All together, table 1 showed that LC/ESI/MSn procedure profiled more than 80 phospholipid molecular species from both T. cuspidata and T. chinensis var. mairei cells. Due to effects of different molecular species on instrument response, the absolute quantification of phospholipids has not been performed in our experiments. The relative abundance of individual molecular species within a phospholipids class was calculated according to Materials and Methods. As shown in table 1, major molecular species composition of PC, PE, PS and PA of T. cuspidata at 2 weeks was similar to 2-week T. chinensis var. mairei. For instance, 16:0/20:4 ( 18:1/18:3 and 18:2/18:2 ) , 16:0/20:3 and 18:2/20:4 PE were prevalent in PE species , which constituted 18.0 % , 13.8 % and 9.3 % of total PE species in T. cuspidata, and 18.7 %, 13.3 %, 8.9 % in T. chinensis var. mairei. PS molecular species profiles were much less complex than profiles of PC and PE, and almost dominated by long-chain polyunsaturated fatty acids ( PUFA ) 24:0/20:4 and 22:0/ 20:4 PS in two Taxus species cells. For PG and PI, the most abundant molecular species were 16:0/18:3 and 16:0/18:2, which have some differences in two Taxus species cells ( * P<0.05 ). In addition, special PUFA ( C20:4 or C20:3 ) were relatively abundant in PE and PC species, including 16:0/20:4, 16:0/20:3, 18:2/20:4, 18:1/20:4 , 18:1/20:3 and 18:0/20:4.

All together, using the LC/ESI/MSn procedure, we profiled more than 80 phospholipids from both T. cuspidata and T. chinensis var. mairei cells. Their molecular ions, Sn-1/Sn-2 carboxylates, and relative abundances were listed in Table 1. Due to the different sensitivities of individual phospholipid to mass spectrometry detection , the absolute quantification of each phospholipid has not been possible in our experiments. The relative abundance of individual molecular species within a phospholipid class was calculated as described in Materials and Methods. As shown in Table 1, the relative abundances of the major species in phospholipid classes of PC, PE, PS and PA of T. cuspidata at 2 weeks was similar to that of T. chinensis var. mairei at 2 weeks. For instance, 16:0/20:4 ( 18:1/18:3 and 18:2/18:2 ) , 16:0/20:3 and 18:2/20:4 PE constituted 18.0 % , 13.8 % and 9.3 % of total PE in T. cuspidata, and 18.7 %, 13.3 %, 8.9 % in T. chinensis var. mairei. Profiles of the PS phospholipids were much less complex than the profiles of PC and PE. They were dominated by long-chain polyunsaturated fatty acids ( PUFA ) 24:0/20:4 and 22:0/ 20:4 PS in both types of Taxus cells . For PG and PI, the most abundant molecular species were 16:0/18:3 and 16:0/18:2 phospholipids whose relative abundances showed some differences in two Taxus cells ( * P<0.05 ). In addition, special PUFA, such as C20:4 or C20:3, was relatively abundant in PE and PC. Some of the other fatty acids were 16:0/20:4, 16:0/20:3, 18:2/20:4, 18:1/20:4, 18:1/20:3 and 18:0/20:4.

3.5. Applying to human plasma samples

The blood from 10 clinical patients was obtained and the plasma concentration of linomycin determined with the proposed method and the results are shown as below (Table 3). As is shown, linomycin was not detected in most patients. These data suggest that the virtual absence of absorption of this drug, which implies negligible passage into the general circulation. However, this can not be confirmed in the absence of information on the extent of metabolism.

3.5. Analysis of clinical samples

The bloods from 10 clinical HE patients who were treated with linomycin orally at a dose of xxx (?) mg/kg were obtained and the plasma concentrations of linomycin were determined with the developed method. This is a test study, not a full course pharmacokinetic study; therefore blood samples were collected only to 4 h after drug administration. As shown in Table 3, linomycin was not detected in most patients in the early hours of drug administration, agreeing with the difficulties of the absorption of this drug. But at 4 h some patients showed low levels of linomycin in their blood. It would be interesting to correlate blood levels of linomycin with clinical observations of the treated patients. The presence or absence of linomycin n in blood may provide some insights into the mechanism of actions of the drug in the treatment of HE patients. A multi-patient full course pharmacokinetic study is underway.