Table 2.

Rough IC₅₀ and volume/dose index values for inhibition of enzyme-selective substrates metabolites formation by pterostilbene.

Enzyme	RDI of Pterostilbene (mg)	IC50 (µM)	V/D index (L/dose)
CYP2C8	250	26.9 ± 5.6	36.30
CYP3A4	250	>100	4.70
UGT1A1	250	>500	<2
UGT1A6	250	26.7 ± 40.7	36.50
UGT1A9	250	>100	3.89
UGT1A8/10	250	92.7 ± 18.4	10.53

Enzyme selective substrates and pooled HLM or HIM were incubated with at least four different concentrations of pterostilbene. All incubations were performed in duplicate. Using nonlinear regression, rough IC₅₀ values were calculated by fitting the IC₅₀ equation to percent of activity remaining (Material and Methods-Data analysis). Values are reported as best fit IC₅₀ (mean ± standard error). All resulting values had r² value for goodness of fit of at least 0.9. Volume per dose index (VDI) values were calculated as mentioned in materials and methods. The recommended daily intake values were determined based on the commercially available products and a previous clinical study (Riche, 2012).