Sanjeet
Plants have great importance due to their nutritive value and they are the major source of medicines which play an important role in the human history. Plants synthesize primary metabolites (proteins, fats, nucleic acids and carbohydrates) by simple substances such as water, carbon dioxide, nitrogen and a number of inorganic salts in small amounts. These primary metabolites are transformed into secondary metabolites (alkaloids, steroids, terpenoids, saponins, flavonoids etc.,) that are used as drugs. Tuber crops are the most important food crops after cereals. They are major sources of energy in developing countries with first population growth and high urbanization rates. Tuber crops find an important place in the dietary habits of small and marginal farmers especially in the food security of tribal population. Tuber cops are important in several aspects. They have a higher biological efficiency as food producers and show the highest rate of dry matter production per day per unit area among all the crops. Tuber crops properties to cure many ailments or check their incidence. Many tropical tuber crops are used in the preparation of stimulants, tonics, carminatives, and expectorants. India holds a rich genetic diversity of tropical tuber crops viz. Cassava, Sweetpotato, Aroids, Yams, and several minor tuber crops. In Odisha wild tuber crops means mainly Dioscorea species due to availability and high rate of consumption in the forests of the states. Other main wild tuber crops are Amorphophalus, Colocasia, and Alocasia species.
1.1. Food Problem
“The World Food Problem” is a phrase familiar from the 1970s, but one that has largely lain dormant for the last decade: throughout the 1980s, concern was less with world food supplies and prices than with the problem of hunger and with individual access to food. The International Conference on Nutrition in 1992 was a high-water mark for this perspective. Hunger has become a global problem of our times. It is a gift of modern development to our society. The present day development process has Strengthened the control of the privileged class over the resources of the earth. The wealthiest 26% of the world's population consumes 80-86% of non-renewable and 34-50% of the wood supplies of the world. ("Our common future:- World Commission of the Environment & Development"). Late Prime Minister, Smt. Indira Gandhi once said in the
Stockholm conference on Environment that "poverty" and "hunger" are the two most pollutants of developing countries where as affluence is the root cause of pollution in developed countries. We now have the capacity to apply science and technology to reduce poverty and improve food security. This paper discusses how science can be used to safely and effectively reduce poverty and improve food security in India and particular in Odisha. In nature, there are uncountable wild and cultivated food plants. Wild food plants are not more explored in India and particularly in Odisha. In Odisha there are number of wild food plants, which are used as food among tribal, rural and even urban communities. Among wild food plants, wild tuber crops play an important role to provide food supplement. It is main dietary food during critical time, famine, and flood and off agricultural seasons.
1.2. Wild Tuber Crops
Tubers are various types of modified plant structures that are enlarged to store nutrients. These plant parts are used as vegetables known as tuber crops. The tuberous plants that are wild in nature and ecology are known as wild tuber crops. In Odisha, several tribal communities depend on Wild Tuber Crops as food for their daily food requirement and also during the period of food shortage and famine. They are used by plant to survive the winter or dry months, to provide energy and nutrients for regrowth during the next growing season, and as a means of sexual reproduction. There are both stem and root tubers.
Stem tuber
A stem tuber forms from thickened rhizomes or stolons. The tops or sides of the tuber produce shoots that grow into typical stems and leaves and the under sides produce roots. They tend to form at the sides of the parent plant and are most often located near the soil surface. The below-ground stem tuber is normally a short-lived storage and regenerative organ developing from a shoot that branch off a mature plant. The offspring or new tubers are attached to a parent tuber or form at the end of a hypogeogenous rhizome. In the fall the plant dies except for the new offspring stem tubers which have one dominant
bud, which in spring regrows a new shoot producing stems and leaves, in summer the tubers decay and new tubers begin to grow. Some plants also form smaller tubers and/or tubercules which act like seeds, producing small plants that resemble (in morphology and size) seedlings. Some stem tubers are long lived such as those of tuberous begonia but many tuberous plants have tubers that survive only until the plants have fully leafed out, at which point the tuber is reduced to a shrivelled up husk.
Stems tubers generally start off as enlargements of the hypocotyls section of a seedling but also sometimes include the first node or two of the epicotyls and the upper section of the root. The stem tuber has a vertical orientation with one or a few vegetative buds on the top and fibrous roots produced on the bottom from a basal section, typically the stem tube has an oblong rounded shape.
