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Journal of Medicinal Plants Studies 2016; 4(2): 90-93, , ISSN 2320-3862, JMPS 2016; 4(2): 90-93, © 2016 JMPS, Received: 08-03-2016, Accepted: 04-04-2016, Ram Singh, Department of Applied, Chemistry, Delhi Technological, University, Delhi – 110 042,, India., , Chemotaxonomy: A Tool for Plant Classification, Ram Singh, Abstract, Nature which consists of so many variabilities of living components of the environment possesses useful,, harmful and inactive chemical constituents. The classification based on these chemical constituents is, known as chemotaxonomy. All the living components of the environment produce secondary metabolites, that are derived from primary metabolites. The chemical structure of the secondary metabolites is often, specific and restricted to taxonomically related organisms. The classification of plants on the basis of, specific class of secondary metabolites and their biosynthetic pathways constitutes chemotaxonomy. Its, study is helpful to taxonomist, phytochemists and pharmacologists to solve selected taxonomical, problems., Keywords: Chemotaxonomy, Chemosystematics, Glycosides, Alkaloid, Plant phenols, , 1. Introduction, Natural Products are produced by all organisms but are mostly known from plants, insects,, fungi, algae and prokaryotes. All of these organisms coexist in ecosystems and interact with, each other in various ways in which chemistry plays a major role[1,2]. Many natural products, are biologically active and have been used for thousands of years as traditional medicines and, as natural poisons. Plants are the major contributors of natural products. Over the years, many, approaches evolved towards the taxonomy of plants. These include morphological, classification, anatomical classification and chemotaxonomic classification. The first two can, be grouped under traditional classifications whereas the third one is modern approach to, classify the plants., The science of chemotaxonomy or chemical taxonomy is used for the classification of plants, on the basis of their chemical constituents. All the living organisms produce secondary, metabolites that are derived from primary metabolites. The chemical structure of the secondary, metabolites and their biosynthetic pathways is often specific and restricted to taxonomically, related organisms and hence useful in classification. This method of classification is, considered better in comparison to traditional method due to the ease of working methodology., In this method of classification, the materials to be analyzed can be dried or crushed. The fresh, or complete materials are not the compulsory requirements[3]., The concept of chemotaxonomy has been elaborated in the past century[4]. According to De, Candolle[4]., 1) Plant taxonomy will be the most useful guide to man in his search for new industrial and, medicinal plants; and, 2) Chemical characteristics of plants will be most valuable to plant taxonomy in the future., Both the statements are having their importance in present day natural product studies. The, rise of chemotaxonomy is mainly due to the advancement in analytical techniques for chemical, analysis that can detect even trace amount of chemical compounds[5]. In plants, the more, popular families that have been studied through chemotaxonomy are Malvaceae,, Ranunculaceae, Magnoliaceae, Polygonaceae, and Solanaceae[6]. The findings of, chemotaxonomic studies are helpful to taxonomist, phytochemists and pharmacologists to, solve selected taxonomical problems., Correspondence, Ram Singh, Department of Applied, Chemistry, Delhi Technological, University, Delhi – 110 042,, India., , 2. Chemotaxonomic Classification, The phenolics, alkaloids, terpenoids and non-protein amino acids, are the four important and, widely exploited groups of compounds utilized for chemotaxonomic classification[7]. These, groups of compounds exhibit a wide variation in chemical diversity, distribution and, function[7,8]. The system of chemotaxonomic classification relies on the chemical similarity of, taxon[9,10]. Three broad categories of compounds are used in chemotaxonomy:, ~ 90 ~

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Journal of Medicinal Plants Studies, , Opisthiole, Parsonsia and Polyscias[22]. Different amino acid, like phenyl alanine, tyrosine, valine, leucine, and isoleucine, are precursor for the biosynthesis of cyanogenic glycosides,, but they are restricted to particular family. For example, a, cyanogenic glycoside synthesized from leucine commonly, occurs in the subfamily amygdaloideae (almond) and, maloideae (apple) of family rosaceae[11]. The glycosides, derived from tyrosine commonly occur in the families of the, order mangnoliales and laurales[11]., , primary metabolites; secondary metabolites and semantices., 2.1 Primary metabolites, Primary metabolites are the compounds that are involved in, the fundamental metabolic pathways. Most of the primary, metabolites are of universal occurrence and