Establishment of high performance liquid chromatographic fingerprint and determination of 4 kinds of phenolic acid bioactive substances of fruitless Lycium barbarum leaves from Ningxia at different harvesting periods

''Fruitless Lycium barbarum leaf (FLBL) are the leaves of a new variety of Lycium barbarum in Ningxia, which exhibit higher content of various nutrients, trace elements, and bioactive substances compared to Lycium barbarum fruits and leaves. However, the health and medicinal value as well as the by-products derived from FLBL have not received sufficient attention, and the contents of main components vary at different harvesting periods. Therefore, for the first time this study aimed to establish high-performance liquid chromatography (HPLC) fingerprints and determine the contents of four phenolic acid bioactive substances during different harvesting periods in order to provide an experimental basis for cultivation, collection, and research on FLBL. The results revealed 17 common peaks among 10 batches samples with a similarity ranging from 0.71 to 0.976. The linear relationships R2 for catechin, epicatechin-catechin, chlorogenic acid, and rutin were determined as 0.9999 each; meanwhile, the average recovery rate ranged from 93.92 % to 120.11 %, with an RSD between 0.91 % and 2.82 %. The precision, repeatability stability (24 h), and recovery rate met the requirements outlined in ''Chinese Pharmacopoeia''. Catechin, epicatechin, and rutin exhibited higher levels from June to August, while chlorogenic acid showed increased levels from July to September. The findings serve as a foundation for quality control measures such as identifying optimal harvest periods or facilitating development and production processes related to Ningxia FLBL.''