COBISS Code 1.01 Agrovoc descriptors: fagopyrum esculentum, buckwheat, fagopyrum tataricum. pseudocereals, tannins, polyphenols, metabolites, antioxidants, leaves, proximate composition, chemical composition Agris category code: F60 Comparison of tannin concentration in young plants of common and tartary buckwheat Drena GADŽO1, Mirha DJIKIĆ1, Teofil GAVRIĆ1, Petra ŠTREKELJ2* Received: July 15, 2009; accepted: September 25, 2010. Delo je prispelo: 15. julija, 2009; sprejeto: 25. septembra, 2010. ABSTRACT The aim of this study was to compare the tannin concentration of young common and tartary buckwheat plants. Tannins are a group of polyphenols, formed as secondary metabolites in plants. Tannins are known as antioxidants and have chemoprotective potential. They occur in many fruits and drinks, such as tea, beer, wine and juices, making them significant in human nutrition. Concentration of tannins was high in upper leaves of tartary buckwheat and in young plants of common buckwheat cv. Bosanka. There are interesting differences between tannin concentration in Bosanka young plants and tartary and Darja buckwheat young plants. Key words: common buckwheat, tartary buckwheat, tannins, fertilization IZVLEČEK PRIMERJAVA KONCENTRACIJE TANINOV V MLADIH RASTLINAH NAVADNE IN TATARSKE AJDE Namen raziskave je primerjava koncentracije tanina v rastlinah navadne in tatarske ajde. Tanini spadajo v skupino polifenolov in so sekundarni produkti metabolizma rastlin. Tanini so močni antioksidanti in delujejo zavirajoče proti nekaterim vrstam raka. Najdemo jih v sadju, čaju, vinu in sokovih, raziskava taninov je pomembna za prehrano ljudi. Koncentracija taninov je bila visoka v zgornjih listih tatarske ajde in mladih rastlinah Bosanke. Pomembne so razlike med koncentracijami taninov pri mladih rastlinah Bosanke in mladih rastlinah tatarske ajde ter Darje. Ključne besede: navadna ajda, tatarska ajda, tanini, gnojenje 1 INTRODUCTION Tartary buckwheat growing Common buckwheat is grown in many countries around the world, in Asia, Europe and South Africa, in Canada, USA, Brazil and in some other places. A large variety of buckwheat foods are being traditionally produced for centuries. Dishes made from buckwheat seed are generally classified in two groups, flour dishes and groats dishes. Other products made from buckwheat are buckwheat floral honey, green buckwheat tea, buckwheat sprouts, and fresh green plant parts used as a vegetable. Buckwheat herb is especially known as a rich source of tannis and other polyphenols (Kreft et al. 2002; Kreft et al., 2006, Kalinova et al., 2006; Kalinova & Vrchotova, 2009). In Europe buckwheat has been grown for centuries and is now, one of the important alternative crops, suitable for ecological growing, without the use of fertilizers or pesticides. It is used for flour and groats products in central and eastern Europe. For many years, cultivation of buckwheat declined, but recent interest in old, traditional foods and a re-evaluation of typical regional products has led to a resurgence in its cultivation. 1 Faculty of Agriculture and Food Science, University of Sarajevo, Zmaja od Bosne 8, BiH 71000 Sarajevo, Bosnia and Herzegovina 2 Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia * Corresponding author, e-mail: petra.strekelj@gmail.com Common buckwheat is grown in all parts of Slovenia and in several regions of Bosnia-Herzegovina. Common and tartary buckwheat was grown in Bosnia-Herzegovina at least before the year 1940 but, since about 1980, this mainly ceased. In Europe, it is traditional growing of tartary buckwheat mostly spread in the cross border region Islek - which covers northern Luxemburg, the Westeifel (Germany) and the border area of the German-speaking part of Belgium. In Bosnia-Herzegovina tartary buckwheat was grown in past ten or twenty years at least in a small extent in the mountain plains south and north of Sarajevo, up to the altitude of about 1000 m (Se photo on the title page of this journal in issue 93-3, 2009). This crop is in Bosnia-Herzegovina now coming back because of the interest for healthy food. Health importance of tannins in the diet The cellular injury caused by oxidative stress and excess of free radicals has been associated with aging and linked to clinical disorders, including cancer, heart disease, and liver damage. Plant derived polyphenols are known for their strong antioxidant potency (Bialonska et al., 2009 b). Tannins are a group of polyphenols that are formed as secondary plants metabolites. They occur in human diet, such as tea, beer, wine and juices, making them significant in human nutrition (Frazier et al., 2010). The antimicrobial activity of tannins is associated with capability to form stable complexes with proteins, starch, and physiological metals, thereby disturbing the metabolic activity of bacterial enzymes, nutrient availability, and functionality of biological membranes (Bialonska et al., 2009 a). The antioxidant properties of tannin are well documented, but the interactions between tannins and proteins is fundamental for their biological activities. Therefore, a better understanding of this interaction will enable clearer explanations for the biological and pharmacological activities of tannin. Frazier et al. (2010) documented that interactions with proteins were exotermic and involved multiple binding sites on the protein. Bialonska et al. (2009 a) reported a potent antioxidant activity of tannin components from pomegranate extracts. The consumption of pomegranate products leads to a significant accumulation of ellagitannins in the large intestines, where they interact with complex gut bacteria. Results showed that pomegranate byproducts and punicalagins inhibited the growth of pathogenic clostridia and Staphyloccocus aureus. Awika et al. (2009) reported that tannin containing sorghum extracts have strong chemoprotective potential (cancers in the gastrointential tract, especially esophageal cancer). The antioxidant activity of buckwheat tannins are not studied yet, therefore the investigations of buckwheat tannins are important. The aim of this study was to compare the tannin concentration in green parts of common and tartary buckwheat, and to evaluate their value as possible functional foods. 