LIQUID-CHROMATOGRAPHIC ANALYSIS, STABILITY AND PROTEIN-BINDING STUDIES OF THE ANTI-HIV AGENT BENZOIC-ACID, [[(1-METHYLETHOXY)THIOXOMETHYL]AMINO]-METHYLETHYL, 1-METHYLETHYL ESTER

A method was developed for the assay of benzoic acid, -chloro-5-[[(1-m ethylethoxyl)thioxomethyl]amino]-, 1-methylethyl ester (NSC 629243) in hamster, mouse, human and, to a limited extent, dog plasma. Protein i n 0.5 ml of plasma was precipitated with four volumes of methanol and the supernatant was analysed for NSC 629243 by LC. Liquid chromatograp hy was carried out on a reversed-phase Nova-Pak C18 column, with a mob ile phase of 60% acetonitrile in water at 1 ml min-1, and the compound was quantified with a UV detector set at 283 nm. Two standard curves of NSC 629243 were needed to cover a concentration range of 0.05-100 m ug ml-1. All standard curves had correlation coefficients >0.999. In p ractice, the minimum quantifiable concentration was approximately 0.05 mug ml-1 in 0.5 ml of plasma. NSC 629943 appeared to have good stabil ity at 37-degrees-C in hamster, human and dog plasma at concentrations of 1 and 50 mug ml-1 (at least 80% remained in plasma after a 4 h inc ubation). Breakdown occurred in mouse plasma after 1 h at 37-degrees-C , with extensive breakdown occurring after 24 h. NSC 629243 was extens ively bound to plasma proteins of Syrian hamsters and humans. The exte nt of binding ranged from a minimum of 88.6% to a maximum of 99.9% ove r a concentration range of ca 1-100 mug ml-1.