Nutrient dense

Pigmented Rice:A diet for Healthier People

Rice is one of the most important crops in the world which is in great demand to feed more than half of the world's population and is being cultivated in a wide area from temperate to tropical zones. It is grown in more than a hundred countries, with a total harvested area of approximately 158 million hectares, producing more than 700 million tons annually. Nearly 640 million tons of rice is grown in Asia, representing 90% of global production. Sub-Saharan Africa produces about 19 million tons and Latin America some 25 million tons. In Asia and sub-Saharan Africa, almost all rice is grown on small farms of 0.5−3 ha.

In recent years, increasing the average life span and interest in correlation between food and human health has vigorously led to nutrigenomic studies. Their research outcomes has characterized the potential role of functional bio-actives in some specialty rice, known as pigmented rice. Pigmented rice has a variety of colored grains like yellow, green, brown, red, purple and black. Due to rich nutritional landscape and antioxidant nutraceuticals, pigmented rice varieties have the potential to promote human health by managing various metabolic impairments. Due to poor awareness, yield ceiling, consumer preferences, staggered market potential, still it represents only 0.1% of total rice production. This bulletin provides information on Global and Indian scenario, the form of bioactive compounds, potential health benefits and a foreseen market for these niche rice varieties. The comprehensive overview also mentions the existing challenges and steps to be taken in this direction.

Overview

Rice is the most widely consumed staple food in the world and the world’s largest producers by far are China and India followed by Indonesia, Bangladesh, Vietnam, Myanmar and Thailand. Two species of domesticated rice exist : the widely cultivated Asian rice ( L.), Oryza sativadomesticated in China some 10,000 years ago, and the lesser-known African rice (Oryza glaberrima S.), domesticated about 3,000 years ago. Realizing the therapeutic potential and global demand, various countries explored their pigmented rice and developed newer varieties. In European countries, Italy and France, the red and black grain varieties of rice with a high content of phytochemical elements have been bred based on Asian varieties. Comprehensive evaluation of traditional rice collections (pigmented & non-pigmented) investigated mainly in South Asian countries like Afghanistan, Bangladesh, Bhutan, India, Nepal, Pakistan, Sri Lanka and deposited in IRRI rice gene bank.

Traditional rice varieties in IRRI gene bank

Global scenario

41Afghanistan

3011Bangladesh

1821Sri Lanka

797Pakistan

1251Nepal

367Bhutan

2826India

Russia 2012Russian Federation State Register of Protected Breeding

Developed by breeding-Mars , Rubin (red-grained)

Russia 2014Russian Federation State Register of Protected Breeding

Developed by breeding -Yuzhnaya Noch (black-grained)

Philippines 2005-2014Heirloom Rice Project

Collected -10114 traditional varieties

UK-Philippines 2016-2018

Enhanced Rice quality for Health (EnRicH)

Characterized - for cell wall polysaccharides and their contribution towards glycemic profile

China 2017 National Natural Science Foundation of China

Developed by genetic engineering - purple endosperm rice “Zijingmii”

CountriesTime

period Project Varieties Developed/Collected/Characterized

Pigmented rice varieties developed, collected and characterized globally

India is home to 6000 rice varieties at present. Originally, India had more than 1,10,000 varieties of rice until 1970, which were replaced by the high yielding semi dwarf cultivarsduring green revolution with its emphasis on monoculture and hybrid crops. Diversity of pigmented rice, known from time immemorial for its nutraceutical benefits and remained as niche rice in various pockets of this country. Most well known are the black rice of Manipur- Chak-hao Amubi, Chak-hao Poireiton Chak-hao Angangba. and Given below is a pigmented rice map of India based on existing scientific evidence available till date.

