Overview on Nutritional and Phytochemical Composition of Finger Millet (Eleusine Coracana): A Review

Millets are small seeded annual cereal crop species belonging to family ―poaceae‖. Millet is a French derived word ―mille‖ which means thousand (Ramashia et al., 2019). One of the wonder varieties of millet family is Finger millet (Eleusine coracana) which is commonly popular as Ragi or manduain India belonging to grass family Gramineae or Poaceae (Singh, 2012). It is native from Ethiopia region but largely grown in Asia and Africa regions of the world.It is a self pollinated crop species with chromosome no. 36 (allotetraploid) distributed in about 10 genera and 20 species in all (Kakri et al., 2020). Finger millet grains are globular in shape of 1.0 to 1.5 mm in diameter. The finger millet kernel consists of 3 main parts namely; seed coat, endosperm and embryo. The outermost layer of the millet is known as pericarp or glume (Ramashia et al., 2019) which has little nutritional significance. The seed coat or the testa of finger millet is multilayered (five layered) making it unique as compared to other members of the millet family. The seed coat, germ, and the endosperm cell walls of the millet are endowed with poly phenols making it rich in phytochemicals (Shobana et al., 2013). The crop was cultivated around 5000 years BCand still is one of the most produced grain species worldwide. Finger millets stands sixth in production in India and fourth in the world after major crops such as wheat, rice, maize, sorghum and bajra (Chandra et al., 2016). India is the largest producer of finger millet accounting to about 60% of world production followed by Ethiopia (Gull et al., 2014). Finger millet is a staple food to many parts of the world primarily in developing countries. It is popular among the low income groups of society and is considered as poor man’sfood (Maharajan et al., 2021). It is majorly grown in dry areas in tropical and subtropical regions with temperature requirement of 8-10 degree Celsius (Singh, 2012) with acidic soil (alluvial, loamy, and sandy) and higher rainfall of 600-1200 cm, matures within a time span of 100-130 days (Gull et al., 2014). It has several varieties (yellow, white, tan, red, brown, or violet color) and apart from all the varieties, red colored variety is mostly cultivated allover the world (Chandra et al., 2016). Finger millet is associated with number of health benefits such as antioxidant, anti-ageing, anti-diabetic, hyperactivity, healing property, anticancer property (Antony Cesar et al., 2018) and maintaining bone health for which it is gaining importance in the field of health and nutrition. This review focuses to get insights of nutritional and health prospects of finger millet (Eleusine coracana) so that value added products can be made out of it.

FIGURE 1: Hierarchical classification of finger millet FIGURE 2: Finger millet 1.1 Nutritional significance of Finger millets: Finger Millets are nutritionally superior to other cereal crops of same variety such as rice and wheat because it serves as an excellent source of carbohydrate (80%), proteins (7–9%) with essential amino acids as well as nonessential amino acids like valine, methionine, and tryptophan, minerals (calcium, phosphorus, potassium, and iron) as well as vitamins (thiamine, niacin, and riboflavin), and fats for which they are extensively been researched (Murtaza et al., 2014). TABLE 1 GENERAL COMPOSITION OF FINGER MILLETS PER 100G Sr. No. Parameter Composition (g) Sources 1 Carbohydrates 72.6 Kakri et al., 2020 2 Proteins 7.7 3 Fats 1.5 Kumar et al., 2016 4 Crude fiber 3.6 5 Dietary fiber 15-22 Ramashia et al., 2019 6 Energy (Kcal) 336 1.2 Mineral and vitamin profile of finger millets: Finger millet is found to be rich in vitamins as well as some minerals, which prove its significant utilization inhuman diets as well. Vitamins such as vitamin A (Retinol), vitamin B1 (Thiamine), vitamin B2 (Riboflavin), vitamin B3 (Niacin), vitamin C (Ascorbic acid) and minerals (phosphorous, potassium, magnesium, calcium, sodium, iron and zinc) are abundantly found in finger millet at valuable composition. TABLE 2 MINERAL AND VITAMIN COMPOSITION OF FINGER MILLETS (ELEUSINE CORACANA) PER 100G Sr. No. Nutrients Composition mg/100g Sources 1 Phosphorus 130-250 2 Potassium 430-490 USDA, 2016 3 Magnesium 78-201 4 Calcium 398 Patel et al., 2014 5 Sodium 11 6 Iron 3.9 Muthamilarasan et al., 2016 7 Zinc 2.3 Vitamins 1 Vitamin B2 (Thiamine) 0.12-0.42 Ramashia et al., 2019 2 Vitamin B1 (Riboflavin) 0.2-0.48 3 Vitamin B3(Niacin) 1.0-1.30 Devi et al., 2011 4 Vitamin C (Ascorbic acid) 1.0 5 Vitamin A (Retinol) 6.0 1.3 Amino acid profile of Finger millet (Eleusine coracana): Finger millet is a complete source of essential as well as nonessential amino acids which are required by human body insufficient amount for proper growth and development of body cells. Essential amino acids such as Valine (4.9-6.9g), methionine (2.5-3.1g), tryptophan (1.1-1.5), Phenyalanine (4.1-5.2g), histidine (2.2), isoleucine (4.3g), leucine (6.6-9.5g), threonine (3.4-4.2g) and nonessential amino acids such as Aspartic acid (6.5-7.9g), glutamic acid (20.3-27.1g), alanine (6.1-6.2g), arginine (2.77-4.5g), cystine (1.7-2.6g), glycine (2.14-4.0), proline (7.0-9.9), serine (3.6-5.1g) and tyrosine (2.79-3.6g) are found in Finger millet (Ramashia et al., 2019; Thapliyal and Singh, 2015). 1.4 Phytochemical composition: Finger millet is found to be rich in certain phytochemicals such as Tannins, steroids, polyphenols, alkaloids, terpenoids, cardiac glycosides, balsams, lignans, phytooestrogens and phytocyanins. Some phenolic acid derivatives (Hydroxybenzoic Gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid), hydroxycinnamic acid derivatives (Ferulic acid, trans—cinnamic acid, p-coumaric acid, caffeic acid, sinapic acid) and some flavonoids such as Quercetin , Proanthocyanidins and condensed tannins (Devi et al., 2011), which are important in healing, aging, prevents deterioration of human health, lowers blood pressure, lowers risk of diabetes, and helps combating the metabolic syndromes (Thilagavathi et al., 2015). 1.5 Chemical structures of major phytochemicals present (a) (b) (c) (d)

