title: Differential activities of the two closely related withanolides, Withaferin A and Withanone: bioinformatics and experimental evidences.
abstract: OBJECTIVE
  Withanolides are naturally occurring chemical compounds. They are secondary metabolites produced via oxidation of steroids and structurally consist of a steroid-backbone bound to a lactone or its derivatives. They are known to protect plants against herbivores and have medicinal value including anti-inflammation, anti-cancer, adaptogenic and anti-oxidant effects. Withaferin A (Wi-A) and Withanone (Wi-N) are two structurally similar withanolides isolated from Withania somnifera, also known as Ashwagandha in Indian Ayurvedic medicine. Ashwagandha alcoholic leaf extract (i-Extract), rich in Wi-N, was shown to kill cancer cells selectively. Furthermore, the two closely related purified phytochemicals, Wi-A and Wi-N, showed differential activity in normal and cancer human cells in vitro and in vivo. We had earlier identified several genes involved in cytotoxicity of i-Extract in human cancer cells by loss-of-function assays using either siRNA or randomized ribozyme library.
  
  
  RESULTS
  In the present study, we have employed bioinformatics tools on four genes, i.e., mortalin, p53, p21 and Nrf2, identified by loss-of-function screenings. We examined the docking efficacy of Wi-N and Wi-A to each of the four targets and found that the two closely related phytochemicals have differential binding properties to the selected cellular targets that can potentially instigate differential molecular effects. We validated these findings by undertaking parallel experiments on specific gene responses to either Wi-N or Wi-A in human normal and cancer cells. We demonstrate that Wi-A that binds strongly to the selected targets acts as a strong cytotoxic agent both for normal and cancer cells. Wi-N, on the other hand, has a weak binding to the targets; it showed milder cytotoxicity towards cancer cells and was safe for normal cells. The present molecular docking analyses and experimental evidence revealed important insights to the use of Wi-A and Wi-N for cancer treatment and development of new anti-cancer phytochemical cocktails.
authors.affiliation: Supercomputer Education and Research Centre, Indian Institute of Science, Bangalore, India.
authors.forename: Kirti
authors.initials: K
authors.lastname: Vaishnavi
authors.forename: Nishant
authors.initials: N
authors.lastname: Saxena
authors.forename: Navjot
authors.initials: N
authors.lastname: Shah
authors.forename: Rumani
authors.initials: R
authors.lastname: Singh
authors.forename: Kavyashree
authors.initials: K
authors.lastname: Manjunath
authors.forename: M
authors.initials: M
authors.lastname: Uthayakumar
authors.forename: Shankar P
authors.initials: SP
authors.lastname: Kanaujia
authors.forename: Sunil C
authors.initials: SC
authors.lastname: Kaul
authors.forename: Kanagaraj
authors.initials: K
authors.lastname: Sekar
authors.forename: Renu
authors.initials: R
authors.lastname: Wadhwa
mesh_terms: D015153:Blotting, Western; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019295:Computational Biology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008515:Medicine, Ayurvedic; D008958:Models, Molecular; D015394:Molecular Structure; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D010936:Plant Extracts / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry*; D013778:Tetrazolium Salts; D013844:Thiazoles; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D032341:Withania / Q000737:chemistry*; D054358:Withanolides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D001616:beta-Galactosidase
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018840:HSP70 Heat-Shock Proteins; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D010936:Plant Extracts; D013778:Tetrazolium Salts; D013844:Thiazoles; D014315:Triterpenes; D016159:Tumor Suppressor Protein p53; D054358:Withanolides; C080352:mortalin; D001616:beta-Galactosidase; C022616:thiazolyl blue; C560597:withanone; C009684:withaferin A; C030693:Ashwagandha