Chemotaxonomy of Medicinal plantCHEMOTAXONOMY:Definition:-The approach of taxonomy in which chemical nature of plants are used in developing classification or in solving taxonomical problems is called chemotaxonomy ,chemosystematics, chemical taxonomy ,chemical plant taxonomy or plant chemo taxonomy are the common names of chemotaxonomy. It gives the close relationship between chemical constituents of plants and their taxonomical status. Chemotaxonomy establishes relationship between the position of the plant and exact understanding of biological evaluation and natural relation ship. Depending upon chemical evidence, plants are classified accurately as alkaloids, flavonoids, carotenoids, polysaccharides, terpenoids, fatty acids (proteins). Purpose of chemotaxonomy:Chemotaxonomy has been used in all levels of classification. Chemical evidences have been used in all the groups of the plant kingdom starting from simple organism like fungi and bacteria up to the most highly advanced and specialized group of Angiosperms. The evidence is used in classification of plants into 2 main purposes. 1. To improve the existing system of plants differentiation. 2. To develop the present day knowledge of natural relationship of plants. o Chemical characters and their use in taxonomy: - Naik divided the chemical characters into 3 categories. 1. Directly visible characters:-Starch grains, raphides, silica ,gypsum ,etc 2. chemical test characters:-phenolic ,betalins, oil fats, waxes ,alkaloids 3. Proteins o On the other hand in 1987 some authors divided the natural chemicals plants products into 2 groups on the basis of molecular weight. 1. Low molecular weight compounds:- That is a molecular weight of 1000 or less than 1000 called as Micromolecules. Ex:-Amino acids, alkaloids, fatty acids, terpenoids, flavonoids. 2. High molecular weight compounds:- with a molecular weight of more than 1000 called as Macromoecules. Ex:-proteins, DNA, RNA complex , Polysaccharides. History of Chemotaxonomy: The concept of classification of plant based on chemical character is not new. it is started in 15th &16th centuries by anatomist Newmann, Grew & James petitver. They recognized similar chemicals or medicinal effects of umbelliferous plants. (carminative)

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Chemotaxonomy of Medicinal plant Greshoff in 1909, suggested that chemical characters should be included in natural classification. Baker and Smith in 1920, worked on single genus Eucalyptus (176)-collected morphological and chemical data and finally concluded on the morphological basis the feather contended leaves having more pinene in their volatile oil. Mc Nair in 1935, says that more closely related taxas produce more similar chemical products. Beale and coworkers in 1940, surveyed 32 species of Tulip for anthocyanin contents and distribution of group of compounds in genus as a taxonomic characters. Conden et.al. in 1944, develop paper chromatography. Bat & smith in 1948, showed that paper chromatography applied to analysis of plant pigments.

Clasification of Chemotaxonomy: based on the taxonomical and chemical knowledge: Descriptive taxonomy Dynamic taxonomy Serotaxonomy Descriptive taxonomy deals with the classification of plant and secondary metabolite and other products like sugar & amino acid. It is also concerned with evolutionary change, chemical convergence and divergence in the plant. Dyanamic taxonomy is based on biosynthetic pathway. Serotaxonomy or semantics is based on pathway of specific proteins and amino acids sequencing in proteins. It is further classified as;1. 2. 3. DNA- primary semantics RNA-secondary semantics Proteins-tertiary semantics

Principle of chemotaxonomyChemical classification of plants is based on their chemical constitutions; i.e. on their molecular characteristics. The same type of metabolites can be the product of two quite different pathways. Different plants sometimes contain secondary constituents belonging to different classes of compound but biosynthetically appear to be same.

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Chemotaxonomy of Medicinal plantChemotaxonomic studies include the investigation of the pattern of compound occurring in the plant and preferentially in all various individual parts of plant such as the bark , wood, leaves , root, cuticles and seed. Such integrated investigations are necessary in order to obtain really convincing evidence for the relationship of plants. Before any important conclusions are drawn about the presence or absence of a particular compound adequate sampling of a large number of members of the species at different stages of development and growing in different environment should be made.

