Lecithin extraction optimisation and synthesis in Hemerocallis citrina Baroni

Abstract

Hemerocallis citrina Baroni (daylily) is an important flower plant, consumed as food and used in traditional Chinese medicine. The daylily flower bud is rich in several functional substances, and lecithin is the most important among them. However, the optimum conditions for extracting lecithin from daylily flower buds are yet to be determined. The objective of this study was to examine the differences in the lecithin contents in daylily, identify the key enzymes and genes involved in lecithin synthesis, and establish the optimal conditions for lecithin extraction and detection by high-performance liquid chromatography. Initial treatment with acetone before ethanol extraction significantly increased the quantity of lecithin extracted compared with that extracted by direct ethanol extraction. The optimum lecithin extraction conditions were as follows: 90% ethanol concentration, 1:20 material-to-solvent ratio, 30 min extraction time, and 40°C extraction temperature. The highest lecithin content was obtained from the flower bud, specifically the stamen (3.49 mg/g). Additionally, the best harvest period for daylily flower buds with regards to lecithin content and nutritional quality was between 18 h before flowering and bloom (0 h). The lecithin content in freeze-dried daylily flower buds was higher than that in oven-dried and sun-dried flower buds. Among the varieties examined, Xiushan Huanghua (H0177) had the highest lecithin content (3.99 mg/g). Furthermore, the activity of phosphatidylethanolamine N-methyltransferase (PEAMT) was significantly higher than that of other enzymes involved in lecithin synthesis. Additionally, genes involved in lecithin synthesis were significantly expressed in the flower buds at different developmental stages. Overall, the findings of this study contribute to the understanding of lecithin synthesis in daylily.