Simple equilibrium dialysis-high-performance liquid chromatographic method for the in vitro assessment of 5-methoxypsoralen bound to human albumin.
Increasingly used in therapeutics, 5-methoxypsoralen (5-MOP), a linear furocoumarin, associated with UVA irradiation (PUVA), is now an established treatment for skin diseases such as vitiligo, mycosis funcoides and particularly psoriasis. Successful PUVA therapy depends on a sufficiently high peak 5-MOP plasma concentration coinciding with the UVA irradiation. However, as with most drugs, only the free plasma fraction is able to enter the target cells and has a pharmacological effect. In this work, the binding of 5-MOP to human albumin was studied in vitro, using a dialysis chamber. Bound and free 5-MOP fractions were quantified by a modification of Stolk's high-performance liquid chromatographic method. Dialysis was performed at 37 degrees C and pH 7.4 for 2 h, against a 4% albumin solution in phosphate buffer. The 5-MOP concentrations used were from 5 x 10(-5) to 5 x 10(-2) g/l in 1 x 10(-1) g/l steps. The 5-MOP bound strongly to human albumin in an unsaturable way. The mean 5-MOP binding to albumin was 95.3%. These results are in accordance with those published by Artuc et al. and not with those of Veronese et al., who found a lower saturable fixation (91%). These two research groups used tritiated 5-MOP. The technique used in this work is simple and inexpensive. It can be employed easily in vivo, e.g., for the assessment of 5-MOP free fractions in different therapeutic conditions.
Makki
S
S
Laboratoires de Chimie Analytique et de Dermatologie et Biologie Cutanée, Faculté de Médecine et Pharmacie, Besançon, France.
Muret
P
P
Renaud
A
A
Agache
P
P
Magnin
P
P
D000078223:5-Methoxypsoralen; D000418:Albumins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003956:Dialysis / Q000295:instrumentation / Q000379:methods; D006801:Humans; D008730:Methoxsalen / Q000032:analysis* / Q000378:metabolism; D011701:PUVA Therapy
D000418:Albumins; D000078223:5-Methoxypsoralen; D008730:Methoxsalen