biosynthesis of vindoline and other indole alkaloids in Catharanthus roseus callus cultures. Plant Growth Regul. 33: 43–49.66 Zhao, J., Zhu, W., and Hu, Q. (2001c). Enhanced catharanthine production in Catharanthus roseus cell cultures by combined elicitor treatment in shake flasks and bioreactors. Enzyme Microb. Technol. 28: 673–681.
67 Zhao, J., Zhu, W.-H., Hu, Q., and Guo, Y.-Q. (2001d). Compact callus cluster suspension cultures of Catharanthus roseus with enhanced indole alkaloid biosynthesis. In Vitro Cell. Dev. Biol. Plant 37: 68–72.
68 Zhou, M.-L., Zhu, X.-M., Shao, J.-R. et al. (2012). An protocol for genetic transformation of Catharanthus roseus by Agrobacterium rhizogenes A4. Appl. Biochem. Biotechnol. 166: 1674–1684.
69 Zhu, J., Wang, M., Wen, W., and Yu, R. (2015). Biosynthesis and regulation of terpenoid indole alkaloids in Catharanthus roseus. Pharmacogn. Rev. 9: 24.
2.24 Centella Species
2.24.1 Ethnopharmacological Properties and Phytochemistry
Centella asiatica (L.) Urban (syn. Hydrocotyle asiatica Linn.; Fam. – Umbelliferae) is naturalized throughout tropical and subtropical regions of India, Pakistan, Sri Lanka, Madagascar, and South Africa, as well as South Pacific and Eastern Europe. C. asiatica is a prostrate and aromatic and flourishes extensively in shady, marshy, damp wetlands (Tripathi et al. 2015). It is used for treatment of skin infections, healing of wounds, enhancement of nerves and brain cell activities, rheumatism, inflammation, syphilis, mental illness, epilepsy, hysteria, dehydration, and diarrhea (Jamil et al. 2007; Shanghai 1977; Yu et al. 2006). This species has been considered as a source of antioxidants (Singh et al. 2010; Subathra et al. 2005). The aerial parts of H. asiatica are used in the treatment of various ailments including body aches, headaches, insanity, asthma, leprosy, ulcers, and eczemas (Mishra 2003; Chaudhuri et al. 1978), as well as lupus, varicose ulcers, psoriasis, diarrhea, fever, amenorrhea, and diseases of the female genitourinary tract and also for relieving anxiety and improving cognition (Baily 1945; Gohil et al. 2010). Imipramine and total triterpenoids isolated from C. asiatica showed antidepressant activity (Chen et al. 2003). The aqueous extract demonstrated antinociceptive and anti-inflammatory against prostaglandin E2-induced paw edema in rats at different doses (Somchit et al. 2004; George et al. 2009), radioprotective (Shobi and Goel 2001; Sharma and Sharma 2002), and antiulcer activities (Cheng and Koo 2000; Cheng et al. 2004; Cho 1981), cognitive function and memory enhancement (Bradwejn et al. 2000; Dev et al. 2009; Tiwari et al. 2008; Wattanathorn et al. 2008), and increase in the dendritic length and dendritic branching points (Mohandas Rao et al. 2006). The in vivo studies have proved that whole extract as well as individual compounds of C. asiatica exhibited neuroprotective effects especially for Alzheimer's disease, Parkinson's disease, learning and memory enhancement, neurotoxicity and other mental illnesses such as depression and anxiety, and epilepsy (Bylka et al. 2014; Chandrika and Prasad Kumarab 2015; Lokanathan et al. 2016; Puttarak et al. 2017).
