2. Podophyllotoxin aryltetralin lignan
Podophyllotoxin (PPT) (Fig.1A ), an aryltetralin lignan, found
naturally in rhizomes and roots of many herbs such as Podophyllum
peltatum, P. hexandrum, Linum album, L. narbonense, (Fig. 1B )
with supplies of PPT from natural sources possibly limited due to the
endangered status of plants in the wild and/or environmental stresses
due to overharvesting and environmental threats (Chaudhari et al., 2014:
Chaurasia et al., 2012). This compound
shows different biological activities, such as vigorous antimitotic and
antiviral activities (Ayres and Loike,
1990; Gross, 2001). In addition
to being important anticancer agent in its own right, it is also a
starting material for the production of different semisynthetic
derivatives such as teniposide, and etoposide which have huge commercial
importance due to their potent effects in Hodgkin’s and non-Hodgkin’s
lymphoma, testicular/small cell lung cancers and acute leukemia
(Gordaliza et al., 2004;
Malik et al., 2014). The main mode of
action of PPT is via inhibition of Topo II, thereby arresting the cell
cycle at the G2 phase and causing DNA breakage and apoptosis via
inhibition of protein tyrosine kinase
(Dholwani et al., 2008). The organic
synthesis of this compound is difficult due to the complicated chemical
structure involving high-cost procedures
(Satake et al., 2013;
Umezawa, 2003).