基于代谢组学分析不同品系化州柚花间差异代谢物

陈婉冰1,毛根林1,钟玉娟2,曾继吾1*

1广东省农业科学院果树研究所·农业农村部南亚热带果树生物学与遗传资源利用重点实验室·广东省果树科学与技术研究重点实验室,广州 510640;2广东省农业科学院蔬菜研究所·广东省蔬菜新技术研究重点实验室,广州 510640)

摘 要:【目的】 研究化州柚(Citrus grandis‘Tomentosa’)正毛、副毛和光青品系的花之间成分差异,为化州柚花在医药和保健领域的开发应用奠定基础。【方法】 选取同一生长期的化州柚正毛、副毛和光青3个品系的花,利用超高效液相色谱-三重四极杆质谱(UPLC-MS/MS)进行次级代谢产物的广泛靶向代谢组学分析,利用气相色谱-四级杆飞行时间质谱(GC-TOF/MS)进行初级代谢产物的非靶向代谢组学分析。通过主成分分析(PCA)揭示3 个品系花间的整体差异,利用正交偏最小二乘法判别分析(OPLS-DA)将3 个品系两两对比,筛选出品系间的差异代谢物。【结果】 UPLCMS/MS检测发现978种代谢物,其中63种代谢物在不同品系花中表现出显著差异。地奥司明、山柰酚-3-O-芸香糖苷、芦丁、牡荆素-2''-O-葡萄糖苷、木犀草素-7-O-芸香糖苷、维采宁-2、芸香柚皮苷、香草酸、佛手苷内酯和橙皮内酯10种化州柚中有效成分在副毛和正毛花中的含量高于光青。GC-TOF/MS检测发现236种代谢物,筛选出11种差异代谢物,包括D-(-)果糖、D-纤维二糖、景天酮庚糖、α-槐糖、丙酮酸、柠檬酸、莽草酸、反式-4-羟基肉桂酸、咖啡酸、阿魏酸和柚皮素-7-O-葡萄糖苷。【结论】 化州柚正毛、副毛和光青3个品系的花在成分上存在显著差异,尤其是副毛和正毛花的有效成分含量高于光青。

关键词:化州柚;化橘红;代谢组学

化州柚(Citrus grandis‘Tomentosa’)是柚[C.grandis(L.)Osbeck]的一个变种,起源于广东化州,是中药化橘红(Exocarpium Citri Grandis)的源植物。化州柚主要有正毛、副毛、光青、黄龙和假西洋等地方品系[1],其中正毛、副毛和光青的主要区别在于果实表面的茸毛形态不同[2]。正毛果实表面茸毛长而密,副毛果实表面茸毛稀且短,光青果实表面光滑无毛(图1)[3]

图1 正毛、副毛和光青3 个品系化州柚花和果实形态
Fig.1 Flower and fruit morphology of three varieties of C.grandis‘Tomentosa’

化州柚花期在3月,开花量大,为保证果实产量和品质,果农一般会进行疏花,疏下的花在化州当地被制成花茶。化州柚花与果实中的有效成分在种类和含量上都较为接近,化州柚花茶同化橘红一样具有理气化痰的功效[4]。柚皮苷被认为是化橘红的主要功效成分[5],其通过对气道炎症以及气道上皮、气道平滑肌的调控发挥消炎、止咳化痰的作用[6-7]。Duan等[8]研究发现幼果期化州柚果实中柚皮苷含量(w,后同)可达果实干质量的28%,而化州柚花中柚皮苷含量也达16%,高于叶片及近成熟果实和成熟果实。化州柚花中挥发油含量约为0.7%,含量较高的成分有D-柠檬烯、γ-萜品烯、β-月桂烯、芳樟醇、反-橙花叔醇等[4]。韩寒冰等[9]从化州柚花和果实的挥发油中分别鉴定出30 种和36 种成分,其中28 种成分相同。

不同品系的化州柚果实在有效成分含量和功效上存在显著差异。Fan等[10]对化州柚中16种有效成分进行定量分析,发现正毛品系含有更多的类黄酮,其野漆树苷的含量明显高于光青。李宇邦等[11]的研究发现毛橘红中柚皮苷、野漆树苷、柚皮素的含量高于光橘红。研究还发现[12-13],由正毛化州柚未成熟果实和近成熟果实外果皮炮制而成的“毛橘红”抗炎和化痰作用最突出,其效果优于由光青化州柚制成的“光橘红”。然而,目前对不同品系的化州柚花之间的成分差异缺乏深入研究。因此,笔者在本研究中选择同一生长期的正毛、副毛和光青3 个品系的化州柚花作为研究对象,运用代谢组学的方法比较它们之间的成分差异,通过多元统计分析筛选出差异代谢物。旨在明确不同品系化州柚花的化学成分差异,为化州柚花的综合利用提供理论依据。

