Approaching strategy to increase the oral bioavailability of berberine, a quaternary ammonium isoquinoline alkaloid: Part 1. Physicochemical and pharmacokinetic properties

Berberine (BBR), a quaternary ammonium isoquinoline alkaloid, is a substrate for P-glycoprotein (P-gp) and cytochrome P450s (CYPs). BBR exhibits a wide variety of pharmacological activities; however, its clinical application is limited due to low oral bioavailability.Physicochemical and pharmacokinetic properties of BBR and its lipophilic metabolites, berberrubine (BRB) and dihydroberberine (DHBBR), were reviewed including solubility/lipophilicity, salt/ion-pair formation, oral bioavailability, first-pass metabolism, and intestinal microbiota-mediated metabolism, by searching research articles using PubMed.Pharmacokinetic analysis of BBR bioavailability data in rats revealed that the oral bioavailability is limited by the extensive CYPs-mediated intestinal first-pass metabolism, insufficient membrane permeability due to the low solubility and P-gp-mediated efflux transport, and the hepatic first-pass metabolism. Various active metabolites are generated by intestinal first-pass metabolism. Intestinal microbiota also contributes to the BBR metabolism and generates lipophilic metabolites; BRB, an active metabolite, and DHBBR, a precursor that can distribute to the brain. The pharmacokinetic analysis of BBR bioavailability data can provide a clue to developing effective dosage routes and/or formulations that can increase the oral bioavailability of BBR.