Jelena Cvejić

Phenolic Compounds in Field Horsetail (Equisetum arvense L.) as Natural Antioxidants

In this paper, the study of antioxidant activity and phenolic composition of three different extracts (EtOAc, n-BuOH and H2O) of field horsetail (Equisetum arvense L.) is presented. The antioxidant activity has been evaluated measuring the total reducing power (expressed by Ascorbate Equivalent Antioxidant Capacity - AEAC), inhibition of lipid peroxidation, and free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazyl (DPPH radical) and nitric oxide (NO), respectively. In addition, the total flavonoid content (TFC) and phenolic constituents of each extract have been determined. The results obtained show that the highest RSC regarding both DPPH and NO radicals is expressed by EtOAc extract (EC50=2.37 μg/mL and EC50=90.07 μg/mL, respectively), and the lowest by H2O extract (EC50=37.2 μg/mL and EC50>333.33 μg/mL, respectively). n-BuOH extract showed the highest total reducing power (AEAC=13.40 μg/mL). Differences in the phenolic composition of examined extracts are found comparing the HPLC chemical profiles. Although, isoquercitrin is the main flavonoid in both EtOAc and n-BuOH extracts, a considerable amount of di-E-caffeoyl-meso-tartaric acid was presented in the n-BuOH extract. In H2O extract high content of phenolic acids and low percentage of flavonoids were detected.

Polyphenol Content and Antioxidant Properties of Colored Soybean Seeds from Central Europe

The antioxidant activity and contents of various polyphenol classes in the seeds of seven soybean varieties of different seed color and one yellow seed cultivar, representing a reference genotype, were evaluated. Total polyphenols and tannins were determined after extraction of plant material with 70% aqueous acetone, and total flavonoids were extracted with methanol and acetic acid, whereas anthocyanins were extracted with 20% aqueous ethanol. In addition, isoflavone content and composition were determined using high-performance liquid chromatography analysis. Antioxidant activity of seed extracts was evaluated by the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity assay. A positive linear correlation between antioxidant activity and contents of total polyphenols and anthocyanins was established. The highest antioxidant activity was observed in the extracts of black and brown varieties, which also showed high levels of all polyphenol classes examined. Yellow seed had the highest total isoflavone content (3.62 mg/g of dry material). The highest concentration of total daidzein was determined in black seeds (>2.0 mg/g of dry material), and the highest total glycitein and genistein contents occurred in the yellow cultivar (0.53 and 1.49 mg/g of dry material, respectively). According to our results, varieties of black and brown seeds could be of special interest not only for their large content of total polyphenols, ranging from 4.94 to 6.22 mg of gallic acid equivalents/g of dry material, but also for their high content of natural antioxidants such as anthocyanins.

Isoflavone composition, total polyphenolic content, and antioxidant activity in soybeans of different origin.

Twenty soybean cultivars, originating from the United States, Russia, Serbia, and China, were analyzed for their isoflavone composition, total polyphenolic content, and antioxidant activity. Isoflavones were extracted by aqueous methanol (80%) and analyzed by high-performance liquid chromatography/diode array detection. Precision and linearity of the applied method were within the standard limits of validation. The highest and the lowest total isoflavone contents were 4.59 and 1.45 mg/g of dried soybean weight, respectively. A significant difference (P < .05) was found in isoflavone concentration among the different cultivars, but it was observed that origin is not a significant factor that could influence isoflavone content in soybeans. Total polyphenolic content varied between 2.13 and 3.45 mg of gallic acid equivalents/g of dried soybean weight. The free radical scavenging activity of soybean extracts assayed by 2,2-diphenyl-1-picrylhydrazyl in terms of 50% inhibitory concentration (IC(50)) ranged from 1.40 to 3.35 mg/mL. Negative correlation between total polyphenolic content and IC(50) was observed, but there was no correlation between total isoflavone content and IC(50). On the basis of this study, soybean cultivars with larger potency for biological activity could be recognized.