Root tubers
A tuberous root or storage root is a modified lateral root, enlarged to function as a storage organ. The enlarged area of the root-tuber, or storage root, can be produced at the end or middle of the root or involve the entire root. It is thus different in origin but similar in function and appearance to a stem tuber. Examples of plants with notable tuberous roots include the sweet potato, cassava, yam, and dahlia. Root tubers are used to perennialize the plant, they store nutrients over periods when the plant cannot actively grow, thus permitting survival from one year to the next. The thickened roots are storage organs that differ from stem tubers. The massive enlargement of secondary roots typically represented by Sweet potato, (Ipomoea batatas), have the internal and external cell and tissue structures of a normal root, they produce adventitious roots and stems which again produce adventitious roots. In root-tubers, there are no nodes and internodes or reduced leaves. Root tubers have one end called the proximal end, which is the end that was attached to the old plant; this end has crown tissue that produces buds which grow into new stems and foliage. The other end of the root tuber is called the distal end, and it normally produces unmodified roots. In stem tubers the order is reversed, with the distal end producing stems. Tuberous roots are biennial in duration: the first year the plant produces root-tubers, and at the end of the growing season, the plant shoots often die, leaving the newly generated tubers. The next growing season, the root-tubers produce new shoots. As the shoots of the new plant grow, the stored reserves of the root-tuber are consumed in the production of new roots, stems and reproductive organs; any remaining root tissue dies concurrently to the plant’s regeneration of next generation of root-tubers.
Root-tubers, along with other storage tissues that plants produce, are consumed by animals as a rich source of nutrients. The root tubers of Arrowhead plants of the genus Sagittaria are eaten by ducks. Plants with root tubers are propagated in late summer to late winter by digging up the tubers and separating them, making sure that each piece has some crown tissue for replanting.
Wild tuber crops in world
Roots and tubers crops are present in the diet of people almost all over the world, the best known being the potato (Solanumtuberosum L.) and cassava (ManihotesculentaCrantz), both of which are of South American origin but are now widely distributed. The potato was domesticated in the Andean region, but there are several species of roots and tubers which originated there and which are still of importance to Andean people, such as yacon(PolymniasonchifoliaPoeppig&Endlicher), white carrot (ArracaciaxanthorrhyzaBrancrof.), mauka (Mirabilis expansa Ruiz &Pavón), maca (LepidiummeyeniiWalp.), achira (Canna edulis Ker Grawler), oca (Oxalis tuberosus Molina), mashua (Tropaeolumtuberosum R. & P.)and ulluco (Ullucustuberosus Lozano).
Wild tuber crops in India
The two hot spots of global biodiversity viz. North Eastern Himalayas and Western Ghats and particularly rich in wild relatives of tropical tuber crops. Safe conservation and sustainable use of plant biodiversity is essential for meeting the present and future needs of tuber crop improvement in India. The Central Tuber Crops Research Institute, Thiruvananthapuram initiated collection of tuber crops germplasm and wild relatives from all over India from 1963 onwards.
There are five major areas of distribution of root and tuber crops in India. These are
I. South-western hilly and coastal region
II. Southern peninsular region
III. Eastern coastal region
IV. North-eastern region and
V. North-western region.
The important tuber crops grown in India and the regions of biodiversity are given in the table below.
Common
Name
|
Scientific
Name
|
Family
|
Vernacular
Name
|
Places/Areas
Grown
|
CASSAVA
|
Manihotesculenta
Crantz
2n=36
|
Euphorbiaceae
|
Maracheenikizhangu& kappa(M); Maravallikizhangu&Ezhalaikizhangu(T);Maraganasu(K); Karrapendalamu(TE)
|
Southern region occasionally in North eastern & Western regions
|
SWEET
POTATO
|
Ipomoea batatus (L.)Lam.
2n=90
|
Convolvulaceae
|
Mithaalu&Shakarkand(H);
Cheenikizhangu&Madhurakizhangu(M);Shakkareivallikizhangu(T); Genasu(K); Chelagada(TE); Ratalu(MR); Lalalu&Rangaalu(B)
|
Introduced and found all over but mostly concentrated in Eastern U.P, Bihar, West Bengal and Odisha.
|
GREATER YAM
|
Dioscoreaalata
(L.)
2n = 40, 60, 80
|
Dioscoreaceae
|
PindAaluk(H); Kachil&
Kavithu(M); Peruvalli
kizhangu&Vetrilaivalli
kizhangu (T)
|
South & North
Eastern region
|
WHITE YAM
|
Dioscorea
rotundata (Poir.)
