BIOCHEMICAL SYNTHESIS, PURIFICATION AND PRELIMINARY PHARMACOLOGICAL EVALUATION OF NORMORPHINE-3-GLUCURONIDE

Normorphine was synthesised from morphine by thermal decomposition of an N-alpha-chloroethylchloroformate adduct, and purified (> 98% purity ) using semipreparative HPLC with ultraviolet detection. Normorphine-3 -glucuronide (NM3G) was biochemically synthesised using the substrate normorphine, uridine diphosphoglucuronic acid and Sprague-Dawley rat l iver microsomes in a 75% yield (relative to normorphine base). The syn thesised NM3G was purified by precipitation and washing with acetonitr ile. Determinations of purity using HPLC with electrochemical and ultr aviolet detection confirmed that the NM3G produced was of high (> 99%) purity. Mass spectrometry, fourier transform infrared spectrophotomet ry and nuclear magnetic resonance spectrometry confirmed the structure , especially placement of the glucuronide moiety at the 3-phenolic pos ition and not at the 17-nitrogen. Administration of NM3G by the intrac erebroventricular (icy) route to rats in doses of 2.5 and 7.5 mu g res ulted in the development of central nervous system (CNS) excitatory be havioural effects including myoclonus, chewing, wet-dog shakes, ataxia and explosive motor behaviour. At an icy dose of 7.5 mu g, NM3G also induced short periods of tonic-clonic convulsive activity. Thus, NM3G elicits CNS excitation following supraspinal administration in a manne r analogous to morphine-3-glucuronide (M3G), the major metabolite of m orphine (1). Further studies are required to determine whether NM3G at tenuates morphine-induced antinociception in se similar manner to M3G.