Flavonoids are abundant polyphenols in nature. They are extensively biotransformed in enterocytes and hepatocytes, where conjugated (methyl, sulfate, and glucuronide) metabolites are formed. However, bacterial microflora in the human intestines also metabolize flavonoids, resulting in the production of smaller phenolic fragments (e.g., hydroxybenzoic, hydroxyacetic and hydroxycinnamic acids, and hydroxybenzenes). Despite the fact that several colonic metabolites appear in the circulation at high concentrations, we have only limited information regarding their pharmacodynamic effects and pharmacokinetic interactions. Therefore, in this in vitro study, we investigated the interactions of 24 microbial flavonoid metabolites with human serum albumin and cytochrome P450 (CYP2C9, 2C19, and 3A4) enzymes. Our results demonstrated that some metabolites (e.g., 2,4-dihydroxyacetophenone, pyrogallol, O-desmethylangolensin, and 2-hydroxy-4-methoxybenzoic acid) form stable complexes with albumin. However, the compounds tested did not considerably displace Site I and II marker drugs from albumin. All CYP isoforms examined were significantly inhibited by O-desmethylangolensin; nevertheless, only its effect on CYP2C9 seems to be relevant. Furthermore, resorcinol and phloroglucinol showed strong inhibitory effects on CYP3A4. Our results demonstrate that, besides flavonoid aglycones and their conjugated derivatives, some colonic metabolites are also able to interact with proteins involved in the pharmacokinetics of drugs.

• Keywords
• CYP450 enzymes, O-desmethylangolensin, colonic flavonoid metabolites, pharmacokinetic interaction, phloroglucinol, polyphenols, resorcinol, serum albumin,
• MeSH
• Erythrocytes enzymology   MeSH
• Flavonoids * chemistry   metabolism   MeSH
• Hepatocytes enzymology   MeSH
• Humans MeSH
• Serum Albumin, Human * chemistry   metabolism   MeSH
• Cytochrome P-450 Enzyme System * chemistry   metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Flavonoids * MeSH
• Serum Albumin, Human * MeSH
• Cytochrome P-450 Enzyme System * MeSH

Sesquiterpenes, 15-carbon compounds formed from three isoprenoid units, are the main components of plant essential oils. Sesquiterpenes occur in human food, but they are principally taken as components of many folk medicines and dietary supplements. The aim of our study was to test and compare the potential inhibitory effect of acyclic sesquiterpenes, trans-nerolidol, cis-nerolidol and farnesol, on the activities of the main xenobiotic-metabolizing enzymes in rat and human liver in vitro. Rat and human subcellular fractions, relatively specific substrates, corresponding coenzymes and HPLC, spectrophotometric or spectrofluorometric analysis of product formation were used. The results showed significant inhibition of cytochromes P450 (namely CYP1A, CYP2B and CYP3A subfamilies) activities by all tested sesquiterpenes in rat as well as in human hepatic microsomes. On the other hand, all tested sesquiterpenes did not significantly affect the activities of carbonyl-reducing enzymes and conjugation enzymes. The results indicate that acyclic sesquiterpenes might affect CYP1A, CYP2B and CYP3A mediated metabolism of concurrently administered drugs and other xenobiotics. The possible drug-sesquiterpene interactions should be verified in in vivo experiments.

• Keywords
• drug-metabolizing enzymes, farnesol, inhibition, nerolidol,
• MeSH
• Farnesol chemistry   pharmacology   MeSH
• Inhibitory Concentration 50 MeSH
• Cytochrome P-450 Enzyme Inhibitors chemistry   pharmacology   MeSH
• Liver enzymology   MeSH
• Kinetics MeSH
• Rats MeSH
• Humans MeSH
• Sesquiterpenes chemistry   pharmacology   MeSH
• Subcellular Fractions enzymology   MeSH
• Cytochrome P-450 Enzyme System metabolism   MeSH
• Xenobiotics metabolism   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Farnesol MeSH
• Cytochrome P-450 Enzyme Inhibitors MeSH
• nerolidol MeSH Browser
• Sesquiterpenes MeSH
• Cytochrome P-450 Enzyme System MeSH
• Xenobiotics MeSH