Samaa Alrushaid

Chemical reactivity and microbicidal action of bethoxazin

Bethoxazin is a new broad spectrum industrial microbicide with applications in material and coating preservation. However, little is known of its reactivity profile and mechanism of action. In this study, we examined the reactivity of bethoxazin toward biologically important nucleophilic groups using UV-vis spectroscopy and LC-MS/MS techniques and found the molecule to be highly electrophilic. Bethoxazin reacted with molecules containing free sulfhydryl groups such as GSH and human serum albumin to form covalent adducts that were detectable by MS, but did not react with amino, carboxylic, phenolic, amino oxo, alcoholic, and phosphate functional groups. Bethoxazin potently inhibited the catalytic activity of yeast DNA topoisomerase II and the growth of yeast BY4742 cells at low micromolar concentrations. However, the reduced form of bethoxazin and GSH-treated bethoxazin were both inactive in these assays. The experimentally determined relative reactivity of bethoxazin and its reduced form analog correlated with their biological activities as well as their quantum-mechanically calculated electrophilicity properties. Taken together, the results suggest that bethoxazin may exert its microbicidal action by reacting with sensitive endogenous sulfhydryl biomolecules of microbial cells. Consistent with this view, the inhibitory activity of bethoxazin on topoisomerase II may be due to its ability to react with critical free cysteine sulfhydryl groups on the enzyme. Our studies have provided for the first time a better understanding of the reactivity of bethoxazin, as well as some insights into the mechanism by which the compound exerts its microbicidal action.

Pharmacokinetic and Toxicodynamic Characterization of a Novel Doxorubicin Derivative

Doxorubicin (Dox) is an effective anti-cancer medication with poor oral bioavailability and systemic toxicities. DoxQ was developed by conjugating Dox to the lymphatically absorbed antioxidant quercetin to improve Dox’s bioavailability and tolerability. The purpose of this study was to characterize the pharmacokinetics and safety of Dox after intravenous (IV) and oral (PO) administration of DoxQ or Dox (10 mg/kg) and investigate the intestinal lymphatic delivery of Dox after PO DoxQ administration in male Sprague–Dawley rats. Drug concentrations in serum, urine, and lymph were quantified by HPLC with fluorescence detection. DoxQ intact IV showed a 5-fold increase in the area under the curve (AUC)—18.6 ± 1.98 compared to 3.97 ± 0.71 μg * h/mL after Dox—and a significant reduction in the volume of distribution (Vss): 0.138 ± 0.015 versus 6.35 ± 1.06 L/kg. The fraction excreted unchanged in urine (fe) of IV DoxQ and Dox was ~5% and ~11%, respectively. Cumulative amounts of Dox in the mesenteric lymph fluid after oral DoxQ were twice as high as Dox in a mesenteric lymph duct cannulation rat model. Oral DoxQ increased AUC of Dox by ~1.5-fold compared to after oral Dox. Concentrations of β-N-Acetylglucosaminidase (NAG) but not cardiac troponin (cTnI) were lower after IV DoxQ than Dox. DoxQ altered the pharmacokinetic disposition of Dox, improved its renal safety and oral bioavailability, and is in part transported through intestinal lymphatics.

Disposition, Metabolism and Histone Deacetylase and Acetyltransferase Inhibition Activity of Tetrahydrocurcumin and Other Curcuminoids