Indian scenario

Pigmented rice map of India

14

13

121110

9

8

76

5

43

2

1 [Jammu & Kashmir] Mirzag, Zag, Khuch, Khuch niver, Niver, Mirsagi, Zager, kawkreer, GS10, GS44, GS51, GS52, GS80, GS83)[Himachal Pradesh] Chhohartu, Jatu, Matali, Karad, Sukara, Katheri, Begumi[Arunachal Pradesh] Lingkang taker ame, Umling ame[Manipur] Chakhao Poireiton, Chakhao Amubi, Wairi Chakhao, Khurkhul Chakhao, Pong Chakhao Chakhao Sempak, Chakhao Anganba and Langphou Chakhao[Assam] Bairing Gurmu, Joradhan, Miren, Maibee, Maichukik, Dimrou, IRAT-141, Bairing, Sakbothung, Buarcha, Sakcharap, Vijoy Bijor and Pakai, Amana Bao,Betu, Biroi, Bogaguni,burali, Dal Bao, Hurupi Bao,Ixojoy, Jul bao, Kenkua bao, kolaguni, kotia Bao, Negheri Bao,Ronga Chokua, Ronga Dariya[Jharkhand] Gora [West Bengal] Kalabiroin, Mamihunger, Annapurna, Kalajeera[Chattisgarh] Dimrou, IRAT-141,Bairing, Sakbothung, Buarcha, Sakcharap, Bairing gurmuJoradhan, Miren, Maibee, Maichukik[Odisha] Kalabati, Keonjhar Kalachampa, Bhatamalli, Bhatachudi, Paradhan, Kandulakathi, Tikichudi, Beda Gurumukhi, Haladiganthi, Malligoindi, Kalachudi, Mallimakada[Maharashtra] Kalabhat[Telangana] Kakirekkalu, Burma black[Karnataka] Kakka, Mappulai samba, Kusum kesar, Rajamudi rice [Tamil Nadu] Vaigunda, Neelam samba, Kala samba, TKM9, Karungkuravai, red Kavuni, black kavuni, Koliyal, Kuruvi kar, Poongar, Kattu Yanam[Kerala] Rakthashali, Njavara, Jyothi, Matta, MO1, MO5, Kari kagga, Matta triveni, Ptb1, 16, 17, 22, 23, 25, 29, 30 (Hraswa, Kattamodan, Karuthamodan, chuvannamodan, Kairali, Kanchana, Karthika, Aruna, Makom, Remanika, Revathy, Krishnanjana, Bhagya, Onam, Ahalya 3, Harsha, Varsha, Kunjukunju Varna, Kunjukunju Priya, Chingam, Sabari, Bharathy, Aathira, Aishwarya, Bhadra, Asha, Pavizham, Remya, Kanakom, Renjini, Pavithra, Panchami, Uma, Karishma, Vyttila-1,2,3,4,5, Arathy, Nila, Dhanya,

Over the decades, white grained rice varieties got preferred and the wild growing ancestors having colored grain have been only grown and consumed due to its cultural and therapeutic significance. Histochemical characterizations of pigments reported commonly in the pericarp, while few reports also suggest the presence in the endosperm. Black and purple rice have found with the presence of anthocyanins and their production is controlled by a promoter-diverged allele of OsB2, known as Kala4. Similarly, OsRc/Rd (Red pericarp, a homolog of OsB1/OsB2) regulates the pro-anthocyanidin production in the pericarp of red-grained rice. The thickness of pericarp varies among the rice genotypes mainly according to the microstructure (cellular layers), which also determines the quantum of accumulation of pigments.

Pigment accumulation (a) in pericarp (b) both in pericarp & endosperm (adapted from Zhu et al., 2017,Molecular Plant 10, 918–929)

Microstructure of rice depicting pro-anthocyanidins (also known as condensed tannins) [red arrows shows pericarp; cdt-condensed tannins; adapted from Zaupa et al., 2016 Food structure (1): 6-12]

Microstructure of pigmented rice

(a) (b)

(a) black rice: venere (b) white rice: ribe

Nutritional landscape of Pigmented rice

Colored rice varieties are rich in pigments which are majorly antioxidants or functional bio-actives. The temporal expression of pigments during kernel development [till 40 Days after flowering (DAF)] has observed to start after 15DAF. Exclusively they are rich in polyphenols (250-1075 mg/100g) with having high free radical scavenging ability (69-93% by DPPH assay). Most abundant phenolics in black/purple rice are anthocyanins; while pro-anthocyanidins are predominant in red/brown rice varieties. Other than bio-actives, pigmented rice is also reported to have higher contents of total dietary fiber, vitamin B and B compared to white rice. The major 1 2

fatty acids of pigmented rice are palmitic acid, oleic acid and linoleic acid.

