Colorimetric microdilution assay: Validation of a standard method for determination of MIC, IC50%, and IC90% of antimicrobial compounds.

The emergence of multiresistant bacteria directly impacts on the search for new compounds with antimicrobial activity, and it is important the improvement of new techniques are able to determine the minimum inhibitory concentration (MIC) of antimicrobial compounds. The microdilution technique is widely used for saving culture media, reagents and compounds to be tested. However, the literature does not describe a colorimetric method capable of correlating absorbance with concentration of viable microorganisms (CFU mL-1). Therefore, the novelty of this work was the standardization and validation of a colorimetric and quantitative method capable of determining the MIC of several compounds with antimicrobial activity and the conversion of absorbance values to CFU mL-1. The conditions carried out for the method were: the use of 0.125% (w/v) 2,3,5-triphenyltetrazolium chloride (TTC) solution added after 22 h of incubation at 35 °C, followed by 2 more hours of incubation and subsequent reading in a spectrophotometer. The tested microorganisms were: Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 9027) and Candida albicans (ATCC 10231). The method was validated and showed linearity (R2 > 0.95), precision (RSD <26%), accuracy (75% to 122%) and robustness (p > 0.05). The validated parameters ensured the harmonization of methodology to determine not only MIC as well as inhibitory concentrations of 50% (IC50%) and 90% (IC90%) of the antimicrobial compounds.

A Stability-Indicating HPLC-DAD Method for Determination of Ferulic Acid into Microparticles: Development, Validation, Forced Degradation, and Encapsulation Efficiency.

A simple stability-indicating HPLC-DAD method was validated for the determination of ferulic acid (FA) in polymeric microparticles. Chromatographic conditions consisted of a RP C18 column (250 mm × 4.60 mm, 5 µm, 110 Å) using a mixture of methanol and water pH 3.0 (48 : 52 v/v) as mobile phase at a flow rate of 1.0 mL/min with UV detection at 320 nm. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of quantification, limit of detection, accuracy, precision, and robustness provided suitable results regarding all parameters investigated. The calibration curve was linear in the concentration range of 10.0-70.0 µg/mL with a correlation coefficient >0.999. Precision (intraday and interday) was demonstrated by a relative standard deviation lower than 2.0%. Accuracy was assessed by the recovery test of FA from polymeric microparticles (99.02% to 100.73%). Specificity showed no interference from the components of polymeric microparticles or from the degradation products derived from acidic, basic, and photolytic conditions. In conclusion, the method is suitable to be applied to assay FA as bulk drug and into polymeric microparticles and can be used for studying its stability and degradation kinetics.

Caracterização anatômica das folhas de Cunila microcephala Benth. (Lamiaceae) / Anatomic characterization of Cunila microcephala Benth. (Lamiaceae) leaves

No presente trabalho fez-se a análise da organização estrutural da folhas de Cunila microcephala em microscopia fotônica e microscopia eletrônica de varredura. Seguiram-se as técnicas convencionais no preparo do material para obtenção das lâminas semipermanentes. Para a preparação de lâminas permanentes utilizou-se a técnica de inclusão em glicol metacrilato (GMA). A organização estrutural das folhas desta espécie revela: estômatos em ambas as faces com predominância na face abaxial (folha anti-hipoestomática). Os estômatos da face adaxial são do tipo diacítico. As paredes anticlinais das células epidérmicas da face adaxial são sinuosas e apresentam espessamentos irregulares. As epidermes de ambas as faces são uniestratificadas...