Study On The Active Constituents Of Maca By Matrix Assisted Laser Desorption/Ionization Mass Spectrometry

Maca(Lepidium meyenii Walp)is an annual or biennial herb of the Cruciferae family.It contains abundant nutrients and has reasonable nutrition structure.Maca has the characteristic of antioxidantion,anti-fatigue,anti-cancer,improving sexual function,and fertility,neuroprotection,anti-osteoporosis,relieving climacteric syndrome and other biological activities.In recent years,Maca was introduced to plant in Lijiang,Shangri-la and other areas in Yunnan.Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF MS)is a soft ionization technique with high throughput,high sensitivity,high salt tolerance,fast analysis speed,low sample consumption,simple sample preparation and no fragment and other features.In recent years,MALDI imaging technology has been developed rapidly in the field of biology and metabolomics.This technique can simultaneously obtain the spatial information of hundreds of molecular ions in biological tissues.Compared with other traditional imaging methods,MALDI MSI technique does not require special staining or labeling,and has higher detection sensitivity and stronger molecular identification ability.In this thesis,we discussed the use of MALDI technique to analyze the components of Maca.(1)The metabolism and spatial distribution of imidazole alkaloids including Lepidiline A and Lepidiline B in the heart,liver,kidney and spleen of mice were studied by MALDI-TOF MSI technique.The results show that imidazole alkaloids were uniformly distributed in the heart,cortical region of the liver and medulla of the kidney.In addition,no distribution of imidazole alkaloid was found in medulla of liver,cortex of kidney and vascular region of heart tissue.The metabolism and targeting location of imidazole alkaloids in heart,liver,spleen and kidney of mice were obtained by this method,which provided the basis for studying the metabolic mechanism of imidazole alkaloids in vivo.(2)AuNPs colloidal solution synthesized by double solution method has the property of simple preparation,stable solution,and uniform size.AuNPs matrix has the advantages of low background interference,good co-crystallization and high-salt-tolerance in analysis of N-benzyl-octadecanamide.Then AuNPs were further used as MALDI matrix to the analyze biological samples,such as amino acids,carbohydrates,free fatty acids,natural products,and so forth.(3)The chemical constituents and their localization in fresh root tissue of Maca were studied using AuNPs as the MALDI matrix.Amino acids,carbohydrates,imidazole and amide alkaloids in Maca fresh roots were detected by MALDI-TOF MS.The distribution of chemical constituents in fresh root tissue of Maca can be clearly shown in the mass spectrometry imaging.The result verifies the feasibility of AuNPs as a MALDI matrix for analyzing biological samples and imaging plant tissue.