Prediction of potential drug interactions of apigenin based on molecular docking and in vitro inhibition experiments / 中国中药杂志

The purpose of this study was to investigate the effect of apigenin on UGT1 A1 enzyme activity and to predict the potential drug-drug interaction of apigenin in clinical use. First,on the basis of previous experiments,the binding targets and binding strength of apigenin to UGT1 A1 enzyme were predicted by computer molecular docking method. Then the inhibitory effect of apigenin on UGT1 A1 enzyme was evaluated by in vitro human liver microsomal incubation system. Molecular docking results showed that apigenin was docked into the active region of UGT1 A1 enzyme protein F,consistent with the active region of bilirubin docking,with moderate affinity. Apigenin flavone mother nucleus mainly interacted with amino acid residues ILE343 and VAL345 to form hydrophobic binding Pi-Alkyl. At the same time,the hydroxyl group on the mother nucleus and the amino acid residue LYS346 formed an additional hydrogen bond,which increased the binding of the molecule to the protein. These results suggested that the flavonoid mother nucleus structure had a special structure binding to the enzyme protein UGT1 A1,and the introduction of hydroxyl groups into the mother nucleus can increase the binding ability. In vitro inhibition experiments showed that apigenin had a moderate inhibitory effect on UGT1 A1 enzyme in a way of competitive inhibition,which was consistent with the results of molecular docking. The results of two experiments showed that apigenin was the substrate of UGT1 A1 enzyme,which could inhibit the activity of UGT1 A1 enzyme competitively,and there was a risk of drug interaction between apigenin and UGT1 A1 enzyme substrate in clinical use.

Characterization of erythrosine B binding to bovine serum albumin and bilirubin displacement.

The interaction of erythrosine B (ErB), a commonly used dye for coloring foods and drinks, with bovine serum albumin (BSA) was investigated both in the absence and presence of bilirubin (BR) using absorption and absorption difference spectroscopy. ErB binding to BSA was reflected from a significant red shift of 11 nm in the absorption maximum of ErB (527 nm) with the change in absorbance at λmax. Analysis of absorption difference spectroscopic titration results of BSA with increasing concentrations of ErB using Benesi-Hildebrand equation gave the association constant, K as 6.9 104 M-1. BR displacing action of ErB was revealed by a significant blue shift in the absorption maximum, accompanied by a decrease in absorbance difference at λmax in the difference spectrum of BR-BSA complex upon addition of increasing concentrations of ErB. This was further substantiated by fluorescence spectroscopy, as addition of increasing concentrations of ErB to BR-BSA complex caused a significant decrease in fluorescence at 510 nm. The results suggest that ErB binds to a site in the vicinity of BR binding site on BSA. Therefore, intake of ErB may increase the risk of hyperbilirubinemia in the healthy subjects.

Role of bilirubin as antioxidant in neonatal jaundice and effect of ethanolic extract of sweet lime peel on experimentally induced jaundice in rat.

Bilirubin above a threshold level is toxic to human system and is excreted in urinary and through gastrointestinal tract. The role of bilirubin as antioxidant is debatable. This paper aims at elucidating the role of bilirubin as an antioxidant in neonatal jaundice patients. It is observed that bilirubin up to 6 mg/dl in blood acts as an antioxidant and above 12.5 mg/dl is strongly prooxidant. Phototherapy is the accepted therapeutic management of neonatal jaundice and has been shown to enhance the oxidative stress. Approaches have been taken to formulate a herbal medication which will reduce bilirubin level in the neonates without inducing additional damages. The ethanolic extract of sweet lime peel, administered orally at a dose of 72 microg is found to reduce the oxidative stress in erythrocytes of phenylhydrazine-induced jaundiced rats treated with phototherapy.

