ANALYTICAL STUDY ON SOME ANTIDIABETIC DRUGS

Abstract

a and n- acceptors reacts with the basic nitrogenous compounds as n­ donors, to form charge transfer complexes or radical anions according to the polarity of the solvent used (137).

In this part iodine as a-acceptor was used for the analysis of nateglinide and repaglinide in bulk powder and in their dosage forms.

Iodine solution in chloroform displayed an absorption peak at about 505 nm. When the chloroform solution of the drug was added to iodine solution in chloroform, a change was obtained in the absorption band of iodine exhibiting a hypsochromic and a hyperchromic shifts. The charge- transfer complex between the cited drugs and iodine exhibiting two absorption bands at 291 and 362 nm as shown in Figures (50&51) , for nategllinide and repaglinide. The cited drugs react with iodine to form triiodide ion pair , due to the transformation of an "outer complex" to an "inner complex" liberating iodide ions which reacted with the free molecular iodine. In other word, the interaction between the drug and iodine is charge transfer complexation reaction between n-donor and the a­ acceptor iodine according to the following equation

Tri-iodide ion pair

Regarding the third step in the above scheme, iodine alone does not absorb at the wavelength of the maximum absorption , hence the stoichiometry will show only the iodide ion released as a result of one mole of iodine being consumed in the second step (138) . This was postulated on the basis of the molar ratio of nateglinide and repaglinide to iodine (1:1)