Biosynthesis and enrichment of targeted bioactive secondary metabolites through in-vitro and in-planta system and elucidation of their putative biosynthetic pathway
In-vitro biosynthesis and enrichment of targeted cardiac glycosides from Calotropis sp. and Nerium oleander.
The emerging role of cardiac glycosides (CGs) is the prevention and/or treatment of proliferative diseases like cancer [Molecular Interventions 8: 36-49 (2008)]. During last few years several papers have reported promising in-vitro and in-vivo anticancer activity of CGs.
Various CGs viz. calactin, calotoxin, calotropin, frugoside, proceroside, uscharidin, uscharin, uzarigenin, voruscharin, 2”-oxovoruscharin, etc. from Calotropis sp. and oleandrin, cardenolide N-1, oleander, cardenolide N-4, etc. from N. oleander were isolated in recent past. Most of these compounds have prominent cytotoxic effect and UNBS-1450, a semisynthetic cardenolide derivate of 2″-oxovuscharin in Phase I clinical trial [BiochemPharmacol. 81(1):13-23 (2011)]. Various crude extracts and fractions of different parts of these plants have also shown marked anti-cancer and anti-tumor activities. CGs are basically steroid like compounds with two distinct moieties i.e. glycon and aglycon (genin). Chemical synthesis of such compounds is very challenging because of their complex structure. On the other hand, quantity of these compounds in the plant is very less and hence their isolation from plant sources is not cost effective and detrimental to the biodiversity. So, the alternative option for getting these compounds is their production through plant tissue culture techniques. Our group is actively involved to establish the in-vitro biosynthesis and enrichment protocol of some selected bioactive CGs and determination of their putative biosynthetic pathway from C. gigantea and C. procera (DOI: 10.4103/pm.pm_507_18; DOI: 10.1038/srep34464; DOI: 10.1007/s 11 627-0 12-948 1-9). Same type of work is also going on from the plant N. oleander.
In-vitro biosynthesis and enrichment of targeted indole alkaloids from Alstonia scholaris.
The enormous therapeutic importance and biological activities of A. scholaris is mainly due to great diversity of alkaloids. However, indole alkaloids (IAs) are particularly responsible for anticancer and antitumor activities. Out of many IAs present in this species, echitamine and its derivatives are the major ones. Antitumor and anticancer activities of echitamine chloride are well established [Cancer BiochemBiophys 17(1–2):79–88 (1999)]. However, echitamine and its derivatives are mainly concentrated in stem bark and root of the plant and these parts are not recommended for bulk collection. Hence, in-vitro biosynthesis of such IAs through plant tissue culture technique may play a significant role
Our team has standardized the callus induction and proliferation protocol from leaf explants of A. scholaris along with in-vitro biosynthesis and enrichment of four bioactive IAs viz. echitamine, acetylechitamine, tubotaiwine and picrinine. Quantitative estimation of these IAs was performed by using high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). (https://doi.org/10.1007/s10725-019-00570-7; DOI 10.1007/s11240-014-0579-0]. At present, efforts are going on to elucidate the putative biosynthetic pathway of these IAs.
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