Determination of Potential Interactions between Methanol Extract of Aframomum melegueta Seeds (AMSE) and Amlodipine (AML)

Background: The belief in the therapeutic value of herbal preparations makes their concomitant use with orthodox drugs highly probable, which may impact drug concentration assays in biological fluids. Wide use of herbal remedies may not only be due to resource limitations but also to apparent support offered by those who tout these preparations as very safe. Justification for safety is based on natural sources of the preparations which are believed to be devoid of any harm or complications.

Purpose: The present study investigates the potential interactions between the methanol extract of Aframomum melegueta seeds (AMSE) and amlodipine (AML).

Methods: Amlodipine concentrations 2.5, 5.0, 7.5, 10, 12.5, and 15 µg/mL were assayed in vitro with or without AMSE using potassium ferricyanide/FeCl3 (FeCl3/K4(Fe(CN)6)) method. The resulting solution was wavelength-scanned in the 380 – 950 nm range and absorbance read at 393.1, 455.6, and 774.8 nm.

Results: Aframomum melegueta seeds (AMSE), when present in biological fluids and solutions of AML, interfered significantly with FeCl3/K4(Fe(CN))6. The highest interference occurred at 774.8 nm, and 50 µg/mL AMSE gave as much as 1.5 absolute unit increase in absorbance of 2.5 µg/mL when compared to its absence. A spectral scan of the sample revealed two additional peaks at 393.1 and 455.6 nm with only 0.07 and 0.16 nm unit increases in the presence of AMSE. The concentration–absorbance relationship at these two wavelengths satisfied Beer-Lambert’s law. Beyond 15 µg/mL AML at 774.8 nm, Beer- Lambert’s law was not followed. Phenolic hydroxyl groups of flavonoids, though capable of direct ferric chloride reaction with its OH group to produce classical color reaction between phenols and ferric chloride, may be acting as a reducing agent and reacting like AML with the same reagents.

Conclusion: This study highlights the potential interactions between components of the methanol extract of Aframomum melegueta seeds on assay methods of AML. Furthermore, reliable concentration measurements have been made at 393.1 or 455.6 nm. This should be kept in mind when carrying out drug measurements in populations where concurrent use of herbal remedies is highly probable. The study demonstrates the potential of such interactions from herbal components with measurements of other clinically used drugs, a possibility that should be kept in mind when carrying out drug measurements in populations where concurrent use of herbal remedies is highly probable.