title: Mechanisms of cytotoxicity of 2- or 2,6-di-tert-butylphenols and 2-methoxyphenols in terms of inhibition rate constant and a theoretical parameter.
abstract: To clarify the mechanism of phenol toxicity, the radical-scavenging activity of 2- or 2,6-di-tert-butyl- and 2-methoxy-substituted phenols was investigated by combining two distinct approaches: first, the induction period method for methacrylate polymerization initiated by benzoyl peroxide or 2,2'-azobisisobutyronitrile; and secondly, 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test. The homolytic bond dissociation enthalpy (BDE) and ionization potential (IP(koopman)) were calculated by the DFT/B3LYP method. The cytotoxicity was investigated using tumor cells (human submandibular gland carcinoma cells, HSG; human promyelocytic leukemia cells, HL-60) and primary cells (human gingival fibroblasts, HGF; human periodontal ligament fibroblasts, HPLF; human pulp fibroblasts, HPF) derived from oral tissues. The cytotoxicity between tumor and primary cells was similar, except for eugenol dimer showing less toxicity for primary cells. The DPPH assay was not useful for tert-butylphenols due to their steric hindrance. For both HSG and HGF cells, a linear relationship was found between 50% cytotoxic concentration (CC(50)) and inhibition rate constant (k(inh)), but not BDE, IP, or logP. The acceptable quantitative structure-activity relationships (QSAR) obtained for cytotoxicity vs. k(inh) suggested that the cytotoxicity of phenols may be dependent on radical reactions. The cytotoxicity of vanillin and 3,5-di-tert-butyl-4-hydroxy-benzaldehyde with large k(inh) values, weak antioxidants was markedly less than that of 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol and curcumin with small k(inh) values, potent antioxidants.
authors.affiliation: Department of Applied Function Molecules, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-Ku, 101-0062 Tokyo, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kadoma
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ito
authors.forename: Toshiko
authors.initials: T
authors.lastname: Atsumi
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Fujisawa
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000633:toxicity; D001547:Benzaldehydes / Q000737:chemistry / Q000633:toxicity; D002084:Butylated Hydroxytoluene / Q000031:analogs & derivatives / Q000737:chemistry / Q000633:toxicity; D045744:Cell Line, Tumor; D003474:Curcumin / Q000737:chemistry / Q000633:toxicity; D005054:Eugenol / Q000633:toxicity; D018922:HL-60 Cells; D006801:Humans; D007700:Kinetics; D010636:Phenols / Q000737:chemistry* / Q000633:toxicity*; D021281:Quantitative Structure-Activity Relationship
chemical_list: D000975:Antioxidants; D001547:Benzaldehydes; D010636:Phenols; D002084:Butylated Hydroxytoluene; D005054:Eugenol; C513957:3,5-di-tert-butyl-4-hydroxybenzaldehyde; C019584:2,4,6-tri-tert-butylphenol; C100058:vanillin; D003474:Curcumin