Metabolic fingerprinting revealed the exclusive and predominant bio-actives present in pigmented rice

Changes in expression of pigments in black rice during kernel development. A : 1 DAF, B : 3 DAF, C : 5 DAF, D : 7 DAF, E : 9 DAF, F : 11 DAF, G : 15 DAF, H : 30 DAF, I : 40 DAF [Lee et al., 2012. Korean

]J. Crop Sci. 57(2): 127-131

Bio-actives present in pigmented rice

Exclusively present Predominantly present

Anthocyanins

cyanidin-3-glucosidepeonidin-3-glucoside

peonidin-3-O-rutinosidedelphinidin-3-O-glucosidecyanidin 3-O-sophoroside

cyanidin 3,5-O -diglucosidecyanidin 3-O-rutinoside

keracyanin (C3rutinoside0Cl)malvidin glucoside

catechinepicatechins

pro-anthocyanidin dimerspro-anthocyanidin trimers

Pro-antho-cyanidins

Flavones/flavanols

apigeninkaempferolquercetin

isorhamnetin zeaxanthinbeta carotene

lutein

Carotenoids

Phenolicacids

Others

SterolsTocopherols

tocotrienolstocopherols

oryzanolsitosterol

stigmasterolcampesterolphytosterol

inositolfolic acid-lipoic acidα

pangamic acidphytic acid

gallic acidferulic acidsinapic acidellagic acid

catechuic acid

[Partially adapted from Kusano et al.,2015 Molecular Plant 8(1):58-67]

Potential health endorsements

Oxidative stress (OS), the major hidden reason behind various disease etiologies occurs when production of reactive oxygen species (ROS) overwhelms the inherent antioxidant system. Such OS leads to cellular damage which end in apoptosis. Such redox imbalance kick starts a cascade of genomic, epigenomic, transcriptomic, proteomic as well as metabolic factors that leads to inflammation associated cell death.Pigmented rice rich in antioxidants like anthocyanins, pro-anthocyanidins, tocopherols, carotenoids etc, efficiently chelate the free radicals which are the hidden reasons behind life style disorders.

Anti-oxidant effect

Role of antioxidant in preventing/managing ROS induced metabolic alterations

Nitrate radical scavenging by anthocyanins

Cellular oxidative burst & potential markers

Oxidativeburst

Isoprostanes,Hydroxy-nonenan

AGEs, glycolipids,glycoproteins

hydroxyl guanine,nitroguanine

Nitro tyrosine,carbonyls

Cellular lipidPeroxidation

Cellular DNAOxidation

CellularGlycoxidation

Cellularprotein

Oxidation

Anti-obesity effectPigmented rice has proved to have effect in weight reduction as it contains higher fiber and less digestible starch content, which assists to stop signals of hunger and discourage excessive consumption.Oxidative stress induced inflammation being key signal during obese condition and antioxidant rich pigmented rice has possible role in its alleviation.Supplementing with pigmented rice/extracts significantly reduced body weight gain and lipid accumulation in the liver and adipose tissue in animal models as well as in clinical trials. Triglyceride, total cholesterol, and low-density lipoprotein-cholesterol levels in serum were decreased by supplementation, whereas high-density lipoprotein-cholesterol level significantly increased. This, in turn, decreased PPARγ, SREBP-1c, FASN, ACC, and HMGCOR-A and increased LXRα, PPARα, and CPT1α at the gene level. Further, it lowered PPARγ and elevated PPARα, p-ACC/ACC, and p-AMPKα/AMPKα at the protein level. Additionally, treatment decreased germinated brown rice gene expression of NPC1L1, ACAT2, MTTP, which regulated lipid absorption in the intestine and preserved CYP7A1, ABCG5/8 that transported cholesterol from the liver and enterocytes to the intestinal lumen.

