Studies On Chemical Chatacterization Of Carotenoids In Lycium Barbarum L.and Its Inhibitory Effect On 5α-Reductase

Objective:Lycium fruits,the dry and mature fruit of Lycium barbarum L.,are a good source for medicine and food,and have rich chemical components,which has the effect of nourishing the liver and kidney and benefiting the eyesight.Most studies were focus on the water-soluble component,such as Lycium barbarum polysaccharides,betaine,and less on the fat-soluble pigments in Lycium fruits.However,the research on the efficient and green enrichment and characterization methods of fat-soluble pigments,which are mainly free and bound carotenoids,as well as the correlation with the traditional efficacy of Lycium fruits is still in the fuzzy stage.Therefore,this topic is to solve the problem of the lack of green,efficient enrichment,characterization method and quality evaluation of the fat-soluble components,and provide a basis for the establishment of scientific and comprehensive quality standard of Lycium fruits.Methods:Based on the comparison with traditional extraction methods,a greener and more efficient DES extraction method of Lycium carotenoids was established,which included systematic optimization of deep eutectic solvent(DES),composition ratio,solid-liquid ratio and extraction time.A greener and more efficient method,ultra-performance convergence chromatography coupled with quadrupole time-of-flight mass spectrometry(UPC~2-Q-TOF-MS~E),was established for the characterization and identification of Lycium carotenoids instead of Ultra performance liquid chromatography(UPLC).Based on the 5α-reductase screening system of Ha Ca T cells in vitro,the monomers with potential inhibition of 5α-reductase activity were gradually screened out from the extracts,different fractions of Lycium fruits.Thin-layer chromatography(TLC)qualitative identification and UPC~2-PDA quantitative analysis method were established to analysis zeaxanthin dipalmitate(ZD),which was index component on the basis of component characterization and activity evaluation.The different content of ether extract and ZD in Lycium fruits from different producing areas were compared,which provided theoretical basis for comprehensive evaluation of the quality of Lycium fruits.Results:Compared with traditional solvent extraction,DES extraction was greener and more efficient in the enrichment of Lycium carotenoids.The extraction conditions of deep eutectic solvent were determined as follows:choline chloride-malonic acid 1:1(mol/mol),the solid-liquid ratio of the sample to DES was 1:2(w/w),and the extraction time was 4 h.Compared with UPLC method,UPC~2 can significantly get shorter analysis time,better chromatographic peak separation,and more abundant chromatographic information.A total of 17 chromatographic peaks were found in the UPC~2-Q-TOF-MS~E fingerprint,and 16 chromatographic peaks were identified,which mainly consisted of 2 free carotenoids and 14 ester carotenoids.Lycium carotenoids had been shown to have potential 5α-reductase inhibitory activity by 5α-reductase screening activity of Ha Ca T cells in vitro experienment,among which ZD had the strongest activity.TLC qualitative identification and UPC~2-PDA content determination method of ZD were established on the basis of the composition characterization and activity evaluation.This method is specific,reproducible and can be used in quality control of Lycium fruits from different regions,which will provide a scientific basis for subsequent medlar quality standards improve research.Conclusions:Based on the concept of green chemistry,this study was aimed at realizing greener and more efficient enrichment and characterization of Lycium carotenoids by establishing the method of DES extraction combined with UPC~2-Q-TOF-MS~E.At the same time,ZD showed potential 5α-reductase inhibitory activity,which provided a basis for further searching for active components to inhibit benign prostatic hyperplasia(BPH)from Lycium fruits and revealing the traditional functional material basis of Lycium fruits that nourishing liver and kidney.The TLC qualitative and UPC~2-PDA content determination methods of ZD provided a scientific basis for the establishment of scientific quality standard that could effectively identify the authenticity of Lycium fruits and reflected the inherent quality,and laid a foundation for the establishment of the quality standard of Lycium fruits genuine medicinal materials.