The development of the monograph of a commonly used Chinese medicine, Lini Semen, for the Hong Kong Chinese Materia Medica Standards (HKCMMS) was recorded. HKCMMS is a set of reliable and internationally recognized standards of Chinese medicine. The monograph of Lini Semen was proposed, endorsed, and under editorial phase for the publication of the 9th volume of HKCMMS. In the proposed HKCMMS monograph of Lini Semen, besides regular content such as macroscopic and microscopic identification, and TLC identification, a HPLC fingerprint method and two assay methods were developed. All methods were well-established and validated. TLC identification: Lini Semen n-hexane extract is identified on a HPTLC Silica gel RP-18 plate, with α-linolenic acid and linoleic acid as the markers. The developing system consisted of acetone, acetic acid and dichloromethane in the ratio of 5:4:2. The spraying reagent was 5% sulphuric acid - ethanol solution and the plate was observed under 366 nm. HPLC fingerprint: Fingerprint of Lini Semen was conducted on a HPLC system with a C8 column. Mobile phase consisted of (A) water and (B) acetonitrile and isopropanol (9:1). Six characteristic peaks, including α-linolenic acid and linoleic acid were detected under 210 nm. Assay: α-Linolenic acid and linoleic acid were detected from Lini Semen n-hexane extract under the same HPLC condition of the fingerprint of Lini Semen. The proposed total content of α-linolenic acid and linoleic acid was not less than 0.56%. Secoisolariciresinol diglucoside (SDG) was detected from hydrolysed Lini Semen extract by HPLC system with a C18 column. Mobile phase consisted of (A) water and (B) acetonitrile. The detection wavelength was 280 nm. The proposed content of SDG was not less than 0.81%. Conclusion: It is the first time to propose a HPLC fingerprint and introduce SDG as a assay marker of Lini Semen in a regional standard monograph. The established methods for TLC identification, HPLC fingerprint, assay of the total content of α-linolenic acid and linoleic acid, as well as assay for SDG were validated with in-house and inter-laboratory comparison to prove that the methods are reliable.

Erythromycin is a macrolide antibiotic used mainly in the treatment of infections caused by gram-positive organisms. Erythromycin base is rap idly degraded in acidic media necessitating the use of structurally modified erythromycin derivatives or acid resistant dosage forms in order to decrease gastric inactivation of the drug. The majority of pharmacokinetic studies to-date have utilized relatively non-specific microbiological assay procedures which are unable to differentiate between concentrations of active erythromycin base and the inactive pro-drug derivatives. A high-performance liquid chromatographic (HPLC) technique is described for the simultaneous determination of erythromycin base and propionate (inactive pro-drug form) in human serum and urine following the oral administration of erythromycin estolate, an acid stable derivative of erythromycin. The method involves a solid-phase extraction step prior to chromatography on a C18 reversed-phase column with coulometric electrochemical detection. Sample handling and storage techniques are presented which minimize hydrolysis of the inactive ester moiety between sample collection and analysis, thereby more accurately reflecting the in vivo situation than in previously published studies. Results from single dose pharmacokinetic studies indicate that only 10-15% of the total erythromycin concentration in vivo is present as the active base component following oral administration of erythromycin estolate. This percentage increases to approximately 25% during multiple dose administration. Novel urinary excretion data are presented which reveal that approximately 40% and 55% of the total erythromycin excreted in urine is excreted as erythromycin base following single and multiple dosages respectively. Computer fitting of mean serum concentration-time data revealed that an open one compartment model with linear first order absorption and elimination best described the absorption and disposition of erythromycin, although poor computer fits for individual data sets were observed. Some evidence of non-linear elimination is presented utilizing both compartmental and non-compartmental pharmacokinetic techniques. Large intra-and inter-personal variability in erythromycin absorption and disposition was experienced which was evaluated in five subjects who each received one 500 mg erythromycin estolate tablet from the same batch, on three separate occasions. In addition. an HPLC method is described for the analysis of "total erythromycin" concentrations following erythromycin estolate administration which involves hydrolysis of the ester component prior to chromatography. as well as an HPLC method utilizing amperometric electrochemical detection capable of monitoring the stability of erythromycin base in stored biological fluids. These methods were uti I ized in various stability studies involving erythromycin base and propionate as well as for the analysis of erythromycin estolate dosage forms.

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The stationary phase on chemically modified supports for liquid chromatography is described as a mixture of the surface-bonded species, the active unmodified surface, and associated mobile phase components. Each of these three factors in stationary phase formation is examined and improved qualitative and quantitative descriptions of the stationary phase are provided. The role of the active unmodified surface was examined by synthesizing a carbon support and chemically modifying it with octyl groups. The modified carbon had a greater affinity for lipophilic probes than an octyl silica. The lipophilicity of the octyl carbon was attenuated relative to the unmodified carbon. The physical state of the bonded species in C(,18) and C(,8) packings was studied using carbon-13 NMR. Peak widths of 2-7 ppm indicated a liquid-like nature but with restricted movement. Only the 7 to 10 carbons in a C(,18) chain farthest from the surface were sufficiently motile to produce a signal. The C(,8) packing showed more rigid chains with only the top 3 or 4 carbons responding. The liquid-like nature of a C(,18) chain increased with the lipophilic character of the solvent, indicating that solvation of the bonded species was directly related to the mobile phase composition. Changes in temperature had little effect on the physical state of the bonded species, but chromatographic enthalpy measurements showed that changes in stationary phase composition could be induced by warming the column and held by subsequent cooling. Quantitative measurements of stationary phase compositions revealed linear distribution isotherms for the organic modifiers methanol, acetonitrile, and tetrahydrofuran. Chromatographic selectivities for homologous n-alkanols correlated linearly with organic modifier concentrations in the stationary phases. The stationary phase volumes, which increased with increasing modifier concentrations, are interpreted as constituting filling of the pores in the support with a gradient of modifier enrichment toward the surface.

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Yeung Wing Cheung. / Bibliography : leaf 91 / Thesis (M.Phil.)--Chinese University of Hong Kong, 1982