Preparation of 2‐[¹²⁵I] iodohistamine‐labelled Δ⁸‐tetrahydrocannabinol‐11‐oic acid for use in cannabinoid radioimmunoassay

Abstract

A simple method is described for the preparation of 2‐[125I]iodohistamine‐labelled Δ8‐tetrahydrocannabinol‐11‐oic acid with high specific activity for use in radioimmunoassay. This compound is produced in high yield and shows excellent radiochemical stability when stored at 4°C. The radiolabelled cannabinoid has been shown to bind avidly to four different broadly specific cannabinoid antisera. It is the only [125I] labelled cannabinoid suitable for use in radioimmunoassay with such antisera.

No-Carrier-Added Radiohalogenation Methods with Heavy Halogens

“…Primarily developed for protein labeling (for a review see [261]), a series of coupling agents in addition to the famous BOLTON-HUNTER reagent [262] have been used, in which chloramine-T is generally applied for the radiohalogenation [7]. Recently, this method has also been extended to the labeling of small sensitive or non-activated substrates via radiohalogenation of histamine [263,264] and hydroxyphenyl substituents [265]. Concerning the mechanism for these organic oxidizing agents, it may be assumed that halogen chlorides are formed as intermediates in inert aprotic solvents, as indicated by the addition products from NCS [216] and DCT [249,251 Reaction with olefins.…”