GC-MS法结合酸酯化预处理测定不同地区油茶籽油脂肪酸含量

该研究在比较酸酯化和碱酯化预处理方法基础上,采用气相色谱-质谱联用（GC-MS）技术,对湖南、广东、江西、云南、广西、海南6个地区油茶籽油的脂肪酸种类、相对含量和比例进行了分析。结果显示,除油酸、芥酸、二十三碳酸和二十四碳烯酸外,酸酯化和碱酯化法处理后检测出的其他脂肪酸之间均存在显著差异（p<0.05）,且酸酯化法更适合茶油脂肪酸检测。茶油中肉豆蔻酸、十七酸、亚麻酸、花生酸、芥酸和二十四碳烯酸的最高含量均来自于湖南茶油样品,分别为0.10%、0.11%、0.20%、0.09%、0.17%和0.07%;棕榈烯酸含量最高的是广东茶油样品,为0.12%;棕榈酸含量最高的是广西茶油样品,为12.97%;亚油酸含量最高的样品产自江西,达15.58%;硬脂酸和油酸含量最高的样品均源自于海南,分别为3.74%和73.70%。油茶籽油在不同的产地其营养特性各不相同,广东和江西茶油的多不饱和脂肪酸含量最高,分别为15.33%和15.67%;云南茶油脂肪酸总不饱和程度最高,达85.74%;湖南和海南茶油稳定性较好,易于保存。该研究为了解我国油茶各主产区的茶油营养价值差异提供理论依据和参考信息。     

高效液相色谱法测定油茶饼粕多糖组成

提出并对比了3种分析油茶饼粕多糖组成的高效液相色谱方法——氨基柱-折光示差检测器法、氨基柱-串级质谱法、1-苯基-3-甲基-5-吡唑啉酮柱前衍生-C18柱-紫外检测器法（柱前衍生法）。综合考虑分离效果、灵敏度、仪器成本等因素,最终选定柱前衍生法。柱前衍生法可同时测定油茶饼粕多糖中的鼠李糖、甘露糖、葡萄糖、半乳糖、木糖、阿拉伯糖、葡萄糖醛酸、半乳糖醛酸,线性关系良好（线性系数>0.99）,检出限为0.02~0.29 mg/L,定量限为0.06~0.96 mg/L;单糖及糖醛酸的加标回收率分别为77.2%~111.9%、60.1%~87.0%;峰面积日内精密度为0.08%~3.77%,日间精密度为0.39%~17.15%。利用柱前衍生法检测油茶饼粕多糖样品,结果显示所检的4个样品中均含有5种或6种单糖及2种糖醛酸,且含量最高的组分均为葡萄糖。     

索氏法提取和测定油茶籽油的条件优化

除富含不饱和脂肪酸的茶油外,油茶中还含有茶多糖、茶皂素、茶多酚等多种生物活性成分。以油茶生物活性物质的提取和制备为前提,本研究以简单、有效地提取茶油为目标,以油茶籽含油率为指标,在索氏抽提法单因素实验基础上,选择提取时间、提取温度、提取溶剂种类和单次样品重量为影响因素进行正交优化实验。结果表明,油茶索氏提取的最佳条件为:提取时间6 h、提取温度80℃、有机溶剂丙酮、单次样品重量4 g。该条件下茶籽含油率达43.24%±0.53%。该条件下测得4种油茶整籽和种仁的含油率从高到低依次为广宁红花油茶、普通油茶、小果油茶和高州油茶;广宁红花油茶的整籽和种仁含油率均最高,且饼粕含油率最低,分别为49.7%、67.5%和6.1%。优化后的油茶索氏抽提条件,适用于茶油成分的有效提取和针对油茶籽油的定量分析。      

Volatile Dimethyl Disulfide from Guava Plants Regulate Developmental Performance of Asian Citrus Psyllid through Activation of Defense Responses in Neighboring Orange Plants

Intercropping with guava (Psidium guajava L.) can assist with the management of Asian citrus psyllid (ACP, Diaphorina citri Kuwayama), the insect vector of the huanglongbing pathogen, in citrus orchards. Sulfur volatiles have a repellent activity and physiological effects, as well as being important components of guava volatiles. In this study, we tested whether the sulfur volatiles emitted by guava plants play a role in plant–plant communications and trigger anti-herbivore activities against ACP in sweet orange plants (Citrus sinensis L. Osbeck). Real-time determination using a proton-transfer-reaction mass spectrometer (PTR-MS) showed that guava plants continuously release methanethiol, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), and the contents increased rapidly after mechanical damage. The exposure of orange plants to DMDS resulted in the suppression of the developmental performance of ACP. The differential elevation of salicylic acid (SA) levels; the expression of phenylalanine ammonia lyase (PAL), salicylate-O-methyl transferase (SMT), and pathogenesis-related (PR1) genes; the activities of defense-related enzymes PAL, polyphenol oxidase (PPO), and peroxidase (POD); and the total polyphenol content were observed in DMDS-exposed orange plants. The emission of volatiles including myrcene, nonanal, decanal, and methyl salicylate (MeSA) was increased. In addition, phenylpropanoid and flavonoid biosynthesis, and aromatic amino acid (such as phenylalanine, tyrosine, and tryptophan) metabolic pathways were induced. Altogether, our results indicated that DMDS from guava plants can activate defense responses in eavesdropping orange plants and boost their herbivore resistance to ACP, which suggests the possibility of using DMDS as a novel approach for the management of ACP in citrus orchards.