Performance Evaluation of Affinity Column Mediated Immunometric Assay for Tacrolimus / 대한진단검사의학회지

BACKGROUND: Therapeutic drug monitoring (TDM) of tacrolimus is essential because of narrow therapeutic range and poor correlation of dose to blood concentration. Affinity Column Mediated Immunometric Assay (ACMIA) does not require a pretreatment steps in measurement of tacrolimus. In this study, we evaluated the performance of tacrolimus assay using ACMIA (Dimension RxL Max, Dade Behring). METHODS: The imprecision, the linearity and the detection limits and the interferences by bilirubin and chyle, and correlation with hematocrit for tacrolimus by ACMIA were evaluated according to Clinical and Laboratory Standards Institute guidelines EP5-A2, EP6-A, EP17-A, EP9-A2, and EP7-A2. Method comparison studies with microparticle enzyme immunoassay (MEIA) (IMx Tacrolimus II, Abbott Laboratories) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) (Waters 2795 Quattromicro API, Micromass) were also performed. RESULTS: The total imprecision for low, middle and high level was 12.8%, 9.0% and 6.7%, respectively. The range of tacrolimus from 3.1 ng/mL to 35.4 ng/mL showed a clinically relevant linearity. The limit of detection and the functional sensitivity were 0.24 ng/mL and 0.72 ng/mL, respectively. Tacrolimus concentration measurement (Tac-CM) with ACMIA did not show significant interferences with bile and chyle and also did not show significant correlation with hematocrit. In comparison study for Tac-CM with MEIA and LC-MS/MS, Tac-CM with ACMIA showed a good correlation with MEIA (r=0.950) and LC-MS/MS (r=0.946). CONCLUSIONS: The imprecision, linearity, detection limits, interference and correlation of Tac-CM with ACMIA were suitable for clinical use. Tac-CM with ACMIA could reduce turn around time and help clinicians to manage transplant patients on immunosuppressant therapy.

Interactions of Unconjugated Bilirubin with Bile Acid by Rapid Solvent Partition / 대한간학회지

BACKGROUND/AIMS: Our previous studies of ionization and solubility of unconjugated bilirubin (UCB) yielded inappropriately large differences between the two carboxylic pK'a values of UCB. These data, however, were not ideal due to crystal effects, matastability, impurities of the bilirubin, and imprecision of analyses at low UCB. METHODS: The sodium salt of taurocholate (TC) was purified and dissolved in water to 100 mM. Chloroform (CHCl3) was purified by vacuum distillation. Buffers used were: citrate from pH 4 to 6, phosphate from pH 6 to 8, and borate above pH 8. All had an ionic strength of 0.10. The problems were minimized by rapid solvent partition of UCB from CHCl3 into buffered aqueous NaCl, and a new, accurate assay of low UCB in the aqueous phase which was achieved by concentrating the UCB through back extraction into small volumes of CHCl3. RESULTS: In contrast with the crystal dissolution studies, the two pK'a value were similar. H2B0, not HB-, was the dominant UCB species in the pH range of bile (6.0 to 8.0). The aqueous solubilities of UCB were 90 to 98% less. Less than 0.01% of the bile salt partitioned into the CHCl3 phase and self-association of B= was negligible. UCB solubilities in 50 mM TC were 2 to 10% of those obtained by crystal dissolution, and, up to pH 7.9, were below the maximum UCB concentration in normal human bile. CONCLUSIONS: We suggest that the markedly increased binding of UCB with each ionization step is due to the disruption of the internal hydrogen bonds of the ionized carboxyl groups on interaction with the bile salt. We propose to extend the study of partition to determine the activity and the degradation products of calcium salts of unbound bilirubin fractions.

Thalassemic serum impairs endothelial cell growth in vitro.

Endothelial cells cultured for 3 days in the presence of hemoglobin H pooled sera had significantly decreased cell proliferation compared to those in normal serum. Inhibition was demonstrated at a concentration of 20% pooled serum in the cultured medium. Further decrease was shown in the presence of 30% pooled hemoglobin H sera. Sera from two genotypes of Hb H disease (alpha-thal 1/alpha-thal 2 and alpha-thal 1/Hb Constant Spring) had the same degree of inhibitory effect. Pooled sera from beta-thal/Hb E patients (both splenectomized or nonsplenectomized cases) had no such inhibitory effect. However, at day 4 and 5, the growth pattern relatively declined. Bilirubin at a concentration greater than 4.0 mg% in the medium 199 also caused significant decrease in cell proliferation. Since the diluted Hb H serum had bilirubin less than 4.0 mg%, the inhibitory effect of the pooled HbH serum is thus not due to effect of bilirubin. The difference between HbH and beta-thal/HbE sera in terms of inhibition of endothelial cell proliferation is the new finding that needs further investigation to explain vascularization and hemostasis in the patients of these two genotypes.