1 材料和方法

1.1 材料与试剂

正毛、副毛和光青3个品系化州柚花,采集自广东省化州市化橘红药材开发有限公司GMP 标准苗圃。内标核糖醇和2-氯苯丙氨酸购自德国Sigma-Aldrich 公司;甲氧胺盐购自上海梯希爱公司;N,O-双(三甲基硅)三氟乙酰胺(BSTFA)(含1%三甲基氯硅烷TMCS)购自美国REGIS Technologies 公司;饱和脂肪酸甲酯(FAMEs)购自德国Dr.Ehrenstorfer公司;氯仿和吡啶(色谱纯)及甲醇、乙腈和甲酸(质谱纯)购自美国Thermo Fisher Scientific公司。

1.2 仪器与设备

ExionLC AD-trap 6500+UPLC-MS/MS 液质联用仪,美国Sciex 公司生产;7890B GC 气相色谱仪,美国安捷伦公司生产;PEGASUS HT飞行时间质谱仪,美国LECO公司生产;Millipore D23 UV纯水仪,美国Merck 公司生产;Heraeus Fresco17 高速离心机,美国Thermo Fisher Scientific 公司生产;LNGT98真空干燥仪,太仓市华美生化仪器厂生产。

1.3 试验方法

1.3.1 UPLC-MS/MS样本前处理 称取50 mg冷冻干燥研磨后的样本加入700 μL 含0.1%2-氯苯丙氨酸内标的25%甲醇水溶液,然后冰水浴超声提取5 min,重复提取3 次后在混匀仪上4 ℃过夜,然后将样本在4 ℃下13 800g 离心15 min,取上清液经0.22 μm 微孔滤膜过滤,用提取液稀释上清液20倍,涡旋30 s,每个样本各取50 μL 混合成质控(QC)样本,-80 ℃储存直到上机检测。

1.3.2 GC-QTOF/MS样本前处理 称取50 mg冷冻干燥研磨后的样本加入500 μL 含核糖醇内标的25%甲醇水溶液,然后冰水浴超声提取5 min,重复提取3次后在4 ℃下13 800g 离心15 min,每个样本各取100 μL上清液混合成QC样本。将试验样本及QC样本在真空浓缩器中干燥,然后加入50 μL溶解于吡啶的20 mg·mL-1甲氧胺盐试剂,混匀后在烘箱中80 ℃孵育30 min,再加入70 μL BSTFA(含1%TMCS)70 ℃孵育1.5 h,冷却至室温后向混合的样本中加入5 μL FAMEs(溶于氯仿),随机顺序上机检测。

1.3.3 UPLC-MS/MS数据采集 液相色谱采用Waters Acquity UPLC HSS T3(2.1 mm×100 mm,1.8 μm)色谱柱,流动相A 相为0.1%甲酸水,B 相为乙腈,梯度洗脱:0 min,98% A;0.5 min,98% A;10 min,50%A;11 min,5%A;13 min,5%A;13.1 min,98%A;15 min,98%A。流速为0.4 mL·min-1,进样体积为2 μL,柱温为40 ℃。质谱采用ESI 离子源,以多反应监测模式(MRM)进行质谱分析。离子源参数如下:离子化电压+5500/-4500 V,气帘气35 psi,温度400 ℃,喷雾气60 psi,辅助加热气60 psi。样品随机进样,每个样本正离子模式和负离子模式各进1针,在每进3针样本后,进1针QC样本和1针空白样本(25%甲醇),进行质量控制和矫正峰的漂移。所有质谱数据采集及目标化合物定量分析工作均通过SCIEX Analyst Work Station Software (Version 1.6.3)来完成。使用MSconventer 软件将质谱原始转成TXT 格式再使用自撰写R 程序包结合自建数据库完成提峰、注释等工作。