2n =40
|
Dioscoreaceae
|
SafedAaluk (H);
African kachil(M);
African vallikizhangu(T),
|
Introduced to
India and
spread to South
and North
Eastern region
|
LESSER
YAM
|
Dioscorea
esculenta(Lour.)
Burk.
2n =30-100
|
Dioscoreaceae
|
Kayu(H) ; Cheruvalli
kizhangu,
Cherukizhangu ,
Nana kizhangu,
Mukkizhangu(M) ;
Siruvallikizhangu (T)
|
South, N.E &
Eastern region
|
POTATO YAM
|
D. bulbifera var.
Sativa
2n = 40,60
.
|
Dioscoreaceae
|
Mekkachil&
Erachikachil (M)
|
Southern, North
East and
Eastern region
|
TARO
|
Colocasia
esculenta(L.)
Schott
2n =28,42
|
Araceae
|
Arvi , Kachalu&
Ghuiya(H); Kachu(S);
Chempu(M);
Seppan-kizhangu (T);
Kachchi(K); Shamagadde(K);
Chamadumpa&
Chemagadda(TE);
Alu(MR); Kachu(B)
|
Throughout
India with
greater diversity
in North east,
Eastern region
and South
|
TANNIA
|
Xanthosoma
Sagittifolium
2n =26
|
Araceae
|
Palchempu(M)
|
South and North
eastern region
|
ELEPHANT
FOOT YAM
|
Amorphophallus
Paeoniifolius
(Dennst.) Nicolson
2n =28
|
Zamim-kand&
Gimmikand(H); Arsaghna&Balukand(S); Chena(M)
Karnai-kilangu(T);
Suvarnagadde(K);
Kanda(TE);
Suran(MR); Ol(B)
|
Southern, North; East and Eastern region
| |
CHINESE
POTATO
|
Solenostemon
Rotundifolius
(Poir.) J.K. Morton
Plectranthus
Rotundifolius
2n = 60
|
Labiatae
|
Koorkakizhangu(M);
Simkizhangu(T)
|
Southern parts
of India
|
YAM BEAN
|
Pachyrrhizus
erosus(L.)
2n=26
|
Leguminosae
|
MisriKand (H); Pachi
kizhangu (M)
|
North Eastern
region
|
WINGED
BEAN
|
Psophocarpus
etragonolobus (L.)
D.C.
2n =26
|
Leguminosae
|
Chadhurapayar&
Goa payar (M)
|
South & North
East
|
WEST
INDIAN
ARROW
ROOT
|
Maranta
arundinaceaeL.
2n = 48
|
Marantaceae
|
Koova (M)
|
Adapted to plain
areas with high
rain fall;
shade loving
|
H – Hindi, S- Sanskrit, M-Malayalam, MR-Marathi, TE-Telugu, T-Tamil,
K-Kannada, B-Bengali, NE – North east.
1.3. Wild Tuber Crops of Odisha
Wild tuber crops are easily available in all forest parts of Odisha. In Odisha wild tuber crops means mainly Dioscorea species due to availability and high rate of consumption in the forests of the states. Other main wild tuber crops are Amorphophalus, Colocasia, and Alocasia species. They are the source of food as well as money for Tribal and Rural communities. Majority of tribal population of Odisha lives in forest ecosystem and has its own sociocultural pattern, tradition and typical food practices. They grow food grains for 8-10 months, however, for rest, they depend on the forest. Mostly their diet comprises variety of unconventional foods, viz, edible forms of flowers, fruits, tubers, leaves etc. Tuber crops are considered as the third important crops after cereal and grain legume. So in times of scarcity or when the staple food is in short supply, people are mostly dependent upon various types of tuber crops. Tuber crops play vital role in food security and nutrition of not only tribal and lower income group people of Odisha but sweet potato, yam crops are common ingredients in vegetable uses in Odisha and the main vegetable in the “Prasad” of Lord Jagannath.
1.4. Value of Wild Tuber Crops as Food as well as Medicine
Forest is treasury of several wild foods which could be next supplement in our diet and have ability to fight against food security and different microbial pathogen. Wild tuber crops have great economic value as they are used as food as well as traditional medicine.
