Electrochemical and crystal structural analysis ofα- and dehydro-α-lapachones

Understanding and predicting the potency of ROS-based enzyme inhibitors, exemplified by naphthoquinones and ubiquitin specific protease-2

Recent studies have suggested that selective targeting of overexpressed enzymes in cancer cells by small molecules that induce the formation of reactive oxygen species (ROS) could be a viable approach in cancer therapy. One such example is the inactivation of ubiquitin specific protease-2 (USP2)-an emerging drug target to combat prostate cancer-by β-lapachone, which has been identified to involve oxidation of the catalytic cysteine's thiol residue to sulfinic acid. A rational design of β-lapachone analogs with improved activity requires a much better understanding of the variables that determine ROS production by this class of molecules. This crucial aspect was addressed via modulation of its 1,2-naphthoquinone scaffold and establishment of a structure/activity relationship, regarding its ability to reduce molecular oxygen to a ROS. The same series of compounds was also examined in terms of their inhibitory effect on the enzymatic activity of USP2. One deduction from these investigations was that the ortho-quinone motif in β-lapachone is much better suited for the catalytic reduction of oxygen than the para-quinone motif and some approved quinone based drugs. A broader conclusion, obtained from the series of compounds with ortho-quinone motifs, is that only the agents whose redox potential is in the narrow range of -0.3 ± 0.1 V (vs. Ag/AgCl in pH 7.5 aqueous buffer) induce the formation of ROS. The excellent correlation between the ROS production ability and the USP2 inhibition potency emphasizes that the relatively easy, fast, and reliable testing of electrocatalytic oxygen reduction by small molecules might be applied to screening and evaluating new drug candidates for similar targets.

Cytotoxicity of lapachol metabolites produced by probiotics

Probiotics are currently added to a variety of functional foods to provide health benefits to the host and are commonly used by patients with gastrointestinal complaints or diseases. The therapeutic effects of lapachol continue to inspire studies to obtain derivatives with improved bioactivity and lower unwanted effects. Therefore, the general goal of this study was to show that probiotics are able to convert lapachol and are important to assess the effects of bacterial metabolism on drug performance and toxicity. The microbial transformations of lapachol were carried out by Bifidobacterium sp. and Lactobacillus acidophilus and different metabolites were produced in mixed and isolated cultures. The cytotoxic activities against breast cancer and normal fibroblast cell lines of the isolated metabolites (4α-hydroxy-2,2-dimethyl-5-oxo-2,3,4,4α,5,9β-hexahydroindeno[1,2-β]pyran-9β-carboxilic acid, a new metabolite produced by mixed culture and dehydro-α-lapachone produced by isolated cultures) were assessed and compared with those of lapachol. The new metabolite displayed a lower activity against a breast cancer cell line (IC50 = 532.7 μmol l(-1) ) than lapachol (IC50 = 72.3 μmol l(-1) ), while dehydro-α-lapachone (IC50 = 10.4 μmol l(-1) ) displayed a higher activity than lapachol. The present study is the first to demonstrate that probiotics are capable of converting lapachol into the most effective cytotoxic compound against a breast cancer cell line.

SIGNIFICANCE AND IMPACT OF THE STUDY

Probiotics have been used in dairy products to promote human health and have the ability to metabolize drugs and other xenobiotics. Naphthoquinones, such as lapachol, are considered privileged scaffolds due to their high propensity to interact with biological targets. The present study is the first to demonstrate that probiotics are capable of converting lapachol into the most effective cytotoxic compound against a breast cancer cell line. The developed approach highlights the importance of probiotics to assess the effects of bacterial metabolism on drug performance and toxicity.

Determination of the depth profile distribution of guest species in microporous materials using the voltammetry of immobilized particles methodology: application to lapachol attachment to palygorskite and kaolinite

In-depth profile distribution of guest species hosted in inorganic microporous matrixes is determined using electrochemical data.

Ethyl (2S,4R)-4-(4-bromophenyl)-2-hydroxy-5,10-dioxo-3,4,5,10-tetrahydro-2H-benzo[g]chromene-2-carboxylate

In the crystal structure of the title compound, C₂₂H₁₇BrO₆, the quinone ring makes a dihedral angle of 81.84 (3)° with the benzene ring. The chiral C atoms, viz. the ring C atoms bearing the hydr­oxy and bromo­phenyl substituents, exhibit R and S configurations, respectively. The terminal ethyl group of the –CO₂CH₂CH₃ group is disordered over two sets of sites with site-occupancy factors of 0.64 (1) and 0.36 (1). Inter­molecular O—H⋯O inter­actions further stabilize the crystal packing.