Lamotrigine and valproate pharmacokinetics interactions in epileptic patients

SummaryLamotrigine (LTG, 3,5-diamino-6- (2,3-dichlorphenyl)-l,2,4-triazine) is an antiepileptic drug used mainly for partial and generalized seizures. The efficacy of LTG in treating resistant partial seizures was optimized when it was combined with valproate (VPA). The aim of this study was to investigate the influence of VPA on LTG pharmacokinetics in epileptic patients. Methods: 38 patients were randomly divided into two groups, one given LTG (n=18) and the other given LTG+VPA(n=20). The first group consisted of 10 females (32.50 ± 12.46 years old, 67.80 ± 15.18 kg) and 8 males (24.88 ± 8.92 years old, 69.88 ± 11.41 kg) and the second group consisted of 9 females (28.33 ± 6.52 years old, 62.89 ± 13.28 kg) and 11 males (37.64 ± 10.43 years old, 85.64±15.4 kg). Patients were either administered an oral dose of LTG (157 ± 74 mg/day) or LTG+VPA (150 ± 83.11 mg/day & 774 ± 330 mg/day respectively). LTG steady state serum concentrations were determined 1.5–8 h post dose. Analyses were performed by a validated HPLC method. Results: LTG serum concentrations were increased significantly from 4.67 ± 3.66 and 9.56 ± 5.27 μg/ml by concomitant administration of VPA. Discussion: The inhibition of LTG metabolism by VPA was shown to have a marked effect on LTG kinetics. This inhibitory effect was complicated further by inter-patients variation in body weight and gender. This emphasizes the importance of continuous monitoring of LTG serum concentrations on an individual basis. Accordingly, if the use of potentially interacting drugs cannot be avoided, adverse reactions can be minimized by dose adjustments guided by careful monitoring of clinical response and measurement of LTG serum concentrations.

Effect of potassium channel opener pinacidil on the contractions elicited electrically or by noradrenaline in the human radial artery.

In order to discover an agent that can prevent spasm of the human radial artery, the aim of our study was to evaluate the effect of the K(+) channel opener, pinacidil, on contractions in the radial artery. Contractions of the radial artery were evoked by exogenously applied noradrenaline or by electrical field stimulation (EFS, 20Hz, neurogenic). Pinacidil induced concentration-dependent inhibition of both EFS- and noradrenaline-evoked contractions of the radial artery. Glibenclamide, a selective blocker of ATP-sensitive K(+) channels (Kir6.x containing subunit) antagonized in the same manner the pinacidil-induced inhibition of neurogenic contractions and contractions evoked by exogenous noradrenaline. The inhibition of pinacidil relaxation by tetraethylammonium (TEA), a blocker of Ca-sensitive K(+) (K(Ca)) channels, was more pronounced in EFS-contracted preparations. A blocker of voltage-sensitive K(+) (K(V)) channels, 4-aminopyridine (4-AP), inhibited pinacidil relaxation only in EFS-contracted preparations. In order to test the presence of different K(+) channels, immunohistochemistry of K(+) channels expression in the radial artery was performed. The vascular wall of the human radial artery showed variable positivity with the following applied antibodies: Kv1.2, Kv1.3, Kir6.1, and K(Ca)1.1. The antibodies against Kv1.6, Kv2.1, and Kir6.2 channel subunits were completely negative. These results suggest that the inhibitory effect of pinacidil on contractions of the human radial artery might be postsynaptic and associated with opening of smooth muscle Kir6.1-containing K(ATP) channels. TEA- and 4-AP-sensitive K(+) channels may also contribute to pinacidil effect in the human radial artery.

Heavy metals content in Serbian old plum brandies

Seven elements, namely, arsenic, lead, cadmium, copper, zinc, iron and manganese were determined in 31 samples of Serbian plum brandies by applying atomic spectrometry techniques. Flame atomic absorption spectrometry was used for quantification of copper, iron, zinc, manganese, lead and cadmium; and hydride generation atomic spectrometry absorption for arsenic quantification. Measured concentrations of heavy metals and arsenic was assessed according to the Serbian regulations, official regulations of some other countries and in respect of microelements content in other similar distilled alcoholic beverages. Amounts of microelements in maximal recommended daily and weekly intake of plum brandy were determined. The influence of production (home made and industrial), type of wooden barrel (oak and mulberry), and duration of ageing process on the content of Zn, Cu, Fe and Mn in plum brandies, as well as coefficient of correlation between Cu content and pH value were also studied. [Projekat Ministarstva nauke Republike Srbije, br. 172053]

Varietal phenolic composition of Probus, Rumenika and Frankovka red wines from Fruška Gora (Serbia) and changes in main compounds during maceration

Red wine is a rich source of different phenolic compounds which contribute to sensorial characteristics and can exhibit various biological properties. The amount of phenolics in wine depends on various factors such as grape variety, environmental conditions and production technology. The extraction of individual polyphenolic compounds during maceration was investigated in this paper. Preliminary determination of specific phenolic compositions in wines produced from grape varieties characteristic for Fruška Gora region (Probus, Frankovka and Rumenika) was also performed. A general trend in extraction of some compounds as well as specific characteristics for each variety regarding phenolic composition was observed. Obtained results showed that among wines of different varieties and vintages, statistically significant differences existed in the content of most analysed phenolics. Wines made from Probus variety were characterised by very high anthocyanin content and Frankovka wines by high content of syringic acid while high contents of piceid (resveratrol), catechin and gallic acid were specific for Rumenika variety. Obtained results have shown that Probus variety has especially great winemaking potential considering high content of phenolic compounds (especially anthocyanins), as well as intensive and stable colour.

