Evaluation of Safety and Interactions with Conventional Drugs of Commercially Available Soybean Extract-containing Dietary Supplements

Dietary supplements based on soybean extracts are widely used for a myriad of indications, but there is evidence that isoflavones, components of these supplements affect cytochrome activity. Alteration in pharmacodynamics of cytochrome-substrate drugs after co-administration with dietary supplements based on soybean extracts offers information on clinically significant herb-drug interactions that can cause unanticipated adverse reactions or therapeutic failures. Moreover, herbal drugs can contribute to the development and severity of drug-induced liver injury. Therefore, the aim of this study was to examine the effect of commercially available dietary supplements based on soybean extracts on liver and renal function, oxidative stress and pharmacodynamics of several conventional drugs. After quantification of isoflavones in the supplement using high-performance liquid chromatography with a diode-array detector, pharmacological tests such as hot-plate, rotarod, pentobarbital-induced sleeping time were performed on Swiss albino mice treated with soybean extracts and several central nervous system acting drugs. Liver, renal function, and oxidative status in liver homogenates were determined in healthy and Wistar rats subjected to oxidative stress with carbon tetrachloride. Dietary supplements based on soybean extracts weakened the analgesic activity of codeine, significantly potentiated diazepam-induced motor coordination impairment at 10th and 30th minute after diazepam administration, but had the opposite effect on alprazolam effect. Soybean extracts pretreated group also exhibited significantly shorter pentobarbital sleep induction and sleeping time. Soybean extracts administration did not affect the liver and renal function and ameliorated oxidative stress caused by carbon tetrachloride. Despite exhibiting no negative effects on liver and renal function and demonstrated antioxidant in vivo potential, the safety of soybean extracts in addition to conventional drugs is questionable. The results of our study implicate the potential of dietary supplements based on soybean extracts for serious herb-drug interactions.