utilized by the, plant itself for growth and development[11,12]. These, compounds are ubiquitous in nature and hence play little role, in chemotaxonomic classification. However, these molecules, sometimes serve as useful chemotaxonomic behavior on the, basis of their quantities. For example, carbohydrate, sedoheptulose (Figure 1) is present in genus sedum in large, quantity. Therefore, the accumulation of sedoheptulose in the, species of genus sedum serves as a useful chemical character, in chemotaxonomy[11]., The water soluble polysaccharides (WSP) are also used as, chemotaxonomic markers. The gas liquid chromatographic, analysis on WSP from annatto tree (Bixa orellana L.), showed hemispherical type contained 38% rhamnose, while, conical and ovate types contained 17% and 34% glucose,, respectively. Thus, glucose and rhamnose content of WSP, could be used to distinguish the three landraces of annatto, trees[13]., , OH, , OH, , HO, , OH, O, , OH, , OH, , Figure 1: Sedoheptulose, CH2OH, OH, OH, , O, , O, O, , OH, , O, , OH, , OH, , 2.2 Secondary metabolites, Secondary metabolites are the compounds that usually, perform non-essential functions in the plants[11]. They are, used for protection and defense against predators and, pathogens. These compounds are of restricted occurrence, and hence very useful for chemotaxonomic classification., Some of the major group of secondary metabolites includes, glycoside, alkaloid, volatile oil, flavonoid, plant phenols and, terpenoids., , OH, OH, , OH, CH2OH, , CH2OH, OH, , O, , OH, , Cascaroside, , OH, , Aloin, , OH, , O, , OH, , OH, , Fig 2: Aloin and Cascaroside, , 2.2.3 Glucosinolates in chemotaxonomy, Glucosinolates are sulfur- and nitrogen-containing plant, secondary metabolites common in the order Capparales,, which includes the Brassicaceae family (Figure 3)[23]. On the, basis of alkyl component of glucosinolate compound,, brassica species can be differentiated. For example, Brassica, juncea (mustard) from Indian subcontinent contain 3-butenyl, glucosinolate and allylglucosinolate while those from Asiatic, country contain only allyl compound[24,25]. So, ancestry of, Indian species is doubtful, because that is the hybrid of B., nigra (allylglucosinate) and B. compestris (3-butenyl, glucosinate)., , 2.2.1 Glycosides in chemotaxonomy, Glycosides are the compounds in which one or more sugars, are combined with non-sugar molecules through glycosidic, linkage. Based on the linkage, the glycosides are grouped as, O-glycoside, C-glycoside, N-glycoside and S-glycoside. The, distribution of O-glycosides like rhein is very common, so it, has little chemotaxonomic value. The R. rugosa flavonol, glycosides were shown to be important chemotaxonomic, markers for the classification of species in Cinnamomeae[14]., The use of flavonol glycosides as chemotaxonomic markers, could be useful for the identification of Rosa species, belonging to sections Gallicanae, Cinnamomeae, Caninae,, and Synstylae[14]. The C-glycosides like aloin, cascaroside, which possess a direct carbon linkage between sugar and, non-sugar are not very prevalent in nature. They are found in, some plants containing anthraquinone derivatives[15,16] such, as aloin in aloe-liliaceae[17,18] cascaroside in cascararhamnaceae (Figure 2)[19]. S-Glycosides Sinigrin are, examplified by those produce isothiocyanate on hydrolysis., These compounds are characteristic of the family cruciferae,, moringaceae, capparaceae. So these families have, phylogenetic relationship[20]., , OH, , R, , S, , HO, HO, OH, , N, -O3S, , O, , R = Variable side chain from amino acids, , 2.2.2 Cyanogenic glycoside in chemotaxonomy, The cyanogenic glycosides are the compounds responsible, for providing defensive mechanism to plants[11]. Plant species, have ability to produce hydrogen cyanide (HCN) by, enzymatic hydrolysis of cyanogenic glycosides by the, process called cyanogenesis[21]. Cyanogenesis is reported for, the first time in the genera Beilschmiedia, Cardwellia,, Cleistanthus,, Elaeocarpus,, Embelia,, Mischocarpus,, , Fig 3: Glucosinolates, , 2.2.4 Alkaloid in Chemotaxonomy, Alkaloids are heterocyclic nitrogen containing basic, compounds[26,27]. But, few non-heterocyclic alkaloids are also, present. Chemotaxonomic analysis based on alkaloids, depends upon the type of parent base compound present in, the alkaloids. The indole alkaloids contain indole as the, ~ 91 ~