(Adapted from Liu et al., 2019 Journal of Functional Foods 3:17-32)

Anti-cancer effectIncreasing evidence from animal, epidemiological and clinical investigations suggest that dietary anthocyanins/phenolic acids have potential to prevent chronic diseases, including cancers. Anti-metastasis potential of black rice anthocyanins through human epidermal growth factor receptor 2 (ErbB2) has been established.Recent work demonstrates that pigmented rice bran extracts are helpful in attenuating inflammation and inflammation induced cancer progression.

Nutritional psychiatry is a growing discipline that focuses on the use of food and supplements to provide these essential nutrients as part of an integrated or alternative treatment for mental health disorders. Pigmented rice being rich source of antioxidant cocktail, could play role in this which will be beneficial for future generations.

B o o s t s i m m u n i t y, quench stress induced free radicals; High Fe & Mn content.

Black rice is broadly known as enriched rice and has been used in traditional medicine. Being gluten free, it is suitable for celiac patients also.

The dietary fiber per serving is remarkable in pigmented rice. Among which insoluble fiber enables to protect against constipation, bloating and other undesirable digestive symptoms. While soluble fiber like resistant starch act as prebiotic for healthy gut microbiome.

Consumption of pigmented rice can detoxify the body and purify the liver with the use of elevated antioxidant levels in the rice. The anti-oxidative status of blood, liver, and the aorta assessed resulted with less oxidative stress.

Immune health

Anti-allergic

Digestive health

Detoxification

Infiltration of inflammatory cells

Secretion of pro-inflammatory cytokines(Interleukin 6, Tumor Necrosis Factor (TNF)- )α

Samyor et al., 2017 International Journal of Food Science and Technology doi:10.1111/ijfs.13378

Anti-metastasis effect *

Other general health benefits*

*

Anti-diabetic effectAsians are known to have a genetic predisposition to poor insulin secretion by pancreatic β-cells and their insulin secretion is prone to decline with β-cell exhaustion.Pigmented rice rich in spectrum of antioxidants like anthocyanins have thus been studied for its anti-diabetic effect using & models.in vitro in vivo A significant reduction in glycosylated hemoglobin, fasting glucose, and improvements in serum insulin level has been observed in mice models treated with pigmented rice extracts.Anthocyanins have deciphered to play pivotal role in regulating glucose uptake in the intestine and muscle via regulating the secretion of insulin from the pancreas through modulating glucose transporter (GLUT) receptors, thus bestowing the anti-diabetic effect.

Figure depicts the role of pigmented rice in regulating blood glucose homeostasis through inter-organ communication. Pancreas regulates glucose using insulin and glucagon in response to food intake. Further Insulin also acts on peripheral tissues (liver, adipose tissue and skeletal muscles) to increase glucose uptake, resulting in decreased blood glucose levels. [Green lines denotes the normal glucose response and red lines denotes the response during hyperglycemic conditions].

During fastingblood glucose

levels

After mealsblood glucose

levels

Normalblood

glucoselevels

4.4-6.1 mMor

80-125mg/dL

Glycogenesis

GluconeogenesisLiver

Adipose

Muscle

Glucose uptake

Glucose uptake

GlucogenolysisGluconeogenesisGlucagon

Insulin

Glucose

Role of red rice “Anti-aging & managing glucose homeostasis”

Red rice was characterized by a high quantity of oligomeric procyanidins (0.2 mg/g) with

more than 60% of total phytochemicals found in the rice seeds. Procyanidins are high

molecular weight polymers or complex flavan-3-ol polymers that consist mainly of catechin,

epicatechin, gallocatechin, and epigallocatechin units that can also be found in rice germ and

bran.

