Tomas Drevinskas

Evaluation of phytochemical composition of fresh and dried raw material of introduced Chamerion angustifolium L. using chromatographic, spectrophotometric and chemometric techniques

Due to the wide spectrum of biological activities, Chamerion angustifolium L. as medicinal plant is used for the production of food supplements. However, it should be kept in mind that quality (biological activity) of the herb depends on its geographic origin, the way of raw material preparation or extraction and chemotype. The purpose of this study was to evaluate and compare the compositions of volatile, non-volatile compounds and antioxidant activities of C. angustifolium grown in Kaunas Botanical Garden after the introduction from different locations in Lithuania. The compositions of fresh and air-dried samples were compared. The profile of volatile compounds was analyzed using headspace solid phase microextraction coupled with GC/MS. trans-2-Hexenal (16.0-55.9% of all volatiles) and trans-anethole (2.6-46.2%) were determined only in the dried samples, while cis-3-hexenol (17.5-68.6%) only in fresh samples. Caryophyllenes (α- and β-) were found in all analyzed samples, contributing together from 2.4% to 52.3% of all volatiles according to the origin and preparation (fresh or dried) of a sample. Total amount of phenolic compounds, total content of flavonoids and radical scavenging activity (using 2,2-diphenyl-1-picrylhydrazyl (DPPH)) were determined using spectrophotometric assays. The variation of total phenolic compounds content was dependent on the sample origin, moreover, drying reduced amount of phenolics 1.5-3.5 times. The DPPH free radical scavenging activity was in the range of 238.6-557.1mg/g (expressed in rutin equivalents) in the fresh samples and drastically reduced to 119.9-124.8 mg/g after drying. The qualitative analysis of phenolic compounds in the aqueous methanolic extracts of C. angustifolium was performed by means of HPLC with UV detection. Oenothein B and rutin were predominant in the samples; also caffeic and chlorogenic acids, and quercetin were determined. Chemometric methods, namely principal component analysis, hierarchical cluster analysis and K-means clustering analysis, were applied for evaluation of the results. Chemometric analysis showed existence of different chemotypes of C. angustifolium L. and their relation to the geographic origin.

Capacitance‐to‐digital: A single chip detector for capillary electrophoresis

A capacitance‐to‐digital converter integrated circuit was implemented in an automated CE device as a single chip detector. In this paper, design and hardware issues related to the fabrication and application of a miniature detector for contactless measurement of complex impedance are discussed. The capacitance‐to‐digital converter integrated circuit was used as the whole detector. The advantage of this setup is that the single integrated circuit provides digital data and neither additional signal conditioning nor analog‐to‐digital converter is required. Different separation conditions were used to evaluate the detection characteristics of the constructed detection unit. A 1 μM LOD for sodium and a 1.6 μM LOD for potassium ions were revealed for the detector. The detection system designed is competitive with miniaturized contactless conductivity detectors or UV absorbance detectors with respect to overall parameters (sensitivity, resolution, power consumption properties, and size). The obtained separation and detection results show that such detection technique can be used as an extremely low power consuming and space saving solution for CE detection with potential applications in environmental monitoring, process control, and various analytical measurements.

Capacitance‐to‐digital: The upgrades of single chip detector

The capacitance‐to‐digital single chip detector was upgraded. The paper discusses hardware issues and benefits of the designed/upgraded detector. The device can be operated from rechargeable lithium‐ion battery as stand‐alone, portable system and is capable of transmitting real‐time data wirelessly. The detector and additional modules (battery, battery holder, microcontroller board, wireless module) weight is less than 85 g. Electrophoretic separation in low conductivity 20 mM MES/L‐His buffer, pH 6.1, was performed in order to evaluate detection parameters. The system is capable of quantification of potassium ions down to 0.31 μM. Investigation of differential signal acquisition configuration showed improved performance regarding external noise and temperature fluctuations. The system can be a solution for stand‐alone, field‐portable capillary format separation detector.

Effect of molecular weight of chitosan on the shelf life and other quality parameters of three different cultivars of Actinidia kolomikta (kiwifruit)

The kiwi fruit, Actinidia kolomikta, has valuable properties such as high antioxidant activity, high vitamin C, polyphenols, chlorophylls and organic acids content, but the species are hardly commercialized due to their short shelf life (less than two days). In this study three different cultivars of A. kolomikta (Anykšta, Sentiabrskaya and VIR2) were coated with low, medium and high molecular weight chitosan bio-polymer with the aim to extend the shelf life. The changes in fruit firmness, mass, phenolic compound content, vitamin C content and subjective criteria (withering level, decoloration level and aesthetic appearance) were monitored. It was observed that high molecular weight chitosan had higher positive effect on the shelf life of Sentiabrskaya and Anykšta cultivars than VIR2. Low molecular weight chitosan was found effective on VIR2.