1.3.4 GC-QTOF/MS数据采集 气相色谱采用Agilent DB-5MS 毛细管柱(30 m×250 μm×0.25 μm,J W Scientific,Folsom,CA,USA),以不分流的方式进1 μL 样品。以氦气为载气,隔垫吹扫流速为3 mL·min-1,柱流速为1 mL·min-1。程序升温条件为:初始温度50 ℃,保持1 min;然后以10 ℃·min-1的速率升至310 ℃,然后在310 ℃下保持8 min。前进样口温度为280 ℃,传输线温度为280 ℃,离子源温度为250 ℃。电离电压为70 eV。在溶剂延迟6.25 min 后,以12.5 scan·s-1的速率,在m/z 范围为50~500 的全扫描模式下获得质谱数据。使用ChromaTOF 软件(V 4.3x,LECO)对质谱数据进行峰提取、基线矫正、解卷积、峰积分、峰对齐等处理。使用LECO-Fiehn Rtx5 数据库通过质谱匹配及保留时间指数匹配进行化合物的注解。最后,将QC 样本中检出率50%以下或RSD>30%的峰去除。

1.3.5 代谢组学数据分析 将采集到的UPLC-MS/MS 和GC-QTOF/MS 数据采用SIMCA(V 14.1,Umetrics)进行多元统计分析。数据在对数(Log)转换和Mean-centered 尺度化后,进行3 个品系样本的PCA 分析和品系间两两对比的OPLS-DA 分析。以OPLS-DA 模型中的变量投影重要性分析值(VIP)、差异倍数(Fold change,FC)以及单因素方差分析(student’s t-test)的p值综合筛选UPLC-MS/MS检测到的差异代谢物。以OPLS-DA分析得到的S-plot图筛选GC-TOF/MS 检测到的差异代谢物。用R 软件和Origin(V 9.1,OriginLab)软件进行数据可视化。

2 结果与分析

2.1 UPLC-MS/MS广泛靶向数据主成分分析

通过与自建数据库比对,从正毛、副毛和光青3组共9 个样本中检测到978 种代谢物,其中黄酮类154种,占比15.75%;酚类129种,占比13.19%;生物碱108 种,占比11.04%;萜类90 种,占比9.20%。此外,还检测到香豆素、木质素、脂质、植物激素、芳香族化合物、糖和糖醇、有机酸及其衍生物、氨基酸及其衍生物、甾体及其衍生物以及核苷酸及其衍生物等,检测到的各类代谢物数量如表1。为描绘正毛、副毛和光青3 个品系间代谢物的整体差异,对以上检测到的代谢物进行主成分分析(PCA)。得分图(图2)显示主成分1 和主成分2 的贡献率分别为44.4%和8.5%,且正毛、副毛和光青3组样本点完全分离,说明3个品系成分差异显著,并且检测到的代谢物能够代表三者之间的差异。

表1 UPLC-MS/MS广泛靶向代谢组学检测的代谢物种类和数量
Table 1 The classification and quantity of metabolites detected by widely-targeted metabolomics using UPLCMS/MS

种类Classification氨基酸及其衍生物Amino acid and its derivatives芳香族化合物Benzenes酚类Phenols核苷酸及其衍生物Nucleotide and its derivates黄酮类Flavonoids生物碱Alkaloids糖类Carbohydrates萜类Terpenoids香豆素及木质素类Coumarins and Lignans有机酸及其衍生物Organic acids脂质Lipids植物激素Phytohormones甾体及其衍生物Steroids andsteroid derivatives其他Others数量Quantity 44 21 129 27 154 108 22 90 54 49 46 15 30 198占比Proportion/%4.50 2.14 13.19 2.76 15.75 11.04 2.25 9.20 5.52 5.01 4.70 1.53 3.07 19.33

图2 UPLC-MS/MS 检测的代谢物主成分分析
Fig.2 Principal component analysis(PCA)of metabolites detected by UPLC-MS/MS

