以液相層析電灑游離串聯質譜法進行類胡蘿蔔素代謝體分析

Abstract

類胡蘿蔔素為廣泛存在於食物中的天然色素，具有多樣的立體異構與官能基修飾形式，並具備光保護、抗氧化等生理功能。蜆為濾食性動物，透過濾取水中微藻攝食，可將微藻所含之類胡蘿蔔素經由體內酵素產生代謝轉化，進而形成多種類胡蘿蔔素衍生物，除具備潛在的生理功能與應用價值外，亦可作為反映生物攝食來源與棲地環境之化學指標。儘管植物與藻類中的類胡蘿蔔素的生合成途徑已被廣泛研究，其在動物體內的代謝轉化機制仍未明確。本研究使用高效能液相層析電噴灑游離串聯質譜法 (HPLC-ESI-MS/MS) 建立類胡蘿蔔素之分析平台，用於進行類胡蘿蔔素及其代謝物之譜型分布，並進一步闡明濾食動物進食後類胡蘿蔔素的代謝轉換關係。首先經游離條件優化，發現以1 mM 乙酸銨作為修飾劑可提供最佳的離子化效率，並進一步調整噴霧電壓、氣體流速與溫度以提升整體訊號強度與穩定性。分析過程結合管柱滯留時間、紫外光吸收光譜與串聯質譜特徵碎片訊號，鑑定出33種類胡蘿蔔素。進一步針對藻類與淡水黃金蜆 (Corbicula fluminea) 樣品進行比較分析，藻類樣品呈現組成多樣的類胡蘿蔔素與具分類差異之譜型，特徵化合物如fucoxanthin與astaxanthin於不同藻門中被檢測到；黃金蜆樣品除藻源類胡蘿蔔素外，亦發現多種代謝衍生物，如diadinoxanthin、pectenol、pectenolone等，推測其轉化過程涉及氧化還原、環氧基開環與烯炔鍵轉換等反應機制。此外，本研究亦針對微藻類樣品與黃金蜆樣品進行比較，結果顯示蜆體內代謝衍生物與藻水中類胡蘿蔔素間具有結構轉換關聯性，並與現有文獻所提出之代謝途徑模型相符。本研究說明質譜技術在類胡蘿蔔素結構鑑定上的應用潛力，也展現類胡蘿蔔素於水產養殖與物種溯源研究中的應用潛力。

Carotenoids are important colorants with structural diversity in food, characterized by varying ring structures and oxygenated functional groups. As filter-feeding organisms, clams can uptake microalgae from their aquatic environment and metabolically convert ingested algal carotenoids via endogenous enzymes into structurally modified derivatives. These carotenoid metabolites not only exhibit potential physiological and applicative value but also serve as chemical indicators reflecting dietary sources and habitat conditions. While carotenoid biosynthetic pathways in plants and algae have been well studied, their metabolic transformations in animals remain less understood. In this study, a high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) platform was established for comprehensive carotenoid profiling and metabolite analysis. Ionization efficiency was optimized using different modifiers, with 1 mM ammonium acetate found to provide the highest ionization efficiency for most carotenoids. Additionally, optimal ionization performance was achieved by fine-tuning parameters such as spray voltage, gas flow rate, and temperature. The developed method identified 33 carotenoids through a combined analysis of retention time, UV spectra, and the characteristic MS/MS fragmentation patterns. Comparative analysis of algae and clams revealed structural correlations between carotenoid profiles and their biological sources. Algal samples contained highly oxidized carotenoids, including fucoxanthin and astaxanthin were found as characteristic compounds in specific algal phyla. In addition, clams samples shared some algae compounds and also contained multiple metabolic derivatives such as diadinoxanthin, pectenol and pectenolone. These findings suggest clam carotenoid metabolism involves oxidation, reduction, epoxide ring-opening, and allenic bond rearrangement. Further comparisons between algal samples and clams revealed that structural correlations observed align with proposed metabolic pathway models, supporting the hypothesis of multi-step carotenoid transformation. This study demonstrates that mass spectrometry-based structural elucidation can reveal detailed carotenoid metabolic networks, providing insights for species traceability, aquaculture applications, and the development of functional foods based on natural carotenoids.