Nutritional value of vegetable Amaranth us tricolor L. seedlings grown in Moscow region

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Nutritional value of vegetable Amaranth us tricolor L. seedlings grown in Moscow region

Iskren G. Sergiev*¹, Desislava A. Todorova¹, Valentina K. Gins², Svetlana M. Motyleva³, Ekaterina M. Gins⁴, Evgeny A. Moskalev⁴

'Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Sofia, Bulgaria

²Federal Scientific Vegetable Center, VNIISSOK village, Russian Federation

³All-Russian Horticultural Institute for Breeding, Agrotechnology and Nursery,

Moscow, Russian Federation

⁴Lorch Potato Research Institute,

Kraskovo village, Moscow Region, Russian Federation

Abstract

The use of amperometric express method made it possible to measure quickly and evaluate content of water- and alcohol-soluble antioxidants in extracts from Amaranthus tricolor L. plants. Accumulation of low molecular weight antioxidants: ascorbic acid, beta-cyanine (amaranthine) and the total content of antioxidants in various organs of Valentina amaranth seedlings were studied. The maximum amount of low molecular weight antioxidants accumulates in leaves, compared with roots and stems of seedlings grown in open and protected ground. In open ground conditions, amaranth leaves and stems have 1.5-fold and 2-fold increased level of ascorbic acid than seedlings grown in protected ground. But the total content of water-soluble antioxidants in leaves and roots of seedlings is lower compared to seedlings of protected ground. Minimum amount of antioxidants was found in alcohol extracts of stems and roots in open ground, while the total content of antioxidants in stems and roots was 1.6 fold higher in seedlings grown in protected soil. The content of amaranthine is comparable in the studied organs of amaranth seedlings of both cultivation variants. The data obtained allow to recommend use of leaves and stems of amaranth seedlings grown in open and protected ground (early spring and autumn), as a preventive antioxidant dietary product.

Key words: Amaranthus tricolor L. seedlings, water and alcohol extracts, low molecular weight antioxidants, amaranthine, ascorbic acid, open ground, protected ground

Аннотация

И.Г. Сергиев¹, Д.А. Тодорова¹, В.К. Гинс², С.М. Мотылева³,

Е.М. Гинс⁴, Е.А. Москалев⁴

'Институт физиологии и генетики Болгарской академии наук, София, Болгария

²Федеральный научный центр овощеводства, п. ВНИИССОК, Московская область, Российская Федерация Всероссийский селекционно-технологический институт садоводства и питомниководства,

Москва, Российская Федерация

Всероссийский научно-исследовательский институт картофельного хозяйства имени А.Г. Лорха,

Использование амперометрического экспресс-метода позволило оперативно измерить и оценить содержание водо- и спирторастворимых антиоксидантов в экстрактах из растений Amaranthus tricolorL. Исследовали накопление низкомолекулярных антиоксидантов: аскорбиновой кислоты, бетацианина -- амарантина и суммарное содержание антиоксидантов в различных органах сеянцев амаранта сорта Валентина. Максимальное количество низкомолекулярных антиоксидантов накапливается в листьях, по сравнению с корнями и стеблями сеянцев, выращенных в открытом и защищенном грунте. В условиях открытого грунта уровень аскорбиновой кислоты в листьях в 1,5 и в стеблях амаранта в 2 раза выше, чем в сеянцах в защищенном грунте. В то время как суммарное содержание водорастворимых антиоксидантов в листьях и корнях сеянцев меньше по сравнению с сеянцами защищенного грунта. В спиртовых экстрактах стеблей и корней обнаружено минимальное количество антиоксидантов в открытом грунте, при этом суммарное содержание антиоксидантов в стеблях и корнях в 1,6 раза выше у сеянцев защищенного грунта. Содержание амарантина сравнимо в исследованных органах сеянцев амаранта обоих вариантов выращивания. Полученные данные позволяют рекомендовать использование листьев и стеблей сеянцев амаранта, выращенных в открытом и защищенном грунте (ранней весной и осенью), в качестве профилактического антиоксидантного продукта диетического назначения.

Ключевые слова: сеянцы Amaranthus tricolorL., водные и спиртовые экстракты, низкомолекулярные антиоксиданты, амарантин, аскорбиновая кислота, открытый грунт, защищенный грунт

Introduction

In hot and humid regions of the world, edible species of leafy amaranths (genus Amaranthus) are considered to be popular vegetable crops: A. tricolor, A. blitum, A. dubius, A. cruentus and A. Viridis [1--3]. In many countries of Africa and Southeast

Asia, India, southern China, amaranth leafy greens are widely used for food purposes, growing it as parsley, leaves and stems of which are used for food purposes. Young plants of vegetable species of amaranth are used in a variety of salads, appetizers, side dishes, soups, fillings for confectionery, drinks, pasta and even traditional medicine [4--7].

Such widespread use of vegetable amaranth as a food product is explained by a number of reasons, including the fact that spicy aromatic plants are practically not grown in these countries, and amaranth makes up for greens in many dishes [8, 9]. The popularity of amaranth vegetables is due to their mild piquant taste and high nutritional value, leaves of which are rich in gluten-free protein, vitamins, minerals, especially calcium, iron, as well as biologically active substances [10]. In addition, in a number of countries there is a shortage of animal protein, and leaves of amaranth vegetable species contain up to 20 % of a complete protein, balanced for essential amino acids. Therefore, population of these regions replenishes the lack of dietary protein by leaves of wild vegetable amaranth, growing seedlings and preparing various diets based on them [11].

