Concentration for 50% inhibition

IC with bovine enzyme which is very similar to the human one. Inhibitor concentration for 50% inhibition. K of substrate (phenyl a-D-mannopyranoside). K of substrate (4-nitrophenyl a-D-manno-pyranoside). K of substrate (4-nitrophenyl D-glucosiduronic acid). K of substrate (4-nitrophenyl 2-acetamido-2-deoxy- o-glueoside). Inhibitors were chitotetraono-1,5-lactone and chitotetraose, respectively. 

Absorption, distribution, metabolism, and elimination P-glycoprotein Pharmacokinetics/pharmacodynamics Concentration for 50% inhibition of the function of the delayed rectifier channel encoded by the human ether... 

Some representative examples are given of plant sources of the cited compounds (further plant sources can be readily accessed via the Web). ICjo (concentration for 50% inhibition) values are given in round brackets. Ka (dissociation constant) or K (enzyme-inhibitor dissociation constant) values are given in square brackets. For convenience compounds are grouped into alkaloids (also encompassing N-containing aromatic pseudoalkaloids), phenolics, terpenes and other compounds and are listed alphabetically within these four groupings. 

Many studies of inhibition of animal or fungal enzymes by plant-derived compounds or related synthetic compounds have involved assaying the enzyme in standard reaction conditions in the presence of increasing concentrations of the test compounds. From such analyses one can determine IC-)() values (concentrations for 50% inhibition) for the test compounds. However such ICj() values can be markedly affected by the assay conditions used. Thus if the compound is a competitive inhibitor then the IG-)() value will be much lower when determined at much lower concentrations of substrate. As indicated above, A) values can be determined from kinetic analysis as outlined above. However such in vitro determinations have to be qualified in relation to different in vivo conditions including possible competing ligands and compound-sequestering entities in vivo. 

Debord and colleagues correlated LSER and TLSER parameters with the concentration for 50% inhibition, C50 (M), at 298 K for arylesterase by 11 aliphatic alcohols. The LSER parameters gave rise to Eqs. [28a-b], and the TLSER yielded Eqs. [29a-b]. There are two isozymes, A and B separate equations were derived for each. The intercepts were insignificant in all four equations so no deviation is listed. Here we use the common transform pCso = - log C50-... 

The I50 (molar concentration for 50% inhibition) in vitro Na+,K+-ATPase inhibitory activities of the genins were determined using rat brain Na+,K+-ATPase (E.C. 3.6.1.3), the preparation and assay of which have been reported previously by our laboratories (28,29). Rat brain enzyme was used in these studies for two reasons (1) the ease of preparation of high activity... 

Table 7-4. Selectivity of Dihydrofolate Reductase Inhibition (nM Concentration for 50% Inhibition)...

The osmoticum used had a marked effect on the inhibitory potency of FCCP and the non-carbanilates (Table IV). For the non-carbanilate herbicides and FCCP, valinomycin-induced swelling of mitochondria suspended in isotonic KCl was inhibited at much lower concentrations of the herbicides than when the mitochondria were suspended in isotonic KSCN. For the carbanilates, the molar concentration for 50% inhibition of valinomycin-induced swelling of mitochondria suspended in KSCN was about twice the... 

Tea extracts and tea polyphenols inhibit copper- and peroxide-induced oxidation of LDL in vitro (116,123,124). The inhibitory concentration for 50% reduction (IC q) values for inhibition of copper-induced oxidation of LDL by some phenoHc antioxidants are Hsted in Table 7. The IC q for epigaHocatechin gaHate was found to be 0.075 p.mM, which was the most potent of all the phenoHc antioxidants tested (123,124). Similar results have been reported elsewhere (115,116,125,126). 

Insect Growth-Inhibitory Activity of Some Meliaceae and Rutaceae Limonoids. Values are the Dietary Concentrations for 50% Growth Inhibition (EC50)... 

Epstein-Barr virus early antigen induction. Methanol extract of the dried leaf, in cell culture at a concentration of 1 pg/mL, was inactive. The assay was designed for tumor-promoting activity . Two diastere-oisomers of 2,7,1 l-cembratriene-4,6-diol (a- and 3-CBT) from the neutral fractions of cigarette smoke condensate, in Raji cells, produced potent inhibitory effects on the induction of Epstein-Barr virus (EBV)-EA by 12-0-tetradecanoylphorbol-13-acetate (TPA). The doses of a- and P-CBT required for 50% inhibition of EBV-EA induction by TPA were 7.7 and 6.7 mg/mL, respectively. Application of a- and P-CBT to mouse skin before treatment with TPA, inhibited TPA-induced ornithine decarboxylase activity in a dose-dependent manner. Application of 16.5 pM/mouse of a- and p-CBT resulted... 

Source Ichimura et al. (2003). Permission has been obtained for use of copyrighted material from Elsevier B.V. a IC50, concentration of the peptide required for 50% inhibition of ACE activity. 

The more detailed data for the above these biochemical tests of morusin (3) were as follows [73]. As shown in Fig. (8), morusin (3) caused dose-dependent inhibition of the specific binding [3H]TPA to a mouse skin particulate fraction. The concentration of morusin (3) for 50% inhibition (ED5o) was 57 pmol/L, whereas that of unlabelled TP A was 4 nmol/L. 

The quality of the phenol antioxidants was assessed by Vinson et al. (1999) using the IC50 for LDL + VLDL (very low density lipoprotein) oxidation, with smaller values indicating a higher quality. Quality of the antioxidants was due to free-radical scavenging activity and not chelation as the concentration of polyphenols for 50% inhibition was < 1 xM and cupric ion 25 xM in the oxidation medium. There was less percent variation within the groups for this parameter than for the total polyphenol content. The quality order was dark chocolate > cocoa > milk chocolate. The dark chocolate and cocoa were significantly different from the milk chocolate (p < 0.05), but not... 

The symbol LC50 means lethal concentration for 50% of a test population. The symbol EC50 means efficiency concentration for mobility suppression of 50% a test population. The symbol IC50 means inhibition concentration for 50% of a population in a test for respiratory suppression. 

ALS was isolated from barley seedlings as a 0-33% Ammonium Sulfate precipitate and examined for inhibition by TP. It is apparent from Figure 5 that the enzyme is very sensitive to the compound. The 1(50) value (concentration required for 50% inhibition) was calculated to be 0.047 uM. This value is within the range reported for CS tested against ALS from different species (19). Imidazolinones are less potent with 1(50) values in the range 2-12 uM (26). ALS isolated from several species and their 1(50) values for TP is shown in Table I. 

Tischer and Strotmann ( 7), the binding constant corresponds to the inhibition constant, i. e. the I,. value (the concentration necessary for 50% inhibition of photosynthetic electron transport), provided the I. value is extrapolated to zero chlorophyll concentration. The value of 527 molecules of chlorophyll per molecule of bound inhibitor indicates that roughly one molecule of herbicide binds per electron transport chain, because about 400-600 molecules of chlorophyll are considered to be associated with each electron transport chain. 

---