Bone Regeneration Effect of Cassia occidentalis Linn. Extract and Its Isolated Compounds
Brijesh Kumar, Vikas Bajpai, Vikaskumar Gond, Subhashis Pal, Naibedya Chattopadhyay in Phytochemistry of Plants of Genus Cassia, 2021
In a widely used model of iatrogenic osteoporosis obtained by the administration of a corticosteroid, methylprednisolone (MP), CSE (250 mg/kg) and CBE (100 mg/kg) mitigated MP-induced bone loss and strength by osteogenic as well as anti-catabolic actions. Even at a 2.5-fold lesser dose than CSE, the osteogenic effect of CBE was significantly greater than CSE. Both CSE and CBE mitigated MP-induced loss of body weight and electrolyte imbalances with later being more effective (Pal et al., 2019). Through an LC-MS/MS method, apigenin, isovitexin, luteolin, emodin and trihydroxyflavone were detected in adult rat plasma after an oral administration of CSE (500 mg/kg) (Pal et al., 2019). These compounds were stable in simulated gastric and intestinal fluids but were metabolized in rat liver microsomes. The development of bioanalytical methods for pharmacokinetics and in vitro stability studies of osteogenic compounds will be useful for the phase 1 clinical trial.
General Introduction
David N. Brindley, John R. Sabine in Phosphatidate Phosphohydrolase, 2017
The other purpose of this experiment was to investigate the Mg2+ requirement of the cytosolic phosphohydrolase when it translocates to the endoplasmic reticulum as a result of incubating these membranes with oleic acid (Chapter 2, Section IV.B). In order to do this the microsomal fraction was washed with 10 mg albumin per milliliter and then recovered by a second centrifugation step.94 This has the effect of removing endogenous fatty acids from the membranes and displacing phosphatidate phosphohydrolase59 as can be seen in Figure 3a. The cytosolic fraction was centrifuged twice to effect a more complete removal of particulate material. The translocation of the cytosolic phosphohydrolase was performed by mixing the washed microsomal fraction with the cytosolic fraction and incubating for 10 min at 37°C with 0.75 mM oleate. The second cytosol and the microsomes were then separated by centrifugation. Incubating with oleate resulted in a decrease in the cytosolic activity of the phosphohydrolase which was paralleled by the appearance of this enzyme in the microsomal fraction (Figure 3). The phosphohydrolase in the microsomal and soluble fractions exhibited a similar marked stimulation by Mg2+. These results indicate that the cytosolic phosphohydrolase does not lose its Mg2+ requirement when it becomes bound to membranes and further confirm that the enzyme translocates.
Alcohol
S.J. Mulé, Henry Brill in Chemical and Biological Aspects of Drug Dependence, 2019
Hepatic microsomes are responsible for a large number of metabolic functions. On theoretical grounds one can postulate that several of these functions (which have not as yet been extensively studied) will be found to be affected by either acute or chronic ethanol consumption. One can now anticipate a number of reports, such as the prevention of hyperbilirubinemia of the newborn by ethanol,147 attributed to induction of microsomal uridine - diphosphate-glucuronyl transferase.148 The possible role of microsomal changes (induced by ethanol consumption) in the development of ethanol dependence is particularly intriguing, as discussed subsequently.
Species differences in oxidative metabolism of regorafenib
Published in Xenobiotica, 2021
Ayaka Kojima, Ayuka Sogabe, Masayuki Nadai, Miki Katoh
Regorafenib was incubated with microsomes at 37 °C in an nicotinamide adenine dinucleotide phosphate generating system (1 mM MgCl2, 5 mM glucose-6-phosphate, 1 U glucose-6-phosphate dehydrogenase, and 0.28 mM β-nicotinamide-adenine dinucleotide phosphate), which produces the reduced form of nicotinamide adenine dinucleotide phosphate, and 100 mM potassium phosphate buffer (pH 7.4). Regorafenib concentrations in experiments using liver and small intestinal microsomes ranged from 0.1 to 100 μM (HLM and MLM), 0.25 to 100 μM (HIM), or 1 to 100 μM (CMLM, CMIM, RLM, RIM and MIM). Protein concentrations of microsomes were 0.05 mg/mL (HLM, HIM, CMLM, and CMIM) or 0.1 mg/mL (RLM, RIM, MLM, and MIM). The reaction mixture was incubated at 37 °C for 10 min (HLM, HIM, and CMLM), 20 min (CMIM, RLM, MLM, and MIM), or 30 min (RIM). In the preliminary study, we confirmed the linearity of M-2 and M-3 formation with regard to the protein or CYP concentrations and incubation time.
Employing in vitro metabolism to guide design of F-labelled PET probes of novel α-synuclein binding bifunctional compounds
Published in Xenobiotica, 2021
Chukwunonso K. Nwabufo, Omozojie P. Aigbogun, Kevin J.H Allen, Madeline N. Owens, Jeremy S. Lee, Christopher P. Phenix, Ed S. Krol
Phase 1 metabolic studies utilizing hepatic microsomes in vitro are a typical first step in understanding drug metabolism. An advantage of using microsomes as an in vitro drug metabolism model is the ability to focus on generating sufficient amounts of presumptive P450-mediated phase I metabolites without contribution from other competing systems such as phase II metabolism and transporter-mediated processes (Temporal et al. 2017). It is our goal to use hepatic microsomes to determine whether our bifunctional compounds undergo Phase 1 metabolism and to identify those metabolic products. Several animal models of Parkinson’s disease exist so we have decided to carry out our assessment of in vitro metabolism using liver microsomes from several animals (mouse and rat) as well as human liver microsomes. An additional benefit to determining the metabolic stability of our bifunctional compounds is that knowledge of the regiochemistry of metabolic reactions can potentially inform less metabolically labile positions for incorporation of fluorine in our PET probe bifunctional analogues.
Drug metabolic stability in early drug discovery to develop potential lead compounds
Published in Drug Metabolism Reviews, 2021
Siva Nageswara Rao Gajula, Nimisha Nadimpalli, Rajesh Sonti
Liver microsomes are the subcellular fractions derived from the liver's endoplasmic reticulum obtained by differential high-speed centrifugation. Microsomes are the most preferred in vitro models in drug discovery as they offer numerous advantages; in particular, they are easy to prepare, store, and amenable to high-throughput screening (HTS). Microsomes contain Phase I oxidative CYP enzymes but lack an intact cell membrane, requiring relevant cofactors to carry out the metabolic activity. If the intrinsic clearance occurs through Phase II metabolism, the microsomes model system must be avoided as they lack Phase II metabolic enzymes except for the UDP-glucuronosyltransferase (UGT). The endoplasmic reticulum membrane obstructs the binding of substrates and cofactors to the active site of the UGTs by acting as a diffusional barrier (Meech and Mackenzie 1997). The disruption of this diffusional barrier using a pore-forming agent like alamethicin is essential to remove the latency of UGTs in the incubation (Fisher et al. 2000).
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