Direct incorporation of orally administered riboflavin tetranicotinate into portal blood of rabbit.

From the pharmacological interest of fat-soluble riboflavin derivatives such as B2 But (1) and B2-Nic (2), it is important to show whether these compounds are, when ad ministered orally, incorporated through gastro intestinal tract into blood stream of mammals without losing their intactness of the ester bonds at 2•L, 3•L, 4•L and 5•L position. To test this, B2-Nic may be suitable because it is fairly soluble in water despite its considerable lipo philic nature, and is less susceptible to pan creatic lipase action than B2-But (3). In the present paper, evidence for the gastro-intestinal absorption of B-Nic is briefly described. Male rabbit weighing about 3kg was administered orally with 500mg per kg body weight of B2-Nic which was dissolved in a fixed volume of 0.5 N HCl. As a control run, another rabbit was administered with the same volume of the solvent. At 2 hours after the oral administration, rabbits were anesthesized with urethane, and heparin was introduced into blood stream from their ear vein. Then, 10ml of blood was collected from the portal vein of each rabbit and mixed with 40ml of a mixture of 1 N HCl-CH3000Na buffer (pH 2) and methanol (3:1, v/v) with FIG. 1 TLC pattern of the phenol extract of portal blood front rabbit administered orally with 500mg of B2-Nic per kg of body weight