STUDIA CHEMIA - Issue no.3 / 2022 - Table of contents

The antioxidant activity of coffee brews was determined in batch conditions by means of a Briggs-Rauscher oscillating system. This method consists of the measurement of the inhibition time caused by the addition of a diluted coffee sample to the oscillating system. The inhibition time vs. the relative concentration of the diluted coffee sample shows linear dependence. The slope of these lines was used to calculate a relative antioxidant activity for each sample. It was concluded that the method of preparation greatly influenced the resulting coffee brew, with the filtering method showing the best results with up to 50% higher antioxidant activity. As such, it was chosen as a standard to compare activity values. It can also be noted that decaffeinated coffee samples show significantly lower activity than caffeine-containing ones.

Keywords: Briggs-Rauscher oscillating reaction, inhibitory effect, analytical method, coffee extract, antioxidant activity

Medicinal plants are a valuable source of lead compounds and novel drugs. The Hypericum L. species traditionally treats skin wounds, sciatica, and depression. Presently, only a small percentage of the Hypericum species have been phytochemically characterised and 60% still requires analysis. Ethanolic and methanolic extracts were obtained by ultrasound assisted extraction and maceration extraction methods. Polyphenols, sterols, methoxyflavones, hyperforin and hypericin were detected through HPLC-MS analysis. ABTS assay was used to evaluate the total antioxidant capacity. H. maculatum and H. moserianum had the highest antioxidant capacity. The most abundant polyphenol in H. humifusum, H. moserianum and H. miraclepistache was chlorogenic acid. For H. maculatum and H. perforatum, hyperoside and rutoside were the most abundant polyphenols. Sterols and methoxyflavones were quantified for the first time in all the species. β-sitosterol was the most abundant sterol across all species and ergosterol was absent in all species. Hispidulin was the only methoxyflavone (in small concentrations) found in all species except H. miracle-pistache. Hypericin was absent in H. moserianum and H. miracle-pistache and was most abundant in H. maculatum. Interestingly, H. miracle-pistache had higher concentrations of hyperforin than H. perforatum. The phytochemical profile of analysed Hypericum species prove to be a valuable bioactive’s source.

Keywords: Phytochemical analysis, antioxidant activity, Hypericum species, hyperforin, hypericin

The numerous applications of metallic nanoparticles in different fields such as materials science, medicine, biology, led to the rapid development of various synthesis methods of these nanomaterials, among which the biogenic approach in obtaining nanoparticles has been proved to be an efficient alternative compared to other methods. The present study aims to investigate the potential of goji berries extract as source of bioactive compounds able to reduce the silver ions and to stabilize the resulting nanoparticles. Reaction parameters such as pH and AgNO3 concentration were analyzed and optimized in order to obtain spherical, well dispersed and high yield silver nanoparticles. Five different pH values (6; 7; 8; 9; 10) and five ratios fruit extract: silver nitrate solution (1:1; 1:3; 1:7; 1:10; 1:15) were investigated and it was found that the silver nanoparticles obtained at pH=9 and 1:10 ratio demonstrated the highest monodispersity and were obtained in the highest yield. The obtained nanoparticles were characterized in terms of their size and shape using transmission electron microscopy (TEM) and UV-vis spectroscopy.

Keywords: silver nanoparticles, goji berries

This paper presents a report about the extraction of resveratrol with ethanol (EtOH) from red grape pomace (RGP) Vitis vinifera L. (Cluj, Transylvania region, Romania) and obtaining a dietary supplement with zinc on grape pomace support. The concentration of resveratrol (Rv) from the extract was spectrophotometrically determined at 305 nm wavelength, and was found to be 145 mg Rv/L. The material resulting after the extraction of resveratrol was processed to obtain a zinc dietary supplement support. The thermodynamic parameters, including Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of Zn2+ biosorption were calculated and the results indicate that the process is endothermic and spontaneous. The Zn2+ biosorption kinetics was analysed using pseudo-first- and pseudo-second-order models. The results indicate that biosorption of Zn2+ aqueous solution onto grape pomace support is best described by the pseudo-second-order model.

Keywords: zinc, resveratrol, red grape pomace, food supplement, biosorption, kinetics.

