The of Human Metabolome Technologies America, Inc.

24 Denby Road, Suite 217, Boston, MA 02134 p. 617-987-0554 f. 617-902-2434 Lipids and [email protected]

THE STORY OF RICE LIPID CONTENT

Rice (Oryza sativa L.) is one of the quality of rice. A number of studies have shown with a few exceptions, there is no Phosphatidylcholine most important crops cul- that rice oil reduces the substantial difference in total lipid Oryza sativa, or Asian rice, con- CH2 tivated in the world; it feeds more tains two broad groups: indica harmful cholesterol (LDL) without content. − than half of the world’s popula- changing good cholesterol (HDL). R COO CH O

(long-grain) and japonica − − − −OOCRˈ + tion. Metabolome analysis, the On the other hand, reports Phosphatidylethanolamine (short-grain). Other types of CH2 O P O CH2CH2N(CH3)3 investigation of all cellular me- Asian rice include glutinous rice showed that the hydrolysis and ox- ʺ − − tabolites, has become an import- idation of rice are responsible CH2 O

and aromatic rice. All varieties of − − − − − for rice aging and deterioration of O ant strategy for gaining insight rice can be processed post-har- R COO CH Phosphatidyldimethylethanolamine − − into functional biology around vest as either white or brown grain flavor during storage, and − −OOCRˈ � low-oil rice cultivars are more suit- CH2 O P O CH2CH2NH2 CH understanding the flavor, health rice, affecting flavor, texture and 2 ʺ − − benefits, aroma and cultivation nutritive value. In short-grain rice able for grain storage The lipids of OH R COO CH− O these rice brans comprised mainly − − − − processes in rice production. − − varieties, including japonica vari- − −OOCRˈ triacylglycerols (TAG) and phos- CH O P O CH CH N(CH ) Japanese rice contains well-bal- eties of Asian rice, grains tend to Phosphatidylmonomethylethanolamine 2 2 2 3 2 pholipids (PL) (Graph Lipid Distri- ʺ − − anced nutritional elements. It has stick together when cooked. This CH OH bution). The PL components 2 − − − − an ample supply of vegetable is not to be confused with gluti- − O Figure B: Lipid Structures Acyl glyceride lipids consist of a glycerol core, a , calcium and . nous (or ‘sticky’) rice. included phosphatidyl R COO CH charged terminus of ethanolamine, monomethylethanolamine, dimethy- − −

(PC), phosphatidyl ethanolamine − −OOCRˈ lethanolamine or trimethylethanolamine (Choline) with two long chain or While rice also contains an abun- The stickiness of Japanese (PE) and phosphatidyl inositol (PI) CH2 O P O CH2CH2NHCH3 very long chain fatty acids that can be saturated or unsaturated R’ or R”. dant supply of dietary fiber, the rice―the way the individual ʺ − − (Figure B: Lipid Structures). Com- OH level of saturated fats, whose grains cling together―is due to − − − − Other over-consumption is thought to parison of the different cultivars its high proportion of starch. Phosphotidyl Inositol 4.5% be linked to lifestyle-related showed, Starch is itself composed of amy- 1.2% illnesses, is relatively modest. lose and amylopectin. Their pro- Phosphotidyl Ethanolamine Cooked rice is composed of portions can vary according to 1.3% about 60% water. Eating a por- the variety of rice, but in gen- tion of about 200 grams of pre- eral if the level of amylose Phosphotidyl Choline pared rice means you are eating is low and amylopectin 3.2% only about 80 grams of actual is high, you get sticky Free Fatty rice. The level of water content in rice―the kind of Acids (FAA) rice relative to the water content rice grown in 4.4% in other comparable foods Japan. means that the level of calories is less. Rice is a food that encourag- Tri Acyl es not only health, but beauty. Glyerides The commitment to improving 85.3% quality in Japanese rice continues unabated. This includes improv- ing the quality of rice itself, as well as, striving for cultivation that follows environmentally sus- tainable practices. Rice grain CROSS SECTION RICE PLANT quality is an important economic trait that influences rice produc- Oryza sativa L. rice plant is tion in many rice-producing separated into 5 major areas. Although the fat in rice components: grain is low (2–3%) and is con- centrated in the germ and bran Grain fractions, it is a key determinant of the processing and cooking

