Secondary Metabolites of Medicinal Plants. Bharat Singh
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2.4 Adhatoda Species
2.4.1 Ethnopharmacological Properties and Phytochemistry
Adhatoda vasica syn. Justicia adhatoda syn. Adhatoda zeylanica (Medic.) (Fam. – Acanthaceae) is a medicinal plant native to Asia, widely used in Siddha, Ayurvedic, and Unani systems of medicine as well as in homeopathy. The plant genus is distributed in Sri Lanka, Bangladesh, India, Pakistan, Malaysia, China, and Panama. Leaf infusion is considered as an excellent agent for the eradication of white ants, flies, and mosquitoes and used to relieve to headache (Gamble 1902; Jayaweera 1981; Khursheed et al. 2010). The boiled leaf extract along with fruit powder of Phyllanthus emblica, mixed with honey, is used in asthma treatment (Khan and Yadava 2010). The fresh leaf juice is added to honey and ginger juice and used as remedy for cough, chronic bronchitis, and asthma (Ahmed et al. 2007). Leaf juice is prescribed in malarial fever (Manandhar 1991). Bruised fresh leaves are used to treat snake bites (Roberts 1931). Paste is prepared from fresh root and is applied on the abdomen and vagina, minutes before childbirth for easy delivery (Hussain and Hore 2007). The root is useful as an expectorant and antispasmodic, and the infusion is used as an anthelmintic. Fresh flowers are used in high fever and gonorrhea (Ahmad and Javed 2007). The leaves and flowers possess expectorant and anti-asthmatic properties (Malhotra 1996). The fruits are recommended for the relief from cold, antispasmodic, and bronchitis (Atta et al. 1986).
The phytochemical analysis revealed that phenols, tannins, alkaloids, anthraquinone, saponins, flavonoids were present in the J. adhatoda (Pathak 1970). It contains bitter quinazoline alkaloid as vasicine, vasicinone, 2-aminobenzylamine (Wasserman and Kuo 1991; Amine and Mehta 1959; Suthar et al. 2009), vasicinol, adhatodine, adhatonine, adhvasinone, anisotine and hydroxypeganine, 2-acetylbenzylamine (Lahiri and Prahdan 1964; Ignacimuthus and Shanmugam 2010), and vasicoline (Joshi et al. 1996; Ahmad et al. 2009). The 1,2,3,9-tetrahydro-5-methoxypyrrol[2,1-b]quinazolin-3-ol, vasicinolone, and deoxyvasicinone were characterized from the leaves of A. vasica (Potewar et al. 2008; Bhatt et al. 2010). The roots also contain vasicinal, vasicinone and adhatonine, daucosterol, adhavasine, vasicol, vasicoline, vasicolinone (Ahmad et al. 2009; Singh et al. 2011). The presence of α-amyrin, apigenin, astragalin, kaempferol, quercetin, neoandrographolide, vitexin, and alkanes were confirmed in the flowers of A. vasica (Haq et al. 1967; Al-Amin et al. 2012). Pharmacologically and biologically the Adhatoda species has antibacterial (Shahwar et al. 2012) and anti-inflammatory activities (Chakraborty and Brantner 2001; Dhankhar et al. 2011; Singh and Sharma 2013). The 3α-hydroxyoleanane-5-ene and taraxerone from aerial parts (Sultana et al. 2005; Singh et al. 2011), desmethoxyaniflorine, 7-methoxyvasicinone (Thappa et al. 1996), anisotine, 3-hydroxyanisotine, vasnetine, vasicolinone, and vasicol have been isolated from the leaves of A. vasica (Joshi et al. 1994; Singh et al. 2015). The 3α-hydroxy-D-friedoolean-5-ene, epitaraxerol, and peganidine have been identified from the aerial parts of A. vasica (Atta-Ur-Rahman et al. 1997).
2.4.2 Culture Conditions
Plant growth hormones influence the growth of cell biomass and production of secondary metabolites in cell cultures of plants. The optimized culture conditions can induce the biosynthesis and accumulation of plant secondary metabolites (Bhojwani and Razdan 1996; Subathra and Mohana 2011). The cell culture studies of A. vasica were established on Murashige and Skoog culture medium (Murashige and Skoog 1962; Singh and Sharma 2013). Elicitation is being exploited as important technique and has opened new avenues for the enhancement of production of secondary metabolites (Pirian and Piri 2012). Salicylic acid and methyl jasmonate are plant growth hormones that induce the production of secondary plant products (Jirage et al. 1999). Several types of elicitors were used to increase the synthesis of phenolic compounds in cell cultures of Vitis vinifera (Riedel et al. 2012; Kauss et al. 1993). Polysaccharides also elicited manifold increase in the production of anthraquinones and other compounds in suspension cultures of Rubia as well as other plant species (Jin et al. 1999; Karuppusamy 2009; Rao and Ravishankar 2002; Wong 2003). The amino acids were added in cell cultures to enhance the production of terpenoid indole alkaloids in Catharanthus roseus (Gaviraj and Veerasham 2006). The effect of salts on the accumulation of secondary metabolites at 50 mM concentration was assessed, and it is found that NaCl increased the production of alkaloids in Rauvolfia tetraphylla (Mohana Priya et al. 2011; Anitha and Kumari 2006).
Amino acids play significant roles in catalyzing the reactions of secondary metabolism in plants (Pratelli and Pilot 2014). It has been reported that methyl jasmonate increases the accumulation of amino acids in suspension cultures of Scrophularia striata (Sadeghnezhad et al. 2016). Methionine and aspartic acid were added as elicitors in the cell suspension cultures of Nicotiana tabacum and showed twofold increase (serine, glutamic acid, aspartic acid) in accumulation of free amino acids (Dougall 1965). With feeding of NaCl and CoCl2, the cell cultures of Mesembryanthemum crystallinum and Zea mays maintained 5% extra synthesis of proline as well as total amino acids (Thomas et al. 1992; Jaleel et al. 2009).