2.2 UPLC-MS/MS广泛靶向代谢组差异代谢物筛选

采用OPLS-DA模型将正毛、副毛和光青3组样本进行两两对比。以单因素方差分析(student’s ttest)p 值小于0.05、差异倍数(Fold change,FC)大于2或者小于0.5,以及OPLS-DA模型中变量投影重要性分析值(VIP)大于1 这3 个条件筛选差异代谢物。从ZM vs FM 中筛选出34 种代谢物,其中25 种上调,9种下调;从ZM vs GQ中筛选出48种代谢物,其中37种上调,11种下调;从FM vs GQ中筛选出58种代谢物,其中34 种代谢物上调,24 种代谢物下调。以差异倍数(FC)和p值分别为横纵坐标作火山图对数据进行可视化(图3)。共有芸香柚皮苷、野漆树苷、橙皮内酯、芦丁、木犀草素-7-O-芸香糖苷、邻苯三酚、驴食草酚、9-甲氧基-α-拉帕醌、无梗五加苷B、荭草苷、8-甲基壬烯酸酯、甜茶苷、5-尿嘧啶核苷酸、7-甲基鸟嘌呤和Nemorensine 15 种代谢物在两组比较中同时具有差异。将各组对比中上调及下调前15 位的代谢物以火柴杆图的形式展示,如图4。将以上火柴杆图中所示代谢物汇总,共有63 种代谢物,以热图的形式展示其在3 个品系间的相对丰度,并将代谢物和样品都进行基于欧式距离(Euclidean distance)的聚类分析,结果如图5。地奥司明、山柰酚-3-O-芸香糖苷、芦丁、牡荆素-2''-O-葡萄糖苷、木犀草素-7-O-芸香糖苷、维采宁-2、芸香柚皮苷、香草酸、佛手苷内酯和橙皮内酯这10 种化州柚中活性物质在正毛、副毛中的含量高于光青,说明副毛和正毛化州柚花可能具有更高的保健和药用价值。

图3 UPLC-MS/MS 检测的代谢物火山图
Fig.3 Volcano plot of metabolites detected by UPLC-MS/MS

图4 UPLC-MS/MS 差异代谢物差异倍数火柴杆图
Fig.4 Matchstick Analysis of differential metabolites detected by UPLC-MS/MS

图5 UPLC-MS/MS 差异代谢物热图
Fig.5 UPLC-MS/MS differential metabolites heatmap

2.3 GC-TOF/MS非靶向数据主成分分析

从正毛、副毛和光青3 个品系样本的GC-TOF/MS原始数据中共提取到594个质谱峰,与标准数据库比对后共检测到236 个代谢物,其中有机酸及其衍生物66 种,占比27.97%;有机氧化合物60 种,占比25.42%;脂质23种,占比9.75%;苯及其衍生物17种,占比7.20%,其他类代谢物的占比如图6。以上述代谢物归一化后的相对丰度为变量进行PCA 分析,得分图如图7。主成分1和主成分2的贡献度分别为39.8%和17.1%,并且ZM、FM和GQ3组样本点的分离度良好,说明以上代谢物可以代表正毛、副毛和光青3个品系之间的差异。

图6 GC-TOF/MS 非靶向代谢组学检测的代谢物种类和数量
Fig.6 The classification and quantity of metabolites detected by untargeted metabolomics using GC-TOF/MS

图7 GC-TOF/MS 检测的代谢物主成分分析
Fig.7 Principal component analysis(PCA)of metabolites detected by GC-TOF/MS

2.4 GC-TOF/MS非靶向代谢组差异代谢物筛选

以检测到的236种代谢物的相对丰度为变量,采用OPLS-DA模型对正毛、副毛和光青3个品系进行两两对比,筛选差异代谢物。将OPLS-DA分析的结果以S-plots 的形式进行展示,如图8,横坐标p[1]为负载向量在主成分1上的协方差,纵坐标p(corr)[1]为负载向量与主成分1的相关性,以|p(corr)[1]|>0.5,|p[1]|>0.15为条件筛选差异代谢物。从FM vs ZM中筛选出6种差异代谢物,柚皮素-7-O-葡萄糖苷和柠檬酸上调,咖啡酸、反式-4-羟基肉桂酸、阿魏酸和丙酮酸下调。从GQ vs ZM中筛选出8种差异代谢物,柚皮素-7-O-葡萄糖苷、莽草酸、柠檬酸和景天酮庚糖上调,D-纤维二糖、咖啡酸、α-槐糖和D-(-)-果糖下调。从GQ vs FM中筛选出7种差异代谢物,柚皮素-7-O-葡萄糖苷、阿魏酸、丙酮酸、景天酮庚糖和反式-4-羟基肉桂酸上调,D-纤维二糖和D-(-)-果糖下调。上述差异代谢物汇总后共有11种,其中D-(-)-果糖、α-槐糖、丙酮酸、咖啡酸、阿魏酸、柚皮素-7-O-葡萄糖苷在3组对比中都有差异,D-纤维二糖、景天酮庚糖、柠檬酸、莽草酸、反式-4-羟基肉桂酸在两组对比中有差异。上述差异代谢物在正毛、副毛和光青3组中的相对含量如图9所示。