Flag Leaf FATTY ACID CONTENT

Free fatty acids (FFA) released by Tiller hydrolysis of the lipid during stor- age exert influences flavor and cooking quality of rice. To reduce risk of atherosclerosis, obesity, Stem () and maturity-onset diabetes, people are recommended that edible fat should have a reduced saturated fatty acid content and a linoleic acid (unsaturated fat) Lipid Roots con- content amounting to at least the grain, one third of the total fatty acids tent and stearic the flag leaf, (Graph Unsat vs Sat FFA). FAAs the tiller, contribute significantly to the acid, oleic overall acceptability of rice grains acid, and the stem (straw), by serving as sensory active linoleic acid con- and the roots. tents can be flavor agents in cooked rice. Rice Upon harvest, the grain contains the edible kernel generally contains a majority of significantly affected that is polished rice. unsaturated fats (Graph % fatty by variety and cropping acids). Edible oil is important as year with palmitoleic acid source of energy, essential fatty and linolenic acid contents can acids for cell structure and pros- be affected by cropping year (Fig- taglandins, and a vehicle for ure A: Long Chain Fatty Acids). oil-soluble vitamins and for cell structure and membrane func- tions and control of blood lipids.

O

H3C OH Palmitic acid (16:0) O

H3C OH Stearic acid (18:0) O H C 3 OH Oleic acid (18:1) O H C 3 OH Linoleic acid (18:2) O

H3C Fat Content OH Liniolenic acid (18:3)

Figure A: Long Chain Fatty Acids The major long chain fatty acids in rice plants include more abundant unsaturated fatty acids like Oleic and Linoleic acids compared to the less abundant and less healthy saturated fatty acids like Palmitic acid.

DID YOU KNOW? (STATISTA.COM, RICEPEDIA.ORG) REFERENCES

Integrated Metabolomics and Phytochemical Genomics Approaches for *Time-resolved Metabolomics Reveals Metabolic Modulation in Rice Foliage, Estimated Rice Revenue Japan JP Yen 808.5 Billion in 2020. Studies on Rice, Gigascience (5) 11 (2016), Y. Okazaki and K. Saito (RIKEN BMC Syst Biol. Jun 18; 2:51 (2008), S. Sato, M. Arita, T. Soga, T. Nishioka and M. Center for Sustainable Resource Science, Japan). Tomita (Keio University, Japan).

Using Metabolomic Approaches to Explore Chemical Diversity in Rice, *Atlas of Rice Grain Filling-Related Metabolism Under High Temperature: In Japan, the on average per person consumption is around 43 kg Mol Plant. Jan 8(1):58-67 (2015), M. Kusano, Z. Yang, Y. Okazaki, R. Joint Analysis of Metabolome and Transcriptome Demonstrated Inhibition of Nakabayashi, A. Fukushima, K. Saito, (RIKEN Center for Sustainable Resource Starch Accumulation and Induction of Amino Acid Accumulation, Plant Cell of rice per year, or around 117 grams a day. Science, Japan). Physiol. 51(5): 795-809 (2010), H. Yamakawa and M. Hakata (National Agricultural Research Center, Japan). Lipid Content and Fatty Acid Composition of Rice, JARQ Vol. 16 (4) (1983), H. Taira (National Food Institute, Japan). *Capillary-Electrophoresis Mass Spectrometry Based Metabolomics Volume rice produced in Japan is 1,822 mKg / year. Variation in Fatty Acid Distribution of Different Acyl Lipids in Rice Brans, (3), 505-514 (2011), H. Yoshida, T. Tanigawa I. Kuriyama, N. Yoshida, Y. Tomiyama and Y. Mizushina (Kobe Gakuin University, Japan). The Biochemistry of Rice Human Metabolome Technologies America, Inc.

