OBJECTIVETo determine the plasma protein binding rates of brucine and strychnine in total alkaloids from the seed of Strychnou nux-vomica, and make comparison with the single components at the same concentration.

METHODUltrafiltration was employed to determine the rat the plasma protein binding rate of the alkaloids from the seed of S. nux-vomica. The plasma concentrations were measured by RP-HPLC.

RESULTThe protein binding rates of brucine were (65.60 3.01)%, (68.20 +/- 7.80)%, (59.58 +/- 3.78)% when the plasma concentrations was 0.520, 1.300, 2.600 mg x L(-1), respectively. The protein binding rates of strychnine was (66.17 +/- 6.36)%, (67.10 +/- 2.52)%, (57.21 +/- 0.79)% when the plasma concentrations were 0.936, 2.340, 4.680 mg x L(-1) respectively. As to the total alkaloids from the seed of S. nux-vomica, The protein binding rate of brucine was (62.19 +/- 2.45)%, (69.55 +/- 5.84)%, (61.76 +/- 3.68)% when the plasma concentrations were 0.519, 1.288, 2.607 mg x L(-1), respectively. And the protein binding rates of strychnine were (54.79 +/- 3.55)%, (57.13 +/- 4.49)%, (59.31 +/- 3.65)% when the plasma concentrations were 0.940, 2.338, 4.674 mg x L(-1), respectively.

CONCLUSIONBrucine and strychnine have medium capacity in binding to plasma protein. In comparison with the single component of the same concentration, the protein binding rate of brucine in total alkaloids shows little difference, while there seems to be an obvious decrease for strychnine.