Chapter 1 – Phytoestrogens: “Estrogene-Like” Phytochemicals

Phytoestrogens, also called “dietary estrogens,” are nonsteroidal phytochemicals structurally similar to female hormone estradiol (17-β-estradiol). According to the chemical structure, this group of compounds consists of the following subgroups: isoflavones, coumestans, lignans, as well as stilbenes and prenylated flavonoids. Isoflavones are the most investigated class of phytoestrogens. Soybeans (Glycine max) and red clover (Trifolium pratense) are the most important plant sources of these bioactive nonnutrients. The major isoflavone aglycones in soybeans are genistein, daidzein, and glycitein, which are also present as corresponding glycosides (β-glycoside, acetyl-β-glycoside, malonyl-β-glycoside). Major isoflavones present in red clover include biochanin A and formononetin, while genistein and daidzein are also present. It has been shown that different factors influence the content of isoflavones in plant sources. Various studies are focused on determination of these factors. The aim is to produce and/or select a raw material for further processing into food ingredients or dietary supplements which, due to their favorable characteristics, may enhance health benefits of these products. As bioactive compounds structurally similar to estrogen, phytoestrogens have the ability to bind to estrogen receptors either activating or blocking them, depending on the type of estrogen receptors. Their estrogenic and/or antiestrogenic effects are also shown to be tissue specific. Beside the estrogenic and antiestrogenic activity, phytoestrogens possess capacity for other biological activities. Numerous potential health benefits of these compounds have been investigated, including effects on cancer, vascular diseases, osteoporosis, and menopausal symptoms. Epidemiologic evidence and collected experimental data from animal studies highly suggest beneficial effects of isoflavones on health, but the clinical data in favor of such effects are still to be obtained. Due to their assumed beneficial effects, use of products and supplements containing isoflavones has significantly increased. These products are widely commercialized in many countries as alternative therapy for alleviating menopausal discomforts and for the prevention of diseases such as osteoporosis or breast cancer. Dietary supplements, containing phytoestrogens, are often a blend of extracts from different plants, and usually contain extracts from soy and red clover. Results obtained from analysis of phytoestrogens content in dietary supplements showed no uniformity in the profile and concentration of these compounds among the products of a particular category. The phytoestrogen levels also vary from batch to batch and product to product, causing more difficulties in interpretation of results. Current results indicate that the beneficial effects of phytoestrogens are strongly supported by synergistic effect with other phytochemicals in plants.

The differential effect of resveratrol on the renal artery of normal and diabetic rats

Results Resveratrol relaxed RA of normal rats more potently than RA of rats with diabetes (EC50 8 and 50 μM, respectively). L-NAME and methylene blue partly antagonized the relaxation of RA of normal animals only. A nonselective blocker of voltage-gated K (KV) channels, 4-aminopyridine (4-AP) partly inhibited the relaxation of RA of normal as well as of diabetic rats. However, margatoxin, a selective antagonist of KV1.x channels, completely antagonized the relaxation of RA of diabetic rats only. Glibenclamide, a highly selective blocker of ATP-sensitive K channels, did not block resveratrolinduced relaxation in both experimental models. Conclusions In conclusion, we have shown that resveratrol induces a strong endothelium-dependent relaxation of RA of normal rats, and that 4-AP-sensitive K channels are involved in this relaxation. In diabetic rats, resveratrol induced NO-independent relaxation and maragtoxinsensitive K channels are involved.

Isoflavone Content and Composition in Soybean

Soybean seed has been used in a diet of East-Asian population for centuries. Western population has raised interest in this item after numerous epidemiological and clinical studies have showed that, due to the large consumption of soybean, there is less incidence of cardio-vascular disease, osteoporosis, and certain types of cancer in Japan and China, in comparison to western countries (Scheiber et al., 2001; Chiechi et al., 2002; Potter et al., 1998; Barnes et al, 1994; Adlercreutz & Mazur 1997; Sarkar & Li, 2003; Lee et al., 2003b; Moriguchi et al., 2004; Ikeda et al., 2006; Wu et al., 2008). Several classes of biologically active compounds are found in soybean, but it is considered that isoflavones are most responsible for its favourable influence on health (Crouse et al., 1999). Isoflavones are natural occurring substances, present in some plants, which are structurally similar to estrogens and can exibit weak estrogen-like effects. For this reason, they are classified as phytoestrogens: plant-derived compounds with activity similar to estrogens. Isoflavones are not widespread in nature and can be found almost exclusively in the plants of the Leguminosae family (Anderson & Wolf, 1995; Philips et al., 2002; Romani et al., 2003). In that sence soybean is one of few isoflavone sources in human nutrition, which explains its wide use through different food products and isoflavone-rich dietary supplements.