoesters and oligoester mixtures are described.
Eflornithine Prodrugs, Conjugates and Salts, and Methods of Use Thereof
申请人:Xu Feng
公开号:US20100120727A1
公开(公告)日:2010-05-13
In one aspect, the present invention provides a composition of a covalent conjugate of an eflornithine analog with an anti-inflammatory drug. In another aspect, the present invention provides a composition of an eflornithine prodrug. In another aspect, the present invention provides a composition of an eflornithine or its derivatives aspirin salt. In another aspect, the present invention provides methods for treating or preventing cancer using the conjugates or salts of eflornithine analogs or eflornithine prodrugs.
Compounds are provided having the structure of Formula (I) or a pharmaceutically acceptable isomer, racemate, hydrate, solvate, isotope, or salt thereof, wherein R1, R2, X1, X2, Y1, and Y2 are as defined herein. Such compounds function as thyromimetics and have utility for treating diseases such as neurodegenerative disorders and fibrotic diseases. Pharmaceutical compositions containing such compounds are also provided, as are methods of their use and preparation.
[EN] DERIVATIVES OF AMANITA TOXINS AND THEIR CONJUGATION TO A CELL BINDING MOLECULE<br/>[FR] DÉRIVÉS DE TOXINES D'AMANITES ET LEUR CONJUGAISON À UNE MOLÉCULE DE LIAISON CELLULAIRE
申请人:HANGZHOU DAC BIOTECH CO LTD
公开号:WO2017046658A1
公开(公告)日:2017-03-23
Derivatives of Amernita toxins of Formula (I), wherein, formula (a) R 1, R 2, R 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, X, L, m, n and Q are defined herein. The preparation of the derivatives. The therapeutic use of the derivatives in the targeted treatment of cancers, autoimmune disorders, and infectious diseases.