engleski

HPLC-DAD-MS DETERMINATION AND CHARACTERIZATION OF CYTOCHROME P450 MEDIATED METABOLISM OF FLAVONOIDS

Flavonoids are plant products abundant in every day diet rich in vegetables and fruits. They have many salutary effects, of which their antioxidative, cardiovascular, and anticarcinogenic are the most extensively studied. This group of compounds is characterized with C6-C3-C6 skeleton i.e. benzopyran ring to which phenyl is bound (Figure 1). They are divided in classes based on structure of ring C. Diversity of these compounds comes from hydroxylation and subsequent methylation and glycosylation of hydroxyl groups located on rings A and B. Most dominant enzymes in metabolism of xenobiotics are cytochrome P450. This superfamily of enzymes catalyzes 75 % of drug metabolism. Next group of enzymes are uridinediphospho-glucuronosyltransferases. Cytochromes P450 have most significant role in phase I reactions i.e. oxidations and reductions ; over 95 % of these reactions is catalyzed by P450s. These reactions are extremely diverse and include, but are not limited to, aliphatic and aromatic hydroxylations, N and S oxidations, C- N bond cleavage (demethylations, dealkylations, deaminations), C-C cleavage (aromatization), etc. Some of the most significant cytochromes P450 that are involved in drug metabolism are CYP3A4, CYP2D6, CYP2E1, CYP2C9 and CYP2C19. Objective of this study was to screen metabolism of 30 flavonoids using human liver microsomes and recombinant liver cytochrome P450 enzymes. For this purpose, HPLC method coupled with UV detector and MS TOF was developed. This method combined separation power of HPLC and determination of accurate mass of unknown metabolites using MS TOF. Most flavonoids could be separated based on retention time even though there are subtle differences in flavonoid structures. Structures of metabolites were elucidated using accurate mass data, retention time and were confirmed using flavonoid standards.

flavonoids, metabolism

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