Likewise, new endophyte, Xylaria sp. occurring in C. acuminata was isolated,
and it was noticed that this fungus could produce 10-hydroxy-CPT, but failed to
produce CPT (Liu et al. 2010). Endophytic microbes that can biosynthesize CPT
have been witnessed by many researchers, however, attenuation of CPT synthesis is
one of the chief problems in this area of studies.
Later, study by Shweta et al. (2013), described 3 endophytes, namely Phomopsis
sp., Fomitopsis sp., and Alternaria alternate that occurred in the shrub species,
Miquelia dentata Bedd. These fungi produced CPT, 9-methoxy-CPT, and
10-hydroxy-CPT. The obtained yield of CPT from these species was found to be
about 42, 73, and 55 lg/g DW, respectively for Phomopsis sp., Fomitopsis sp., and
A. alternate. About 161 endophytic fungal species were isolated from C. acuminata, and among them, only one fungus, i.e., Botryosphaeria dothidea X-4 was
shown to be capable of producing 9-methoxy-CPT (Ding et al. 2013).
Likewise, 3 new endophytic fungi (Aspergillus sp. LY355, Aspergillus
sp. LY341, and Trichoderma atroviride LY357) were isolated from C. acuminata.
These species yielded CPT content of 42.9, 7.9, and 197.8 lg per liter of broth
culture, respectively. However, repeated sub-culturing of these fungal strains were
reported to lead to the diminishing of CPT-yielding ability. However, there was a
persistent production of CPT by Aspergillus sp. LY357 strain until the eighth
generation of sub-culturing (Pu et al. 2013; Kai et al. 2015; Uzma et al. 2018).
An investigation of Soujanya et al. (2017) reported the association of 4 new
bacterial strains with the stems, fruits, and leaves of Pyrenacantha volubilis,
belonging to Icacinanceae plant family. The identified bacteria included B. amyloliquefaciens (KY741854), Bacillus sp. (KP125956), Bacillus sp. (KP125955),
and B. subtilis (KY741853). All these isolates were reported to produce CPT as
revealed by the use of electrospray ionization mass spectrometry (ESI–MS) and
nuclear magnetic resonance spectroscopy (NMR) analysis. The crude extract of
these bacterial isolates were analyzed for their antitumor activity on colon cancer
cells, and the results have shown that crude extracts exhibiting effective cytotoxicity. Also, their study evaluated the part played by plasmid in producing CPT. They
proposed the potential role of a plasmid (5 kbp) in bacteria to biosynthesize CPT.
However, the exact mechanisms are yet to be revealed. B. subtilis, KY741853
strain, producing CPT was attenuated after sub-culturing in the culture medium.
In another study, solid-state fermentation was utilized to culture the endophytic
fungus, Fusarium oxysporum, and evaluated for its capability to produce CPT
(Bhalkar et al. 2016). According to them, soybean meal, among different substrates
utilized was observed to be the best medium for producing CPT effectively by F.
oxysporum under optimized solid-state fermentation conditions. The use of soyabean meal substrate was effective in yielding CPT content of about 128 mg/l dry
weight after 3 days of growth in a bioreactor. In addition, the use of whey (the
liquid remaining after milk) as a moisture source in solid-state fermentation played
an important role in augmenting the yield of CPT. The application of this developed
process can be environmentally very effective, and it is evidenced by the fact that
after fermentation stage, there was a significant reduction in the levels of biological
oxygen demand (BOD), chemical oxygen demand (COD), total soluble solids
9 Camptothecin: Occurrence, Chemistry and Mode of Action
319
and it was noticed that this fungus could produce 10-hydroxy-CPT, but failed to
produce CPT (Liu et al. 2010). Endophytic microbes that can biosynthesize CPT
have been witnessed by many researchers, however, attenuation of CPT synthesis is
one of the chief problems in this area of studies.
Later, study by Shweta et al. (2013), described 3 endophytes, namely Phomopsis
sp., Fomitopsis sp., and Alternaria alternate that occurred in the shrub species,
Miquelia dentata Bedd. These fungi produced CPT, 9-methoxy-CPT, and
10-hydroxy-CPT. The obtained yield of CPT from these species was found to be
about 42, 73, and 55 lg/g DW, respectively for Phomopsis sp., Fomitopsis sp., and
A. alternate. About 161 endophytic fungal species were isolated from C. acuminata, and among them, only one fungus, i.e., Botryosphaeria dothidea X-4 was
shown to be capable of producing 9-methoxy-CPT (Ding et al. 2013).
Likewise, 3 new endophytic fungi (Aspergillus sp. LY355, Aspergillus
sp. LY341, and Trichoderma atroviride LY357) were isolated from C. acuminata.
These species yielded CPT content of 42.9, 7.9, and 197.8 lg per liter of broth
culture, respectively. However, repeated sub-culturing of these fungal strains were
reported to lead to the diminishing of CPT-yielding ability. However, there was a
persistent production of CPT by Aspergillus sp. LY357 strain until the eighth
generation of sub-culturing (Pu et al. 2013; Kai et al. 2015; Uzma et al. 2018).
An investigation of Soujanya et al. (2017) reported the association of 4 new
bacterial strains with the stems, fruits, and leaves of Pyrenacantha volubilis,
belonging to Icacinanceae plant family. The identified bacteria included B. amyloliquefaciens (KY741854), Bacillus sp. (KP125956), Bacillus sp. (KP125955),
and B. subtilis (KY741853). All these isolates were reported to produce CPT as
revealed by the use of electrospray ionization mass spectrometry (ESI–MS) and
nuclear magnetic resonance spectroscopy (NMR) analysis. The crude extract of
these bacterial isolates were analyzed for their antitumor activity on colon cancer
cells, and the results have shown that crude extracts exhibiting effective cytotoxicity. Also, their study evaluated the part played by plasmid in producing CPT. They
proposed the potential role of a plasmid (5 kbp) in bacteria to biosynthesize CPT.
However, the exact mechanisms are yet to be revealed. B. subtilis, KY741853
strain, producing CPT was attenuated after sub-culturing in the culture medium.
In another study, solid-state fermentation was utilized to culture the endophytic
fungus, Fusarium oxysporum, and evaluated for its capability to produce CPT
(Bhalkar et al. 2016). According to them, soybean meal, among different substrates
utilized was observed to be the best medium for producing CPT effectively by F.
oxysporum under optimized solid-state fermentation conditions. The use of soyabean meal substrate was effective in yielding CPT content of about 128 mg/l dry
weight after 3 days of growth in a bioreactor. In addition, the use of whey (the
liquid remaining after milk) as a moisture source in solid-state fermentation played
an important role in augmenting the yield of CPT. The application of this developed
process can be environmentally very effective, and it is evidenced by the fact that
after fermentation stage, there was a significant reduction in the levels of biological
oxygen demand (BOD), chemical oxygen demand (COD), total soluble solids
9 Camptothecin: Occurrence, Chemistry and Mode of Action
319