图8 代谢物的OPLS-DA 分析S-plot 图
Fig.8 S-plot of metabolites in the in OPLS-DA model

图9 GC-TOF/MS 差异代谢物在不同品系间的相对含量
Fig.9 The relative abundance of differential metabolites detected by GC-TOF/MS among different cultivars

3 讨 论

评价食用和药用植物的品质往往需要对其中的氨基酸、糖、有机酸、维生素等初级代谢物和酚酸、黄酮、生物碱、萜类等次级代谢产物的组成和含量进行综合评估,采用传统的检测和定量方法存在成本高、耗时长、过程复杂等问题,越来越多的研究开始采用代谢组学完成食品和药用植物中代谢物的高通量整体分析[14]。通过液质联用(LC-MS)、气质联用(GCMS)和核磁共振(nuclear magnetic resonance,NMR)平台,采集植物样品中成百上千种代谢物的信息,再通过多元统计分析从中筛选出不同品种、品系,不同生长时期以及不同处理方式的植物样本中差异代谢物或者标志物,是代谢组学在植物学领域的经典研究方法,广泛应用于遗传育种、资源鉴定和保护以及天然产物开发与利用等研究领域[15]

笔者在本研究中利用超高效液相色谱-三重四极杆质谱(UPLC-MS/MS)和气相色谱-四级杆飞行时间质谱(GC-TOF/MS)分别进行广泛靶向代谢组学和非靶向代谢组学分析,从化州柚正毛、副毛和光青3 个品系的花中分别筛选出63 种和11 种差异代谢物。野漆树苷、维采宁-2、芸香柚皮苷、地奥司明和木犀草素-7-O-芸香糖苷、山柰酚-3-O-芸香糖苷、芦丁等是已经报道的化州柚中主要的类黄酮成分[16]。笔者在本研究中发现地奥司明、山柰酚-3-O-芸香糖苷、芦丁、牡荆素-2''-O-葡萄糖苷、木犀草素-7-O-芸香糖苷、维采宁-2 和芸香柚皮苷这6 种类黄酮在正毛和副毛化州柚花中的含量高于光青。这与在化州柚果实中的研究结果相一致[17]。采用正毛和副毛化州柚制成的化橘红被认为具有更高的药用价值,也可能与其更高的类黄酮含量有关[18]。地奥司明、维采宁-2、野漆树苷、芦丁等黄酮类化合物具有抗炎、抗感染、抗肿瘤、预防心脑血管疾病等功效[19-21]。橙皮内酯、佛手柑内酯、小芸木素、白蜡树苷等属于香豆素。橙皮内酯和佛手柑内酯是化州柚中典型的香豆素成分[22]。而白蜡树苷也有研究从酸橙和甜橙花中鉴定到[23]。本研究中橙皮内酯和佛手柑内酯在正毛和副毛花中的含量也显著高于光青。大量研究显示柑橘香豆素具有抗炎、抗癌、抗病毒以及保护心脑血管、神经和消化系统等多种生物学活性[24-26]

筛选出的差异代谢物中还包含香草酸、咖啡酸、阿魏酸等反式-4-羟基肉桂酸等酚酸化合物,以及柠檬酸、莽草酸、果糖、7-甲基鸟嘌呤、5-尿嘧啶核苷酸、二十碳五烯酸等初级代谢产物。这些差异代谢物涉及三羧酸循环、多酚生物合成、嘌呤代谢、果糖和甘露糖代谢等代谢途径。以多酚生物合成为例,酚酸类化合物在植物体内主要由糖酵解及磷酸戊糖途径生成的中间体经莽草酸途径和苯丙烷类代谢途径合成[27],而苯丙烷类代谢途径最终产物对香豆酰辅酶A是类黄酮类化合物合成的重要前体[28]

