Essential oils from Limnocitrus littoralis species in Southcentral coast of Vietnam

Volatile essential oils of seeds, peels, and leaves were obtained from Limnocitrus littoralis (Miq.) Swingle growing wildly in three provinces belonging to the southcentral coast of Vietnam by hydrodistillation method with 2000 mL Clevenger apparatus. Organoleptic properties, specific gravity, refractive index, and optical rotation were analyzed according to international standards ISO (International Organization for Standardization) or AFNOR (French Association of Normalization) standard, at 25 oC. The chemical compositions of essential oils were analysed by GC and GC/MS methods. Essential oil constituents were identified by comparing their mass spectra with those of standard compounds registered in the NIST 2014 and NIST 2020 libraries. Moreover, the identification was also confirmed by collating the observed LRI (linear retention indices) of each constituent with those reported in the compilation of retention indices published by Adams. The observed LRI was calculated by using the equation propounded by van den Dool and Kratz to the homologous series of C9-C20 n-alkanes (Sigma-Aldrich). The relative percentage of each constituent in the oil was determined by peak area normalization采用2000mL克莱文杰（Clevenger）装置的水蒸气蒸馏法，从越南中南部沿海三省野生生长的滨海柠檬橘（Limnocitrus littoralis (Miq.) Swingle）的种子、果皮和叶片中提取得到挥发性精油。在25℃条件下，依据国际标准化组织（ISO, International Organization for Standardization）或法国标准化协会（AFNOR, French Association of Normalization）的国际标准，对其感官特性、比重、折射率以及旋光度进行检测分析。采用气相色谱（GC）及气相色谱-质谱联用法（GC/MS）对精油的化学成分进行分析。通过将待测组分的质谱图与NIST 2014、NIST 2020数据库中收录的标准化合物质谱图进行比对，完成精油组分的定性鉴定。此外，还通过将各组分实测的线性保留指数（LRI, linear retention indices）与亚当斯（Adams）所编著的保留指数汇编中的报道值进行比对，进一步验证组分鉴定结果的准确性。以C9-C20正构烷烃（Sigma-Aldrich）的同系物系列为参照，采用范登杜尔-克拉茨（van den Dool and Kratz）提出的计算公式，得到各组分的实测线性保留指数。采用峰面积归一化法计算精油中各组分的相对百分含量。