ABSTRACT
Several novel spiro derivatives of parthenin (1) have been synthesized by the dipolar cycloaddition using various dipoles viz; benzonitrile oxides, nitrones and azides with exocyclic double bond of C ring (α-methylene-γ-butyrolactone). Majority of the compounds exhibited improved anti-cancer activity compared to the parthenin, when screened for their in vitro cytotoxicity against three human cancer cell lines viz., SW-620, DU-145 and PC-3. In vivo screening of select analog revealed improved anti-cancer activity with low mammalian toxicity as compared to parthenin. The results of the cytotoxicity pattern of these derivatives reveals the SAR of these sesquiterpinoid lactones and possible role of α,ß-unsaturated ketone of parthenin in inhibiting NF-kB. A mechanistic correlation of anti-cancer activity along with in vivo and western blotting experiments has been described.
Subject(s)
Antineoplastic Agents/chemical synthesis , Carcinoma, Ehrlich Tumor/drug therapy , Cell Proliferation/drug effects , DNA Fragmentation/drug effects , NF-kappa B/antagonists & inhibitors , Sesquiterpenes/chemical synthesis , Spiro Compounds/chemical synthesis , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/chemistry , Animals , Antineoplastic Agents/pharmacology , Blotting, Western , Carcinoma, Ehrlich Tumor/pathology , Cell Cycle/drug effects , Cell Line, Tumor , Colonic Neoplasms/drug therapy , Colonic Neoplasms/pathology , Humans , Male , Mice , NF-kappa B/metabolism , Neoplasm Transplantation , Nitriles/chemistry , Oxides/chemistry , Prostatic Neoplasms/drug therapy , Prostatic Neoplasms/pathology , Sesquiterpenes/pharmacology , Spiro Compounds/pharmacology , Structure-Activity RelationshipABSTRACT
Boswellic acids have invariably been reported for their antiproliferative potential in various cell systems. In the present study the growth inhibitory effect of propionyloxy derivative of 11-keto-ß-boswellic acid (PKBA; a semisynthetic analogue of 11-keto-ß-boswellic acid) on HL-60 promyelocytic leukemia cells is being reported for the first time. In the preliminary studies, in vitro cytotoxicity of PKBA was investigated against eight human cancer cell lines viz., IMR-32, SF-295 (both neuroblastoma), PC-3 (prostate), Colo-205 (colon), MCF-7 (breast), OVCAR-5 (ovary), HL-60, Molt-4 (both leukemia) and their respective IC(50) values were found to be 5.95, 7.11, 15.2, 14.5, 15, 15.9, 8.7 & 9.5µg/ml, respectively. For determining the mechanism of cell death in HL-60 cells, PKBA was subjected to different mechanistic studies. DNA relaxation assay of PKBA revealed inhibition of both topoisomerases I & II. The fragmentation analysis of DNA revealed typical ladders indicating the cytotoxic effect to be mediated by induction of apoptosis. The morphologic studies of PKBA showed the presence of true apoptotic bodies. Apoptosis was confirmed further by flow-cytometric detection of sub-G(1) peaks and enhanced annexin-V-FITC binding of the cells. The activation of apoptotic cascade by PKBA in HL-60 cells was found to be associated with the loss of mitochondrial membrane potential, release of cytochrome c, activation of initiator and executioner caspases and cleavage of poly ADP ribose polymerase (PARP). In vivo studies of PKBA revealed anti-tumoral activity against both ascitic and solid murine tumor models. These studies thus demonstrate PKBA to induce apoptosis in HL-60 cells due to the inhibition of topoisomerases I and II.
Subject(s)
Apoptosis/drug effects , DNA Topoisomerases, Type II/metabolism , DNA Topoisomerases, Type I/metabolism , Topoisomerase Inhibitors/pharmacology , Triterpenes/pharmacology , Animals , Cell Proliferation/drug effects , Comet Assay , DNA Damage , Flow Cytometry , HL-60 Cells , Humans , Magnetic Resonance Spectroscopy , Male , Membrane Potential, Mitochondrial/drug effects , Mice , Microscopy, Electron, Scanning , Propionates/chemistry , Propionates/pharmacology , Random Allocation , Spectrometry, Mass, Electrospray Ionization , Triterpenes/chemistryABSTRACT
The acylated analogs of picroside-II were synthesized and tested for immune-adjuvant activity in the presence of weak antigen ovalbumin found to stimulate anti-OVA IgG titer, neutralizing antibody (IgG1 and IgG2a) titer as well as the production of soluble mediators of a Th1 response (IL-2 and IFN-γ) and Th2 response (IL-4) and proliferation of T lymphocytes sub-sets (CD4/CD8). Furthermore, these modified analogs of picroside-II were able to elicit a substantial increase in anti-OVA IgG when compared with OVA alone. These results support the use of acylated analogs particularly PK-II-3 and PK-II-4 as potent enhancer of antigen-specific Th1 and Th2 immune responses and thus are promising immune-adjuvant candidate for vaccines.
