LC-MS/MS quantification of asymmetric dimethyl arginine and symmetric dimethyl arginine in plasma using surrogate matrix and derivatization with fluorescamine.

A novel LC-MS/MS method using a surrogate matrix and derivatization with fluorescamine was developed and validated for simultaneous quantification of asymmetric dimethyl arginine and symmetric dimethyl arginine. Asymmetric dimethyl arginine, symmetric dimethyl arginine and corresponding internal standards were extracted using protein precipitation and derivatization with fluorescamine followed by SPE. Derivatives were analyzed by turbo ion spray LC-MS/MS in the positive ion mode.

Analytical approaches for quantification of a Nrf2 pathway activator: overcoming bioanalytical challenges to support a toxicity study.

Activation of the Nrf2 stress pathway is known to play an important role in the defense mechanism against electrophilic and oxidative damage to biological macromolecules (DNA, lipids, and proteins). Chemical inducers of Nrf2 such as sulforaphane, dimethyl fumarate (Tecfidera®), CDDO-Me (bardoxolone-methyl), and 3-(dimethylamino)-4-((3-isothiocyanatopropyl)(methyl)amino)cyclobut-3-ene-1,2-dione (a synthetic sulforaphane analogue; will be referred to as ) have the ability to react with Keap1 cysteine residues, leading to activation of the Antioxidant Response Element (ARE). Due to their electrophilic nature and poor matrix stability, these compounds represent great challenges when developing bioanalytical methods to evaluate in vivo exposure.

Isotopic labeling experiments that elucidate the mechanism of DNA strand cleavage by the hypoxia-selective antitumor agent 1,2,4-benzotriazine 1,4-di-N-oxide.

The 1,2,4-benzotriazine 1,4-dioxides are an important class of potential anticancer drugs that selectively kill the low-oxygen (hypoxic) cells found in solid tumors. These compounds undergo intracellular one-electron enzymatic reduction to yield an oxygen-sensitive drug radical intermediate that partitions forward, under hypoxic conditions, to generate a highly reactive secondary radical that causes cell killing DNA damage. Here, we characterized bioreductively activated, hypoxia-selective DNA-strand cleavage by 1,2,4-benzotriazine 1,4-dioxide.

Development and validation of a simple and sensitive method for quantification of levodopa and carbidopa in rat and monkey plasma using derivatization and UPLC-MS/MS.

A simple, selective, and sensitive quantitative method has been developed for the simultaneous determination of levodopa and carbidopa in rat and monkey plasma by protein precipitation using acetonitrile containing the derivatizing reagent, flourescamine. Derivatized products of levodopa and carbidopa were separated on a BEH C18 column (2.1 mm × 50 mm; 1.

DNA strand cleaving properties and hypoxia-selective cytotoxicity of 7-chloro-2-thienylcarbonyl-3-trifluoromethylquinoxaline 1,4-dioxide.

The heterocyclic N-oxide, 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, 1), shows promising antitumor activity in preclinical studies, but there is a continuing need to explore new compounds in this general structural category. In the work described here, we examined the properties of 7-chloro-2-thienylcarbonyl-3-trifluoromethylquinoxaline 1,4-dioxide (9h). We find that 9h causes redox-activated, hypoxia-selective DNA cleavage that mirrors the lead compound, tirapazamine, in both mechanism and potency.

Initiation of DNA strand cleavage by 1,2,4-benzotriazine 1,4-dioxide antitumor agents: mechanistic insight from studies of 3-methyl-1,2,4-benzotriazine 1,4-dioxide.

The antitumor agent 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, TPZ, 1) gains medicinal activity through its ability to selectively damage DNA in the hypoxic cells found inside solid tumors. This occurs via one-electron enzymatic reduction of TPZ to yield an oxygen-sensitive drug radical (2) that leads to oxidatively generated DNA damage under hypoxic conditions. Two possible mechanisms have been considered to account for oxidatively generated DNA damage by TPZ.

Synthesis and biological evaluation of new 2-arylcarbonyl-3-trifluoromethylquinoxaline 1,4-di-N-oxide derivatives and their reduced analogues.

As a continuation of our research in the quinoxaline 1,4-di-N-oxide new series of 2-arylcarbonyl-3-trifluoromethylquinoxaline, 1,4-di-N-oxide derivatives have been synthesized and evaluated in a full panel of 60 human tumor cell lines. Selective reductions were carried out on two compounds which allowed us to determine the compound structures by comparison of the 1H NMR spectra. In general, all the di-N-oxidized compounds showed good cytotoxic parameters.

DNA strand damage product analysis provides evidence that the tumor cell-specific cytotoxin tirapazamine produces hydroxyl radical and acts as a surrogate for O(2).

The compound 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, TPZ) is a clinically promising anticancer agent that selectively kills the oxygen-poor (hypoxic) cells found in solid tumors. It has long been known that, under hypoxic conditions, TPZ causes DNA strand damage that is initiated by the abstraction of hydrogen atoms from the deoxyribose phosphate backbone of duplex DNA, but exact chemical mechanisms underlying this process remain unclear. Here we describe detailed characterization of sugar-derived products arising from TPZ-mediated strand damage.