title: In vivo analysis and spatial profiling of phytochemicals in herbal tissue by matrix-assisted laser desorption/ionization mass spectrometry.
abstract: Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was developed for spatial profiling of phytochemicals and secondary metabolites in integrated herbal tissue without solvent extraction. Abundant alkaloid ions, including (+)-menisperine (m/z 356), magnoflorine (m/z 342), stepharanine (m/z 324), protonated sinomenine (m/z 330), protonated sinomendine (m/z 338), and a metabolite at m/z 314, could be directly desorbed from alpha-cyano-4-hydroxycinnamic acid- (CHCA-) coated stem tissue of Sinomenium acutum upon N2 laser (337 nm) ablation, while the ion signals desorbed from sinapinic acid- (SA-) coated and 2,5-dihydroxybenzoic acid- (DHB-) coated stem tissue were at least 10 times weaker. Solvent composition in the matrix solution could have significant effects on the ion intensity of the metabolites. Under optimized conditions that maximize the ion intensity and form homogeneous matrix crystals on the tissue surface, spatial distributions of the metabolites localized in different tissue regions, including cortex, phloem, xylem, rim, and pith, and their relative abundances could be semiquantitatively determined. The three metabolites detected at m/z 356, 342, and 314 showed specific distributions in the herbal samples collected from different growing areas, while others were not. By applying principal component analysis (PCA), the characteristic metabolites in specific tissue regions could be easily determined, allowing unambiguous differentiation of the herbal samples from different geographic locations.
authors.affiliation: Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong. kwanmng@hku.hk
authors.forename: Kwan-Ming
authors.initials: KM
authors.lastname: Ng
authors.forename: Zhitao
authors.initials: Z
authors.lastname: Liang
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Ho-Wai
authors.initials: HW
authors.lastname: Tang
authors.forename: Zhongzhen
authors.initials: Z
authors.lastname: Zhao
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
authors.forename: Yung-Chi
authors.initials: YC
authors.lastname: Cheng
mesh_terms: D000470:Alkaloids / Q000032:analysis*; D004365:Drugs, Chinese Herbal / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D012680:Sensitivity and Specificity; D032841:Sinomenium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D000470:Alkaloids; D004365:Drugs, Chinese Herbal; D012997:Solvents