Two Phenolic Diterpenes as Antioxidants

1 INTRODUCTION Experimental studies in recent years show thatphenolic diterpenes are potent antioxidants with highbio-activities of anti-tumor, anti-HIV and anti-mi-crobes[1～4], and they have been developed and ap-plied in medicine, cosmetics, and keeping foods fresh.However, the exact mechanism in which phenolicditerpenes act as those bio-activities are still unex-plored. A series of compounds with similar struc-tures, including carnosol, rosmanol, isorosmanol andso on, were isolated f…     

维生素E类化合物抗氧化活性的理论分析

用半径验方法AM1,对12种维生素E类化合物及2种单酚与羟基自由基反应的活化能、氧氢键离解能D进行了计算。发现Ea、D越低,其抗氧化活性愈高;Ea、D与化合物分子中芳环上烷基取代基的数目、种类及位置有关;14个化合物的反应活化能均小于56kJ·mol-1;从反应物到过渡态氧原子上的净电荷减少。     

DFT Study on the Antioxidant Activity of a Modeled p-Terphenyl Derivative

Relationships between the structure characteristics of natural p-terphenyl com- pounds isolated from three edible mushrooms (Thelephora ganbajun, Thelephora aeronautical, and Boletopsis grisea) indigenous to China and their mechanism of antioxidant activity were studied. Geometry structures of terphenyl molecule and four corresponding radicals, bond dissociation energy (BDE), frontier orbitals (HOMO and LUMO) and single electron density were calculated using DFT methods (B3LYP/6-311G**). The computational results which are consistent with the experimental data well show that terphenyl molecule scavenges DPPH radical by hydrogen abstract mechanism and the high antioxidant activity depends on the substitution position of hydroxyls. Two active 7-, 8-hydroxyls facilitate the hydrogen abstraction due to the intramolecular hydrogen bond and the resonance effect makes 4-hydroxyl radical more stable.