Application of Ultra-High Performance Liquid Chromatography Fingerprint with Chemical Pattern Recognition in Quality Evaluation of Bitter Thorn Nectar

The fingerprints of 28 batches of bitter thorn nectar samples from different origins were established by ultra-high performance liquid chromatography (UHPLC), and the quality of samples were studied by UHPLC fringerprints combined with chemical pattern recognition, which provided the basis for the identification of adulteration and discrimination of origin of bitter thorn nectar. Bitter thorn nectar sample (20 g) was taken, and dissolved by 15 mL of water with vortex, and 15 mL of ethyl acetate was added into the mixture for extraction with vortex. After centrifugation, the supernatant was taken, and 10 mL of ethyl acetate was added into the residue for repeat extraction. The supernatants obtained were combined and blown to near dryness by nitrogen at 30 ℃, the residue was redissolved by 1 mL of methanol, and the mixed solution was filtered through a 0.22 μm organic membrane. The filtrate obtained was injected into ultra-high performance liquid chromatograph, with ACQUITY UPLC BEH C₁₈ column as stationary phase, and 0.1% (volume fraction) formic acid solution and methanol solution containing 0.1% formic acid as mobile phase system for gradient elution, and determined by diode array detector at the detection wavelength of 280 nm. The fingerprints of 28 batches of bitter thorn nectar samples and reference fingerprint were obtained by the Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine (2012.130723 edition), and 22 common peaks were obtained. By comparing with the chromatograms of the mixed reference solutions, 9 common peaks were identified, and the corresponding compounds were p-hydroxybenzoic acid, caffeic acid, p-coumaric acid, ferulic acid, erucinic acid, methyl eugenate, quercetin, kaempferol and albumin. The similarities between fingerprints of 28 batches of bitter thorn nectar samples and reference fingerprint were in the range of 0.909-0.993, and the similarities between fingerprints of pseudo bitter thorn nectar samples and reference fingerprint were in the range of 0.251-0.853 by simulated adulteration detection analysis of rape honey and locust honey mixed with different mass concentrations (5%-50%). The 28 batches of bitter thorn nectar samples were studied by hierarchical cluster analysis, principal component analysis and orthogonal partial least square-discriminant analysis. The results showed that 28 batches of bitter thorn nectar samples were divided into three categories by the three methods, with the samples from Huixian county for one category, and the samples from Liangdang county for two categories. The quantitative analysis of 9 compounds identified showed that the linear ranges of the standard curves of 9 compounds were in the range of 0.5-200.0 mg·L^-1, with the same detection limit (3S/N) of 0.01 mg·kg^-1. The contents of p-hydroxybenzoic acid, erucinic acid, quercetin and kaempferol in 28 batches of bitter thorn nectar samples were higher, but that of each component in each batch of sample was significantly different.