Table 1.

Cathinone, cathine and norephedrine concentrations in the khat-extract stock solution, and in experimental cell cultures

	Cathinone		Cathine		Norephedrine
	Mw 150.1		Mw 152.1		Mw 152.1
	mg ml-1	M	mg ml-1	M	mg ml-1	M
khat-extract stock solution	2.5	1.7 × 10-2	3.0	2.0 × 10-2	0.3	2.0 × 10-3
10-3 dilution	2.5 × 10-3	1.7 × 10-5	3 × 10-3	2.0 × 10-5	3 × 10-4	2.0 × 10-6
3.16 × 10-4 dilution	7.9 × 10-4	5.4 × 10-6	9.5 × 10-4	6.3 × 10-6	9.5 × 10-5	6.3 × 10-7

The stock solution concentrations were determined based on HPLC-MS-MS analyses [30].