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In this study, a simple, sensitive, and rapid analytical method was developed by ultra-performance liquid chromatography (UPLC) coupled with tandem quadrupole mass spectrometry (MS) for the determination of nootkatone in normal and chronic kidney disease (CKD) rat plasma using clarithromycin as internal standard. After sample preparation by simple liquid–liquid extraction, chromatography was performed on an Acquity UPLC BEH C18 column (2.1 × 50 mm, 1.7 mm particle size) using gradient elution with the mobile phase composed of acetonitrile and water acidified with 0.1% (v/v) formic acid. Detection was achieved by electrospray ionisation MS under the multiple selective reaction monitoring mode. The linear range was 0.01‒500 ng/mL with the square regression coefficient (r) of 0.9975. The lower limit of quantification was 0.01 ng/mL. The intra- and inter-day precision was under 5% and the stability accuracy was between 3.6 and 7.0%. The average recoveries from spiked plasma samples were >83% and matrix effect was over 81%. The developed method was successfully applied to the pharmacokinetic study of nootkatone in normal and CKD rats after an oral administration of 50 mg/kg nootkaone. The results showed the cmax and area under curve of nootkaone were greatly decreased, meanwhile Vd/F and t1/2 were markedly increased in CKD rats. The pharmacokinetic characteristics of nootkatone in rats were significantly altered in CKD rats. [ABSTRACT FROM AUTHOR]

Ethnopharmacological relevance The flower of Abelmoschus manihot (Linn.) Medicus ( A. manihot), as a traditional Chinese Herbal medicine, was used widely in China with efficacy of inducing diuresis for treating strangurtia, and subdhing swelling and detoxicating. It has been reported that Huangkui capsule, prepared by the extract of the flower of A. manihot , can reduce the content of urinary protein, serum creatinine and serum urea nitrogen in nephropathy rats and processes renoprotective activity, while the action mechanism need to illuminate deeply. Aims of the study In this study, we investigated the protection effect of Huangkui capsule on tubulointerstitial fibrosis in chronic renal failure (CRF) rats and its mechanism against high glucose-induced epithelial to mesenchymal transition (EMT) in renal tubular epithelial cells (HK-2) of its bioactive components. Materials and methods The animals were divided into normal group, CRF model group and Huangkui capsule-treated group. Hematoxylin eosin (HE) staining and Masson staining were applied to observe pathological changes in renal tissue of different groups. Biochemical indicators including serum urea nitrogen (BUN), urine protein (UP) and serum creatinine (Scr) were measured according to the manufacturer's instructions of kits. HK-2 cell damaged model was established to access the protection effect and action mechanism of five main flavonoids from Huangkui capsule. The experimental cells were divided into eight groups: control group, model group, positive drug group and five main flavonoids treated groups. The dichlorodihydrofluorescein diacetate (DCFH-DA) assay was used to determine the reactive oxygen species (ROS) in different groups. Western blot was applied to analyze the expression of pathogenesis-related proteins in different groups. Results The results stated that Huangkui capsule significantly inhibited the elevation of Scr, BUN, UP, the expression of α-smooth muscle actin (α-SMA), phosphorylation-extracellular signal-regulated kinase (p-ERK1/2), NADPH Oxidase 1, NADPH Oxidase 2 and NADPH Oxidase 4 in adenine-induced CRF rats. The main bioactive components of quercetin (QT), hyperoside (HY), isoquercitrin (IQT), gossypetin-8- O - β -D-glucuronide (GG) and quercetin-3′- O -glucoside (QG) at the dosage of 100 µM, like NADPH oxidase inhibitor diphenyleneiodonium, exhibited a significant effect on inhibiting the expression of α-SMA, p-ERK1/2, NADPH Oxidase 1, NADPH Oxidase 2 and NADPH Oxidase 4 in high glucose-induced HK-2 cells, especially GG. Conclusions These results demonstrated that Huangkui capsule and the flavonoids components prevent tubulointerstitial fibrosis in CRF rat involvement in the action mechanism of inhibiting NADPH oxidase/ROS/ERK pathway. [ABSTRACT FROM AUTHOR]