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Journal of Medicinal Plants Studies, , parent base. More than 2,500 indole alkaloids were isolated, mainly from three plant families, Rubiaceae, Loganiaceae, and Apocynaceae. These are formed from two building, blocks secologanin and tryptamine or tryptophane through a, single precursor, strictosidine, and suggesting relationship, between these families[28,29]. Other indole alkaloids like, physostigmine (Figure 4) obtained from Physostigma, venenosum (family Leguminosae)[30] yohimbine from, Rauwolfia serpentine (family Apocyanaceae)[31], and, corynanthe yohimbe (family Rubiaceae)[32] and Vinblastine, from vincarosea(family Apocyanaeae)[33]., , pathways can be used to assign its taxonomic position., 4. Acknowledgments - The author is grateful to Council of, Scientific & Industrial Research (CSIR), India, for financial, support., 5. References, 1. Reynolds T. The evolution of chemosystematics., Phytochemistry 2007; 68:2887-2895., 2. Larsen TO, Smedsgaard J, Nielsen KF, Hansen ME,, Frisvad, JC., Phenotypic, taxonomy, and metabolite profiling in microbial drug discovery., Natural Product Report 2007; 22:672-695., 3. Ankanna S, Suhrulatha D, Savithramma N., Chemotaxonomical studies of some important, monocotyledons. Botany Research International 2012;, 5:90-96., 4. De Candolle AP. Essaisur les propridtdsmédicales des, plantes, cornparees avec leurs forms extérieuresetleur, classification naturelle, Second Edition, Paris, 1816., 5. Bhargava VV, Patel SC, Desai KS. Importance of, terpenoids and essential oils in chemotaxonomic, approach. International Journal of Herbal Medicine., 2013; 1:14-21., 6. Sivarajan VV. Introduction to the Principles of Plant, Taxonomy, Cambridge University Press, 1991., 7. Smith PM. The Chemotaxonomy of plants London,, Edward Arnold, 1976., 8. Hegnauer R. Phytochemistry and plant taxonomy-an, essay on the chemotaxonomy of higher plants., Phytochemistry 1986; 25:1519-1535., 9. Atal CK. Cultivation and utilization of aromatic plants,, 1st ed, Council of Scientific and Industrial Research,, New Delhi, 1982, 15-21., 10. Rasool R, Ganai BA, Akbar S, Kamili AN, Masood A., Phytochemical screening of Prunella vulgaris l. - an, important medicinal plant of Kashmir. Pakistan Journal, of Pharmaceutical Science. 2010; 23:399-402., 11. Singh P. An introduction to biodiversity, Ane Books Pvt, Ltd, 2010, 51., 12. Singh P. Plant taxonomy: past, present and future, edited, by R Gupta, TERI, 2012, 233., 13. Parimalan R, Mahendranath G, Giridhar P. Analysis of, water soluble polysaccharides as a potential, chemotaxonomic marker for landraces in Bixaorellana., Indian Journal of Biochemistry and Biophysics., 2014; 51:81-86., 14. Sarangowa O, Kanazawa T, Nishizawa M, Myoda T,, Bai C, Yamagishi T. Flavonol glycosides in the petal of, Rosa, species, as, chemotaxonomic, markers., Phytochemistry 2014; 107:61-68., 15. Singh R, Geetanjali, Chauhan SMS. 9, 10Anthraquinones and other biologically active, compounds from the Genus Rubia. Chemistry and, Biodiversity 2004; 1:1241-1264., 16. Singh R, Geetanjali. Isolation and synthesis of, anthraquinones, and, related, compounds, of Rubiacordifolia. Journal of Serbian Chemical Society., 2005; 70:937-942., 17. Chiang HM, Lin YT, Hsiao PL, Su YH, Tsao HT, Wen, KC. Determination of marked components - aloin and, aloe-emodin - in Aloe vera before and after hydrolysis., Journal of Food Drug Analysis. 2012; 20:646-652., 18. Grün M, Franz G. In vitro biosynthesis of the Cglycosidic bond in aloin. Planta 1981; 152:562-564., , H3C, H2N, , O, , CH3, , O, , CH3, Fig 4: Physostigmine, , The Pyridine and Piperidine alkaloids like Lobeline obtained, from Lobelia inflate family Lobeliaceae[34]. Nicotine, obtained from Nicotiana tobaccum family Solanaceae[35]., Anabasine obtained from Nicotiana gluaca family, chenopodiaceae[36]. The presence of these alkaloids explains, the importance of these alkaloids in taxonomical analysis., Anabasine occurs in tobacco, where it is formed from lysine, and nicotinic acid, where as in the legume and chenopod, species this can be synthesized from two molecules of, lysine[36]. Similarly, the alkaloids like isoquinoline alkaloids,, tropane alkaloids, indole alkaloids etc have also been a, useful tool for taxonomic classification of plants[37]., 2.2.5 Plant Phenol in chemotaxonomy, Polyphenols are among the most widespread class of, metabolites in nature, and their distribution is almost, ubiquitous. It is estimated that 100,000 to 200,000 secondary, metabolites exist[38] and some 20% of the carbon fixed by, photosynthesis is channeled into the phenylpropanoid, pathway, thus generating the majority of the naturaloccurring phenolics[38,39]. 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, plant phenols include flavones, flavanones, isoflavanones,, isoflavonoids, anthocyanidins and chalcones. All flavonoids, have common biosynthetic origin and therefore it possess the, same basic structural element. For example, 2phenylchromone 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, benzopyrilium: anthocyanin and 2-phenyl chromone:, flavone, flavanol, isoflavone[40]. A chemotaxonomic study of, practically all the species of the genus Aloe showed that, flavonoids occur as major compounds in 31 out of a total of, 380 species investigated[41]., 3. Summary, With the advancement of analytical techniques, today so, many groups of plants are there in which phytochemical data, has contributed to extensive taxonomic improvements. The, presence or absence of a particular phytochemical in a plant, along with the knowledge of its biochemical synthetic, ~ 92 ~