Chemical constituents variation of seed oil of the Chinese tallow tree (Sapium sebiferum (L.) Roxb) at different harvesting time

Sapium sebiferum (L.) Roxb, has a long history of being used as an oil-producing plant due to its high oil content of the seeds. In recent years, the seed oil of this tree has gained considerable interest as an ideal material to produce biodiesel. To optimize the harvesting time of the seed, we tracked the variation of chemical constituents of seed oil harvested in different days (from October 1, 2021 to November 30, 2021). Firstly, the chemical constituents and fatty acid profile of external wax and internal kernel oil were studied, using nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS) as structure elucidation tools. Secondly, the constituent variation of external wax and kernel oil from different harvesting time was analyzed by 1H NMR and chemometrics tool. The results showed that unsaturated fatty acids in the kernel oil accumulated during harvesting time, while the external wax was progressively oxidized to formic acid due to exposure to air. Since the kernel oil was seal off from oxygen, no oxidation process was observed in it. Considering for the quality and total weight of lipids for biodiesel manufacturing, we suggest that the optimal harvesting time for seeds of S. sebiferum should be early November, when the fruit undergo complete cracking and the seeds are initially exposure to air. This information is practically helpful for optimizing the production of biodiesel from S. sebiferum and other similar oil-producing plants.