. Author manuscript; available in PMC: 2012 Aug 15.

Published in final edited form as: Chem Res Toxicol. 2011 Jul 20;24(8):1327–1337. doi: 10.1021/tx200218u

Table 5.

Effects of Preincubation Time on the Inhibition of P450 2A6- and 2A13-Dependent Coumarin 7-Hydroxylation Activities by BSC and m-XSC

	coumarin 7-hydroxylation (nmol/min/nmol P450)

	without preincubation	with preincubation
P450 2A6
control	3.26 (100)	3.06 (100)
+ BSC (4.3 µM)	1.70 (52)	1.52 (50)
+ m-XSC (0.68 µM)	1.56 (48)	1.46 (48)
P450 2A13
control	1.04 (100)	0.98 (100)
+ BSC (1.2 µM)	0.49 (47)	0.48 (49)
+ m-XSC (0.22 µM)	0.59 (56)	0.53 (54)

BSC and m-XSC were preincubated with recombinant P450 2A6 and 2A13 systems fortified with NADPH for 0 or 15 min and the catalytic activities were determined after adding 1.0 µM coumarin. Values in parentheses indicate % of control. Results are presented as means of triplicate determinations. There were no significant differences in the inhibition of coumarin 7-hydroxylation activities by BSC and m-XSC with and without preincubation.