The lack of insight into the types of HPLC columns available in the market also influenced their decision to select the right column in their analysis to a large extent. This is particularly disadvantageous for those who have sufficient access to select the HPLC column they need for the best result. Other than that, HPLC column types are often very limited discussed in the class. Every so often they tend to modify their method to fit whatever HPLC column available in their laboratory instead of looking for the column type best suited to their experiments. Some chemical analysts, especially those working in the food sector, often find it difficult to choose the HPLC columns for their research. The method was fit for the quantification of losartan in plasma samples from patients under antihypertensive therapy, being useful in therapeutic drug monitoring, pharmacokinetics and bioequivalence studies. Recoveries higher than 80% were obtained. The developed method was validated according to Brazilian Health Regulatory Agency (ANVISA), United States Food and Drug Administration (US FDA) and European Medicines Agency (EMA) guidelines and presented selectivity, precision, accuracy, and linearity in the concentration ranges of 50-1200 ng/mL for losartan and 20-1700 ng/mL for valsartan. The injection volume was 10 μL and fluorescence detection was performed at excitation and emission wavelengths of 250 and 375 nm, respectively. The separation was performed on a biphenyl core-shell (100 ×4.6 mm 2.6 μm) column, using 0.1% (v/v) triethylamine solution and methanol (pH 3.2) as mobile phase, at 0.7 mL/min, in gradient elution. Extraction conditions were optimized by means of a 2³ factorial design with center points. The functionalized nanotubes were packed in solid phase extraction cartridges. The nanotubes were synthesized using the chemical vapor deposition technique, purified by acid treatment, functionalized with octadecylamine in a microwave reactor, and characterized by different techniques. In this study, boron nitride nanotubes functionalized with octadecyl groups were used for the first time as sorbent for extraction of losartan and valsartan, the most used angiotensin receptor blockers in the clinical practice, from human plasma. The limitations of silica-based sorbents boosted the development of new extraction phases. nucifera stamen ethanolic extract as a tyrosinase and collagenase inhibitor in cosmetic applications, as well as the utility of the current separation method. These current findings are the first report to suggest the possibility to employ N. The evaluation of potential skin anti-aging action showed that the stamen extract has higher potential to inhibit tyrosinase and collagenase compared with its whole flower. Stamen ethanolic extract showed the highest protective effect against reactive oxygen/nitrogen species formation, as confirmed by cellular antioxidant assay using a yeast model. The results indicated that stamen ethanolic extract has higher concentration of in vitro and in cellulo antioxidant flavonoids than other floral components. The optimal separation of the main flavonoids from the stamen ethanolic extract was effectively achieved using a core-shell column. Thus, this present study focuses on the following: (1) the application of high-performance liquid chromatography with photodiode array detection for a validated separation and quantification of flavonoids from stamen (2) the Nelumbo nucifera stamen’s in vitro and in cellulo antioxidant activities as well as (3) its potential regarding the inhibition of skin aging enzymes for cosmetic applications. However, to date, only few studies were conducted on its stamen, which is the most important ingredient for herbal medicines, teas and other phytopharmaceutical products. Many studies reported on the phytochemicals and biological activities of its leaves and seeds. Nelumbo nucifera Gaertn., or the so-called sacred lotus, is a useful aquatic plant in the Nelumbonaceae family that has long been used to prepare teas, traditional medicines as well as foods.
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