Anthocyanins are plant pigments occurring in flowers and berry fruits. Since a phenomenon of food-drug interactions is increasingly emerging, we examined the effects of 21 major anthocyanins and the extracts from 3 food supplements containing anthocyanins on the aryl hydrocarbon receptor (AhR) – cytochrome P450 CYP1A1 signaling pathway in human hepatocytes and human hepatic HepG2 and intestinal LS174T cancer cells. Pelargonidin-3-O-rutinoside (PEL-2) and cyanidin-3,5-O-diglucoside (CYA-3) dose-dependently activated AhR, as revealed by gene reporter assay. PEL-2 and CYA-3 induced CYP1A1 mRNA but not protein in HepG2 and LS174T cells. Neither compound induced CYP1A1 mRNA and protein in four different primary human hepatocytes cultures. The effects of PEL-2 and CYA-3 on AhR occurred by ligand-dependent and ligand-independent mechanisms, respectively, as demonstrated by ligand binding assay. In a direct enzyme inhibition assay, none of the antocyanins tested inhibited the CYP1A1 marker activity to less than 50% even at 100 µM concentration. PEL-2 and CYA-3 at 100 µM inhibited CYP1A1 to 79% and 65%, respectively. In conclusion, with exception of PEL-2 and CYA-3, there were no effects of 19 major anthocyanins and 3 food supplements containing anthocyanins on AhR-CYP1A1 signaling, implying zero potential of these compounds for food-drug interactions with respect to AhR-CYP1A1 pathway.

Anthocyanidins and anthocyanins are pharmacologically active constituents of various berry fruits, such as blueberry and cranberry. These compounds are also contained in massively used nutritional supplements based on extracts or dry matter from berry fruits. The current study evaluated the effects of anthocyanidins and anthocyanins on the expression and catalytic activity of major drug-metabolizing enzymes CYP2C9, CYP2A6, CYP2B6, and CYP3A4 in primary cultures of human hepatocytes and human liver microsomes. Expression of mRNA was quantified by qRT-PCR. Expression of proteins was evaluated by Western blotting and immunochemiluminescence. The catalytic activity of CYP enzymes was measured by HPLC using specific enzyme substrates. Tested anthocyanidins (6) and anthocyanins (21) did not induce the expression of mRNA and protein of CYP2C9, CYP2A6, CYP2B6, and CYP3A4 genes in human hepatocytes. Catalytic activities of CYP2C9, CYP2A6, CYP2B6, and CYP3A4 enzymes were inhibited by all anthocyanidins to different extents (e.g., delphinidin inhibits CYP3A4 by >90% at 100 μM with IC50 = 32 μM). Of 21 anthocyanins tested, only cyanidin-3-O-rhamnoside (CYP3A4 by >75% at 100 μM with IC50 = 44 μM) and two glycosides of delphinidin significantly inhibited examined cytochromes P450. It may be concluded that in the ranges of common ingestion of either food or dietary supplement an induction or significant inhibition of CYP2C9, CYP2A6, CYP2B6, and CYP3A4 activity is most probably not expected.

1. Nucleotide analogues comprise an important class of drugs used in treatment of viral infections but also cancer. These drugs affect the structural integrity of DNA and activate different pathways and processes in the cell and may directly or indirectly influence the drug metabolizing system. Adefovir dipivoxil (AD) and tenofovir disoproxil (TD) are nucleotide analogues approved for the treatment of chronic hepatitis B and/or HIV/AIDS infection. 2. To evaluate the risk of their drug-drug interactions on the level of drug metabolism, an effect of both compounds on cytochromes P450 expression was studied using cDNA microarrays, real-time RT-PCR and immunoblotting. Mice were given intraperitoneally 25 mg/kg of AD or TD, respectively. As a positive control, a combination of prototypic cytochromes P450 (CYP) inducers, phenobarbital and β-naphthoflavone was chosen. 3. The data obtained showed a significant CYP induction in the positive control group, but no clinically significant induction of CYP genes by AD or TD was observed. Our results support the evidence of safety of AD and TD with respect to drug-drug interactions based on enzyme induction. These findings are important as a plethora of new antivirals of different types are being tested and introduced to clinical practice, mostly to be used in combinations.