School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China.
J Chromatogr A. 2009 Dec 18;1216(51):8867-73. doi: 10.1016/j.chroma.2009.10.087. Epub 2009 Nov 5.
In the present work, vacuum microwave-assisted extraction (VMAE) was to perform microwave-assisted extraction in vacuum. Two well-known antioxidants, vitamin C from guava and green pepper, and vitamin E (alpha-tocopherol and gamma-tocopherol) from soybean and tea leaves, which were easy to be oxidized, were chosen as representative target compounds for the evaluation of VMAE. The extraction yields of vitamin C, alpha-tocopherol and gamma-tocopherol in VMAE and those in MAE performed in atmosphere (air-MAE) were compared and the effects of extraction time, extraction temperature and sample matrix were studied. Moreover, the effects of the oxygen and subpressure invacuo were also discussed via performed MAE in N(2) atmosphere (N(2)-MAE). The extraction yields of vitamin C, alpha-tocopherol and gamma-tocopherol in VMAE were higher than that in air-MAE, 35% increments of vitamin C from green pepper, 22% increments of alpha-tocopherol and 47% increments of gamma-tocopherol from tea leaves were obtained, respectively. The comparable increased extraction yields of vitamin C, alpha-tocopherol and gamma-tocopherol in N(2)-MAE to that in air-MAE confirmed that oxygen in system was the crucial factor for the oxidation of vitamin C and vitamin E, VMAE was beneficial for the extraction of these oxygen-sensitive compounds. In addition, the subpressure invacuo in the VMAE system also showed positive affect on the extraction yields. On the basis of preventing oxidation and improving extraction efficiency of target compounds because of less oxygen and subpressure invacuo in the extraction system, VMAE has good potential for the extraction of oxygen-sensitive and thermosensitive compounds from plant samples.
在本工作中，真空微波辅助提取（VMAE）是在真空中进行微波辅助提取。选择两种易被氧化的著名抗氧化剂，来自番石榴和青椒的维生素 C，以及来自大豆和茶叶的维生素 E（α-生育酚和γ-生育酚），作为代表目标化合物来评估 VMAE。比较了 VMAE 和在大气中（空气-MAE）进行的 MAE 中维生素 C、α-生育酚和γ-生育酚的提取率，并研究了提取时间、提取温度和样品基质的影响。此外，还通过在 N 2 气氛下进行的 MAE（N 2 -MAE）探讨了真空和负压下的氧气的影响。VMAE 中维生素 C、α-生育酚和γ-生育酚的提取率高于空气-MAE，分别从青椒中获得了 35%的维生素 C 、从茶叶中获得了 22%的α-生育酚和 47%的γ-生育酚。N 2 -MAE 中维生素 C、α-生育酚和γ-生育酚的可比提取率增加与空气-MAE 相当，这证实了系统中的氧气是维生素 C 和维生素 E 氧化的关键因素，VMAE 有利于这些对氧敏感化合物的提取。此外，VMAE 系统中的真空度也对提取率有积极影响。由于提取系统中氧气和真空度较低，VMAE 可以防止目标化合物氧化并提高提取效率，因此具有从植物样品中提取对氧敏感和热敏化合物的潜力。
