9.3 Natural Sources of Camptothecin
9.3.1 Camptothecin from Plants
The botanical classification assists in understanding the presence of phytocompounds in plant species (Larsson 2007). Plant-origin secondary metabolites with
similar chemo-structures can be present in dissimilar families of the plant kingdom.
Likewise, CPT occurs in different plant species of the distinct orders and families of
angiosperms. Owing to high market value, CPT-producing plant species have been
scientifically explored in recent years. Further, plant-based CPT biosynthesis still
remains as the best and suitable route for production, because of its limited natural
sources and productivity. The occurrence of CPT is commonly distributed among
angiosperms (Wink 2003; Oberlies and Kroll 2004; Pu et al. 2019). The isolation
and characterization of CPT was performed firstly by Wall et al. (1996) from C.
acuminata. Later, it was re-isolated from a medicinal plant, O. mungos L. that
belongs to the Rubiaceae family (Tafur et al. 1979). Remarkably, C. acuminata and
O. mungos belongs to totally dissimilar phylogenetic clades, however, they possessed similar biosynthetic competency for CPT (Pu et al. 2019). This discovery
revitalized the knowledge of distribution patterns of CPT in plants. Over the next
two decades, CPT-producing plant species were identified and isolated from a few
other plant species that belong to different plant families, i.e., Icacinaceae,
Apocynaceae, and Rubiaceae. These plants include Mostuea brunonis Didr.
(Loganiaceae), Tabernaemontana alternifolia L. (Apocynaceae; syn. Ervatamia
heyneana (Wall.) T.Cooke); O. filistipula Miq. and O. pumila Champ. ex Benth.
(Rubiaceae); Nothapodytes nimmoniana (Grah.) Mabb., Nothapodytes obtusifolia
(Merr.) R. A. Howard., Nothapodytes obscura C.Y. Wu. and Merrilliodendron
megacarpum (Hemsl.) Sleumer. (Icacinaceae). These plants sources have the
potential to serve as alternatives to obtain CPT. Nevertheless, only in two species,
namely C. acuminata and N. nimmoniana, the basic accumulation patterns of CPT
is detailed so far (Gunasekera et al. 1981; Arisawa et al. 1981; Arbain et al. 1993;
Liu et al. 1998; Ramesha et al. 2008; Bai and Song 2014; Upadhya et al. 2014;
Kaushik et al. 2015; Isah and Mujib 2015; Prakash et al. 2016; Pu et al. 2019). CPT
occurs in leaves, bark, seeds, fruits of C. acuminata, however the maximum
quantity can be obtained from young leaves of C. acuminata, which is about 5 mg/
g DW (dry weight). The matured leaves contain minimum levels of CPT, which is
250% lesser than that can be obtained from the bark, and ten-fold lesser than that
can be obtained from young leaves (Lopez et al. 1994; Li et al. 2000; Yan et al.
2003; Kaushik et al. 2015; Prakash et al. 2016).
The increased exploration of plant resources for CPT-producing capability have
resulted in the documentation of 34 new plant species that belong to Apocynaceae,
Rubiaceae, Gelsemiaceae, Betulaceae, Icacinaceae, Nyssaceae, Meliaceae, and
Violaceae. Among them, the majority of plant species belong to Rubiaceae and
Icacinaceae family. Importantly, most of these described plant species have their
natural distribution in the South-East Asian nations, exclusively in the south part of
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9.3.1 Camptothecin from Plants
The botanical classification assists in understanding the presence of phytocompounds in plant species (Larsson 2007). Plant-origin secondary metabolites with
similar chemo-structures can be present in dissimilar families of the plant kingdom.
Likewise, CPT occurs in different plant species of the distinct orders and families of
angiosperms. Owing to high market value, CPT-producing plant species have been
scientifically explored in recent years. Further, plant-based CPT biosynthesis still
remains as the best and suitable route for production, because of its limited natural
sources and productivity. The occurrence of CPT is commonly distributed among
angiosperms (Wink 2003; Oberlies and Kroll 2004; Pu et al. 2019). The isolation
and characterization of CPT was performed firstly by Wall et al. (1996) from C.
acuminata. Later, it was re-isolated from a medicinal plant, O. mungos L. that
belongs to the Rubiaceae family (Tafur et al. 1979). Remarkably, C. acuminata and
O. mungos belongs to totally dissimilar phylogenetic clades, however, they possessed similar biosynthetic competency for CPT (Pu et al. 2019). This discovery
revitalized the knowledge of distribution patterns of CPT in plants. Over the next
two decades, CPT-producing plant species were identified and isolated from a few
other plant species that belong to different plant families, i.e., Icacinaceae,
Apocynaceae, and Rubiaceae. These plants include Mostuea brunonis Didr.
(Loganiaceae), Tabernaemontana alternifolia L. (Apocynaceae; syn. Ervatamia
heyneana (Wall.) T.Cooke); O. filistipula Miq. and O. pumila Champ. ex Benth.
(Rubiaceae); Nothapodytes nimmoniana (Grah.) Mabb., Nothapodytes obtusifolia
(Merr.) R. A. Howard., Nothapodytes obscura C.Y. Wu. and Merrilliodendron
megacarpum (Hemsl.) Sleumer. (Icacinaceae). These plants sources have the
potential to serve as alternatives to obtain CPT. Nevertheless, only in two species,
namely C. acuminata and N. nimmoniana, the basic accumulation patterns of CPT
is detailed so far (Gunasekera et al. 1981; Arisawa et al. 1981; Arbain et al. 1993;
Liu et al. 1998; Ramesha et al. 2008; Bai and Song 2014; Upadhya et al. 2014;
Kaushik et al. 2015; Isah and Mujib 2015; Prakash et al. 2016; Pu et al. 2019). CPT
occurs in leaves, bark, seeds, fruits of C. acuminata, however the maximum
quantity can be obtained from young leaves of C. acuminata, which is about 5 mg/
g DW (dry weight). The matured leaves contain minimum levels of CPT, which is
250% lesser than that can be obtained from the bark, and ten-fold lesser than that
can be obtained from young leaves (Lopez et al. 1994; Li et al. 2000; Yan et al.
2003; Kaushik et al. 2015; Prakash et al. 2016).
The increased exploration of plant resources for CPT-producing capability have
resulted in the documentation of 34 new plant species that belong to Apocynaceae,
Rubiaceae, Gelsemiaceae, Betulaceae, Icacinaceae, Nyssaceae, Meliaceae, and
Violaceae. Among them, the majority of plant species belong to Rubiaceae and
Icacinaceae family. Importantly, most of these described plant species have their
natural distribution in the South-East Asian nations, exclusively in the south part of
316
M. K. Swamy et al.