Pharmacokinetics of B-Ring Unsubstituted Flavones

Abstract

B-ring unsubstituted flavones (of which the most widely known are chrysin, baicalein, wogonin, and oroxylin A) are 2-phenylchromen-4-one molecules of which the B-ring is devoid of any hydroxy, methoxy, or other substituent. They may be found naturally in a number of herbal products used for therapeutic purposes, and several have been designed by researchers and obtained in the laboratory. They have generated interest in the scientific community for their potential use in a variety of pathologies, and understanding their pharmacokinetics is important for a grasp of their optimal use. Based on a comprehensive survey of the relevant literature, this paper examines their absorption (with deglycosylation as a preliminary step) and their fate in the body, from metabolism to excretion. Differences among species (inter-individual) and within the same species (intra-individual) variability have been examined based on the available data, and finally, knowledge gaps and directions of future research are discussed.

Keywords: B-ring unsubstituted flavones; baicalein; chrysin; oroxylin A; pharmacokinetics; wogonin.

Figure 1

Basic chemical structures of different classes of flavonoids.

Figure 2

Representative chemical structures of B-ring unsubstituted flavones.

Figure 3

Schematic representation of different recycling scheme applicable to flavonoids. A: aglycones; G: glucuronide; β-GUS: β-glucuronidase; UGT: UDP-glucuronosyltransferases; ST: sulfotransferases.