Phase and baseline of all NMR spectra were adjusted by MestReNova software, and the TMSP (Trimethylsilylpropanoic acid) peak was set as 0 ppm. The text was derived after calculating piecewise integration, with 0.002 ppm as the interval. Data preprocessing was performed with self-prepared MATLAB script. Data points within 0.6–9.5 ppm were kept and the peak water interval (4.5–5.2 ppm) was removed. For each spectrum, 4450 bins were kept. To reduce the difference due to different sample concentration, the dilution factor of each sample was calculated according to a control spectrum after probabilistic quotient normalization (PQN) 