柑橘属植物花量过大会导致坐果率低,对花朵进行稀疏处理是必不可少的管理措施。柑橘花香味馥郁清爽,将疏下的花制作成精油和花茶可以提高柑橘的经济价值。沙田柚[29]、温州蜜柑[30]、甜橙和酸橙花[23]都已被开发为精油或花茶产品。化州柚花在化州当地也被用来制作花茶,但目前对化州柚花的成分分析、加工工艺和功能活性的研究较少,化州柚花茶并没有得到广泛应用和推广。本研究对3个不同品系化州柚花的成分进行了鉴定,并筛选出不同品系间的差异代谢物,为未来的品种改良、药物开发和保健产品设计提供研究基础。

4 结 论

通过代谢组学比较化州柚正毛、副毛和光青3个品系花中的代谢物差异。利用UPLC-MS/MS 进行广泛靶向代谢组学分析,筛选出63 种差异代谢物。其中,地奥司明、山柰酚-3-O-芸香糖苷、芦丁、牡荆素-2''-O-葡萄糖苷、木犀草素-7-O-芸香糖苷、维采宁-2、芸香柚皮苷、香草酸、佛手苷内酯和橙皮内酯这10 种化州柚中活性物质含量在正毛和副毛花中高于光青中。此外,基于GC-TOF/MS 进行非靶向代谢组学分析,共筛选出11 种差异代谢物,分别为D-(-)果糖、D-纤维二糖、景天酮庚糖、α-槐糖、丙酮酸、柠檬酸、莽草酸、反式-4-羟基肉桂酸、咖啡酸、阿魏酸和柚皮素-7-O-葡萄糖苷。笔者在本研究中探讨不同品系化州柚花的成分差异,发现正毛和副毛化州柚花的有效成分含量显著高于光青花,说明正毛和副毛化州柚花可能具有更高的药用和保健价值,为化州柚花精油或花茶产品的开发提供了理论依据,有望促进化橘红的综合利用与产业发展。

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Metabolomic analysis of differential metabolites among different cultivars of Citrus grandis‘Tomentosa’flowers

CHEN Wanbing1,MAO Genlin1,ZHONG Yujuan2,ZENG Jiwu1*

(1Institute of Fruit Tree Research,Guangdong Academy of Agricultural Sciences/Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization,Ministry of Agriculture and Rural Affairs/Guangdong Provincial Key Laboratory of Science and Technology Research on Fruit Tree, Guangzhou 510640, Guangdong, China;2Vegetable Research Institute, Guangdong Academy of Agricultural Sciences/Guangdong Key Laboratory for New Technology Research of Vegetables,Guangzhou 510640,Guangdong,China)