24 Denby Road, Suite 217, Boston, MA 02134 p. 617-987-0554 f. 617-902-2434 Amino Acids and Polar Metabolites [email protected]

IMPROVING RICE PRODUCTION FLAVOR AND AROMA

Rice is one of our most important acids in 29S may increase the The flavor of rice differs by type est prices in the global important aroma compound in food crops and provides an es- plant susceptibility as host of rice and depends on if it has rice market. The rice. However, three other amine sential part of the daily dietary response to necrotrophic patho- been polished (i.e. brown or strength of fragrance heterocycles: 2-acetylpyrrole, intake for nearly half of the gens. On the other side, chloro- white rice) and, of course, cook- differs between pyrrole and 1-pyrroline also cor- world’s population. However, rice genic acid was primarily higher in ing methods. Those varieties and relate strongly with the production worldwide is affected 32R (resistant) strains. These me- considerations are obvious to the most production of aromaticity and by various biotic and environ- tabolomic results suggest that most of us. But flavor may also highly fra- related through biochemical mental stresses. Among all biotic the accumulation of chlorogenic vary by genetics, the growing grant stresses, pathogen infections are acid could be related to the resis- environment, type of fertilizer varieties tend considered as major constraints tance to pathogen as Chlorogenic and cultural practices, the timing to be the most Figure A: Chlorogenic acid is biosynthesized for rice production as 10 to 30 acid levels are maintained high in of draining and harvesting the from the amino acid Phenylalanine and popular among consumers. per cent of the annual rice har- 32R resistant strains perhaps to field, harvest moisture content, maybe a chemical that provides pathogen There is a fragrant rice variety vest is lost due to disease infec- prepare for defense against a rough rice drying conditions, final resistance to riceplants. called ‘Four Houses’, meaning Oxidative Stress Response tion. Of many different infec- pathogen infection in advance moisture content, storage condi- over 200 volatile compounds that when this rice is cooking, tions, a common and severe dis- (Figure A: Chlorogenic pathway). tions, degree of milling, and also present in rice. However, after its fragrance is enjoyed by ease in rice is sheath blight. Rice finally also washing and soaking over 30 years of research, little is people four houses away. sheath blight disease is caused practices and serving tempera- known about the relationships Emphasizing strong fra- by Rhizoctonia solani and has led ture of the cooked rice. There between the numerous volatile grance through variety to large scale crop losses, espe- are over a dozen different compounds and aroma/flavor. naming indicates the cially in Japan. Rhizoctonia solani aromas and flavors in rice. Analy- Fragrant (or aromatic) rice com- value that consumers is a fungus that can affect rice ses have mands the place on highly fra- production by reducing crop pro- found high- grant rice. Heat Degradation Maillard Reaction duction through the inhibition of 2-acetyl-1-pyrro- germination. line (2AP) is the ht However, genetic breeding has lig most B successfully introduced species h at e resistant varieties. Infection h S resistance strains (32R) have shown different physiological responses than infection suscep- tible rice lines (29S). Several key The aroma of rice can originate from a major metabolie, 2-AP, enzymes and metabolites in the that is biosynthesized from polyamines by oxidative stress phenylpropanoid phenylalanine or through (glucose) or amino acid (ornithine) by heat degradation. Other chemical intermediates includ- ammonia lyase enzyme and shi- ing 2-acetylpyrrole and 1-pyrroline may contribute to kimate pathways are observed to oder. have increased after R. solani infection. Phenylpropanoid, pathways. Oxidative stress trans- amino acid and shikimate path- forms putrescine to ways are involved in plant de- 4-aminobutanal (4-ABA), 4-ABA fense mechanisms during patho- can then further convert to γ-am- gen infection. Plant metabolites, inobutyric acid (GABA), especially amino acids and phe- 2-acetylpyrrole or 1-pyrroline. nols that are involved in plant de- GABA is a signaling metabolite fense to R. solani infection while 2-acetylpyrrole can con- include glutamate, GABA, gly- tribute to aroma. 1-pyrroline cine, histidine, phenylalanine, can combine with methylglyox- serine, tryptophan, tyrosine, al to from 2-AP. In addition, and pipecolic acid that are 1-pyrroline can be formed abundant in 29S (susceptible) from the heat denaturation by species and influenced by the a maillard reaction from amino presence of R. solani. The en- acids proline and ornithine. hancement of specific amino Methylglyoxal can be formed from the heat decomposition of glucose. Together, these POLAR METABOLITES metabolomic pathways provide new insights into the production of 2AP, and evidence for under- The metabolites in rice can be standing the pathways leading to categorized into two groups, the accumulation of aroma in fra- primary and secondary. Primary grant rice. metabolites include polar metab- olites, glucose, , lipids, vitamins, free amino acids and free fatty acids, those needed to provide fuel and energy for cellu- CROSS SECTION RICE GRAIN lar growth, while secondary metabolites include complex and purine metabolites that include flavo- bases; group noids and terpenes that adjust to B included environmental stress (water, salt, organic acids and Cereal Germ temperature), as well as, provid- sugar phosphates; ing additional health benefits for group C included nucle- Bran Residue human consumption. Among otides and coenzymes; and these primary metabolites, the group D containing neutral Bran concentrations of certain free sugars (Chart A: Prominent amino acids (FAA) have been Concentrations of Polar Metabo- Chaff linked directly to the taste scores lites nmol/g (wt)). of rice. This apparent relation- ship between the palatability of cooked rice and the FAA profile of Glucose Metab Other rice grains has generated a grow- 1.0% 0.6% ing interest in research on the physiological basis of FAA accu- mulation in rice grains. FAAs contribute significantly to the overall acceptability of rice grains by serving as sensory active Energy Metabolism flavor agents in cooked rice. FAA accumulation is a complicated process involving a complex of biochemical networks and control mechanisms. Metabo- lites existing in glycolysis, the tricarboxylic acid cycle, the pentose phosphate pathway (oxidative and reductive), photo- respiration, and amino acid biosynthesis, can be classified into four groups. Group A contained amino acids, amines, Chart A: Prominent Concentrations of Polar Metabolites nmol/g (wt) Graph B: Dry Weight Japonica Rice (mg/100g)

