Metabolism bioavailability

Degenhardt, P. and Winterhalter, E., HSCCC a powerful tool for the preparative isolation of bioactive compounds, in Biologically-Active Phytochemicals in Food Analysis, Metabolism, Bioavailability and Function, Pfannhauser, W. et ah, Eds., Royal Society of Chemistry, Cambridge, 2001, 143. 

In solution, the anthocyanins actually might exist in equilibrium with essentially four molecular forms - the flavylium cation, the quinoidal base, the hemiacetal base and chalcone [19]. The relative amounts of the four structure forms depends on both the pH and the difference in structure of the anthocyanins [20-22], Generally, anthocyanins exist primarily as the stable flavylium cation above pH 2. This uniqueness in the chemical structure is one of the important key factors affecting their absorption, metabolism, bioavailability and, consequently, the biological responses of the human body to anthocyanins. 

Disposition in the Body. Rapidly and almost completely absorbed after oral administration but undergoes extensive first-pass metabolism bioavailability about 5 to 10%. About 90% of an oral dose is excreted in the urine in 24 hours with about 40% as the glucuronide conjugate of the active metabolite 4-hydroxy-alprenolol, 5% as free 4-hydroxyalprenolol, 20 to 30% as alprenolol glucuronide, 1% as desisopropylalprenolol, and less than 1% as unchanged drug unknown metabolites account for the remainder of the dose. 

Disposition in the Body. Readily absorbed after oral administration, but undergoes extensive first-pass metabolism bioavailability about 40%. The major metabolite is the sulphoxide, but A -demethylation and A -oxidation also occur. After daily oral doses, up to about 30% is excreted in the urine in 24 hours as chlorprothixene sulphoxide, and up to about 40% is eliminated in the faeces also as the sulphoxide. 

Disposition in the Body. Readily and completely absorbed but undergoes considerable first-pass metabolism bioavailability about 40%. Rapidly distributed and concentrated in the brain, lungs, liver, and kidneys. The main metabolic reaction is N-demethylation which produces norpropoxyphene, the major metabolite, and also dinorpropoxyphene which is dehydrated to cyclic dinorpropoxyphene. Norpropoxyphene has less than half the activity of dextropropoxyphene. In 24 hours, about 35% of a dose is excreted in urine with about 13% of the dose as norpropoxyphene and up to 5% as unchanged drug. A total of 60 to 70% of a dose is excreted in urine in about 5 days about 18% of the dose may be eliminated in the faeces over the same period. 

Disposition in the Body. Well absorbed after oral administration but appears to undergo extensive first-pass metabolism bioavailability about 20%. Little is known about the metabolic fate... 

Disposition in the Body. Slowly but completely absorbed following oral administration. It appears to undergo significant first-pass metabolism bioavailability about 70%. After intravenous administration, about 57% of a dose is excreted in the urine and 30% in the faeces over a period of 21 days less than 10% of the dose is excreted as unchanged drug. The principal metabolite is the desmethyl derivative, which has been shown to be active in animals, but hydroxylation also occurs to form phenolic derivatives which may be further converted to aromatic methoxy ethers or excreted as glucuronide conjugates A -oxidation also occurs and maprotiline A -oxide has been reported to be active numerous minor metabolites have been identified in urine. 

Disposition in the Body. Absorbed from the gastro-intestinal tract but there is extensive first-pass metabolism bioavailability about 30%. It is metabolised to pethidine and norpethidine. Up to about 5% of a dose is excreted unchanged in the urine, with about 18% as norpethidine and 2% as pethidine, in two to three days. The urinary excretion of unchanged phenoperidine is increased to about 7% when the urine is acidified. 

Disposition in the Body. Rapidly and completely absorbed after oral administration, but subject to extensive first-pass metabolism bioavailability about 25%. The main metabolic reaction is conjugation with sulphate at the phenol position minor metabolites formed are jS-(4-hydroxyphenoxy)lactic acid and prenalterol glucuronide. About 90% of a dose is excreted in the urine in 24 hours. After an intravenous dose, about 60% is excreted unchanged with about 35% as the sulphate after oral administration, about 15% is excreted unchanged, with about 80% as the sulphate. 

Ramesh, A., Inyang, F., Hood, D.B., Archibong, A.E., Knuckles, M.E., Nyanda, A.M. (2001b). Metabolism, bioavailability, and toxicokinetics of benzo(a)pyrene in F344 rats following oral administration. Exp. Toxic. Pathol. 53 275-90. 

Oleszek, W. Sitek, M. Stochmal, A. Cheeke, P., Antioxidant properties of Yucca schidigera products. In Biologically-active Phytochemicals in Food. Analysis, Metabolism, Bioavailability and Function., Pfannhauser, W. Fenwick, G. R. Khokhar, S. Eds. Royal Society of Chemistry 2001 pp 303-306. 

In conclusion, whatever its origin, the use of biological information constitutes a preferential source for original molecule research. It offers creative approaches that do not rest on the exploitation of routine pharmacological models. Once the lead molecule is identified, it will immediately be the object of thorough studies to. elucidate its molecular mechanism of action. Simultaneously, one will proceed to the synthesis of structural analogues, as well as to the establishment of structure-activity relationships, and to the optimization of all the important parameters for its development potency, selectivity, metabolism, bioavailability, toxicity, cost price, etc. In other terms, even if the initial discovery was purely fortuitous, subsequent research must be marked by a very important effort of rationalization. 

The objective of this paper is to address and investigate some of the factors that singly or in combination may cause the apparent loss of linear correlation between bioconcentration factors in fish and Kq. These are exposure time, metabolism, bioavailability, membrane permeation and lipid water partitioning. First, it is useful to review the mathematical background. 

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