Abstract:【Objective】 Citrus grandis‘Tomentosa’(CGT) is an ancient variant of pomelo [C. grandis(L.) Osbeck ] native to Huazhou, Guangdong Province. It is the raw material source for the traditional Chinese medicine Huajuhong (Exocarpium Citri Grandis). Based on the morphology of the fruit trichomes,CGT can be divided into different local strains:Zhengmao(ZM),Fumao(FM),and Guangqing(GQ). ZM fruits have dense and long trichomes on the surface, while FM fruits have relatively short and sparse trichomes, and GQ fruits have a smooth surface without trichomes. The differences in trichome coverage between the ZM,FM,and GQ have significant implications for their medicinal properties and potential applications in traditional Chinese medicine.The effective components in the flowers of CGT are similar to those in its fruits, possessing expectorant and anti-inflammatory effects. Therefore,locals often collect excess flowers and use them to make flower tea.The floral morphology of different strains of CGT is nearly indistinguishable,yet their differences in composition and medicinal value remain largely unexplored. The objective of this study is to explore the variances in composition among the flowers of ZM, FM, and GQ, aiming to establish a basis for the utilization of these CGT flowers in medicine and healthcare.【Methods】 Flowers from the three varieties of CGT, namely ZM,FM,and GQ,were collected during the same growth period.Metabolites from the flowers were extracted using 25% methanol-water with 2-chlorophenylalanine as the internal standard for widely targeted metabolomics based on UPLC-MS/MS.Mass spectrometry data was collected using the Multiple Reaction Monitoring (MRM) mode of triple quadrupole mass spectrometry. Metabolite annotation was conducted using an in-house database developed by Biotree company. Using adonitol as an internal standard, metabolites from the flowers were extracted with 25% methanol-water, followed by oximation and silylation derivatization, and then subjected to un-targeted metabolomics analysis using gas chromatography-time of flight mass spectrometry (GC-TOF/MS). Principal Component Analysis (PCA)was employed to reveal the overall differences among the three strains. Subsequently, Orthogonal Partial Least Squares Discriminant Analysis(OPLS-DA)was utilized to compare the strains pairwise.Differential metabolites were screened based on Variable Importance in Projection (VIP) values in the OPLS-DA model, fold change (FC), and p-values from student's t-test.【Results】 UPLC-MS/MS detected a total of 978 metabolites.The PCA score plot showed that the contributions of principal components 1 and 2 were 44.4% and 8.5%, respectively. The sample points for the ZM, FM, and GQ groups were clearly separated, indicating significant compositional differences among flowers of the three CGT strains.OPLS-DA analysis revealed 63 differential metabolites,mainly flavonoids,coumarins,terpenoids, and alkaloids. From the ZM vs FM comparison, 34 metabolites were identified as differentially expressed, with 25 upregulated and 9 downregulated. From the ZM vs GQ comparison, 48 metabolites were identified, with 37 upregulated and 11 downregulated. From the FM vs GQ comparison, 58 metabolites were identified, with 34 upregulated and 24 downregulated.Among these differential metabolites, ten effective components of CGT flowers were found in higher concentrations in the FM and ZM strains compared to the GQ strain. These components included bergapten, diosmin, meranzin,kaempferol-3-O-rutinoside, rutin,Vitexin-2"-O-glucoside, leteolin-7-O-rutinoside, vanillic acid, vicenin-2, and narirutin. GC-TOF/MS detected a total of 236 metabolites, primarily including organic oxides, organic acids, lipids, and benzene derivatives. The PCA score plot showed that the contribution rates of principal components 1 and 2 were 39.8%and 17.1%,respectively,indicating significant differences among the ZM, FM, and GQ strains. OPLS-DA analysis revealed 11 differential metabolites.From the FM vs ZM comparison, 6 metabolites were identified, with upregulation of naringenin-7-Oglucoside and citric acid,and downregulation of caffeic acid,trans-4-hydroxycinnamic acid,ferulic acid,and pyruvic acid.From the GQ vs ZM comparison,8 metabolites were identified,with upregulation of naringenin-7-O-glucoside, shikimic acid, citric acid, and sedoheptulose, and downregulation of Dcellobiose, caffeic acid, α-sophorose, and D-(-)-fructose. From the GQ vs FM comparison, 7 differential metabolites were identified,with upregulation of naringenin-7-O-glucoside,ferulic acid,pyruvic acid, sedoheptulose, and trans-4-hydroxycinnamic acid, and downregulation of D-cellobiose and D-(-)-fructose.【Conclusion】 The flowers of the three strains of CGT, ZM, FM, and GQ, exhibit significant differences in their composition.Flavonoids and coumarin compounds are the primary effective components in both the fruits and flowers of CGT. This study revealed that the flowers of the ZM and FM strains contain notably higher concentrations of 7 flavonoids (diosmin, kaempferol-3-O-rutinoside, rutin, vitexin-2"-O-glucoside, luteolin-7-O-rutinoside, vicenin-2, and narirutin) and 2 coumarins (bergaten and meranzin) compared to those of the GQ strain.Additionally, the identified differential metabolites include phenolic acids such as vanillic acid,caffeic acid,ferulic acid,and trans-4-hydroxycinnamic acid,as well as primary metabolites like citric acid,shikimic acid,fructose,7-methylguanine,uridine,and eicosapentaenoic acid. These differential metabolites are involved in various metabolic pathways,including the tricarboxylic acid cycle, polyphenol biosynthesis, purine metabolism, and fructose and mannose metabolism.

Key words:Citrus grandis‘Tomentosa’;Exocarpium Citri Grands;Metabonomics

中图分类号:S666.3

文献标志码:A

文章编号:1009-9980(2024)10-1990-12

DOI:10.13925/j.cnki.gsxb.20240285

收稿日期:2024-06-05

接受日期:2024-08-13

基金项目:国家重点研发计划(2023YFD2300605);国家现代农业(柑橘)产业技术体系(No.CARS-26);广东省农业科学院食品营养与健康研究中心建设运行经费(XTXM 202205);广州市科技计划项目(2023A04J0143)

作者简介:陈婉冰,女,助理研究员,主要从事柑橘加工和功能活性开发研究。E-mail:chenwanbing@gdaas.cn

*通信作者 Author for correspondence.E-mail:jiwuzeng@163.com