Inhibitory interaction of flavonoids with organic anion transporter 3 and their structure-activity relationships for predicting nephroprotective effects.

The organic anion transporter 3 (OAT3), an important renal uptake transporter, is associated with drug-induced acute kidney injury (AKI). Screening and identifying potent OAT3 inhibitors with little toxicity in natural products, especially flavonoids, in reducing OAT3-mediated AKI is of great value. The five strongest OAT3 inhibitors from the 97 flavonoids markedly decreased aristolochic acid I-induced cytotoxicity and alleviated methotrexate-induced nephrotoxicity. The pharmacophore model clarified hydrogen bond acceptors and hydrophobic groups are the critical pharmacophores. These findings would provide valuable information in predicting the potential risks of flavonoid-containing food/herb-drug interactions and optimizing flavonoid structure to alleviate OAT3-related AKI.

Permeation of Boswellia extract in the Caco-2 model and possible interactions of its constituents KBA and AKBA with OATP1B3 and MRP2.

Traditionally Boswellia serrata extract is used in the Indian Ayurvedic medicine for the treatment of inflammatory diseases. In 2002 the EMEA designated Boswellia an orphan drug status for the treatment of peritumoral oedema. Pharmacokinetic studies yielded low plasma concentrations of the active ingredients 11-keto-beta-boswellic acid (KBA) and 3-acetyl-11-keto-beta-boswellic acid (AKBA). In continuation of the tests investigating the factors limiting bioavailability of boswellic acids, the present study examined the permeability of KBA and AKBA in human Caco-2 cell lines. In addition, the interaction of KBA and AKBA with the organic anion transporter OATP1B3 and the multi drug resistant proteins P-glycoprotein and MRP2 was evaluated using partly fluorescent-based assays. The permeability studies revealed poor permeability of AKBA and moderate absorption of KBA with a P(app) value of 1.69 x 10(-6) cm/s. Most of KBA and AKBA were found to be retained by the Caco-2 monolayer. Neither KBA nor AKBA could be identified as substrates of P-glycoprotein. However, both KBA and AKBA modulated the activity of OATP1B3 and MRP2, indicating that therapeutic relevant interactions with other anionic drugs may be expected. The results of the present study provide the first explanation for the pharmacokinetic properties of KBA and AKBA.