Different stages of Chemotaxonomic investigation:1. 2. 3. 4. Choice of group, taxonomic survey and sound sampling modification of suitable chemical techniques Analysis of all material interpretation of data and its comparison from all other sources

According to the interest of investigation the relative stages may vary (for taxonomy, phylogenetic & chemistry) Sound sampling: an understanding of natural variation within a group and phylogenies are helpful in good sampling. The collection of plant sample done: By the help of professional plant collector From national garden and national herbarium From professional plant sellers Personal travel & collection Modification of suitable chemical techniques: Depending upon the choice of investigator, what class of material is likely to exhibit useful variation at the taxonomic level. Intraspecific chemical variation Qualitative and quantitative variation between different parts of same plant Variation due to Seasonal and environmental fluctuation Analysis of the material: qualitative and quantitative analysis is done by phytochemical screening, electrophoresis, chromatography, finger print, and spectroscopy. All the spectra obtained from different technique should be analyses.

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Chemotaxonomy of Medicinal plantInterpretation and comparison of data: All the data obtained from chemistry, phylogenetic and taxonomy is interpreted & depending upon the evidence the classification of plant should be reconsidered. If only a minor change occurs in the match of chemical and other variation then the classification is essentially confirmed.

Three broad categories of compounds are used in Chemotaxonomy:- .1. Primary metabolites 2. Secondary metabolites, 3. Semantices. Primary metabolites, are parts of vital metabolic pathways, most of them are of universal occurrence and is utilized by the plant itself for growth and development. Example; starch, chlorophyll, aleurone grain, citric acid, aconitic acid, etc. CARBOHYDRATES IN CHEMOTAXONOMY: Carbohydrates are universal constituents of living organism and widely distributed in the plant. Thus, carbohydrate is having little chemotaxonomic significance, but some of the rare sugars having chemotaxonomic significance. Eg. 6-Deoxy hexose; 2, 6-Dideoxy hexose; Gentiobiose & Gentianose; Polyols and polysaccharides,

6-Deoxy hexose: It occurs in the form of methyl ether that is restricted to certain family. So the presence or absence of such sugars is help in the study of phylogenetic relationship. Ex. L-thevetose and D-digitalose are used as cardiotonic. 2, 6-Dideoxy hexose: Cardinolides containing D-digitoxose, L-oleandrose, D-cyamarose sugars are particularly abundant in family apocynaceae and asclepiadaceae (both are group of unrelated family). Gentiobiose and gentianose: These are uncommon sugar in amygdalin, characteristic of family rosaceae and gentianaceae respectively. Polyols: Among monosaccharide derivatives eg. D-sorbitol, D-mannitol and mesoxylitol; D-sorbitol occurs naturally in fruits of various rosaceae family. The presence or absence of these sugar alcohol in rosaceae can be utilized to identify subfamily. It is reported that sorbitol is present in all species belong to subfamily of rosaceae like spiraeoidae, pomoidae, prunoidae, and rosoidae, but in species of ulmaria genus belong to

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Chemotaxonomy of Medicinal plantrosoidae, sorbitol is absent. So, the absence of this chemotaxonomy marker confirms the removal of ulmaria from spiraeoidae to rosoidae. Polysaccharides: It is condensation of large number of monosaccharide molecules. That is universal in the energy storage forms eg. Starch, dextran, fructan, cellulose, and inulin. Among these polysaccharides inulin is characteristic of family compositae, while the fructan is present in family graminae. Thus, polysaccharide is also utilized in confirming phylogenetic relationship. Eg. Tropical and subtropical species of grasses accumulate starch in their leaves, while temperate grasses accumulate fructans.

