目的 基質(zhì)輔助激光解析質(zhì)譜成像（matrix-assisted laser desorption/ionization mass spectrometry imaging，MALDI-MSI）是一種新型的分子成像技術(shù)，具有樣本處理簡(jiǎn)單、免標(biāo)記、空間分辨率高、檢測(cè)范圍廣以及可視化的特點(diǎn)。通過(guò)MALDI-MSI技術(shù)探索皂苷類物質(zhì)在桔梗Platycodon grandiflorum中的空間分布特征。方法 根據(jù)桔梗浸提液在2,5-二羥基苯甲酸（2,5-dihydroxybenzoic acid，DHB）、α-氰基-4-羥基肉桂酸（α-cyano-4-hydroxycinnamic acid，CHCA）、9-氨基吖啶（9-aminoacridine，9-AA）3種基質(zhì)作用下采集的質(zhì)譜信號(hào)響應(yīng)強(qiáng)度，選擇DHB作為成像的噴涂基質(zhì)。將厚度為25 μm的桔梗冷凍切片經(jīng)真空干燥后，使用基質(zhì)噴涂?jī)x在循環(huán)60次、濕度為40 %，孵育時(shí)間為30 s的條件下，將DHB均勻地覆蓋于切片上。在正離子反射模式下采集質(zhì)量范圍為m/z 200～1 600的質(zhì)譜信號(hào)用于MALDI-MSI分析。結(jié)果 在桔梗的周皮、韌皮部、形成層、木質(zhì)部和髓部，觀察到12種具有顯著空間分布差異的離子峰。經(jīng)傅里葉變換離子回旋共振質(zhì)譜（fourier transform ion cyclotron resonance mass spectrometry，F(xiàn)T-ICR MS）分析其精確相對(duì)分子質(zhì)量、分子式、同位素峰以及碎片離子，最終確認(rèn)為桔梗皂苷D、桔梗皂苷C、桔梗皂苷E和桔梗皂苷J(rèn)等12種桔梗皂苷。結(jié)論 為桔梗中皂苷類成分空間分布情況的表征提供了可視化的方法。

Objective Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is an innovative technology, which has the characteristics of simple sample processing, absence of labeling, high spatial resolution, wide detection range and visualization capabilities. The spatial distribution characteristics of saponins in Platycodon grandiflorum were studied by MALDI-MSI technique. Methods Mass spectrometry signals were obtained from the mixtures of P. grandiflorum extract with three matrices, including 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), and 9-aminoacridine (9-AA). DHB was confirmed as the preferred imaging spray matrix. After 25 μm thick frozen sections of P. grandiflorum being vacuum dried, DHB was uniformly sprayed on the section surface using a matrix sprayer under conditions of 60 cycles, 40% humidity, and an incubation time of 30 s. Mass spectrum signals with a mass range of 200—1 600 m/z were collected in positive ion reflection mode for MALDI-MSI analysis. Results The results showed that 12 kinds of ion peaks with significant spatial distribution difference were observed in periderm, phloem, cambium, xylem and pith of P. grandiflorum. The precise molecular weight, molecular formula, isotopic peak and fragment ions were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and 12 kinds of saponins were identified. Conclusion This study provided a visualization method for the characterization of the spatial distribution of saponins in P. grandiflorum.

R284.1