Studies On The Synthesis Of 4-methoxy Cinnamoyl Glycerols And Pegylated Esters

P-methoxycinnamic acid is a better organic ultraviolet(UV)filter and can effectively absorb 280-320nm UV.Because of its poor solubility in water or oil system,p-methoxycinnamic acid have to be modified as p-methoxycinnamates.P-methoxycinnamates have been widely used as UV filters in sunscreen products.In order to produce more p-methoxycinnamates,p-methoxycinnamic acid was modified through esterification with polyhydric alcohols(such as glycerol,polyethylene glycol)or coconut oil to obtain hydrophilicity or lipophilicity p-methoxycinnamates.And their UV absorption and photo-stability properties are evaluated,which could promote the development of functional lipids and sunscreen products.First,the synthesis of p-methoxycinnamic acid monoglyceride(4-MCAMG)for the esterification of p-methoxycinnamic acid with glycerol,acidic ion exchange resin(Amberlyst@15)was investigated as catalyst.The optimal reaction conditions were as follows:reaction temperature 130~oC.,the molar ratio of 4-MCA to glycerol 1:10,the amount of catalyst 20%(based on the mass of 4-MCA),reaction time 3h.The yield of 4-MCAMG was 69.6%and the conversion of the 4-MCA was 91.9%under the optimal conditions.The structure of 4-MCAMG was determined by ~1H NMR.4-MCAMG had a higher absorption peak at 280-320 nm in the UV spectrum,which retained the UV absorption characteristics of4-MCA.The photo-stability of 4-MCAMG was better.After ultraviolet irradiation for 72 h,4-MCAMG still has more than 75%of ultraviolet absorption effect.The actual sample test proved that 4-MCAMG could effectively prevent the damage of UV to the hair.Second,the esterification of p-methoxycinnamic acid with PEG-200,PEG-400,and PEG-600 using acidic ion exchange resins as catalysts to obtain p-methoxycinnamic acid polyethylene glycol-200 esters(4-MCAPEG-200),p-methoxycinnamic acid polyethylene glycol-400 esters(4-MCAPEG-400)and p-methoxycinnamic acid polyethylene glycol-600esters(4-MCAPEG-600)were investigated,respectively.The optimum reaction conditions for the synthesis of 4-MCAPEG-200 was as follows:the molar ratio of PEG-200 to 4-MCA 10:1,6%(PEG-200 wt%)of A-35 as catalyst,120~oC,5h.Under this condition,the yield of4-MCAPEG-200 was 97.6±0.4%.The optimal reaction conditions for the synthesis of4-MCAPEG-400 was as follows:the molar ratio of PEG-400 to p-methoxycinnamic acid 10:1,6%(PEG-400 wt%)of A-35 as catalyst,reaction temperature 130~oC,reaction time 7h.the yield of 4-MCAPEG-200 was 96.2±1.3%under the optimal conditions.The optimal reaction conditions for the synthesis of 4-MCAPEG-600 was as follows:the molar ratio of PEG-600 to p-methoxycinnamic acid 10:1,3%(PEG-600 wt%)of A-35 as catalyst at 140~oC,providing the yield of 4-MCAPEG-600 of 98.3±0.6%.The ESI-MS analysis confirmed that the products were 4-MCAPEG esters.The three kinds of 4-MCAPEG esters had a higher absorption peak at 280-320 nm in the UV spectrum.The photo-stability test showed that 4-MCAPEG still has more than 75%of UV absorption effect under ultraviolet irradiation for 72h.In the hair sample experiment,it was proved that three kinds of 4-MCAPEG ester could protect the hair from the damage of ultraviolet rays.The effect of the three esters on the UV resistance of the hair samples was:4-MCAPEG-200>4-MCAPEG-400>4-MCAPEG-600.With the aim to enhance the stability and lipophilicity of 4-MCA,4-MCA structured lipids were prepared by the transesterification of methyl p-methoxycinnamate with coconut oil,using the Novozym435 as catalyst.The optimal reaction conditions for the synthesis of p-methoxycinnamic acid glycerides was as follows:7%of Novozym435 enzyme as catalyst,the molar ratio of p-methoxycinnamic acid to coconut oil 1:2,70~oC,96 h.Under the optimal reaction condition,the conversion of methyl p-methoxycinnamate reached 95.5%.By HPLC-ESI-MS analysis,the main products of the reaction were p-methoxycinnamoyl diglyceride(4-MCADG)and p-methoxycinnamoyl triglyceride(4-MCATG).Finally,using a new type of deep eutectic solvent(DES)as catalyst and solvent,the esterification of coconut oil with 4-MCA to obtain p-methoxycinnamic acid glycerides was studied.The optimum reaction conditions were obtained as follows:oil to DES(v/v)1:2,the molar ratio of 4-MCA:coconut oil 1:1,140~oC,5h,the conversion of 4-MCA reached 98.98%.By ESI-MS analysis,the final products were mainly 4-MCATG and 4-MCADG.The photo-stability test showed that the UV absorption effect of 4-MCATG under UV irradiation from 12 h to 72 h was about 36.5%,and fluctuated around 85.3%under incandescent light bulb irradiation from 12 h to 72 h.The UV absorption effect of 4-MCADG fluctuated above22.4%exposure to UV light for 12 h-72 h,and fluctuated around 60%under incandescent light bulb irradiation from 12 h to 72 h.From these results,it can be seen that the photo-stability of 4-MCATG was better than 4-MCADG.