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Related Concept Videos

Bioavailability: Overview01:13

Bioavailability: Overview

Bioavailability refers to the proportion of an unaltered drug that, after administration, enters the systemic circulation and can be distributed to the desired action site. Factors such as gastrointestinal (GI) absorption and liver biotransformation influence the bioavailability of a drug when it is administered orally. When a drug is administered intravenously, it enters the systemic circulation directly; by definition, its bioavailability is assumed to be 100%. The bioavailability of an...
Therapeutic Index01:13

Therapeutic Index

The therapeutic index of a drug is a key parameter in pharmacology that quantifies the relative safety of a drug by calculating the ratio between the dose that causes toxicity in half the population (50%) to the dose that proves to be effective for half the population (50%). It provides a spectrum of doses for a particular drug ranging from effective to potentially toxic. To illustrate, consider an anticoagulant agent like warfarin. It possesses a narrow window within its therapeutic index to...
Factors Affecting Drug Biotransformation: Biological01:19

Factors Affecting Drug Biotransformation: Biological

Biological factors significantly impact drug metabolism, influencing drug clearance, efficacy, and potential toxicity.
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Bioavailability: Overview01:17

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Bioavailability refers to the proportion of an administered drug that reaches the systemic circulation in its active, unaltered form. It is a crucial pharmacokinetic parameter that determines the effectiveness of a drug in achieving its intended therapeutic outcomes. The route of administration significantly influences bioavailability, with intravenous administration achieving 100% bioavailability as the drug directly enters the bloodstream. In contrast, oral administration often results in...
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Bioactivation is a metabolic process that transforms less reactive substances into highly reactive metabolites, initiating tissue toxicity. This transformation can lead to various toxic effects, including carcinogenesis and teratogenesis. Reactive metabolites are classified into two main types: electrophiles and free radicals.Electrophiles are electron-deficient species and are produced primarily by the enzyme cytochrome P-450 during the metabolism of compounds containing carbon, nitrogen, or...

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Related Experiment Video

Updated: Jun 25, 2026

Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein
14:32

Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein

Published on: January 28, 2013

1-alpha-Tocopherylacetate: biological activity.

H WEISER, G BRUBACHER, O WISS

    Science (New York, N.Y.)
    |April 5, 1963
    PubMed
    Summary
    This summary is machine-generated.

    dl-alpha-tocopheryl acetate exhibits 42% of the biological activity of d-alpha-tocopheryl acetate, confirming established potency ratios. Both phytol and isophytol derived dl-alpha-tocopheryl acetate preparations showed equal efficacy in hemolysis tests.

    Keywords:
    VITAMIN E

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    Quantitative Analysis of Dietary Vitamin A Metabolites in Murine Ocular and Non-Ocular Tissues Using High-Performance Liquid Chromatography
    05:03

    Quantitative Analysis of Dietary Vitamin A Metabolites in Murine Ocular and Non-Ocular Tissues Using High-Performance Liquid Chromatography

    Published on: December 27, 2024

    Area of Science:

    • Biochemistry
    • Nutritional Science
    • Pharmacology

    Background:

    • Vitamin E isomers, specifically tocopheryl acetates, possess varying biological activities.
    • Understanding the relative potencies of different vitamin E forms is crucial for nutritional and therapeutic applications.
    • The rat hemolysis test is a standard assay for evaluating vitamin E activity.

    Purpose of the Study:

    • To quantify the biological activity of l-alpha-Tocopheryl acetate relative to d-alpha-tocopheryl acetate.
    • To establish a precise potency ratio between these vitamin E forms.
    • To compare the efficacy of dl-alpha-tocopheryl acetate derived from different precursors.

    Main Methods:

    • Utilizing the rat hemolysis test to assess the biological activity of tocopheryl acetate isomers.
    • Comparing the protective effects against hemolysis induced by different vitamin E preparations.
    • Quantifying the activity of l-alpha-Tocopheryl acetate against a standard d-alpha-tocopheryl acetate.

    Main Results:

    • l-alpha-Tocopheryl acetate demonstrated 42% of the activity of d-alpha-tocopheryl acetate in the rat hemolysis assay.
    • A potency ratio of 1.4:1.0 was established for d-alpha-tocopheryl acetate versus dl-alpha-tocopheryl acetate.
    • dl-alpha-Tocopheryl acetate synthesized from both phytol and isophytol exhibited equivalent activity.

    Conclusions:

    • The established potency ratio confirms the currently accepted biological ratio for these vitamin E forms.
    • The source of dl-alpha-tocopheryl acetate (phytol or isophytol) does not influence its biological activity in this assay.
    • These findings support the accurate assessment of vitamin E nutritional value and therapeutic potential.