Amaranth seedlings (young plants) are a commercial product in some countries. In Indonesia, amaranth vegetables are grown on an area of 2000 hectares. In tropical countries, amaranth is sown year-round. Due to the short development cycle of seedlings (7-8 weeks), they are cut for food several times a year.

Cultivation of vegetable amaranth in non-chernozem zone faces a number of problems. For example, return cold in spring months of April-May does not allow sowing of amaranth seeds in open ground before the end of May or the beginning of June; moisture deficiency in dry years can ruin the crop, since amaranth seedlings require more watering, compared to adult plants. In addition, amaranth seedlings in open ground can suffer from weeds, whose growth rate is much higher than growth of amaranth seedlings, and later snails can harm young seedlings [12]. When growing amaranth seedlings in a protected ground, such problems do not occur. Therefore, it is important to represent change patterns in the main morphological and biochemical parameters that determine productivity and nutritional and pharmacopoeial value of seedlings grown in open and protected ground.

The aim of the work was to study morphological and biochemical parameters of amaranth seedlings when growing them in open and protected ground for food use.

Materials and methods

The object of the study are vegetable amaranth plants (Amaranthus tricolor L.) of Valentina cultivar originated in Russian Research Institute of Selection and Seed Production of Vegetable Crops (Moscow Region). Cassettes with pre-moistened peat mixture were used for sowing seeds. Sowing depth was 0.5.. .1 cm. After 4 weeks, the seedlings were transplanted into soil in protected and open ground [13]. Plants were grown on sod-podzolic soil with a heavy mechanical composition at night temperature of 8.14 °C and day temperature 9.25 °C in open ground, and at night temperature 14.17 °C and day temperature 22.30 °C in protected ground.

Young plants aged 6-7 weeks were cut off and morphometric indicators were studied: plant height, mass of plants, leaves, stem, root, length and width of leaf blades. In the experiment, amaranth plants of Valentina cultivar grown in protected and open ground were compared. From each experimental plot, 15 plants were collected.

Biochemical studies were carried out in the Laboratory of physiology and biochemistry of introduction and functional products of Federal Scientific Technological Center in 2018. Aqueous and alcoholic extracts of leaves, stems and roots of seedlings were used in the experiments.

Extraction of crushed leaves and other plant organs was carried out with distilled water at room temperature (water ratio 1:10), followed by centrifugation at 10,000 rpm. Amount of amaranthine in aqueous extracts was determined spectrophotometrically considering a molar extinction coefficient of 5.66-10⁴-M^-1-cm^-1 and a molar weight of 726.6 [14]. Content of reduced form of ascorbic acid (AA) was determined by iodo- metric method based on titration of ascorbic acid in colored extracts with potassium iodate in acidic medium in presence of potassium iodide and starch [15]. The total content of antioxidants was determined by amperometric method, the result was expressed in gallic acid equivalents mEq.GK/g. The measurements were performed on a Tsvet- Yauza 01-AA device in a constant current mode [16]. The samples were crushed on a homogenizer in presence of a certain volume of extracting liquid (double-distilled water, 96% ethanol) at 20...25 °C. Then, the homogenizer was centrifuged at 10,000 g for 15 minutes at 4 °C. An aliquot of the supernatant was used to determine the total antioxidant content, if necessary diluting.

The tables 1--4 show the arithmetic mean values and standard deviations.

Results and discussions

Dark-colored A. tricolor seeds of Valentina cultivar germinated with an interval of two days. A slower increase in seedling height was observed in the stage of the first pair of true leaves and a sharp increase in plant height with development of subsequent leaves. Seedlings having well-developed cotyledons and first pair of true leaves were transplanted into protected and open ground.

Analysis of morphometric parameters of plant before cutting revealed that amaranth seedlings grown in sheltered soil had significantly higher morphometric indicators compared to seedlings grown in open ground.

The photosynthetic productivity of aerial parts of plants was significantly higher in seedlings in protected soil. When growing amaranth plants in protected ground at seedling stage, a more massive main shoot (stem) with a smaller mass of leaves is formed compared to open ground plants. Study of structure of seedlings' crop showed that aerial mass of seedlings grown in open ground have 52 % of leaves, 35 % of stems, while young plants in protected ground form 42 % of leaves and 44 % of stems.

Table 1Determination of structure of Valentina seedlings grown in open and protected ground

It is interesting to note that root mass of seedlings of both variants was 13.. .14 % of the aboveground mass. This suggests that photosynthetic metabolites in plants of open ground are accumulated in large quantities in leaves, while they are distributed almost evenly between leaves and stems in plants of protected ground.

Gluten-free protein, balanced for essential amino acids, and biologically active substances with antioxidant activity that affect physiological functions of the human body, effectively participating in metabolic and protective reactions comprise nutritional and pharmacopoeial value of Valentina leaves (amaranth A. tricolor L.) [17]. Ascorbic acid is a necessary component for human life. Some vegetable crops accumulate ascorbic acid in high concentrations: bell pepper -- up to 200 mg%, leafy vegetable plants: vegetable chrysanthemum -- up to 80 mg%, watercress and coriander -- up to 150 mg% [18].

Table 2Ascorbic acid in Valentina amaranth plant organs