Adrenergic Beta-2 Receptor (ADRB2) is a member of Gprotein coupled receptors family, which has served as targets for more than 30% of top-selling drugs in the market. Recently, an enhanced dataset of ligands and decoys for ADRB2 has publicly available. However, the original retrospective structure-based virtual screening campaign accompanying the dataset showed relatively poor quality with enrichment factor of true positives at 1% false positives (EF 1% ) value of 3.9. In this article, the construction and retrospective validation of a structure-based virtual screening protocol by employing PLANTS1.2 as the molecular docking software and PyPLIF as an alternative post docking scoring functions are presented. The results show that the developed protocols have better quality compared the original structure-based virtual screening with EF 1% values of 24.24 and 8.22 by using ChemPLP from PLANTS1.2 and by using Tc-PLIF from PyPLIF, respectively. Further investigation by performing systematic filtering resulted in the identification of D113, S203, and N293 as molecular determinants in ADRB2-ligand binding.

In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+ and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of aqueous oxytocin solutions was determined by RP-HPLC and HP-SEC after 4 weeks of storage at either 4°C or 55°C. Addition of sodium or potassium ions to acetate- or citrate-buffered solutions did not increase stability, nor did the addition of divalent metal ions to acetate buffer. However, the stability of aqueous oxytocin in aqueous formulations was improved in the presence of 5 and 10 mM citrate buffer in combination with at least 2 mM CaCl2, MgCl2, or ZnCl2 and depended on the divalent metal ion concentration. Isothermal titration calorimetric measurements were predictive for the stabilization effects observed during the stability study. Formulations in citrate buffer that had an improved stability displayed a strong interaction between oxytocin and Ca2+, Mg2+, or Zn2+, while formulations in acetate buffer did not. In conclusion, our study shows that divalent metal ions in combination with citrate buffer strongly improved the stability of oxytocin in aqueous solutions.

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Poor bioavailability has been reported as a major challenge in the development of curcumin as a pharmaceutical agent. However, co-administration of curcumin with piperine has been shown to improve curcumin bioavailability. Therefore, to assure product control quality, an analytical method needs to be developed for the determination of curcumin and piperine content in a dosage form formulation. The objective of this study was to develop a simple isocratic reversed-phase HPLC (RP-HPLC) method to simultaneously quantify curcumin and piperine content in solid dispersion based microparticle formulation containing Curcuma longa and Piper nigrum extracts. The method was validated according to the International Council for Harmonization (ICH) guideline. Chromatographic separation of three curcuminoids and piperine could be achieved using acetonitrile-methanol-water of 65:5:35 %, at a flow rate of 1 mL/min and a wavelength of 353 nm for detection. Resolution (Rs) of 3.57 and 1.68 for piperine and curcumin, respectively, a theoretical plate number (N) > 8000 and a tailing factor (T) < 1.5 indicate a satisfactory separation of the compounds. The calibration curve was linear from 1.25-15 μg/mL and 2.5–30 μg/mL for piperine and curcumin, respectively, with the correlation coefficient of >0.999. The intra-day/inter-day accuracy and precision demonstrated a recovery of 99.54–101.50%/99.38–99.89% and 100.78–102.51%/101.15–102.47% with a Relative Standard Deviation (RSD) of 0.53–0.95%/0.13–1.44 % and 0.28–1.62%/0.46–1.14% for piperine/curcumin. The limit of detection (LOD) were 0.27 and 0.42 μg/mL, for piperine and curcumin, which reveals an adequate sensitivity. A solid dispersion based microparticle formulation containing C. longa and P. nigrum extracts confirmed the validity of the developed method as a recovery of 91.14% and 99.14% for piperine and curcumin, respectively. In conclusion, all the tested parameters confirm the precision, accuracy, and reliability of the method for the simultaneous analysis of curcumin and piperine within a microparticle formulation containing C. longa and P. nigrum extracts.

Objective: Curcumin and piperine exibit poor aqueous solubility and dissolution. Solid dispersion technology is a promising way to improve dissolution of lipophilic compounds. Therefore, to investigate the dissolution behavior, an accurate determination of curcumin and piperine concentrations in a sample containing 0.5 wt-% SLS in sodium phosphate buffer as the dissolution medium was required. The goal of research was to investigate whether UV-Vis spectroscopy can be used to accurately determine curcumin and piperine concentrations in aqueous solutions. Method: Stock solutions (1 mg/mL) of curcumin and piperine were prepared in methanol. A series of solutions for calibration were prepared by mixing the stock solutions in various ratios after which they were diluted with dissolution medium (0.5%-wt sodium lauryl sulfate in 20 mM phosphate buffer; pH 6.0). Solutions of curcumin (2μg/mL) and piperine (1 μg/mL were subjected to overlay scan in a UV-VIS spectrophotometer in each λ max of 430 and 335.5 nm for curcumin and piperine, respectively. The method was validated according ICH requirements, such as specificity, linearity, accuracy, precision, limit of detection and limit of quantification. Results: At a concentration range of 0.1 to 5μg/mL, calibration curves of curcumin and piperine showed linearity with R 2 = 0.9980 and 0.9982, respectively. Precision and accuracy was confirmed by AOAC. Furthermore, LOD of both compounds was 0.23 μg/mL and LOQ of curcumin and piperine was 0.72 and 0.69 μg/mL, respectively. Conclusion: UV-Vis spectroscopy can be used to accurately determine curcumin and piperine concentrations in dissolution samples obtained during screening the dissolution behavior of solid dispersions containing these compounds.