Development and validation of a liquid chromatographic method with diode array detection for the determination of anthraquinones, flavonoids and other natural dyes in aged silk

Validation of an HPLC-DAD Method for Quercetin Quantification in Nanoparticles

The evaluation of the efficacy of incorporation of quercetin in nanoparticles is crucial, both for the development and quality control of pharmaceutical formulations. The validation of analytical methods for the precise quantification of quercetin is useful for the evaluation of various potential quercetin delivery systems and quercetin pharmacokinetics. This work aimed to validate a high-performance liquid chromatography with diode array detection (HPLC-DAD) method for quercetin detection and quantification in nanoparticles. Different mobile phase conditions and detection wavelengths (254 and 368 nm) were tested, and the major validation parameters were assessed (precision, accuracy, linearity, sensitivity, stability, and selectivity). The best peak resolution was obtained when quercetin was analyzed at 368 nm with a mobile phase of 1.5% acetic acid and a water/acetonitrile/methanol ratio of 55:40:5. Under these conditions, quercetin also eluted rapidly (retention time of 3.6 min). The method proved to be linear (R2 > 0.995), specific, and repeatable (variation coefficient between 2.4% and 6.7%) and presented intermediate precision (variation coefficient between 7.2% and 9.4%). The accuracy of the analysis ranged between 88.6% and 110.7%, and detection and quantification limits were 0.046 and 0.14 µg/mL, respectively. Quercetin solutions were more stable when stored at 4 °C than at room temperature or -20 °C. This validated method satisfied more parameters of bias assessment than most recent methods for quercetin determination and presented itself as more sensitive and efficient than general spectrophotometric methods. The method was successfully used for the analysis of quercetin incorporation in nanoparticles and will be evaluated in the future for its adequacy for the determination of quercetin in more complex matrices.

Fluorescence enhancement of flavonoids and its application in ingredient determination for some traditional Chinese medicines by CE-LIF

Flavonoids are widely used in the treatment of various diseases due to their antioxidant, anti-inflammatory, anticancer and antiviral properties. Fluorescence detection is rarely applied for the determination of flavonoids because of their weak fluorescence. In this work, a method of fluorescence enhancement of flavonoids was firstly introduced by using sodium acetate for flavonoid derivatization. The study discovered that flavonoids, with a hydroxyl at the C3 position, had the ability to emit strong fluorescence after derivatization. Five flavonoids, kaempferide, galangin, isorhamnetin, kaempferol and quercetin, having a special structure, were selected, derivatized and analyzed by capillary electrophoresis with laser-induced fluorescence detection. Under the optimal conditions, the five flavonoids could be completely separated within 3 minutes. Good linear relationships were obtained for all analytes and the limits of detection for the five flavonoids were in the range of 1.18-4.67 × 10^-7 mol L^-1. Finally, the method was applied to the determination of flavonoids in five traditional Chinese medicines: aster, chamomile, galangal, tangerine peel and cacumen biotae. Flavonoids were successfully found in all these medicines by the developed method. The recoveries were in the range of 84.2-111%. The method developed in this study was fast, sensitive and reliable for the determination of flavonoids.

Non-destructive distinction of single seed for Medicago sativa and Melilotus officinalis by capillary electrophoresis with laser-induced fluorescence detection

Flavonoids are a class of natural polyphenolic compounds with great health benefits, and the development of methods for their analysis is of continuing interest. In this work, apigenin, kaempferol and formononetin were selected as the typical representatives of flavone, flavonol and isoflavone, three subclasses of flavonoids. Fluorescence studies revealed that tetraborate complexation could significantly sensitize the weak intrinsic fluorescence of flavonoids in solution, with a maximum of 137-fold for kaempferol. Subsequently, an integrated strategy of derivatization and separation was proposed for the universal analysis of flavonoids by capillary electrophoresis (CE) with 405 nm laser-induced fluorescence (LIF) detection. Using a running buffer consisting of 20 mM sodium tetraborate, 10 mM SDS and 10% methanol (pH 8.5), the dynamic derivatization was realized in the capillary, and the baseline separation was achieved within 10 min, with the detection limits of 0.92-35.46 nM (S/N=3) for the total of 9 flavonoids. The developed CE-LIF method was employed to the quantitative analysis of some flavonoids in Medicago sativa (alfalfa) plants and granulated alfalfa with the recoveries of 80.55-94.25%. Combined with the principal component analysis, the developed method was successfully applied to the non-destructive distinction of single seed for alfalfa and Melilotus officinalis (sweet clover), two forage grass seeds with very similar apparent morphology. Furthermore, this method was used to continuously monitor the substance metabolism during the soaking process at the level of single seed.

