Application of salting-out thin layer chromatography in computational prediction of minimum inhibitory concentration and blood-brain barrier penetration of some selected fluoroquinolones

Menthol- and thymol-based ciprofloxacin derivatives against Mycobacterium tuberculosis: in vitro activity, lipophilicity, and computational studies

In this work, we investigated the antitubercular properties of Ciprofloxacin derivatives conjugated with menthol and thymol moieties. For the sixteen derivatives, we established minimal inhibitory concentrations (MIC) using isolates of Mycobacterium tuberculosis that were resistant or susceptible to other antibiotics. For the most potent compound 1-cyclopropyl-6-fluoro-7-{4-[6-((1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-6-oxohexyl]piperazin-1-yl}-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6), we determined fractional inhibitory concentration index (FICI) values to confirm antibacterial susceptibility and synergistic effects with other reference drugs. In addition, chromatographic studies of all the derivatives demonstrated a significant three to four-fold increase in lipophilicity and affinity to phospholipids compared to Ciprofloxacin. Finally, we conducted structure-based studies of the investigated compounds using molecular docking and taking into account protein target mutations associated with fluoroquinolone resistance. In summary, our findings indicate that the investigated compounds possess tuberculostatic properties, with some showing similar or even better activity against resistant strains compared to reference drugs. Increased lipophilicity and affinity to phospholipids of the new derivatives can offer several advantages for new drug candidates, beyond just improved cell membrane penetration. However, further studies are needed to fully understand their safety, efficacy, and mechanism of action.

QSRR modeling of the chromatographic retention behavior of some quinolone and sulfonamide antibacterial agents using firefly algorithm coupled to support vector machine

Quinolone and sulfonamide are two classes of antibacterial agents with an opulent history of medicinal chemistry features that contribute to their bacterial spectrum, efficacy, pharmacokinetics, and adverse effect profiles. The urgent need for their use, combined with the escalating rate of their resistance, necessitates the development of suitable analytical methods that accelerate and facilitate their analysis. In this study, the advanced firefly algorithm (FFA) coupled with support vector regression (SVR) was used to select the most significant descriptors and to construct two quantitative structure-retention relationship (QSRR) models using a series of 11 selected quinolone and 13 sulfonamide drugs, respectively, to predict their retention behavior in HPLC. Precisely, the effect of the pH value and acetonitrile composition in the mobile phase on the retention behavior of quinolones and sulfonamides, respectively, were studied. The obtained QSRR models performed well in both internal and external validations, demonstrating their robustness and predictive ability. Y-randomization validation demonstrated that the obtained models did not result by statistical chance. Moreover, the obtained results shed the light on the molecular features that influence the retention behavior of these two classes under the current chromatographic conditions.

Lipophilicity study of different cephalosporins: Computational prediction of minimum inhibitory concentration using salting-out chromatography

The chromatographic and lipophilicity characters of seven cephalosporins of different four classes (cephradine, cefaclor, cefprozil, cefixime, cefotaxime, ceftazidime and cefepime) were examined by salting out thin-layer chromatography (SOTLC). SOTLC using ammonium sulfate salt was employed to predict the lipophilicity of the proposed drugs via their retention behavior. The calculated R_M0 values showed liner relationship with the molar concentration of ammonium sulfate in mobile phase in the range of 0.5-2.5 mol/L. Additionally, quantitative structure retention relationship (QSRR) was generated to figure out the relationship between the calculated chromatographic parameters (R_M0 and C₀) and log P of the studied cephalosporins. Good correlations were found between the chromatographically obtained retention parameters (R_M0 and C₀) and some molecular descriptors of the examined drugs. Furthermore, an efficient QSAR model was carried out using the calculated chromatographic parameters (R_M0 and C₀) and log P of the studied cephalosporins to predict minimum inhibitory concentration (MIC) and blood brain barrier (BBB) penetration of the examined drugs. The study was extended to separate and quantify the selected antibiotics in their pure forms and pharmaceutical formulations. Normal phase thin layer chromatographic (NP-TLC) method using a usable developing system of acetone: methanol: water: ammonium hydroxide: glacial acetic acid (90: 10: 18: 3: 2, by volume) was successfully applied to resolve the studied cephalosporins. Linearity was achieved in the range of 0.2-3 µg/mL for most of the studied antibiotics. The developed SOTLC method can be considered as a good start alternative to reversed phase thin layer chromatography (RP-TLC) for prediction of the lipophilic properties of examined cephalosporins. Moreover, the proposed NP-TLC densitometric method can be easily applied for quality control analysis of the chosen drugs and other structurally related components.