Tetrahydrocurcumin (THC), curcumin and calebin-A are curcuminoids found in turmeric (Curcuma longa). Curcuminoids have been established to have a variety of pharmacological activities and are used as natural health supplements. The purpose of this study was to identify the metabolism, excretion, antioxidant, anti-inflammatory and anticancer properties of these curcuminoids and to determine disposition of THC in rats after oral administration. We developed a UHPLC–MS/MS assay for THC in rat serum and urine. THC shows multiple redistribution phases with corresponding increases in urinary excretion rate. In-vitro antioxidant activity, histone deacetylase (HDAC) activity, histone acetyltransferase (HAT) activity and anti-inflammatory inhibitory activity were examined using commercial assay kits. Anticancer activity was determined in Sup-T1 lymphoma cells. Our results indicate THC was poorly absorbed after oral administration and primarily excreted via non-renal routes. All curcuminoids exhibited multiple pharmacological effects in vitro, including potent antioxidant activity as well as inhibition of CYP2C9, CYP3A4 and lipoxygenase activity without affecting the release of TNF-α. Unlike curcumin and calebin-A, THC did not inhibit HDAC1 and PCAF and displayed a weaker growth inhibition activity against Sup-T1 cells. We show evidence for the first time that curcumin and calebin-A inhibit HAT and PCAF, possibly through a Michael-addition mechanism.

Simultaneous quantification of reparixin and paclitaxel in plasma and urine using ultra performance liquid chromatography-tandem mass spectroscopy (UHPLC-MS/MS): Application to a preclinical pharmacokinetic study in rats.

A liquid chromatography-tandem mass spectroscopy (LC-MS/MS) assay was developed and validated to simultaneously quantify anticancer drugs reparixin and paclitaxel in this study. The compounds were extracted from plasma and urine samples by protein precipitation with acetone (supplemented with 0.1% formic acid). Chromatographic separation was achieved using a C18 column, and drug molecules were ionized using dual ion source electrospray and atmospheric pressure chemical ionization (DUIS: ESI-APCI). Reparixin and paclitaxel were quantified using negative and positive multiple reaction monitoring (MRM) mode, respectively. Stable isotope palcitaxel-D5 was used as the internal standard (IS). The assay was validated for specificity, recovery, carryover and sample stability under various storage conditions; it was also successfully applied to measure drug concentrations collected from a pharmacokinetic study in rats. The results confirmed that the assay was accurate and simple in quantifying both reparixin and paclitaxel in plasma and urine with minimal sample pretreatment.

Pharmacological characterization of liquiritigenin, a chiral flavonoid in licorice.

Liquiritigenin is a chiral flavonoid present in plant based food, nutraceuticals, and traditional medicines. It is also an important ingredient present in licorice. The purpose of this study is to explore the pharmacological activity of racemic liquiritigenin utilizing several in vitro assays with relevant roles in colon cancer and diabetes. Where possible, the pure enantiomers were tested to identify the stereospecific contribution to the activity. In vitro antioxidant, anticancer, anti-inflammatory activities (cyclooxygenase inhibition), antidiabetic activities (alpha-amylase and alpha-glucosidase inhibition) as well as cytochrome P450 (CYP450) inhibitory activities were assessed. Racemic liquiritigenin demonstrated a dose-dependent inhibition of alpha-amylase enzyme whereas its pure enantiomers did not. Racemic liquiritigenin showed moderate antiproliferative activity on a HT-29 (human colorectal adenocarcinoma) cancer cell line that was dose-dependent and potent inhibitory effects on the cyclooxygenase-2 enzyme. The flavonoid did not inhibit the activity of cytochrome CYP2D6 over the concentration range studied but was a potent antioxidant. The current study demonstrated the importance of understanding the stereospecific pharmacological effects of liquiritigenin enantiomers in alpha-amylase inhibition.

Stereospecific pharmacokinetic characterization of liquiritigenin in the rat

Liquiritigenin is a chiral flavonoid present in licorice and other medicinal plants. The nature of its biological fate with respect to the individual enantiomers has not been examined. In this study, we characterize, for the first time, the stereoselective pharmacokinetics of liquiritigenin. Liquiritigenin was intravenously (20 mg/kg) and orally (50 mg/kg) administered to male Sprague-Dawley rats (n = 4 per route of administration). Concentrations in serum and urine were characterized via stereospecific reversed-phase, isocratic HPLC method with UV detection. Serum concentrations were quantified but rapidly fell to undetectable levels. S-liquiritigenin showed a short half-life (0.25-0.54 h), while a better estimation of half-life (26-77 h) and other pharmacokinetic parameters was observed using urinary data. The flavonoid is predominantly excreted via non-renal routes (fe values of 0.16-3.46 %), and undergoes rapid and extensive phase II metabolism. Chiral differences in the chemical structure of the compound result in some pharmacokinetic differences. Serum concentrations rapidly declined, making modeling difficult. S-liquiritigenin showed an increased urinary half-life.