Secondary metabolites present in plant, is used for protection and defence. Eg. Glycoside, alkaloid, volatile oil, flavonoid and plant phenol. Glycosides in chemotaxonomy:Glycosides are compounds in which one or more sugars are combined with non-sugar components by glycosidic linkage or by hemiacetal linkage involving oxygen (Oglycoside). Depending upon the linkage the glycoside may be classified as: O-glycoside; eg. Rhein. C-glycoside; eg. Aloin, cascaroside. N-glycoside; eg. Adenosine. S-glycoside; eg. Sinigrine. Distribution of O-glycosides is widespread, so it is having little chemotaxonomic value. The nature of sugar moiety and its position of attachment to aglycone maybe characteristics of cardiac glycosides. Eg. L-thevetose, D-digitalose, Dcymarose,L-oleandrose (cardiotonic) C-glycosides, which possess a direct carbon linkage between sugar and non-sugar are rare in nature. They are found in some plants containing anthraquinone derivatives eg. Aloin in aloe-liliaceae; cascaroside in cascara-rhamnaceae. About 25 C-glycosides of flavonoid group are known more are flavone and few iso-flavone and flavanone, these are plant phenol, but studied in C-glycosides. S-glycosides are examplified by those produce isothiocyanate on hydrolysis. These compounds are characteristic of the family cruciferae, moringaceae, capparaceae. So these family having phylogenetic relationship.

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Chemotaxonomy of Medicinal plantCyanogenetic glycoside in chemotaxonomy:Plant species having ability to produce hydrogen cyanide by enzymatic hydrolysis are common in family Rosaceae, Passifloraceae, Leguminosae, Gramineae. Different amino acid like phenyl alanine, tyrosine, valine, leucine, and isoleucine are precursor for the biosynthesis of cyanogenetic glycosides, but they are restricted to particular family. Example: Leucine-Leguminosae and sapindaceae. On the basis of amino acid precursors some conclusion may be derived, at family level cyanogenetic glycoside amygdaline synthesized from phenyl alanine, restricted rosaceae, but same compound synthesized from amino acid valine or isoleucine is restricted to Leguminosae. The accumulation of cyanogenetic glycoside is also significant in confirming the position of certain family.

Thioglucoside in chemotaxonomy:These are responsible for the characteristic flavors of various plants or family brassicaceae and few related family like, Capparidaceae, Tropaeolaceae and Resedaceae. On the basis of alkyl component of glucosinolate compound, brassica species can be differentiated eg. Brassica juncea (mustard) from Indian subcontinent contain 3-butenyl glucosinate and allyl glucosinate while those from Asiatic country contain only allyl compound. So ancestry of Indian species is doubtful, because that is hybrid of B. nigra (allyl glucosinate) and B. compestris (3-butenyl glucosinate).

ALKALOID IN CHEMOTAXONOMYAlkaloids are compounds, containing heterocyclic nitrogen, basic character and complex molecular structure. Such compounds are restricted to plant kingdom. o True alkaloids have a nitrogen-containing nucleus derived from biogenetic amine. o Proto alkaloids derived from amino acids, but lack a heterocyclic ring. Natural protoalkaloids are usually simple amines e.g. ephedrine , mescaline.Some times they may be precursor of true alkaloids. o Pseudo alkaloids biologically unrelated to amino acids.Most of them derived from- terpenes, sterols , nicotinic acid or purines.

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Chemotaxonomy of Medicinal plantOccurrence and Distribution:Higher plants particularly in the dicotyledons, abundance in the Angiosperms families Apocynaceae, Papaveraceae, Ranculaceae, Rubiaceae, Rutaceae, Solanaceae, but less frequent in lower plants and fungi. In plants, alkaloids, due to their basic nature, generally exist as a salt of organic acid like, oxalic acid, citric acid, malic acid,, tartaric acid, tannic acid etc. Some alkaloids like narceine and nicotine are occurring free in nature. A few alkaloids occur as glycoside of sugars like glucose, rhamnose, and galactose. E.g. alkaloids of solanum and veratrum groups as amides (Piperine), as esters (Atropine, Cocaine) of organic acid.