In addition to abovementioned properties, the C. asiatica also possessed a wide range of biological activities such as antipsoriatic (Sampson et al. 2001), hepatoprotective (Pingale 2008), anticonvulsant (Sudha et al. 2002), sedative (Wijeweera et al. 2006), immunostimulant (Wang et al. 2003), cardioprotective (Gnanapragasam et al. 2004; Raghavendra et al. 2009), antidiabetic (Venu Gopal Rao and Mastan 2007), cytotoxic and antitumor (Lee et al. 2002; Bunpo et al. 2004; Babu et al. 1995), antiviral (Yoosook et al. 2000), antibacterial (Zaidan et al. 2005), insecticidal (Senthilkumar et al. 2009), antifungal (Naz and Ahmad 2009; Ullah et al. 2009), antioxidant (Hamid et al. 2002; Jayashree et al. 2003; Bajpai et al. 2005; Pittella et al. 2009), and for venous deficiency (Pointel et al. 1987; Cesarone et al. 2001). Aqueous extracts of C. asiatica showed anti-psoriatic effects (Sampson et al. 2001). The 23-O-acetylmadecassoside, asiatic acid, madecassic acid, asiaticoside C, asiaticoside F, asiaticoside, madecassoside, and 23-O-acetylasiaticoside B with sitosterol 3-O-β-glucoside, stigmasterol 3-O-β-glucoside, quercetin-3-O-β-D-glucuronide (Rumalla et al. 2010; Schaneberg et al. 2003), asiaticoside A and asiaticoside B, [O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)]-O-β-D-glucopyranose ester of 2α,3β,6β,23α-tetrahydroxy-urs-12-ene-28-oic acid and [O-α-spl-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)]-O-β-D-glucopyranose ester of 2α,3β,6β,23α-tetrahydroxyolean-12-ene-28-oic acid (Sahu et al. 1989), and brahmic acid have been isolated from C. asiatica (Singh and Rastogi 1968).
Similarly, asiaticosides C, D, E, and F asiaticoside, madecassoside, and scheffuroside B were isolated from the butanol fraction of the EtOH extract of C. asiatica (Jiang et al. 2005). The (2α,3β,4α)-23-(acetyloxy)-2,3-dihydroxyurs-12-en-28-oic acid O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, (2α,3β)-2,3-dihydroxyurs-12-en-28-oic acid, O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, asiatic acid 6-O-β-D-glycopyranosyl-β-D-glucopyranosyl ester, (3β,4α)-3,23-dihydroxyurs-12-en-28-oic acid, and O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester were separated from this plant species (Xing et al. 2009). The ursane- and oleanane-type triterpene oligoglycosides; centellasaponins B, C, and D; madecassoside; asiaticoside; asiaticoside B; and sceffoleoside A have been isolated from Centella of Sri Lanka. The chemical structures of centellasaponins B, C, and D, madecassic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside, madasiatic acid 28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside, 3β,6β,23-trihydroxyolean-12-en-28-oic acid, 28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (Matsuda et al. 2001), 3-O-[α-L-arabinopyranosyl] 2α,3β,6β,23α-tetrahydroxyurs-12-ene-28-oic acid, 6β-hydroxyasiatic acid (Shukla et al. 2000), 2α,3β,23-trihydroxyurs-20-en-28-oic acid and 2α,3β,23-trihydroxyurs-20-en-28-oic acid, O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester (Yu et al. 2007), 23-acetyloxy-2α,3β-dihydroxyurs-12-en-28-oic acid, 28-O-αL-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-6-D-glucopyranosyl ester, 2α,3β,6β-trihydroxyurs-12-en-28-oic acid, 3β,6β,23-trihydroxyurs-12-en-28-oic acid, 2α,3β,6β-trihydroxyolean-12-en-28-oic acid, and 3β,6β,23-trihydroxyolean-12-en-28-oic acid were determined by spectral data analysis (Kuroda et al. 2001). The 11,12-dehydroursolic acid lactone, ursolic acid, pomolic acid, 2α,3α-dihydroxyurs-12-en-28-oic acid, 3-epimaslinic acid, asiatic acid, corosolic acid, 8-acetoxy-1,9-pentadecadiene-4,6-diyn-3-ol, β-sitosterol 3-O-β-glucopyranoside, and rosmarinic acid were isolated from C. asiatica and showed antiproliferative activity against human uterine carcinoma (HeLa) and murine melanoma (B16F10) cells (Yoshida et al. 2005). The centellin, asiaticin, centellicin, asiaticoside, kaempferol, madecassoside, madecassic acid, and quercetin were identified and estimated from C. asiatica (Siddiqui et al. 2007; Hashim et al. 2011), but the isolated triterpenes did not exhibit significant cytotoxic activity against human leukemia-60 (HL-60), human squamous cells-2 (HSC-2), HSG, and human gingival fibroblasts (HGF) cell lines (Kuroda et al. 2001; Rafamantanana et al. 2009). The β-caryophyllene, α-humulene, and germacrene-D along with 41 sesquiterpenes were separated and identified by GC–MS analysis from the aerial parts of C. asiatica (Wong and Tan 1994; Verma et al. 1999). Similarly, the triterpenoid saponins such as asiaticoside and madecassoside, collectively called centelloids, were also identified from aqueous extract (Azerad 2016; Kim et al. 2009).
