建立苦茶油中植物固醇組成與含量之分析平台

Abstract

苦茶油為國人常使用的油脂，其主要的脂肪酸組成與橄欖油相似，其單元不飽和脂肪酸－油酸(oleic acid)的含量達70%以上。然而未精製的植物油中常會含有較高的植物固醇與植物的二次代謝物，如三萜類物質可作為油脂的指標成分。因此本研究希望建立苦茶油中的主要植物固醇及三萜類之組成與含量的分析平台，並了解苦茶油中植物固醇及三萜類的輪廓特徵。實驗利用NH2固相萃取去除極性較低之脂肪酸及酯化態固醇後，收集苦茶油中的游離態、酯化醣苷態和酚酸態之三萜類及植物固醇，經液相層析分離，藉由大氣壓力游離法(APCI)正電模式，以及利用三段式四極桿進行質量分析，並挑選特徵離子及其產生的特徵碎片，與三萜類及植物固醇標準品進行定性及定量，以建立苦茶油中游離態三萜類及植物固醇之種類及含量。同時也利用氣相層析串聯質譜分析苦茶油中植物固醇及三萜類的含量。液相層析串聯二次質譜的實驗結果發現苦茶油中含有游離態三萜類β-amyrin以及∆5-植物固醇的同分異構物。氣相層析串聯質譜的結果顯示苦茶油含有特殊的∆7-植物固醇並以∆7-sitosterol含量最高，其次為三萜類β-amyrin、lanosterol、lupeol及-amyrin為主。此結果與市面上大部分未精製植物油中主要的植物固醇(∆5-sterol)不同，因此可以利用苦茶油中植物固醇組成的特異性作為苦茶油的指標成分。

Camellia seed oil is commonly used in Taiwan. The fatty acid compositions of camellia seed oil are similar to those of olive oil. Particularly, oleic acid is the major component of mono-unsaturated fatty acid. Unrefined vegetable oils often contain plant sterols and their secondary metabolites, such as triterpens which can be compositional fingerprints of vegetable oils. Thus, the aim of this study was to establish the analysis platform to profile the composition and content of the main phytosterols and triterpenes in camellia seed oils as characteristic compounds. Samples were prepared using NH2 solid phase extraction followed by collecting free sterols, steryl ferulates, acylated steryl glycosides and triterpenes. The triterpenes and different types of sterols were separated by reverse phase ultra-performance liquid chromatography (UPLC) and determinated and quantified by tandem mass sepctrometry in positve atmospheric pressure chemical ionization (APCI-MS/MS). Esterified sterols or triterpenes in camellia seed oils were furtherdeterminated by gas chromatography mass spectrometry (GC-MS). The results of UPLC-APCI-MS/MS showed that isomers of ∆5-sterols and a triterpene, β-amyrin, were aboundant in camellia seed oils. In the results of GC-MS, we further confirmed that the phytosterols in camellia seed oils were ∆7-phytosterols, particularly ∆7-sitosterol. β-Amyrin、lanosterol、lupeol and β-amyrin were also the triterpenoid presented in the unrefined camellia seed oil. Our results clearly demonstrated that the profiles of phytoterol and triterpenoids in camellia seed oil are distinct from the major phytosterols (Δ5-sterol) in most unrefined vegetable oils. The unique profile of the phytoterol and triterpenoids can be good markers to identify camellia seed oils.