Micellar High-Performance Liquid Chromatographic Separation of Serum Bilirubin Species with Direct Sample Injection

Effective oral treatment of unconjugated hyperbilirubinemia in Gunn rats

We sought to develop an oral treatment for unconjugated hyperbilirubinemia. In the Gunn rat model of unconjugated hyperbilirubinemia, dietary supplementation with the lipase inhibitor orlistat (Orl) or with calcium phosphate (CaP) decreases plasma unconjugated bilirubin (UCB) levels. We determined whether Orl, CaP, or their combination is superior to phototherapy, the conventional treatment, and whether the effects of Orl and CaP are influenced by dietary fat content. Gunn rats were treated with Orl (200 mg/kg chow), CaP (20 g/kg chow), Orl + CaP, or continuous phototherapy (19 muW/cm(2)/nm) during a low-fat (LF) diet (13 energy%) or high-fat (HF) diet (35 energy%). Plasma UCB and fecal fat excretion were measured before, during, and/or at the end of treatment. Orl treatment for 2 weeks (HF diet) reduced plasma UCB concentrations similar to phototherapy (-34% and -28%, respectively); the combination of both was more effective than either treatment alone (-48%; P < .001). After 3 weeks of a HF diet, plasma UCB was 46% lower compared with the LF diet (P < .001). Plasma UCB concentrations were negatively correlated with fecal fat excretion (r = -0.96; P < .001). Irrespective of dietary fat content, 3 weeks of combined treatment (Orl + CaP) decreased plasma UCB by approximately 50% (P < .01) and was more effective than phototherapy (P < .05) at the intensity provided. In conclusion, plasma UCB concentrations in Gunn rats are negatively related to fecal fat excretion and dietary fat content. Orlistat is equally effective as phototherapy for the treatment of unconjugated hyperbilirubinemia in Gunn rats, and combined oral treatment with Orl + CaP is more effective than phototherapy. The present results support the feasibility of an efficient oral treatment of unconjugated hyperbilirubinemia.

Orlistat treatment increases fecal bilirubin excretion and decreases plasma bilirubin concentrations in hyperbilirubinemic Gunn rats

OBJECTIVE

To determine whether serum levels of unconjugated bilirubin (UCB) can be decreased by enhancing fecal fat excretion.

STUDY DESIGN

Gunn rats were fed a high-fat diet (control) or the same diet mixed with the lipase inhibitor orlistat. At regular intervals, plasma UCB concentrations were determined and 72-hour fat balances were performed.

RESULTS

Orlistat treatment decreased plasma UCB concentrations (at 3 weeks; 100 mg/kg, -33%+/-8%, P<.05; 200 mg/kg, -46%+/-10%, P<.01). Within days of treatment, orlistat treatment increased fecal excretion of UCB (at day 3; +220%, P<.05). During 24 weeks of orlistat treatment (200 mg/kg diet), the plasma bilirubin concentrations were continuously approximately 35% lower than in control rats. Plasma UCB concentrations were inversely correlated with the amount of fecal fat excretion (n=12, r=-0.87, P<.001).

CONCLUSIONS

In Gunn rats, orlistat treatment increases the fecal excretion of fat and enhances the disposal of UCB. This approach could lead to novel strategies for prevention and treatment of unconjugated hyperbilirubinemia in patients.

Pharmaceutical applications of micelles in chromatography and electrophoresis

This review surveys the use of micelles as separation media in chromatography and electrophoresis. Applications to pharmaceuticals whose molecular masses are relatively small are focused on in this review. In high-performance liquid chromatography (HPLC), chromatography using micelles and reversed-phase stationary phases such as octadecylsilylized silica gel (ODS) columns is known as micellar liquid chromatography (MLC). The main application of MLC to pharmaceutical analysis is the same as in ion-pair chromatography using alkylsulfonate or tetraalkylammonium. In most cases, selectivity is much improved compared with other short alkyl chain ion-pairing agents such as pentanesulfonate or octanesulfonate. Direct plasma/serum injection can be successful in MLC. Separation of small ions is also successful by using gel filtration columns and micellar solutions. In electrophoresis, especially capillary electrophoresis (CE), micelles are used as pseudo-stationary phases in capillary zone electrophoresis (CZE). This mode is called micellar electrokinetic chromatography (MEKC). Most of the drug analysis can be performed by using the MEKC mode because of its wide applicability. Enantiomer separation, separation of amino acids and closely related peptides, separation of very complex mixtures, determination of drugs in biological samples etc. as well as separation of electrically neutral drugs can be successfully achieved by MEKC. Microemulsion electrokinetic chromatography (MEEKC), in which surfactants are also used in forming the microemulsion, is successful for the separation of electrically neutral drugs as in MEKC. This review mainly describes the typical applications of MLC and MEKC for the analysis of pharmaceuticals.