Many infectious diseases are known to be treated with herbal remedies throughout the history of mankind. Plants still continue to be almost the exclusive source of antimicrobial compounds for the majority of world’s population. The WHO reported that 80% of the world’s population rely chiefly on traditional medicine and a major part of traditional therapies involve the use of plant as a antimicrobial agent against various types of infections caused by microbes. Discovery of antimicrobial compounds were one of the most important findings of the 20th century. These natural compounds found in many plants have been used to treat human diseases caused by microbes. Over the last decade, there has been rapid growth in the use of alternative medicines. Natural products, including many plants traditionally used as medicinal herbs against microbial infections are being revaluated as key components in future microbial science. Odisha the most picturesque state in eastern India occupies a unique place in the tribal map of the country having largest number of tribal communities. Almost all tribal groups have been using wild tuber crops as traditional medicine. Wild tubers are highly acrid and cause irritation in throat and mouth due to excessive amount of calcium oxalate present in tubers still than tribal peoples using more and more wild tubers as food and traditional medicine with traditional method of processing, therefore systemic rigorous scientific studies of frequently used tubers are needed.
In Odisha, wild tuber crops contain good amount of carbohydrates, fibre and other nutrients as well as anti-nutritional compounds with different types of bioactive which revels the anti-microbial and other pharmacological activity. Tubers are eaten for the treatment of poor appetite, asthma and cough among tribal community.
2.1. Definition of Biochemical
The four main classes of molecules in biochemistry are carbohydrates lipids, proteins, and nucleic acids. Many biological molecules are polymers: in this terminology, monomers are relatively small micromolecules that are linked together to create large macromolecules, which are known as polymers. When monomers are linked together to synthesize a biological polymer, they undergo a process called dehydration synthesis. Different macromolecules can assemble in larger complexes, often needed for biological activity.
2.2. Major Biochemical
Carbohydrates are made from monomers called monosaccharide. Some of this monosaccharide includes glucose (C6H12O6), fructose (C6H12O6), and deoxyribose (C5H10O4).
The function of carbohydrates includes energy storage and providing structure. Sugars are carbohydrates, but not all carbohydrates are sugars. There are more carbohydrates on Earth than any other known type of biomolecule; they are used to store energy and genetic information, as well as play important roles in cell to cell interactions and communications.
Proteins are very large molecules – macro-biopolymers – made from monomers called amino acids. There are 20 standard amino acids, each containing a carboxyl group, an amino group, and a side chain (known as an "R" group). The "R" group is what makes each amino acid different, and the properties of the side-chains greatly influence the overall three-dimensional conformation of a protein. When amino acids combine, they form a special bond called a peptide bond through dehydration synthesis, and become a polypeptide or protein.
The term lipid comprises a diverse range of molecules and to some extent is a catchall for relatively water-insoluble or nonpolar compounds of biological origin, including waxes, fatty acids fatty-acid derived phospholipids sphingolipids glycolipids, and terpenoids (e.g., retinoid and steroids). Some lipids are linear aliphatic molecules, while others have ring structures. Some are aromatic, while others are not. Some are flexible, while others are rigid.
Most lipids have some polar character in addition to being largely nonpolar. In general, the bulk of their structure is nonpolar or hydrophobic ("water-fearing"), meaning that it does not interact well with polar solvents like water. Another part of their structure is polar or hydrophilic ("water-loving") and will tend to associate with polar solvents like water. This makes them amphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case of cholesterol, the polar group is a mere -OH (hydroxyl or alcohol). In the case of phospholipids, the polar groups are considerably larger and more polar.
Lipids are an integral part of our daily diet. Most oils and milk products that we use for cooking and eating like butter, cheese, ghee etc., are composed of fats vegetable oils are rich in various polyunsaturated fatty acids (PUFA). Lipid-containing foods undergo digestion within the body and are broken into fatty acids and glycerol, which are the final degradation products of fats and lipids.
A nucleic acid is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in all living cells and viruses. Aside from the genetic material of the cell, nucleic acids often play a role as second messengers as well as forming the base molecule for adenosine triphosphate, the primary energy-carrier molecule found in all living organisms.
Nucleic acid, so called because of its prevalence in cellular nuclei, is the generic name of the family of biopolymers. The monomers are called nucleotides, and each consists of three components: a nitrogenous heterocyclic base (either a purine, or a pyrimidine), a pentose sugar, and a phosphate group. Different nucleic acid types differ in the specific sugar found in their chain (e.g., DNA or deoxyribonucleic acid contains 2-deoxyribose). Also, the nitrogenous bases possible in the two nucleic acids are different: adenine, cytosine, and guanine occur in both RNA and DNA, while thymine occurs only in DNA and uracil occurs in RNA.
