On‐line 2D‐LC‐ESI/MS/MS determination of rifaximin in rat serum

A highly sensitive and selective on‐line two‐dimensional reversed‐phase liquid chromatography/electrospray ionization–tandem mass spectrometry (2D‐LC‐ESI/MS/MS) method was developed and validated to determine rifaximin in rat serum by direct injection. The 2D‐LC‐ESI/MS/MS system consisted of a restricted access media column for trapping proteins as the first dimension and a Waters C₁₈ column as second dimension using 0.1% aqueous acetic acid:acetonitrile as mobile phase in a gradient elution mode. Rifampacin was used as an internal standard. The linear dynamic range was 0.5–10 ng/mL (r² > 0.998). Acceptable precision and accuracy were obtained over the calibration range. The assay was successfully used in analysis of rat serum to support pharmacokinetic studies. Copyright © 2009 John Wiley & Sons, Ltd.     

13C and 15N CP/MAS, 1H–15N SCT CP/MAS and FTIR spectroscopy as tools for qualitative detection of the presence of zwitterionic and non‐ionic forms of ansa‐macrolide 3‐formylrifamycin SV and its derivatives in solid state

¹³C, ¹⁵N CP/MAS, including ¹H–¹³C and ¹H–¹⁵N short contact time CP/MAS experiments, and FTIR methods were applied for detailed structural characterization of ansa‐macrolides as 3‐formylrifamycin SV (1) and its derivatives (2–6) in crystal and in powder forms. Although HPLC chromatograms for 2/CH₃OH and 2/CH₃CCl₃ were the same for rifampicin crystals dissolved in respective solvents, the UV–vis data recorded for them were different in 300–375 nm region. Detailed solid state ¹³C and ¹⁵N CP/MAS NMR and FTIR studies revealed that rifampicin (2), in contrast to 3‐formylrifamycin SV (1) and its amino derivatives (3–6), can occur in pure non‐ionic or zwitterionic forms in crystal and in pure these forms or a mixture of them in a powder. Multinuclear CP/MAS and FTIR studies demonstrated also that 3–6 derivatives were present exclusively in pure zwitterionic forms, both in powder and in crystal. On the basis of the solid state NMR and FTIR studies, two conformers of 3‐formylrifamycin SV were detected in powder form due to the different orientations of carbonyl group of amide moiety. The PM6 molecular modeling at the semi‐empirical level of theory, allowed visualization the most energetically favorable non‐ionic and zwitterionic forms of 1–6 antibiotics, strongly stabilized via intramolecular H‐bonds. FTIR studies indicated that the originally adopted forms of these type antibiotics in crystal or in powder are stable in standard laboratory conditions in time. The results presented point to the fact that because of a possible presence of two forms of rifampicin (compound 2), quantification of the content of this antibiotic in relevant pharmaceuticals needs caution. Copyright © 2013 John Wiley & Sons, Ltd.     

Flow-Injection Electrochemiluminescence Detecting Rifampicin Based on Its Sensitizing Effect

Introduction Rifampicin, a semi synthetic compound, is used primarily in the treatment of tuberculosis, and it is also an excellent amistaphyloco antibiotic when used in combination with other antibiotics, so it is very useful clinically.1 Therefore, the determination of rifampicin has attracted much attention. From now on, techniques for the determination of rifampicin have been primarily based on spectrophotometry,2 double-wavelength thin-layer scan,3 chemiluminescence,4 high performance liq…     

Influence of Moringa oleifera on pharmacokinetic disposition of rifampicin using HPLC‐PDA method: a pre‐clinical study

The influence of active fraction isolated from pods of an indigenous plant, Moringa oleifera (MoAF) was studied on the pharmacokinetic profile of the orally administered frontline anti‐tuberculosis drug rifampicin (20 mg/kg b.w.) in Swiss albino mice. The antibiotic rifampicin alone and in combination with MoAF (0.1 mg/kg b.w.) was administered orally and heparanized blood samples were collected from the orbital plexus of mice for plasma separation at 0, 1, 2, 3, 4 and 5 h, post treatment. Plasma rifampicin concentration, pharmacokinetic parameters and drug metabolizing enzyme (cytochrome P‐450) activity were determined. The pharmacokinetic data revealed that MoAF‐treated animals had significantly increased rifampicin plasma concentration, C_max, K_el, t_½(a), t_½(el), K_a and AUC as well as inhibited rifampicin‐induced cytochrome P‐450 activity. In conclusion, the result of this study suggested that the bioavailability‐enhancing property of MoAF may help to lower the dosage level and shorten the treatment course of rifampicin. Copyright © 2010 John Wiley & Sons, Ltd.     