Criteria for using Alkaloids in taxonomy:Definition of alkaloids Definition of alkaloid plants The type of alkaloids that can be distinguished Homologous and analogous characters

Definition:Alkaloids are more or less toxic substances having physiological action. They are basic in nature, contain heterocyclic nitrogen, and are synthesized in plants from amino acid and or their intermediate derivatives. They are of limited distribution in plant kingdom. But such definition excludes a number of nitrogen containing plant constituents, which are normally thought as alkaloids. E.g. Biological amines like Ephedrine ,Hardenine,Betain ,Cholin, Muscarine. All such alkaloids are separately referred as protoalkaloids or biological amines or amino alkaloids. But when protoalkaloids and true alkaloids occur in same genus or family, both are usually classified as alkaloids. Ex. Hardenine, Mescaline in cactaceae family. Another group of nitrogen compounds that fall outside our definition of alkaloids are mono, sesqui,di-terpenes, steroids, nicotinic acid, purines. These can also be classified according to precursor on which they are based and collectively called as pseudo alkaloids.E.g . Conessine, Caffeine.

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Chemotaxonomy of Medicinal plantDefinition of alkaloid plants:There is no sharp dividing line between alkaloids containing plants and alkaloids free plants. From practical point of view, we can define lower limit as 0.01% of dry weight. Another characteristic of true alkaloid is that it always contains more than one alkaloid. E.g. Ricinine is only alkaloid in Ricinus communis and Genitianine only alkaloid in Gentianaceae, thats why these two bases have been kept outside the class of true alkaloids.

Type of alkaloids that can be distinguished: It has been found that amino acids phenylalanine, ornithine, tryptophan, lysine, histidine, Anthranilic acid are primary precursors of alkaloids in plants. Each of this amino acid can be regarded as starting point for synthesis of one or more types of alkaloids. Therefore we may put the alkaloids into families corresponding to six amino acids mentioned above. There are also numbers of alkaloids which can be regarded as hybrids. E.g. Phenylalanine family Hardenine, Ephedrine, Anahaline group, Papaverine group, Morphine group. Tryptophan family - Ajamaline, Yohimbine, vinblastine etc. Ornithine family - Hygrine, Atropine, Ecgonine etc . Lysine family - Coniine, Anabasine etc.

Homologous and analogous chemical characters:Two similar substances or even same substance may be isolated from two different plants and are taxonomically important if the compounds are derived from exactly same metabolically process. But same compounds or similar compounds are produced by different metabolic pathways in different plants.

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Chemotaxonomy of Medicinal plantE.g. Anabasine in Nicotiana genus (Solanaceae family) is formed from one molecule of lysine on the other hand in Leguminosae family two molecules of lysine are involved. Thus it seems that Anabasine of Solanaceae is not equivalent (homologous) to that in Leguminosae. Similarly quinine has been isolated from several unrelated genera. The quinoline alkaloids of cinchona bark are obviously quite different structurally from yohimbine alkaloids from yohimbe bark but they are closely related biosynthetically and this points to a close relation between the plants in which they occur. Generally ornithine and lysine families of alkaloids are closely related. Therefore, they should be treated as one unit from chemotaxonomic point of view.

Some alkaloids are restricted to only very certain plants e.g.Morphine is restricted to P. somniferum Coniine is restricted to Umbeliferous sp. Strychnine is restricted to strychnos species Accumulation of Isoquinoline alkaloids in families Fumariaceae and Papaveraceae, indicate that there is close relationship between two families. Both families accumulate Isoquinoline alkaloids, and always contain Protopine. There are instances where alkaloid biosynthesis can be helpful to chemotaxomist for arranging the species within genus according to their alkaloid content.

