Riboflavin physical properties

Riboflavin forms fine yellow to orange-yeUow needles with a bitter taste from 2 N acetic acid, alcohol, water, or pyridine. It melts with decomposition at 278—279°C (darkens at ca 240°C). The solubihty of riboflavin in water is 10—13 mg/100 mL at 25—27.5°C, and in absolute ethanol 4.5 mg/100 mL at 27.5°C it is slightly soluble in amyl alcohol, cyclohexanol, benzyl alcohol, amyl acetate, and phenol, but insoluble in ether, chloroform, acetone, and benzene. It is very soluble in dilute alkah, but these solutions are unstable. Various polymorphic crystalline forms of riboflavin exhibit variations in physical properties. In aqueous nicotinamide solution at pH 5, solubihty increases from 0.1 to 2.5% as the nicotinamide concentration increases from 5 to 50% (9). 

The 8a-modified flavins show some remarkable physical properties which differ from those of common flavins. Since these properties are very helpful in the identification of modified 8a-substituted flavocoenzymes originating from biological materials the physical properties are presented briefly here. Compared to riboflavin (Scheme 2, (7), R = H) the visible light absorption properties of (2) to... 

Many compounds form crystals with different molecular arrangements, or polymorphs. These polymorphs may have different physical properties, such as dissolution rate and solubility. The vitamin riboflavin exists in several polymorphic forms, and these have a 20-fold range in aqueous solubility. Polymorphs that have no crystal structure, or amorphic forms, have different physical properties from the crystalline forms. 

The physical properties of the hollow fibers were evaluated after each activation step,following the diffusion coefficient of standard potassium nitrate and riboflavin. As shown in table 2,the activation did not adversely change the peculiarity of semipermeable membrane. 

Rich H, et al. Effects of photochemical riboflavin-mediated crosslinks on the physical properties of collagen constmcts and fibrils. J Mater Sci Mater Med 2014 25(1) 11—21. 

Physical Properties of Flavins. The most striking characteristic of riboflavin and its derivatives is the yellow color. This absorption spectrum reveals three major peaks, at 260 m/i, 375 mju, and 450 m. Both the 375 m and 450 m/u peaks disappear on reduction. This change in absorption permits the extent of oxidation or reduction to be measured spectrophotometrically or visually on reduction the yellow color disappears as the leuco form is produced. The reaction is thought to be as indicated in (II). Eo (pH 0) for simple flavin derivatives is —0.187 volts,... 

H. Rich, M. Odlyha, U. Cheema, V. Mudera, and L. Bozec, Effects of photochemical riboflavin-mediated crosshnks on the physical properties of collagen constructs and fibrils, /. Mater. Sci. Mater. Med., 25 (1), 11-21, 2014. 

The fluorescence of riboflavin and its biological derivatives confirms the interesting changes in physical properties (and probably therefore... 

Another Japanese research group isolated two riboflavin derivatives from the culture filtrate of Schizophyllum commune and called these natural products Schizo-flavin 1 and 2 The physical and chemical properties of these compounds are... 

Carotenoids vs. Flavins. To date, considerable evidence supports the contention that carotenoids are involved in the light-activating mechanism of DPE s O, 4, 5, 7-10). From a purely physical view, a flavin can be perceived as a more likely candidate for activation of DPE s than can a carotenoid. The following molecular properties that favor riboflavin over... 

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