2c:T54c,

Noncellular and cellular in vitro models for predicting intestinal absorption were used to investigate the transport and metabolism of parabens. The biomimetic artificial membrane permeability assay (BAMPA) membrane was constructed by impregnating a lipid solution on a hydrophobic filter. Caco-2 cells at passage numbers 65 to 80 were cultured in either the accelerated 3-day Biocoat™ system or the standard 21-day Transwell™ cell culture system. Paraben transport across the BAMPA system showed a parabolic relationship. The lowest log P (p-hydroxybenzoic acid) and highest log P compounds (heptyl and octyl parabens) had apparent permeabilities (Papp) less than 1.0 × 10^-6 cm/s and Papp was maximal at approximately 8.5 × 10^-6cm/s for the intermediate log P (ethylparaben) compound. With the Biocoat™, a similar parabolic relationship was found. In the 21-day Caco-2 cells, the parabens were metabolized by esterases at to p-hydroxybenzoic acid. In conclusion, the in vitro models added complementary insight into the absorption process, such as the transport route, intrinsic permeability, and extent of metabolism of the parabens. This study indicated that presystemic metabolism of orally ingested parabens to the p-hydroxybenzoic acid in the intestine may limit systemic exposure to alkyl-paraben esters in vivo.

2d:T493,

In drug discovery, the potential of cytochrome P450 inhibition of new chemical entities is frequently quantified in terms of IC₅₀ values. In early drug discovery, a risk classification into low, medium, or high potential inhibitors is often sufficient for ranking and prioritizing of compounds. Although often 6 or more inhibitor concentrations are used to determine the IC₅₀ value, the question arises whether it is possible to predict the risk class based on fewer inhibitor concentrations with comparable reliability. In this article, the authors propose a new integrated 2-point method with inhibitor concentrations chosen in accordance with the risk classification. They analyze its predictive power and the feasibility of not only classifying the compounds into different risk classes but also ranking those compounds that have been binned into the middle risk class. The proposed integrated 2-point method is thus highly suitable for automation. Altogether, it maintains the quality of the prediction while considerably reducing time and cost. The proposed method is applicable to other IC₅₀ assays and risk classifications.

2e:T4c9,

Pantothenate synthetase (PS; EC 6.3.2.1), encoded by the panC gene, catalyzes the essential adenosine triphosphate (ATP)–dependent condensation of D-pantoate and β-alanine to form pantothenate in bacteria, yeast, and plants; pantothenate is a key precursor for the biosynthesis of coenzyme A (CoA) and acyl carrier protein (ACP). Because the enzyme is absent in mammals and both CoA and ACP are essential cofactors for bacterial growth, PS is an attractive chemotherapeutic target. An automated high-throughput screen was developed to identify drugs that inhibit Mycobacterium tuberculosis PS. The activity of PS was measured spectrophotometrically through an enzymatic cascade involving myokinase, pyruvate kinase, and lactate dehydrogenase. The rate of PS ATP utilization was quantitated by the reduction of absorbance due to the oxidation of NADH to NAD⁺ by lactate dehydrogenase, which allowed for an internal control to detect interference from compounds that absorb at 340 nm. This coupled enzymatic reaction was used to screen 4080 compounds in a 96-well format. This discussion describes a novel inhibitor of PS that exhibits potential as an antimicrobial agent.

2f:T5c0,