2 MATERIALS AND METHODS Material: Plants were grown at the experimental field of Faculty of Agriculture and Food Science, University of Sarajevo, in Sarajevo in 2008. Domestic cv. Bosanka, from Bosnia, Slovenian buckwheat cv. Darja and tartary buckwheat from Luxemburg were used in a study, performed in Sarajevo in 2008. Plants were grown without fertilization, or with a standard NPK fertilization; namely granulated mineral fertilizer, N:P:K in relation 4 : 12 : 20, amount 50g/m2. Samples for analyses were collected from young plants (two proper leaves) and at the beginning of flowering separately for lower and upper leaves of the plant. Determination of tannin: Total tannin contents were determined spectrophotometrically using vanillin-HCl reagent, as previously reported (Kreft et al., 2002). Each sample was analyzed in triplicate. The data were evaluated by multifactor ANOVA (Statgraphics Version 4) and significance accepted at P < 0.05. 3 RESULTS AND DISCUSSION Results presented in Fig. 1 show that concentration of tannins was high in upper leaves of tartary buckwheat and low in young plants of Darja. This probably depends on higher impact of sunshine radiation on young plants and on higher positioned leaves of flowering plants. Results in Bosanka are different. Here the tannins buckwheat. The concentration of tannins in Darja was concentration are high in young plants and not in upper lower in comparison to Bosanka and tartary buckwheat. leaves as we observed in tartary buckwheat and Darja Tannins, Bosanka 5 4 3 2 1 0 rh r*rh jn Young plants Lower Upper □ Non-fertilized □ Fertilized Tannins, Tartary rh rh j -- □ Non-fertilized □ Fertilized Young plants Lower Upper Tannins, Darja □ Non-fertilized □ Fertilized Young plants Lower Upper Fig. 1. Tannins in young plants (two leaves), lower and upper leaves in flowering Bosanka - Bosnia domestic common buckwheat variety, tartary buckwheat and common buckwheat Darja; without and with NPK fertilization, respectively (g in 100 g of dry matter). 5 0 Fertilisation had no effect on the concentration of studied substances. We may conclude that fertilization with standard NPK fertilization had no clear impact on the concentration of tannins in buckwheat samples. Studied tartary buckwheat in the upper, light exposed leaves had higher concentration of tannins in comparison to common buckwheat. Except in common buckwheat cv. Bosanka, young plants had lower concentration of tannins in comparison to the upper leaves of flowering plants. In any way, different varieties of buckwheat react differently on environmental factors, influencing the concentration of tannins in green parts of buckwheat plants. 4 ACKNOWLEDGEMENTS This research was financed by Federal Ministry of Education and Science of Bosnia and Herzegovina - No 03-39-5980-95-2/08, and the Slovenian Research Agency through projects J4-9673 and J7-9805. Analyses were performed in the laboratories of the Faculty of Pharmacy, Chair of Pharmaceutical Biology, University of Ljubljana. 5 REFERENCES Awika J.M., Yang L.Y., Browning J.D., Faraj A. 2009. Comparative antioxidant, antiproliferative and phase II enzyme inducing potential of sorghum (Sorghum bicolor) varieties. LWT-Food Science and Technology. 42 : 10411046. Bialonska D., Kasimsetty S.G., Schrader K.K., Ferreira D. 2009 a. The effect of pomegranate (Punica granatum L.) byproducts and ellagitannins on the growth of human gut bacteria. Journal of Agricultural and Food Chemistry. 57: 8344-8349. Bialonska D., Kasimsetty S.G., Khan SI., Ferreira D. 2009 b. Urolithins, intestinal microbial metabolites of pomegranate ellagitannins, exhibit potent antioxidant activity in a cell-based assay. Journal of Agricultural and Food Chemistry. 57: 10181-10186. Frazier R.A., Deaville E.R., Green R.J., Stringano E., Willoughby I., Plant J., Mueller-Harvey I. 2010. Interactions of tea tannins and condensed tannins with proteins. Journal of Pharmaceutical and Biomedical Analysis. 51: 490-495. Germ M., Vollmannova A., Timoracka M., Melichacova S., Stibilj V., Vogrinčič M., Kreft I. 2009. Antioxidative substances of tartary buckwheat sprouts and impact of Se and Zn on the sprout development. V: Park, C. H. , Kreft, I. (Eds.). Proceedings of the International symposium on buckwheat sprouts. Development and utilization of buckwheat sprouts as medicinal natural products: ISBS 2009, Sep. 7-9, Bongpyoung, Korea. 46-53. Kalinova J., Triska, J., Vrchotova N. 2006. Distribution of vitamin E, squalene, epicatechin and rutin in common buckwheat plants (Fagopyrum esculentum Moench). Journal of Agricultural and Food Chemistry . 54, 5330533. Kalinova J., Vrchotova N. 2009. Level of catechin, myricetin, quercetin and isoquercitrin in buckwheat (Fagopyrum esculentum Moench.), changes of their levels during vegetation and their effect on the growth of selected weeds. Journal of Agricultural and Food Chemistry. 57 (7), 2719-2725. Kreft S., Štrukelj B., Gaberščik A., & Kreft I. 2002. Rutin in buckwheat herbs grown at different UV-B radiation levels: comparison of two UV spectrophotometric and an HPLC method. Journal of Experimental Botany. 53 (357), 1801-1804.