DID YOU KNOW? (STATISTA.COM, RICEPEDIA.ORG) REFERENCES

Simultaneous Determination of the Main Metabolites in Rice Leaves Metabolomics and Genomics Combine to Unravel the Pathway for the Japan is 100% self-sufficient in rice, but only 14% and 8% Using Capillary Electrophoresis Mass Spectrometry and Capillary Elec- Presence of Fragrance in Rice, Sci Rep. (7) 8767 (2017), V.D. Daygon, M. trophoresis Diode Array Detection, The Plant Journal (40) 151-163 (2004), Calingacion, L.C. Forster, et. al. (The University of Queensland, Australia). beans. S. Sato, T. Soga, T. Nishioka and M. Tomita (Keio University, Japan). Metabolite profiling of sheath blight disease resistance in rice: in the Metabolome Analysis of Rice Using Liquid Chromatography-Mass Spec- case of positive ion mode analysis by CE/TOF-MS, Plant Production trometry for Characterizing Organ Specificity of Flavonoids with Ant-In- Science 19:2, 279-290 (2016) W-S. Suharti, A. Nose and S-H. Zheng (Saga 85% of the 2.3 million farmers in Japan produce rice. flammatory and Anti-0xidant Activity, Chem. Pharm. Bull. 64(7) 952 – 956 University, Japan). (2016), Z Yang, R. Nakabayashi, T. Mori, S. Takamatsu, S. Kitanaka and K. Rice Sheath Blight: Major Disease in Rice, Int.J.Curr.Microbiol.App.Sci Saito (RIKEN Center for Sustainable Resource Science, Japan). Special Issue-7: 976-988 (2018), V. Turaidar, M. Reddy, R. Anantapur, K. N. The average rice farmer works only 1.65 acres. Krupa, N. Dalawai, C. A. Deepak and K. M. H. Kumar (University of Agricultur- Variation in Free Amino Acid Profile Among Some Rice Cultivars, Breed- al Sciences, India). ing Science 60: 46-54 (2010), J.Kamara, S. Konishi, T. Sasanuma and T. Abe (Yamagata University). *Capillary-Electrophoresis Mass Spectrometry Based Metabolomics