Cytochrome P450 inhibition activities of non-standardized botanical products

Abstract

Ethnopharmacological relevance: R-tab, H-tab and E-cap botanical products are used for the treatment of various ailments. R-tab is traditionally prescribed for improving urination, H-tab is for relieving piles, hemorrhoids, fissures, and rectal inflammation and E-cap is for regulating menstruation.

Aims of the study: To extract the botanical products and determine their potential interaction with the cytochrome P450 (CYP1A2, CYP2D6 and CYP3A4) enzymes.

Materials and methods: R-tab, H-tab and E-cap botanical products were first extracted using solvents and analyzed using HPLC and LC-MS/MS. The effects of methanol extracts on the cytochrome induction and inhibition activities were determined using a series of in vitro assays, including multiplex RT-qPCR, CYP activity assays (P450-Glo™) and LC-MS/MS-based assays. For the CYP induction assay, omeprazole, rifampicin and dexamethasone were used as CYP1A2, CYP2D6 and CYP3A4 inducers, respectively. Ketoconazole and acetaminophen were used as positive and negative controls for the CYP3A4 inhibition assay, whereas furafylline and ketoconazole were used as positive and negative controls for the CYP1A2 inhibition assay.

Results: All three botanical products did not show any significant induction in CYP1A2, CYP2D6 and CYP3A4 mRNA expression. By contrast, R-tab inhibited the mRNA expression of CYP1A2 significantly from the lowest concentration of 0.01 μg/mL, while, H-tab inhibited the mRNA expression of CYP1A2 and CYP3A4 from 0.1 μg/mL. Based on the P450 Glo assays, E-cap extract inhibited the metabolic activity of CYP1A2 with an IC₅₀ value of 37.24 μg/mL. On the other hand, R-tab, H-tab and E-cap showed inhibitory effects on the CYP3A4 enzymatic activity with IC₅₀ values of 17.42, 18.20 and 20.60 μg/mL, respectively. However, using the LC-MS/MS-based methods, the concentration-dependent effects of R-tab and H-tab extracts on the metabolism of testosterone appeared to be more prominent, with IC₅₀ values of 51.90 and 56.90 μg/mL as compared with the rest of the results, which were all above 100 μg/mL CONCLUSION: The CYP3A4 mRNA and enzymatic activity were moderately inhibited by R-tab and H-tab. Methanol extract of botanical products in solid dosage forms can be evaluated for their herb-drug interaction risks using in vitro assays and may provide the minimum data required for safety labeling.

Keywords: Botanical products; CYP induction; CYP inhibition; CYP1A2; CYP3A4; Herb-drug interaction; Safety labeling.