FIGURE 3: a) Galic acid, b) Ferulic acid, c) Quercetind) Proanthocyanidins 1.6 Potential health benefits of Finger millet (Eleusine coracana): 1.6.1 Anti-oxidant activity Studies have concluded that, oxidation of cellular molecules (by reactive oxygen and nitrogen species) has been linked with chronic diseases such as diabetes, heart disease, cancer, and several other normal functions in humans. Dietary plant polyphenols act for reduced risk of cancer, cardiovascular and neuro-degenerative diseases, infections, ageing, and diabetes (Kumar et al., 2016). Seed coat of finger millet grains is high in phenolic compounds (mostly benzoic acid derivatives) that have been shown to have ―antioxidant activity‖. On average, white finger millet contains 0.04–0.09% polyphenols, while brown finger millets contain 0.08–3.47 %. A major fraction of benzoic acid derivatives (gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid), while the rest was either cinnamic acid derivatives (ferulic acid, trans-cinnamic acid, p-coumaric acid, caffeic acid, sinapic acid) or flavonoids (Chethan and Malleshi, 2007) are derived, which are found to be effective against cancer, cardiovascular and neuro-degenerative diseases, infections, ageing, and diabetes. Finger millet is also reported to have inhibition of collagen cross-linking property which reduces the stiffness of elastic tissues in tendons, skin and blood vessels as well (Kumar et al., 2016). 1.6.2 Anti-diabetic properties Diabetes also known as ―Diabetes mellitus‖ is a major health concern that is rapidly increasing in India and several other developing as well developed countries. In a study, chemical synthetic inhibitors of ―glucosidase‖ and ―pancreatic amylase‖ can be effectively used to treat hyperglycemia and finger millet seed coat phenolic extracts were found to be effective inhibitors of these enzymes. (Shobana et al., 2009).Food formulations and preparations based on finger millet have a lower glycemic index and cause a lower glycemic response (Kumar et al., 2016). Certain anti-nutritional factors found in whole finger millet fractions (such as tannins, phenolics, and phytates) may help to reduce glycemic response by reducing starch digestibility and absorption. Independent rat studies have successfully demonstrated that a finger millet diet fastens the wound healing process and delays cataractogenesis (Shobana et al., 2010). 1.6.3 Cardio-protective and Anti-hyperlipidemic properties Cardiac diseases are one of the most severe problems suffered by people worldwide. Risk factors such as high blood pressure, high cholesterol, hypertension, depression, obesity, and diabetes are associated with the problem (Kumar et al., 2016). Finger millet rich diet lowers lipid per oxidation reaction, which reduces the risk of arteriosclerosis and thus provides important protection against strokes and heart attacks. A similar recent study has found that a multigrain formulated diet containing finger millet was effective in controlling lipid and antioxidant metabolism in high cholesterol intake rat models. (Vasant et al., 2014). 1.6.4 Prevention of GIT Disorders Celiac disease (caused by consumption of gluten protein) is one of the most common auto-immune genetic disorders that affect people worldwide. The treatment includes consumption of flour that is free from gluten protein and similar protein structure and non-glutinous nature can be found in finger millet instead of wheat. Chandrasekara and Shahidi, 2012).Finger millet is high insoluble and insoluble dietary fibers, which are resistant to digestion and help in prevention of gastrointestinal problems, colon cancer, cardiovascular diseases and diabetes. Polyphenols, present in outer skin, can help to reduce peptic inflammation and ulcers too (Kumar et al., 2016). Consumption of food products made from finger millet can increase the satiety level, lower calorie intake, and aids weight loss. 1.6.5 Prevention of Osteoporosis bone defects Osteoporosis is a "silent" disease that causes bone loss and is related with porous bones. The prevention of bone diseases such as osteoporosis is aided by a high dietary intake of naturally available calcium. Finger millet is a good source of calcium, with the seeds containing up to 350 to 400 mg/100 g of calcium, which is nearly 5–10 times more than other cereals.(Sanwalka et al., 2011; Kumar et al., 2013).Concluding, finger millet-derived products can be used to promote bone mass development ingrowing children as well as to prevent osteoporosis and other bone diseases in adults and the elderly (Kumar et al., 2016).