Treated with red ricephenolics

HepG2 cells( hepatocyte model)in vitro

Intracellular glucose (C )14

uptakeGlycation potentialExpression of GLUT receptors& gluconeogenic genes

Glycation Damage: A hub for aging & associated disorders

Figure depicts the role of red rice phenolics in managing glucose homeostasis using assays. in vitro Various parameters like C Glucose uptake, 14

expression of GLUT receptors and gluconeogenic genes were validated. The protein glycation in vitro assay developed would also assist in aging studies in future

Role of black rice“Anthocyanins modulate oxidative stress”Major antioxidant, anthocyanins/anthocyanidins modulate oxidative stress by chelating free radicals. More than 500 different anthocyanins and 23 anthocyanidins have been yet reported. Anthocyanins exist as mono-, di-, or tri-O-linked glycosides and acyl glycosides of anthocyanidins in pigmented rice. The sugar moiety may be substituted by aliphatic, hydroxybenzoic, or hydroxycinnamic acids. Major forms are cyanidin 3-O-glucoside (2.8 mg/g) and peonidin-3-O-glucoside (0.5 mg/g).

Anthocyanin profiles using UPLC

Serum & Tissue collection

Rice powder extractOral gavage (200mg/kg)

Abnormal histological atrophy of pancreatic beta islets due to Streptozotocin (STZ) induced hyperglycemia was drastically reduced when supplemented with pigmented rice. Restoration of pancreatic islets in number and size was observed.

In vivo hyperglycemic mouse model

Pancreatic histopathology

The predominant anthocyanins prevent the oxidative stress induced damage of pancreatic islets

Figure depicts the histological effects on pancreatic beta islets due to Streptozotocin (STZ) induced hyperglycemia in mouse model by Haematoxylin and Eosin staining (WR-White rice; BR-Black rice & RR-Red rice; E - extract)

Work carried out at Division of Biochemistry, ICAR-Indian Agricultural Research Institute (IARI) in collaboration with CSIR-Indian Institute of Chemical Biology (IICB), Kolkata

Market potential

The global anthocyanins market was valued at USD 291.7 million in 2014 and is expected to reach USD 387.4 million by 2021, growing at a CAGR of 4.4% from 2015 to 2021

Black rice - Rs. 300-500/KgBlack rice powder (5-25% anthocyanin)

Rs.15,000-20,000/KgPurified anthocyanin (E163)

Rs.30,000-50,000/Kg

Presence of health plus contents gave pigment rice ‘super food’ status and thus fetching premium price (Rs.300-500/Kg)Therapeutic effects of anthocyanins has boomed the fortification industry where varied percentage of anthocyanin has been fortified (2 - 25%) in bread, confectionaries, desserts etc. Black rice farmers are hugely benefitted with the market potential of crude and pure black rice powder which are used as natural colorant (E163) as well as for supplements.

ConclusionPigmented rice is a miracle food and can be a panacea of maladies.The bioactive compounds exclusively and predominantly present in pigmented rice display significant potential with regard to a range of beneficial health effects.There is also the prospect of additional practical implications, not only for agriculture expansion but in the food industry as well. Poor consumer preferences due to palatability issues (eating and cooking qualities) being major limitation, breeding/genetic engineering efforts are need of the hour to escalate the status of this wonder grain.Several pigmented rice varieties have been used to extract nutraceuticals, and these seem to hold a promise in terms of potential cosmeceutical utilization in the new global business era. But currently this is handicapped by lack of efficient high throughput extraction methods, which have to be tackled.Emerging domains of nutritional psychiatry hold new promises, not only for the present generation but also for the future which underlines the importance of health plus compounds in pigmented rice.

Citation:

Published byDivision of BiochemistryICAR-Indian Agricultural Research InstituteNew Delhi

February, 2020

TB-ICN:236/2019

Veda Krishnan , Archana Singh , Susheel Sharma , Haritha Bollinedi , 1 1 2 3

U Mabalirajan , Suneetha Kota , Sandeep Raja , A.K Singh and Shelly Praveen 4 5 6 3 1

(2020) Nutrient dense pigmented rice: A diet for healthier people 1. Division of Biochemistry, ICAR-Indian Agricultural Research Institute (IARI), New Delhi 2. ICAR – Research Complex for NEH Region, Manipur Centre, Imphal 3. Division of Genetics, ICAR-Indian Agricultural Research Institute (IARI), New Delhi 4. CSIR- Indian Institute of Chemical Biology, Kolkata 5. ICAR- Indian Institute of Rice Research, Telangana 6. Acharya N.G. Ranga Agricultural University, Telangana