Effect of oligosaccharide esters and polygalaxanthone Ⅲ from Polygala tenuifolia willd towards cytochrome P450 Enzyme reaction kinetics, metabolic enzyme phenotype, and metabolites of berberine CYP450 enzyme inhibition of berberine in pooled human liver microsomes by cocktail probe drugs Inhibitory mechanism of tetrahydropalmatine enantiomers on cytochrome P450 in human liver microsomes