2.3. Biochemicals and Food value
Several nutritional disorders due to deficiency of Vitamin A, Vitamin C and Calcium could be easily alleviated by consumption of root and tuber crops like cassava, sweet potato, yam and aroids. Root and tuber crops are rich in Vitamins and Minerals. On an average cooked yam have about 2% protein, cassava and sweet potato provide ascorbic acid (Vitamin C) where as cereal based foods have none. Sweet potato also contains important amino acids while
rice is deficient in lysine. The orange and yellow fleshed sweet potato roots and green tops are good source of Vitamin A, which can prevent night blindness and malnutrition prevalent. Besides, sweet potato is rich in anti- oxidant, nutrients like B- carotene, ascorbic acid (Vitamin C), tocoferol (Vitamin E), which can prevent coronary disorder and cancer.
Proximate composition of tuber crops (Grams per 100 g on dry weight basis)
Tuber crops
|
Protein
|
Fat
|
Minerals
|
Fibre
|
Carbohydrates
|
Sweet potato
|
3.6
|
0.8
|
3.0
|
2.3
|
88.0
|
Cassava
|
1.7
|
4.9
|
2.5
|
1.5
|
84.9
|
Yam
|
4.7
|
0.3
|
5.3
|
3.3
|
86.6
|
Colocasia
|
11.6
|
0.4
|
6.3
|
3.7
|
78.5
|
Elephant foot yam
|
5.6
|
0.5
|
3.8
|
3.8
|
86.3
|
3. Bioactive Compounds in Plants
Bioactive compounds in plants can be defined as secondary plant metabolites eliciting pharmacological or toxicological effects in man and animals.Secondary metabolites are produced within the plants besides the primary biosynthetic and metabolic routes for compounds associated with plant growthand development, and are regarded as products of biochemical “side tracks” inthe plant cells and not needed for the daily functioning of the plant. Several ofthem are found to hold various types of important functions in the living plantssuch as protection, attraction or signalling. Most species of plants seem to be capable of producing such compounds. Secondary metabolites are produced within the plants besides the primary biosynthetic and metabolic routes of compounds aimed at plant growth and development, such as carbohydrates, amino acids, proteins and lipids. They canbe regarded as products of biochemical “side tracks” in the plant cells and notneeded for daily functioning of the plant.Phylogenetically, the secondary bioactive compounds in plants appear to berandomly synthesised – but they are not useless junk. Several of them are foundto hold important functions in the living plants.That plants producing bioactive compounds seem to bethe rule rather than the exception. Thus, most plants even common food andfeed plants are capable of producing such compounds. However, the typicalpoisonous or medicinal plants contain higher concentrations of more potentbioactive compounds than food and feed plants.
3.1. What are Plant Bioactive Compounds/Secondary metabolites
• Plants make a variety of less widely distributed compounds such as morphine, caffeine, nicotine, menthol, and rubber. These compounds are the products of secondary metabolism, which is the metabolism of chemicals that occurs irregularly or rarely among plants, and that have no known general metabolic role in plants.
• Secondary metabolites or secondary compounds are compounds that are not required for normal growth and development, and are not made through metabolic pathways common to all plants.
• Most plants have not been examined for secondary compounds and new compounds are discovered almost daily.
• Secondary compounds are grouped into classes based on similar structures, biosynthetic pathways, or the kinds of plants that make them. The largest such classes are the alkaloids, terpenoids, and phenolics.
• Secondary compounds often occur in combination with one or more sugars. These combination molecules are known as glycosides. Usually the sugar is a glucose, galactose or rhamnose. But some plants have unique sugars. Apiose sugar is unique to parsley and its close relatives.
• The most common roles for secondary compounds in plants are ecological roles that govern interactions between plants and other organisms.
• Many secondary compounds are brightly colored pigments like anthocyanin that color flowers red and blue. These attract pollinators and fruit and seed dispersers.
• Nicotine and other toxic compounds may protect the plant from herbivores and microbes.
• Other secondary compounds like rubber and tetrahydrocannabinil (THC) from cannabis plants have no known function in plants.
3.2. Types of Bioactive Compounds
Bioactive compounds in plants are classified according to different criteria. A
presentation based on clinical function – their pharmacological or toxicological effects – is relevant for the clinician, pharmacist or toxicologist. An approach based on biological effects is complicated by the fact that the clinical outcome is not exclusively connected to chemically closely related compounds; even chemically very different molecules might produce similar clinical effects. A botanical categorisation based on families and genera of the plants producing the bioactive compounds might also be relevant, as closely related plant species
most often produce the same or chemically similar bioactive compounds.