Anthraquinone Removal from Cassia obtusifolia Seed Water Extract Using Baking, Stir-Frying, and Adsorption Treatments: Effects on the Chemical Composition, Physicochemical Properties of Polysaccharides, and Antioxidant Activities of the Water Extract

Safety issues of the controversial anthraquinones from Cassia obtusifolia seed water extracts (CWEs) limit its application. This work aimed to remove the anthraquinones of CWEs by baking treatment (BT), stir-frying treatment (ST), and adsorption treatment (AT). Effects of these treatments on the chemical composition, physicochemical properties of polysaccharides, and antioxidant activities of CWEs were analyzed and compared. Results indicated that AT exhibited the best removal effect on the total anthraquinone among the three treatments. After AT, the contents of rhein, emodin, aloe-emodin, and aurantio-obtusin of the CWE were below the limit of detection. In addition, AT increased the contents of neutral sugars in CWEs in comparison to BT and ST. None of the treatments had an obvious influence on the structural characteristics of polysaccharides. However, AT decreased the antioxidant activity of CWEs due to their lower anthraquinone content. In summary, AT was considered as an efficient and simple method to remove anthraquinones, while retaining the features of polysaccharides.

Progress and prediction of multicomponent quantification in complex systems with practical LC-UV methods

Complex systems exist widely, including medicines from natural products, functional foods, and biological samples. The biological activity of complex systems is often the result of the synergistic effect of multiple components. In the quality evaluation of complex samples, multicomponent quantitative analysis (MCQA) is usually needed. To overcome the difficulty in obtaining standard products, scholars have proposed achieving MCQA through the "single standard to determine multiple components (SSDMC)" approach. This method has been used in the determination of multicomponent content in natural source drugs and the analysis of impurities in chemical drugs and has been included in the Chinese Pharmacopoeia. Depending on a convenient (ultra) high-performance liquid chromatography method, how can the repeatability and robustness of the MCQA method be improved? How can the chromatography conditions be optimized to improve the number of quantitative components? How can computer software technology be introduced to improve the efficiency of multicomponent analysis (MCA)? These are the key problems that remain to be solved in practical MCQA. First, this review article summarizes the calculation methods of relative correction factors in the SSDMC approach in the past five years, as well as the method robustness and accuracy evaluation. Second, it also summarizes methods to improve peak capacity and quantitative accuracy in MCA, including column selection and two-dimensional chromatographic analysis technology. Finally, computer software technologies for predicting chromatographic conditions and analytical parameters are introduced, which provides an idea for intelligent method development in MCA. This paper aims to provide methodological ideas for the improvement of complex system analysis, especially MCQA.

Development of the Microemulsion Electrokinetic Capillary Chromatography Method for the Analysis of Disperse Dyes Extracted from Polyester Fibers

The study aimed to develop a method for the separation of dispersed dyes extracted from polyester fibers. Nine commercially available disperse dyes, which were used to dye three polyester fabrics, were tested. Extraction of dyes from 1 cm long threads was carried out in chlorobenzene at 100 °C for 6 h. The separation was performed using microemulsion electrokinetic capillary chromatography (MEEKC) with photodiode array detection. Microemulsion based on a borate buffer with an organic phase of n-octane and butanol and a mixture of surfactants, sodium dodecyl sulphate and sodium cholate, were used. The addition of isopropanol and cyclodextrins to microemulsion resulted in a notable improvement in resolution and selectivity. The content of additives was optimized by using the Doehlert experimental design. Values of the coefficient of variance obtained in the validation process, illustrating the repeatability and intermediate precision of the migration times fit in the range of 0.11–1.24% and 0.58–3.21%, respectively. The developed method was also successfully applied to the differentiation of 28 real samples—polyester threads collected from clothing. The obtained results confirmed that proposed method may be used in the discriminant analysis of polyesters dying by disperse dyes and is promisingly employable in forensic practice.

Application of Capillary Electromigration Methods in the Analysis of Textile Dyes-Review

Fiber traces are one of (micro)traces that can be found at a crime scene. They are easily transferable and, like other forms of evidence, can provide a link between a suspect and a victim. The main purpose of this review is to present methods developed to examine textile dyes extracted for forensic purposes using different capillary electromigration methods (CEMs). Scientific papers, mainly from the 20th century, provide reliable methods for the separation of water-soluble dyes. However, dyes insoluble in aqueous solutions have been and still are a challenge. Another problem is the sensitivity of the developed methods, which is, in most cases, insufficient for forensic examination of dyes extracted from a single fiber preserved at the crime scene. Although the methodologies already developed and presented in this review have the potential to be applied in a comparative analysis of textile dye traces, there seems to be a lot of work to be conducted. Some ideas on how to resolve these problems are presented and discussed in the article.

Textile Dyes from Gokstad Viking Ship’s Grave

The grave from Gokstad in Norway, dating to ca 900 AD, is one of the best-preserved Viking Age ship graves in the world. The grave mound contained a variety of goods along with human remains, buried in a Viking ship. Several textiles, including embroideries and shreds of what might have been the ship’s tent, were also found. The colors of the textile fragments are now severely faded, but the high quality of the embroidery made of gold and silk threads is still apparent. The style of the embroidery is exceptional, having no equivalents in other Scandinavian graves. The analyses by HPLC coupled with both diode array and mass spectrometric detectors revealed that the striped “tent” cloth as well as the silk thread used for the embroidery were originally dyed with anthraquinones of plant origin (alizarin, purpurin, pseudopurpurin, and anthragallol), markers of madder-type dyestuffs.