鲁米诺-过氧化氢化学发光体系测定利福平

基于鲁米诺在碱性条件下可以被H2O2氧化产生化学发光,利福平对此化学发光具有增敏作用这一现象,结合流动注射技术建立了一种直接测定利福平的流动注射化学发光新方法.该方法的线性范围在1.0×10-6～2.0×10-8g·mL-1,检出限为3.0×10-9g·mL-1,对5.0×10-7g·mL-1的利福平连续进行11次平行测定,其相对标准偏差为3.0%.该法已成功测定了利福平胶囊及眼药水中利福平的含量.     

Determination of rifampicin in human plasma by high‐performance liquid chromatography coupled with ultraviolet detection after automatized solid–liquid extraction

A precise and accurate high‐performance liquid chromatography (HPLC) quantification method of rifampicin in human plasma was developed and validated using ultraviolet detection after an automatized solid‐phase extraction. The method was validated with respect to selectivity, extraction recovery, linearity, intra‐ and inter‐day precision, accuracy, lower limit of quantification and stability. Chromatographic separation was performed on a Chromolith RP₈ column using a mixture of 0.05 m acetate buffer pH 5.7–acetonitrile (35:65, v/v) as mobile phase. The compounds were detected at a wavelength of 335 nm with a lower limit of quantification of 0.05 mg/L in human plasma. Retention times for rifampicin and 6,7‐dimethyl‐2,3‐di(2‐pyridyl) quinoxaline used as internal standard were respectively 3.77 and 4.81 min. This robust and exact method was successfully applied in routine for therapeutic drug monitoring in patients treated with rifampicin.     

Antimycobacterial and anticancer activity of newly designed cinnamic acid hydrazides with favorable toxicity profile

A series of twelve novel hybrids of cinnamic acid and thiocarbohydrazones were designed, synthesized in high yield using a simple coupling strategy via acid chlorides, and evaluated for their impact against Mycobacterium tuberculosis (Mtb) and cancer cells survival. Among them, compound 3 demonstrated strong anti-Mtb activity by reducing bacilli survival for>90 % in all three treated Mtb isolates, whereas isoniazid and rifampicin did not. Moreover, compound 3 didn’t affect vitality of HepG-2 cells, implying on advantageous hepatotoxicity profile compared to current therapeutic options for tuberculosis. Compounds 2a and 3b displayed as strong inducers of apoptosis in A549 cells, both activating intrinsic caspase pathway and cell cycle arrest at the G0/G1 phase. Subsequent analyses disclosed differences in their activities, where 3b has ability to induce production of mitochondrial superoxide anions, while 2a significantly inhibited cellular mobility. More importantly, 3b considerably affected viability of HepG-2 and HaCaT cells, whereas 2a had moderate impact only on the later. Molecular modeling studies indicated high permeability and good absorption through the human intestine, and moderate aqueous solubility with poor blood–brain barrier permeability. In summary, our results reveal that novel compounds 3 and 2a represent promising agents for tuberculosis and cancer treatment, respectively, indicating that further investigation needs to be performed to clarify the mechanisms of their anti-Mtb and anticancer activity.     

测定利福平的化学发光新体系

基于碱性介质中铜离子催化过氧化氢可氧化利福平产生化学发光这一现象，并结合流动注射分析技术建立起了一种测定利福平的新方法。该方法测定利福平的线性范围为 ４ × １０－７× １０－４ｇ／ｍｌ，方法的检出限为 ７× １０－８ｇ／ｍＬ，７次平行测定 ２ × １０－５ｇ／ｍＬ利福平的相对标准偏差为 ４．９％。成功地用于利福平眼药水中利福平含量的测定。     

Determination of Rifampicin by Peroxomonosulfate‐Cobalt(II) Chemiluminescence System

Rifampicin can enhance the chemiluminescence (CL) of peroxomonosulfate‐cobalt(II) system, and the CL intensity is strongly dependent on the rifampicin concentrations. Based on this phenomenon, a rapid and sensitive flow injection CL method was developed for the determination of rifampicin. The relative CL intensity was linear with the rifampicin concentration over the range of 5×10^?8 to 1×10^?6 g·mL^?1 (r=0.9991), the detection limit was 7×10^?9 g·mL^?1 (S/N=3), and the relative standard deviation was 2.7% for 6×10^?7 g·mL^?1 rifampicin (n=11). Furthermore, this method was successfully applied to the determination of rifampicin in real eye drop and capsules sample.     

铁氰化钾-钙黄绿素抑制化学发光法测定利福平

在碱性条件下,利福平对铁氰化钾-钙黄绿素化学发光体系有较强的抑制作用,结合流动注射分析技术,建立了一种化学发光测定利福平的新方法。考察了介质浓度、发光试剂浓度等因素的影响,在优化实验条件下,该方法对利福平的检出限为6.81×10-2mg/L,线性范围为0.5~100 mg/L,对50 mg/L的利福平连续进行11次平行测定,其相对标准偏差为0.86%,该方法已成功用于滴眼液及胶囊中利福平含量的测定。