Optimum conditions and verification
The optimum reaction variables for CG synthesis were as follows: load of
Lipozyme 435 25 % (relative to the weight of total substrates), molar
ratio of CA to glycerol 1:150, 80 oC and 10 h. Under
the optimized conditions, CG yield
was 95.0 ± 1.0 %, which was similar with the yield reported in the
literature (Sun & Hu, 2017). However, CG was in the past synthesized by
the transesterification of ethyl caffeate with glycerol, with the
disadvantage of reducing the final reaction efficiency and increasing
cost.
The above optimal reaction conditions were also used to synthesize FG
and p -HCG via esterification of FA and p -HCA with
glycerol, resulting in isolated yields of 82.1 % and 80.7 %
respectively, validating the reaction model in the synthesis of PAGs.