title: Design, economical synthesis and antiplasmodial evaluation of vanillin derived allylated chalcones and their marked synergism with artemisinin against chloroquine resistant strains of Plasmodium falciparum.
abstract: The in vitro blood stage antiplasmodial activity of a series of allylated chalcones based on the licochalcone A as lead molecule was investigated against chloroquine (CQ) sensitive Pf3D7 and CQ resistant PfINDO strains of Plasmodium falciparum using SYBR Green I assay. Of the forty two chalcones tested, eight showed IC50 ≤ 5 μM. Structure-activity relationship (SAR) studies revealed 9 {1-(4-Chlorophenyl)-3-[3-methoxy-4-(prop-2-en-1-yloxy)phenyl]-prop-2-en-1-one} as the most potent (IC50: 2.5 μM) against Pf3D7 with resistance indices of 1.2 and 6.6 against PfDd2 and PfINDO strains, respectively. Later on, the synergistic effects 9 with standard antimalarials {artemisinin (ART) and chloroquine (CQ)} were studied in order to provide the basis for the selection of the best partner drug. In vitro combinations of 9 with ART showed strong synergy against PfINDO (ΣFIC50: 0.31-0.72) but additive to slight antagonistic effects (ΣFIC50: 1.97-2.64) against Pf3D7. ΣFIC50 0.31 of ART+9 combination corresponded to a 320 fold and 3 fold reduction in IC50 of 9 and ART, respectively. Similar combinations of 9 with CQ showed synergy to additivity to mild antagonism against the two strains {ΣFIC50: 0.668-2.269 (PfINDO); 1.45-2.83 (Pf3D7)}. Drug exposure followed by drug withdrawal indicated that 9 taken alone at IC100 killed rings, trophozoites and schizonts of P. falciparum. The combination of ART and 9 (1X ΣFIC100) selectively inhibited the growth of rings while the 2X ΣFIC100 combination of the same caused killing of rings without affecting trophozoites and schizonts. In contrast, the 1X combination of CQ and 9 (ΣFIC100: 0.5) killed rings and trophozoites. DNA fragmentation and loss of mitochondrial membrane potential (ΔΨm) in the 9 treated P. falciparum culture indicated apoptotic death in malaria parasites. Prediction of ADME properties revealed that most of the molecules did not violate Lipinski's parameters and have low TPSA value suggesting good absorption. The results suggest the promising drug-like properties of 9 against CQ resistant Pf and propensity for synergy with classical antimalarial drugs together with easy and economical synthesis.
authors.affiliation: Natural Plant Products Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India.
authors.forename: Nandini
authors.initials: N
authors.lastname: Sharma
authors.affiliation: Malaria Research Laboratory, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Dinesh
authors.initials: D
authors.lastname: Mohanakrishnan
authors.affiliation: Natural Plant Products Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India.
authors.forename: Upendra Kumar
authors.initials: UK
authors.lastname: Sharma
authors.affiliation: Natural Plant Products Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Natural Plant Products Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India.
authors.lastname: Richa
authors.affiliation: Natural Plant Products Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India; Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, Lucknow 226031, UP, India. Electronic address: aksinha08@rediffmail.com.
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Sinha
authors.affiliation: Malaria Research Laboratory, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India. Electronic address: dinkar@icgeb.res.in.
authors.forename: Dinkar
authors.initials: D
authors.lastname: Sahal
mesh_terms: D000962:Antimalarials / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D037621:Artemisinins / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001547:Benzaldehydes / Q000737:chemistry*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D047188:Chalcones / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002738:Chloroquine / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D004351:Drug Resistance / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D015394:Molecular Structure; D021261:Parasitic Sensitivity Tests; D010963:Plasmodium falciparum / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D013329:Structure-Activity Relationship
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D001547:Benzaldehydes; D047188:Chalcones; D002738:Chloroquine; C031327:artemisinin; C100058:vanillin
keywords: Allylated chalcones; Artemisinin; Chloroquine; Plasmodium falciparum; Synergism