In depth investigation of the retention behavior of structurally related β-blockers on RP-HPLC column: Quality by design and quantitative structure-property relationship complementary approaches for optimization and validation

The persistent introduction of new β-blockers motivates the demand for optimizing RP-HPLC well-designed analytical procedures that could be applied to this structurally related and commonly prescribed pharmacological group in order to reduce time and chemicals consumption in quality control units. Betoxolol HCl (BEX) and Carvidolol (CAR) were selected as representative examples to conduct predictive studies based on two complementary approaches, Quality by design (QBD) and Quantitative structure property relationship (QSPR). In concern QBD, a Box-Behnken design was adopted at variable chromatographic parameters to achieve the most proper conditions that might be applied for efficient analysis of the majority of group members. On the other hand, the retention time was chosen as the target property in the QSPR study that was conducted onto seven β. blockers (the two investigated drugs in addition to five other β. blockers) to find the best correlated molecular descriptors to the retention behavior. Both external and internal validation studies have comparable quality with training levels. Hence a simple selection algorithm of conventional features provides robust confirmatory predictive QBD and QSPR models. Derringer's desirability function as as a multi-criteria approach was applied for getting the optimum chromatographic analysis conditions. Efficient analysis of BET and CAR was achieved at column temperatures of 26.00 and 27.50 °C, respectively using acetonitrile and phosphate buffer (pH 4.55) 70:30 v/v as a mobile phase with a flow rate of 1.00 mL/min, and UV detection at 220 nm. The method was validated in accordance to ICH guidelines, and had exhibited acceptable precision, accuracy, linearity, and robustness.

Prolonged infusion of linezolid is associated with improved pharmacokinetic/pharmacodynamic (PK/PD) profiles in patients with external ventricular drains

OBJECTIVE

We previously investigated the pharmacokinetic and pharmacodynamic (PK/PD) parameters of routine linezolid infusions (1 h) in patients with external ventricular drains (EVD). The aim of the study was to determine whether extended linezolid infusions (200 mg/h for 3 h) were more efficacious than short linezolid infusions (600 mg/h for 1 h).

METHODS

We collected cerebrospinal fluid (CSF) and plasma samples from 10 patients who received linezolid infusions after cerebral hemorrhage surgery with EVDs. Linezolid concentrations were measured by high-performance liquid chromatography (HPLC). A Monte Carlo simulation was used to measure the probability of target attainments (PTA) and the PK/PD indexes at four minimum inhibitory concentrations (MIC).

RESULTS

When the same dose (600 mg) was given as an extended infusion (3 h), linezolid reached its maximum concentrations in the plasma and CSF at 3.00 h and 4.40 h, respectively. The mean penetration of linezolid in CSF was 41.31%. Using the parameter of AUC_{0-24 h}/MIC ≥ 100, the plasma PTA provided good coverage at > 90% when MIC was ≤ 1 μg/mL, while the values were 0 in CSF. Using the parameter %T (time) > MIC ≥ 85%, the PTA in both the plasma and CSF provided good coverage when MIC ≤ 2 μg/mL. Compared with routine infusions, prolonged infusion times (3 h) showed increased PTA of linezolid.

CONCLUSIONS

Prolonged infusion times increased the concentration of linezolid in the plasma, leading to improved therapeutic outcomes. However, this improvement did not exist in CSF. Lastly, the PK/PD indicator AUC/MIC ≥ 100 may be used to achieve improved outcomes in patients with critical infections.

Application of separation methods for in vitro prediction of blood-brain barrier permeability-The state of the art

Despite many efforts, drug discovery pipeline is still a highly inefficient process. Nowadays, when combinatorial chemistry enables to synthesize hundreds of new drugs candidates, methods for rapid assessment of biopharmaceutical parameters of new compounds are highly desired. Over one-third of drugs candidates is rejected because of unsatisfactory pharmacokinetic properties. In the drug discovery process, the blood-brain barrier (BBB) permeability plays a critical role for central nervous system active drugs candidates as well as non-central nervous system active drugs. For this reason, knowledge on the BBB permeability of compounds is essential in the development of new medicines. The review was focused on the application of different separation methods for BBB permeability assessment. Both chromatographic and electrophoretic methods were described. In the article, the advantages and limitations of well-established chromatographic methods like immobilized artificial membrane chromatography or micellar liquid chromatography, and less common techniques were discussed. Special attention was devoted to methods were microemulsion is used as mobile or pseudostationary phases.