Abstract
Silymarin, the extract of milk thistle, and its major active flavonolignan silybin, are common products widely used in the phytotherapy of liver diseases. They also have promising effects in protecting the pancreas, kidney, myocardium, and the central nervous system. However, inconsistent results are noted in the different clinical studies due to the low bioavailability of silymarin. Extensive studies were conducted to explore the metabolism and transport of silymarin/silybin as well as the impact of its consumption on the pharmacokinetics of other clinical drugs. Here, we aimed to summarize and highlight the current knowledge of the metabolism and transport of silymarin. It was concluded that the major efflux transporters of silybin are multidrug resistance-associated protein (MRP2) and breast cancer resistance protein (BCRP) based on results from the transporter-overexpressing cell lines and MRP2-deficient (TR−) rats. Nevertheless, compounds that inhibit the efflux transporters MRP2 and BCRP can enhance the absorption and activity of silybin. Although silymarin does inhibit certain drug-metabolizing enzymes and drug transporters, such effects are unlikely to manifest in clinical settings. Overall, silymarin is a safe and well-tolerated phytomedicine.
Highlights
Silymarin, an extraction from the seeds of milk thistle (Silybum marianum), has been used for liver and gallbladder dysfunction in Europe for thousands of years [1,2]
Miranda et al showed that MRP2 was the transporter mainly responsible for the biliary excretion or non-alcoholic fatty liver disease (NAFLD), mutant allele UGT1A1*28 produced little inter-subject of free and conjugated silybin using perfused rat liver from wild type and MRP2-deficient (TR− )
Silybin, and milk thistle extract currently rank among the top-selling botanical supplements or phytomedicines
Summary
An extraction from the seeds of milk thistle (Silybum marianum), has been used for liver and gallbladder dysfunction in Europe for thousands of years [1,2]. Studies have demonstrated that the pharmacological effects of silymarin/silybin are not limited to the treatment of liver diseases. It has promising effects in protecting the pancreas, kidney, myocardium, and central nervous system [6]. [21,22].understanding metabolism hepatitisCC and and nonalcoholic understanding thethe metabolism and and transport of silymarin will importantfor forimproving improvingits its low low bioavailability bioavailability and transport of silymarin will bebe important and resolving resolving the the inconsistencies in clinical outcomes as well as results of in vitro studies.
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