Investigation Of The Mechanism Of Plumbagin On CYP And UGT Enzymes Using The Cocktail Approach

With the prevalence of herbal and western medicines co-administration,the herb-drug interactions mainly mediated by CYP and UGT enzymes often occur.An in vitro cocktail of probe substrates was established to investigate the inhibitory effects of compounds on CYP and UGT enzymes.Firstly,the cocktail approaches for CYP isoforms including CYP1A2,CYP2B6/1,CYP2C9/11,CYP2D6/1,CYP2E1 and CYP3A4/2,and UGT isoforms including UGT1A1,UGT1A3,UGT1A6,UGT1A9/PROG and UGT2B7/AZTG were established in human and rat liver microsomes.Then,the inhibitory effects of many Chinese medicine monomers on CYPs and UGTs were evaluated by the cocktail approaches.The results indicated that plumbagin,a monomer isolated from Plumbago zeylanica L.with anti-inflammatory and anti-cancer properties,was a strong CYP inhibitor,which was not previously investigated.The inhibition of plumbagin on CYPs was not time-dependent.In human liver microsomes,plumbagin was a mixed inhibitor of CYP2B6,CYP2C9,CYP2D6,CYP2E1,CYP3A4 and a non-competitive inhibitor of CYP1A2,with Ki values of 1.62?M,2.16 ?M,1.46 ?M,0.65 ?M,0.88 ?M and 0.15?M respectively.In rat liver microsomes,plumbagin was a mixed inhibitor of CYP1A2 and CYP2D1,and competitive inhibitor of CYP2B1,CYP2C11 and CYP2E1 with Ki values of 2.64 ?M,9.49 ?M,9.93 pM,7.85 ?M and 6.28 ?M respectively.Besides,the inhibition profile of plumbagin on CYP3A2 was the atypical kinetics.In addition,plumbagin had no significant inhibitory effects on UGT enzymes.In summary,the present study established in vitro cocktail methods to evaluate potential CYP-and UGT-mediated drug-drug interactions of Chinese medicine monomers.Then plumbagin was discovered to have strong inhibitory effects on six main CYP isoforms,but no significant effects on UGT enzymes,which provides drug-like property information and guidance for the development and application for this monomer.