16alpha-Hydroxycleroda-3,13 (14)Z-dien-15,16-olide from Polyalthia longifolia: a safe and orally active antileishmanial agent.
OBJECTIVE
New antileishmanials from natural products are urgently needed due to the emergence of drug resistance complicated by severe cytotoxic effects. 16alpha-Hydroxycleroda-3,13 (14)Z-dien-15,16-olide (Compound 1) from Polyalthia longifolia was found to be a potential antileishmanial and non-cytotoxic, as evidenced by long-term survival (>6 months) of treated animals. This prompted us to determine its target and, using molecular modelling, identify the interactions responsible for its specific antileishmanial activity.


METHODS
In vitro activity of compound was assessed using intracellular transgenic green fluorescent protein-stably expressed Leishmania donovani parasites. In vivo activity and survival of animals post-treatment were evaluated in L. donovani-infected hamsters. Known property of clerodane diterpenes as potent human DNA topoisomerase inhibitors led us to evaluate the inhibition of recombinant L. donovani topoisomerase I using relaxation assay. Mode of cell death induced by Compound 1 was assessed by phosphotidylserine exposure post-treatment. Molecular modelling studies were conducted with DNA topoisomerase I to identify the binding interactions responsible for its activity.


RESULTS
Bioassay-guided fractionation led to isolation of Compound 1 as a non-cytotoxic, orally active antileishmanial. Compound 1 inhibited recombinant DNA topoisomerase I which, ultimately, induced apoptosis. Molecular docking studies indicated that five strong hydrogen-bonding interactions and hydrophobic interactions of Compound 1 with L. donovani DNA-topoisomerase are responsible for its antileishmanial activity.


CONCLUSIONS
The data reveal Compound 1 is a potent and safe antileishmanial. The study further exploited the structural determinants responsible for its non-cytotoxic and potent activity, to raise the feasibility of specifically targeting the target enzyme responsible for its activity through rational drug design.
CDRI, CSIR, Lucknow, India.
Pragya
P
Misra
Koneni V
KV
Sashidhara
Suriya Pratap
SP
Singh
Awanish
A
Kumar
Reema
R
Gupta
Shailendra S
SS
Chaudhaery
Souvik Sen
SS
Gupta
H K
HK
Majumder
Anil K
AK
Saxena
Anuradha
A
Dube
D000284:Administration, Oral; D000818:Animals; D000981:Antiprotozoal Agents / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D006224:Cricetinae; D004224:Diterpenes / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D016503:Drug Delivery Systems; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007893:Leishmania donovani / Q000187:drug effects* / Q000201:enzymology; D007898:Leishmaniasis, Visceral / Q000188:drug therapy; D008297:Male; D008958:Models, Molecular; D031044:Polyalthia / Q000737:chemistry*; D059004:Topoisomerase I Inhibitors
D000981:Antiprotozoal Agents; D004224:Diterpenes; D059004:Topoisomerase I Inhibitors; C072581:16-hydroxycleroda-3,13(14)-dien-15,16-olide