Curcumin (CCM) has beneficial effects on human health due to its pharmacological activities, which have a protective role against many diseases. Whey protein concentrate (WPC) is a product from the milk industry that is often used to improve and stabilize different foods. It helps curcumin improve its water solubility, poor bioavailability, low stability, and efficacy. Atomic force microscopy (AFM) was employed to highlight the surface topography of adsorbed films of pure curcumin, pure whey protein concentrate, and their CCM-WPC complex. The obtained results show that individual nanoparticles, NPs, were mobilized into the aqueous dispersion and successfully adsorbed onto the glass slides as thin films. Their NPs shape is rounded, and their diameter differs on each sample, namely about 30 nm for CCM, around 55 nm for WPC, and about 40 nm for the CCM-WPC complex. It proves that both CCM and WPC molecules generate a complex that embeds them in a compact structure. The surface roughness was also monitored, and pure CCM produces the smoothest and uniform film, meanwhile, the presence of WPC makes several pores in the film surface which increases the roughness value. The obtained results provide useful evidence for the application of whey protein as an effective carrier of curcumin, a bioactive polyphenol compound. In addition, this work supports the application of the CCM-WPC complex as health supplements.

Keywords: Curcumin, whey protein concentrate, curcumin-whey protein complex, AFM, nanostructure, roughness

The stability and solubility of curcumin, CCM, can be enhanced by complexation with whey protein concentrate (WPC). The CCM-WPC of 1:1 and 1:0.5 molar ratio complexes were encapsulated by two methods, namely spray drying (SD) and freeze drying (FD). The major objective of this work is to determine the stability and solubility of the CCM-WPC complexes encapsulated by SD and FD method. The X-ray diffraction and thermogravimetric analysis were performed on raw CCM and WPC, and on their complexes. The changes in thermal degradation and in crystallinity suggest the formation of these CCM-WPC complexes. Scanning electron microscopy images showed that the used methods influenced the morphology and the properties of the formed complexes. The stability and solubility of curcumin are enhanced by complexation in both encapsulation methods. However, comparing the used molar ratio and drying methods, the results are various. The solubility of samples obtained by FD method was higher than in the case of the SD method, which can explain the difference of their morphology (FD samples are more amorphous than SD samples). The antioxidant property of curcumin and its protein-complexes compared to vitamin C showed that CCM and its complexes have a lower IC50 value than vitamin C, i.e., the antioxidant effect of CCM is higher. The addition of WPC improved the antioxidant activity of CCM, probably due to its encapsulation in the protein. Our results suggest that the 1CCM-1WPC_SD complex is the best antioxidant from these studied CCM-WPC complexes.

Keywords: curcumin, whey protein concentrate, spray drying, freeze drying, solubility, half-life time, antioxidant property

This study aimed to develop and validate an HPLC method in order to assay the indomethacin from therapeutic transdermal systems (TTS). A TTS with indomethacin and HPMC15k as a film-forming agent was developed. The performance of the method was verified in terms of specificity, linearity, detection limit, quantification limit, and precision. The results proved the developed method specificity no interference being observed in a placebo sample at the retention time corresponding to indomethacin. To evaluate the linearity, concentrations in the range of 1-100 μg/mL were used, proving the existence of a linear relationship between the selected points. The detection limit was 0.93 μg/mL and the quantification limit was 2.80 μg/mL. Indomethacin concentration in the analysed samples indicated a concentration of 95.15±4.15% respecting the official data. The statistical parameter used to evaluate the precision was the relative standard deviation, being used in the case of the evaluated concentrations smaller than 2%. In conclusion, the developed method is specific, reproducible and precise. An advantage of the developed method consists of the short analysis time of 3.53 min, whilst the presence of a single characteristic signal in the TTS samples chromatograms certifies that the indomethacin was quantified successfully from the TTS.

Keywords: HPLC, TTS, indomethacin

The present research was undertaken in order to investigate if some compounds used as natural sweeteners (steviol and sucrose) can be used as EPR dosimeters. The samples were exposed to low doses of gamma ionizing radiation used in the practices of radiodiagnostic medicine and interventional radiology. The EPR spectra of the gamma irradiated compounds reveal large signals, with multiple lines, which are characteristic for the free radicals in the solid state. From the analysis of the dependence of EPR signal of the absorbed dose, it was observed that by γ-irradiation the amount of generated radicals shows a linear dependence, which mean that there exist a possibility to use these two compounds as EPR dosimeters.

Keywords: EPR dosimeters, γ radiation, free radicals, steviol, sucrose

The process parameters were studied during the fabrication of polyvinyl-alcohol (PVA) nanofibers via electrospinning. The factorial experiment design model described electrospinning as an efficient, versatile approach for fabricating nanofibers. The mathematical model was developed by considering the effect of voltage, concentration, the distance between the pin and the collector, and flow rate, respectively. The influence of these parameters on the diameter and morphology of obtained PVA fibers was investigated by transmission electron microscopy (TEM). It was found that the concentration had the most significant influence on the polymer fiber diameter.

Keywords: electrospinning, process parameter, polyvinyl alcohol, response surface method, average fiber diameter