Background: Herbal products have grown steadily across the globe and have increasingly been incorporated
into western medicine for healthcare aims, thereby causing potential pharmacokinetic Herb-drug Interactions
(HDIs) through the inhibition or induction of drug-metabolizing enzymes and transporters. Human Carboxylesterases
1 (CES1) and 2 (CES2) metabolize endogenous and exogenous chemicals including many important therapeutic
medications. The growing number of CES substrate drugs also underscores the importance of the enzymes. Herein,
we summarized those potential inhibitors and inducers coming from herbal constituents toward CES1 and CES2. We
also reviewed the reported HDI studies focusing on herbal products and therapeutic agents metabolized by CES1 or
Methods: We searched in PubMed for manuscript published in English after Jan 1, 2000 combining terms “carboxylesterase
1”, “carboxylesterase 2”, “inhibitor”, “inducer”, “herb-drug interaction”, “inhibitory”, and “herbal supplement”.
We also searched specific websites including FDA and EMA. The data of screened papers were analyzed and
Results: The results showed that more than 50 natural inhibitors of CES1 or CES2, including phenolic chemicals,
triterpenoids, and tanshinones were found from herbs, whereas only few inducers of CES1 and CES2 were reported.
Systemic exposure to some commonly used drugs including oseltamivir, irinotecan, and clopidogrel were changed
when they were co-administered with herb products such as goldenseal, black cohosh, ginger, St. John’s Wort, curcumin,
and some Chinese compound formula in animals.
Conclusion: Nonclinical and clinical studies on HDIs are warranted in the future to provide safety information toward
better clinical outcomes for the combination of herbal products and conventional drugs.