Phenolics are broadly distributed in the plant kingdom and are the most abundantsecondary metabolites of plants. Plant polyphenols have drawn increasing attention due totheir potent antioxidant properties and their marked effects in the prevention of variousoxidative stress associated diseases such as cancer.
Phenolics are compounds possessing one or more aromatic rings with one or more hydroxyl groups.They are broadly distributed in the plant kingdom and are the most abundant secondary metabolites ofplants. Plant phenolics are generallyinvolved in defense against ultraviolet radiation or aggression by pathogens, parasites and predators, aswell as contributing to plants’ colors. They are ubiquitous in all plant organs and are therefore anintegral part of the human diet. Phenolics are widespread constituents of plant foods (fruits, vegetables, cereals, olive, legumes, chocolate, etc.) and beverages (tea, coffee, beer, wine, etc.), and partiallyresponsible for the overall organoleptic properties of plant foods. For example, phenolics contribute to
ALKALOIDS
Alkaloids are naturally occurring chemical compounds containing basic nitrogen atoms. The name derives from the word alkaline andwas used to describe any nitrogen - containing base. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals and are part of the group of natural products (alsocalled secondary metabolites) . Many alkaloids can be purified fromcrude extracts by acid - base extraction. Many alkaloids are toxic toother organisms. They often have pharmacological effects and areused as medications, as recreational drugs, or in entheogenic rituals. Examples are the local aesthetics and stimulant cocaine, the stimulantcaffeine, nicotine, the analgesic morphine, or the antimalarial drugquinine. Some alkaloids have a bitter taste.
Tannin
Tannin (also known as vegetable tannin, natural organic tannins or sometimes tannoid, i.e. a type of biomolecule, as opposed to modern synthetic tannin) is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids. The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather. However, the term "tannin" by extension is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyl) to form strong complexes with proteins and other macromolecules.
There are three major classes of tannins.
1. hydrolysable tannins
2. non-hydrolysable tannins (condensed tannins)
3. pseudo tannins
Hydrolysable tannin
A hydrolysable tannin or pyrogallol -type tannin is a type of tannin that, on heating with hydrochloric or sulphuric acids, yields gallic or ellagic acids.. At the center of a hydrolysable tannin molecule, there is a carbohydrate (usually D-glucose but also cyclitols like quinic or shikimic acids). The hydroxyl groups of the carbohydrate are partially or totally esterified with phenolic groups such as gallic acid in gallotannins or ellagic acids in ellagitannins. Hydrolysable tannins are mixtures of polygalloyl glucoses and/or poly-galloyl quinic acid derivatives containing in between 3 up to 12 gallic acid residues per molecule.Hydrolyzable tannins are hydrolyzed by weak acids or weak bases to produce carbohydrate and phenolic acids.
Terpenoids
Terpenoids are dimers and polymers of 5 carbon precursors called isoprene units (C5 H8). Terpenoids often evaporate from plants and contribute to the haze we see on hot sunny days. They are expensive to make; they often take 2% of the carbon fixed in photosynthesis; carbon that could otherwise be used for sugars.
Carotenoids
Carotenoids belong to the group of bioactives known as the terpenoids, one of the most diverse classes of natural products, comprising over 30,000 different compounds including flavours, fragrances, insect attractants and antibiotics. Carotenoids are structurally diverse compounds that are classified as tetraterpenes. In plants, carotenoids work alongside chlorophyll in photosynthesis, extending the range of light that can be absorbed by the photosynthetic pigments, and giving plant foods that contain carotenoids their distinctive red or orange colours (e.g. lycopene in red tomatoes, lutein in yellow peppers and α- and ß-carotene in orange carrots).
Other sulphur containing compounds
Onions and garlic, which are Allium species, have been an important part of the human diet for thousands of years. Sulphur containing compounds (Salkyl cysteine sulphoxides) are found in all varieties, along with flavonols such as quercetin. It has been suggested that the sulphur containing compounds allicin and ajoene are responsible for claimed health benefits of garlic.
3.3. Importance
Identifying bioactive compounds and establishing their health effects are active areas of scientific inquiry. There are exciting prospects that select bioactive compounds will reduce the risk of many diseases, including chronic diseases such as cardiovascular disease. Recent findings have established that cardiovascular disease is a disease of inflammation, and consequently is amenable to intervention via molecules that have anti-inflammatory effects.
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