Calculation Of Structure And Spectrum Of Bioactive Molecules In Green Tea

China is the hometown of tea.It has a history of growing and drinking tea for thousands of years.Experimental studies have shown that tea contains many organic and biochemical active ingredients,inorganic mineral elements,nutrients and medicinal ingredients.Tea drinking has a lot of health care and pharmacological effects such as refreshing brain,preventing tooth fixation,reducing blood pressure,detoxification,anti-cancer,delaying aging,and relieving nuclear radiation damage.Tea drinking can also prevent some diseases and help your health.There are many kinds of biochemical active ingredients in tea.Among them,tea polyphenols,alkaloids and theanine are mainly.Studying the structure,energy level,chemical activity and spectral properties of these bioactive molecules will help to better understand their antioxidant,refreshing,anti-aging and other effects.Based on the density functional theory(DFT)in the first-principle,the structure of tea polyphenols,alkaloids and theanine molecules in green tea are firstly optimized by using the Gaussian09 software package,and the stable molecular configuration are obtained to ensure that the resulting configuration is the atomic position corresponding to the minimum value of potential energy.Then,the vibration frequency calculation and vibration mode analysis of the stable configuration are carried out,and their infrared spectra are obtained.The vibration modes of each characteristic group corresponding to the main infrared peaks are analyzed.The theoretical and experimental spectra were compared.Using the time-dependent density functional theory(TD-DFT)to calculate the excited states of the above molecules,the transition between the excited states of the molecules and the ultraviolet spectrum are obtained and analyzed.The theoretical UV spectrum is compared with the experimental UV spectrum.The frontier orbitals(the highest occupied molecular orbit(HOMO)and the lowest unoccupied molecular orbit(LUMO)),the Fukui function,the surface electrostatic potential and the average localized ionization energy of tea polyphenols and theanine molecules were calculated and analyzed by using molecular orbital theory.On this basis,the electrophilic and nucleophilic active sites of the two molecules were analyzed.This study provides a theoretical basis for further research on the antioxidant,refreshing and anti-aging effects of green tea.