author(s) : Abdel-Fattah M. Rizk, Ibrahim A. El-Garf and Husseiny A. H. Elgendy

There are over 60 accepted genera of the family Amaranthaceae and over 50 species of Amaranthus (National Research Council, 1984; Saunders and Becker, 1984; Matz, 1991).
Amaranth seeds were an important feed for some American tribes as early as 4000 BC, and species were extensively cropped by both Aztecs and Incas. Most of Amaranthus species, which are cosmopolitan weeds (Amaranthus retroflexus L., Amaranthus hybridus L., Amaranthus powellii S. Watt., Amaranthus spinosus L.) and cultivated amaranth species which can be used as food grain, leafy vegetables, forage and ornamentals.
According to the utilization of cultivated amaranths for human consumption, species can be divided into grain and vegetable amaranths, (1)Vegetable amaranth: most Amaranthus species have edible leaves, and several species (Amaranthus blitum L.; syn. Amaranthus lividus L., Amaranthus viridis L.; syn.. Amaranthus gracilis Desf. and Amaranthus tricolor L.; syn. Amaranthus gangeticus L.) are already widely used as potherbs (boiled greens).
Their mild spinach-like flavour, high yields, ability to grow in hot weather, and high nutritive value have made them popular vegetable crops, perhaps the most widely eaten vegetables in the humid tropics of Africa and Asia, (2) Grain amaranth: belongs to a group of cereal-like grain crops or pseudocereals.
The three principal species considered for grain production include: Amaranthus hypochondriacus L. (syn. Amaranthus leucocarpus S. Watts, Amaranthus frumentaceous) – prince’s feather; Amaranthus cruentus L. syn. Amaranthus paniculatus L. – bush greens, red amaranth, and Amaranthus caudatus L. of two subspecies: subsp. caudatus; and subsp. mantegazzianus Passerini syn.: Amaranthus edulis Spagazzini, named love-liebleeding and Inca wheat, respectively (Mlaker et al., 2010).
An estimated total production by Aztecs was ≈ 15-20 K tones per year before the Spanish Conquest, at which times it was the third ranking crop, following maize and beans (Matz, 1991; Wu and Corke, 1999).
Amaranth has become a successful minor crop with a significant future potential in China (Yue et al., 1993) where it is grown for commercial grain production on some 40,000 ha per year (Wu et al., 1995) with a grain yield of 2200 to 5500 kg ha-1 depending on environmental conditions (Yue et al., 1993; Bejosano and Corke, 1998).
In the last 30 years Amaranthus has been rediscovered as a promising food crop mainly due to its resistance to heat, drought, diseases and pests, and the high nutritional value of both seeds and leaves (e.g. National Research Council, 1984; Saunders and Becker, 1984; Yue et al., 1993; Lanoue et al., 1996; Wu et al., 2000).
In general, Amaranthus species are receiving attention as potential new crops to improve nutrition in the Third World and as potential health food products (e.g. U.S. National Academy of Sciences, 1975; Marx, 1977; Coons, 1982; Singhal and Kulkarni, 1988; Bejosano and Corke, 1998; Wu et al., 2000).

The genus Amaranthus contains species and genotypes that can be used as high quality multipurpose high potential crops for modern agriculture, fod food, feed, and forage uses, and also as ornamental plant or pigment source plant because of its rich colourful leaves, inflorescences, stems and seeds (Paredes-López, 1994).Amaranths are cultivated as pseudo cereals in both Old and New Worlds (Coons, 1982).
In places where grain amaranths are grown for local consumption and form the staple diet of the people (India and Mexico), the seeds are used in a way similar to wheat, being first ground into flour and then made into a dough (Opute, 1979).
De Luquez et al. (1997) reported that Amaranthus mantegazzianus protein concentrate was a good source for the enrichment of bread backing products, special regimen diets, and protein complement for deficient foods. The leaves contain 17.5 to 38.3% dry matter as protein of which 5% is lysine (Oliveira and De Carvallo, 1975).
Vitamins A and C are also present in significant levels. One hundred grams of the vegetable material cooked without oil can contribute 45% of daily vitamin A requirement (Mnkeni et al., 2007).
Compared to spinach, Amaranthus contains three times more vitamin C, calcium and niacin. Compared to lettuce, Amaranthus contains 18 times more vitamin A, 13 times more viamin C, 20 times more calcium and 7 times more iron (Mnkeni et al., 2007).
A study of Allemann et al. (1996) showed that amaranth has the potential to be a valuable source of nutrition in areas in Africa with hot dry climates.
The cooked grain is 90% digestible and because of its ease in digestion it has traditionally been given to those recovering from illness or fasting period (Morales et al., 1988).
Amaranth seed is high in protein (8.8 to 19.5%) which is in turn high lysine and sulphur-containing amino acids that are not frequently found in appreciable amounts in plant proteins (Mnkeni et al., 2007).
The fiber content of amaranth seed is three times of wheat and its iron content is five times more than wheat.
It contains two times more calcium than milk.
Using amaranth in combination with wheat, maize or brown rice resulted in a complete protein as high in food value as fish, red meat and poultry.
The oil from the seeds (5 to 10%) is predominantly unsaturated and is high in linolenic acid and rich in squalene (Dhellot et al., 2006; Mnkeni et al., 2007). About 50 to 60 members of the genus Amaranthus, spread throughout the world used as pot-herbs, ornamentals, grains and dye plants, grow under a wide range of climatic conditions, with yields comparable to those of cereals (Pal and Khoshoo, 1974; Singhal and Kulkarni, 1988).
Amaranthus flavus was among the plants reported by Gupta et al. (1989) as rich sources of macro and micro elements. Simakhina (1998) studied the nutrient comoposition of white, rose and black seed amaranth growing in Ukrania.
He found that the amaranth seeds are rich nutrient source suitable for processing and inclusion into dietary supplement. Amaranth is a crop with multiple purposes, such as food, forage, silage, green manure and animal feed. The green and grain amaranth are rich in protein and essential amino acids, fibers, minerals and vitamins.
The seeds of amaranth have an interesting chemical composition due to its high nutritive value. The seeds have high level of fibers and minerals, especially iron and calcium.
Amaranth oil is a potential alterenative source for squalene (Gamel and Linssen, 2006).A seed of grain amaranth is on average composed of 13.1 to 21.0% of crude protein; 5.6 to 10.9% of crude fat; 48 to 69% of starch; 3.1 to 5.0% (14.2%) of dietary fibre and 2.5 to 4.4% of ash (Mlakar et al., 2010).