Studies on metabolism of vitamin A. Absorption of retinal (vitamin A aldehyde) in rats

1. Young rats with low reserves of vitamin A were dosed with retinal in groundnut oil, and the stomach, the contents, mucosa and muscles of small intestine, the blood and the liver were analysed at periods up to 24hr. after dosing. 2. Up to 6hr. after the dose, retinal was present in high concentrations in the contents, mucosa and muscles of the intestine. Small but significant amounts were present in blood and liver at all times. 3. The intestinal mucosa and muscles always contained small amounts of retinol and its esters. 4. A study of the distribution of the three forms of the vitamin within the mucosal cell showed that most of the mucosal retinal enters the cell unchanged. 5. When protein-depleted rats were similarly given retinal, the rate of reduction of the aldehyde, and the consequent deposition in the liver of retinol and its esters, progressively decreased with reduced protein intake.     

The equilibrium between vitamin A alcohol and aldehyde in the presence of alcohol dehydrogenase

Vitamin A is reversibly dehydrogenated to vitamin A aldehyde (retinene) in isolated retinal rods and in liver extracts containing alcohol dehydrogenase and coenzyme 1.The reaction is probably involved in the utilization of vitamin A for the regeneration of bleached visual purple.The equilibrium constant k_H of the dehydrogenation is 3.3 × 10^?9, about 300 times more favorable to the aldehyde than k_H for ethyl alcohol.     

A lanostane aldehyde from Momordica charantia

A new lanostane aldehyde, charantal (1), was isolated from the ethanolic leaf extract of Momordica charantia together with the known compound, 2,4-bis(2-phenylpropan-2-yl)phenol (2). The structure of compound 1 was elucidated by extensive 1D and 2D NMR and MS experiments. Compound 2 displayed a moderately strong antitubercular activity against Mycobacterium tuberculosis H₃₇Rv (MIC = 14 μg/mL) according to the MABA susceptibility assay.     

A C15 aldehyde from Cucumis sativus

cis-8-Pentadecenal was isolated from a concentrate of cucumber volatiles and characterized by spectral analyses and ozonolysis. The biochemical origin of this compound and other long chain aldehydes isolated from cucumber is discussed.     

Serum vitamin A and vitamin E concentrations after parenteral vitamin A administration in sheep

Twenty primiparous dairy sheep of the Mytilene breed, which were fed with a ration deficient in vitamin A and carotenes, were divided into 2 groups of 10 animals each after a 2-month adaptation period. The animals of group A were administered vitamin A palmitate by intramuscular injection (3500 IU/kg bodyweight), while the animals of group B were used as controls and received only the vehicle of the preparation without vitamin A. Serum vitamin A concentrations increased significantly in the animals of group A compared to the animals of group B (P < 0.01) from the first 24 h post-injection and remained significantly high for 8 days, and at 10 days post-injection they reached the pre-injection levels. The serum vitamin E concentration declined significantly (P < 0.05) in the animals of group A compared to the animals of group B for 8 days, when they reached the pre-injection levels. No changes in serum vitamins A and E levels in the animals of the 2 groups were observed 20 days after the injection of vitamin A.     

Reactivity of vitamin A derivatives and analogues with vitamin A antibodies

Vitamin A antibodies were obtained using retinoic acid conjugated to human serum albumin as an immunogen. The following constraints governed the reactivity of vitamin A analogues with such an anti-serum. The stereochemistry of the side chain is relatively unimportant, and 9- and 13-cis retinal react almost as well as all-trans retinal. The nature of the ring is important; all of the compounds that react readily carry a beta-ionic ring; all of the compounds bearing an aromatic ring react poorly; the two compounds that display intermediate reactivity have non-aromatic 6- and 5-membered rings, respectively.     

A novel aldehyde dextran sulfonate matrix for affinity biosensors

Aldehyde dextran sulfonate (ADS), a modified oligosaccharide polymer, was used to prepare a new matrix structure for affinity biosensors. The principal difference between the ADS matrix and similar structures developed previously results from presence of two active functional groups in the matrix, namely, aldehyde and sulfonate. These groups perform two different functions in the matrix. The aldehyde group is responsible for covalent bonding in the biomaterials, and the negatively charged sulfonate group provides electrostatic attraction of the positively charged biomolecules. By varying the ratio between the aldehyde and sulfonate groups in the matrix, one can control contributions from the two binding modes (covalent and electrostatic). A number of oligosaccharides, such as simple dextran, aldehyde dextran (AD), aldehyde dextran sulfonate (ADS) and aldehyde ethylcellulose (AEC), were used for preparation of matrix structures. The properties of the obtained matrices were analysed and compared. Surface plasmon resonance (SPR) was used as the main technique to characterize the matrix structures.