Histamine interaction with Zn²⁺ and Cu²⁺ porphyrins

Histamine may be present in biological fluids and in pharmaceutical dosage forms such as antiallergenic agents; when in excess, it causes a disorder called histaminosis. Many techniques have been developed to determine the concentration of this compound but the application of such methods is complicated and laborious, requiring expensive equipment and long times. A better alternative is to design chemical sensors. In the work reported here, six metalloporphyrins (Cu²⁺ or Zn²⁺) with different peripheral groups – benzoate, tosylate and carboxylate – were studied. The stability constants for these compounds were determined with histamine at different temperatures. Histamine is strongly bound to metallic porphyrins containing Cu²⁺ and Zn²⁺; however, the binding force does not depend exclusively on the metal center. Stabilization of the complex is strongly influenced, in some cases, by the lateral chains of the porphyrin. This possibility implies that this system can be very selective for this biogenic amine.