Evidences from basic moiety:Pyridine and Piperidine The parent base pyridine occurs in some plants as Lobeline obtained from Lobelia inflata family Lobeliaceae. Nicotine obtained from Nicotiana tobaccum family Solanaceae Anabasine obtained from Nicotiana gluaca family chenopodiaceae. Anabasine occurs in tobacco, where it is formed from lysine and nicotinic acid. In the legume and chenopod species where Anabasine also occurs, it can be synthesized from two molecules of lysine. Isoquinoline Alkaloids Isoquinoline alkaloids are obtained from following plants. E.g. Papaverine is obtained from P. somniferum family Papaveraceae

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Chemotaxonomy of Medicinal plantBerberine is obtained from Hydrastis canadensis family Berberidaceae The amino acid phenylalanine and tyrosine act as precursor for isoquinoline nucleus. Hydrastine which is found in Berberidaceae and Rannunculaceae. Tropane alkaloids Among the best-known members of the group are the solanaceae alkaloids, which are very characteristic of the solanaceae. Atropine and Hyoscyamine serve as example. In erythroxylum, cocaine alkaloids are found which are same in nucleus but do not occur in the solanacae. Ornithine is the precursor Indole Alkaloids Indole alkaloids are found in following plants. Physostigmine obtained from Physostigma venonsum family Leguminosae. Yohimbine obtained from Rauwolfia serpentina family Apocyanaceae. Vinblastine obtained from Catharanthus roseus family Apocyanaeae. Indole alkaloids origination from Phenylalanine as in Erythria alkaloids (Leguminosae) such as Erysopine. In most cases e.g. Tryptamine (Loganiaceae), yohimbine (Apocyanaceae) and strychnine (Loganiaceae) the parent compound is tryptophan.

Plant Phenol in chemotaxonomy:Most commonly occurred phenolic compound is mono or Dihydroxy derivatives of benzoic and cinnamic acid. Phenolic compounds having restricted occurrence may have chemotaxonomic value eg; Trihydroxy derivatives of benzoic acid and cinnamic acid.

Eg: Ellagic acid is absent in fern, gymnosperm and monocotyledon, but it is infrequently found in dicotyledon family. It is useful chemotaxonomic marker in subfamily rosoidae (tribe-kerrieae)-rosaceae. 4-hydroxy benzoic acid and 4-hydroxy phenyl acetic acid have been reported in eight genera of family saxifragaceae, but in case of Astilbe genus, 4-hydroxy phenyl acetic acid is replaced by 2-hydroxy phenyl acetic acid.

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Chemotaxonomy of Medicinal plantCoumarin derivatives are common volatile constituent responsible for odour in many plants. The hydroxylated derivative are having restricted distribution can be utilized as chemotaxonomic marker eg. Umbelliferone occurs widely in Umbelliferae while in Compositae it is characteristic of genus Hieracium (hawkweed). Flavonoids are largest group of phenolic compounds. They are mostly found in the vacuole of higher plant and absent in lower plant.

Different classes of flavanoids: Flavones Flavanone Isoflavanone Isoflavonoids Anthocyanidin Chalcone All flavonoids have common biosynthetic origin and therefore it posses the same basic structural element, e.g. 2-phenylchromone skeleton. They may be present in many classes depending on degree of oxidation of pyran ring which may be open and cyclize into furan ring, e.g. 2-phenyl benzo pyrilium: anthocyanin & 2-phenyl chromone: flavone, flavanol, isoflavone.

Flavone & flavanols and their glycosides are universally distributed but some of the substitution patterns are restricted to certain family, having chemotaxonomic importance. E.g. 6-o-substituted flavonoids in family: Laminaceae,Rutaceae, Asteraceae. 5-deoxy flavone in family: Fabaceae 2-o-substitueted flavonols in family: Laminaceae, Solanaceae. Anthocyanidins, water soluble pigments responsible for red, pink, purple, blue,violet colours to flower and fruit.these pigments occurs as glycoside anthocynidins and their aglycones anthocyanidins. These are rare in gymnosperm but mostly occurs in angiosperm. Except in Caryophyllales.

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