Mechanistically elucidating the in vitro safety and efficacy of a novel doxorubicin derivative

Doxorubicin is an effective anticancer drug; however, it is cardiotoxic and has poor oral bioavazilability. Quercetin is a plant-based flavonoid with inhibitory effects on P-glycoprotein (P-gp) and CYP3A4 and also antioxidant properties. To mitigate these therapeutic barriers, DoxQ, a novel derivative of doxorubicin, was synthesized by conjugating quercetin to doxorubicin. The purpose of this study is to mechanistically elucidate the in vitro safety and efficacy of DoxQ. Drug release in vitro and cellular uptake by multidrug-resistant canine kidney (MDCK-MDR) cells were quantified by HPLC. Antioxidant activity, CYP3A4 inhibition, and P-gp inhibitory effects were examined using commercial assay kits. Drug potency was assessed utilizing triple-negative murine breast cancer cells, and cardiotoxicity was assessed utilizing adult rat and human cardiomyocytes (RL-14). Levels of reactive oxygen species and gene expression of cardiotoxicity markers, oxidative stress markers, and CYP1B1 were determined in RL-14. DoxQ was less cytotoxic to both rat and human cardiomyocytes and retained anticancer activity. Levels of ROS and markers of oxidative stress demonstrate lower oxidative damage induced by DoxQ compared to doxorubicin. DoxQ also inhibited the expression and catalytic activity of CYP1B1. Additionally, DoxQ inhibited CYP3A4 and demonstrated higher cellular uptake by MDCK-MDR cells than doxorubicin. DoxQ provides a novel therapeutic approach to mitigate the cardiotoxicity and poor oral bioavailability of doxorubicin. The cardioprotective mechanism of DoxQ likely involves scavenging ROS and CYP1B1 inhibition, while the mechanism of improving the poor oral bioavailability of doxorubicin is likely related to inhibiting CYP3A4 and P-gp.

DOX-Vit D, a Novel Doxorubicin Delivery Approach, Inhibits Human Osteosarcoma Cell Proliferation by Inducing Apoptosis While Inhibiting Akt and mTOR Signaling Pathways

Doxorubicin (DOX) is a very potent and effective anticancer agent. However, the effectiveness of DOX in osteosarcoma is usually limited by the acquired drug resistance. Recently, Vitamin D (Vit-D) was shown to suppress the growth of many human cancer cells. Taken together, we synthesized DOX-Vit D by conjugating Vit-D to DOX in order to increase the delivery of DOX into cancer cells and mitigate the chemoresistance associated with DOX. For this purpose, MG63 cells were treated with 10 µM DOX or DOX-Vit D for 24 h. Thereafter, MTT, real-time PCR and western blot analysis were used to determine cell proliferation, genes and proteins expression, respectively. Our results showed that DOX-Vit D, but not DOX, significantly elicited an apoptotic signal in MG63 cells as evidenced by induction of death receptor, Caspase-3 and BCLxs genes. Mechanistically, the DOX-Vit D-induced apoptogens were credited to the activation of p-JNK and p-p38 signaling pathway and the inhibition of proliferative proteins, p-Akt and p-mTOR. Our findings propose that DOX-Vit D suppressed the growth of MG63 cells by inducing apoptosis while inhibiting cell survival and proliferative signaling pathways. DOX-Vit D may serve as a novel drug delivery approach to potentiate the delivery of DOX into cancer cells.

Correction to: Mechanistically elucidating the in vitro safety and efficacy of a novel doxorubicin derivative

In the XML of the original article, M. Laird Forrest’s name was tagged incorrectly. M. Laird is his first name.