Analysis of antiproliferative effect of Chamerion angustifolium water extract and its fractions on several breast cancer cell lines

PURPOSE To evaluate the antiproliferative effect of the aerial part of Chamerion angustifolium (L.) Holub. (Onagraceae) extract and its fractions in vitro. This is the first study on the anti-proliferative effect of C. angustifolium on 3 distinct breast cancer cell lines. MATERIAL/METHODS Breast cancer cell lines MCF7, MDA-MB-468 and MDA-MB-231 were exposed to different concentrations of the water extract of C. angustifolium, where DPPH radical scavenging activity was 0.018-0.443mg/ml, expressed in rutin equivalents. Cell growth was analyzed after 24, 48 and 72h of incubation. Solid-phase extraction was applied for the fractionation of C. angustifolium water extract and MDA-MB-468 cell line growth was tested using different fractions. RESULTS The concentrations corresponding to radical scavenging activity of 0.117 and 0.266mg/ml caused MCF7 cells growth inhibition, while in the samples exposed to the highest concentration (0.355 and 0.443mg/ml) no proliferation was register, suggesting cell death. MDA-MB-468 cell analysis showed similar responses. MDA-MB-231 demonstrated cell growth inhibition following the exposure to all analyzed high extract doses (0.117-0.443mg/ml). MDA-MB-468 cells were selected to evaluate the effect of fractions. In the samples exposed to the fraction containing the highest amount (91%) of oenothein B, at the concentration of 0.117mg/ml a pronounced cell growth inhibition while at higher concentrations (0.266 and 0.443mg/ml) no cell proliferation was observed. CONCLUSIONS The consumption of C. angustifolium herb can be advantageous, alongside with conventional breast cancer treatment.

Compensation of the baseline temperature fluctuations for autonomous CE-C4D instrument working in harsh environments

One of the main problems of the remote complex sample analysis instrumentation is that such systems are susceptible to temperature fluctuations. Temperature regulation is energetically ineffective, and it is not used in most of the field portable analytical systems. Separations performed in a changing temperature environment provide electropherograms with considerable baseline fluctuations, resulting in significant errors in detection and integration of the peaks. This paper describes electropherogram baseline compensation that is suitable for the capillary electrophoresis–contactless conductivity detection analytical method. The baseline compensation utilizes linear or polynomial data processing methods, and can be programmed in‐line using simple microcontroller, or on‐line and off‐line in data acquisition software. This method is targeted for field portable and autonomous analytical systems that are utilized in a fluctuating environment.

Optimization of a capillary zone electrophoresis-contactless conductivity detection method for the determination of nisin

Determination of natural preservatives using electrophoretic or chromatographic techniques in fermented milk products is a complex task due to the following reasons: (i) the concentrations of the analytes can be below the detection limits, (ii) complex matrix and comigrating/coeluting compounds in the sample can interfere with the analytes of the interest, (iii) low recovery of the analytes, and (iv) the necessity of complex sample preparation. The aim of this study was to apply capillary zone electrophoresis coupled with contactless conductivity detection for the separation and determination of nisin in fermented milk products. In this work, separation and determination of natural preservative–nisin in fermented milk products is described. Optimized conditions using capillary zone electrophoresis coupled with capacitance‐to‐digital technology based contactless conductivity detector and data conditioning, which filter the noise of the electropherogram adaptively to the peak migration time, allowed precise, accurate, sensitive (limit of quantification: 0.02 μg/mL), and most importantly requiring very minute sample preparation, determination of nisin. Sample preparation includes following steps: (i) extraction/dilution and (ii) centrifugation. This method was applied for the determination of nisin in real samples, i.e. fermented milk products. The values of different nisin forms were ranging from 0.056 ± 0.003 μg/mL to 9.307 ± 0.437 μg/g.

Confirmation of the antiviral properties of medicinal plants via chemical analysis, machine learning methods and antiviral tests: a methodological approach

Medicinal plants are reported to possess antiviral activity, but finding the substances that are responsible for antiviral activity in the complex mixture of the plant extract is an extremely difficult task. In this paper a methodology related to the determination of the antiviral properties of medicinal plant extracts and based on phytochemical analysis, antiviral tests and machine learning methods is described. 16 potentially antiviral medicinal plants were selected, and their chemometric characteristics and antiviral properties were investigated. Three different analytical methods were used for chemical analysis: (i) spectrophotometry, (ii) capillary electrophoresis with contactless conductivity detection, and (iii) gas chromatography-mass spectrometry. 14 attributes were obtained describing the composition of the plant extracts. Viral growth inhibition properties were investigated and 8 candidate plant extracts were selected as being active against viruses. Infectious bronchitis virus was used as a model virus. Machine learning techniques including deep neural network classification, classification and regression tree induction and hierarchical clusterization were used for mining the factors that are responsible for antiviral effects. It was determined that (i) phenolic compounds providing high radical scavenging activity and fractions containing high content of phenolic compounds are positively related to antiviral activity in plant extracts, (ii) hydrophilic compounds that are positively charged (pKa > 4.7) in acidic media and possess medium and low electrophoretic mobility properties are negatively related to antiviral activity in medicinal plants, (iii) phenolic acids with pKa lower than 4.7 are not related to antiviral activity in the extracts, and (iv) volatile compounds in the extracts, including diversity, quantity and different volatility properties, do not affect the antiviral activity of plant extracts. Following the proposed methodological approach, it is possible to confirm which chemometric attributes are responsible for antiviral activity in medicinal plant extracts.