The study of the metabolome within tissues, organisms, cells or biofluids can be carried out by several bioanalytical techniques. Among them, nuclear magnetic resonance (NMR) is one of the principal spectroscopic methods. This is due to a sample rotation technique, high-resolution magic angle spinning (HR-MAS), which targets the analysis of heterogeneous specimens with a bulk sample mass from 5 to 10 mg. Recently, a new approach, high-resolution micro-magic angle spinning (HR-μMAS), has been introduced. It opens, for the first time, the possibility of investigating microscopic specimens (<500 μg) with NMR spectroscopy, strengthening the concept of homogeneous sampling in a heterogeneous specimen. As in all bioanalytical approaches, a clean and reliable sample preparation strategy is a significant component in designing metabolomics (or -omics, in general) studies. The sample preparation for HR-μMAS is consequentially complicated by the μg-scale specimen and has yet to be addressed. This report details the strategies for three specimen types: biofluids, fluid matrices and tissues. It also provides the basis for designing future μMAS NMR studies of microscopic specimens.

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Extraction of Chinese star anise (Illicium verum Hooker) and cinnamon bark (Cinnamomum zeylanicum Nees) was studied by a new solvent extraction technique involving 1,1,2-trichloro-l,2,2-trifluorethane. Thus useful yields of concrete were obtained (21% and 12% respectively). Hydrodistillation of the concretes made it possible to obtain essential oils with yields similar to those obtained by direct hydrodistillation of plant materials (9.5% and 1.1% respectively). GC-MS analysis indicated that the composition of products obtained was similar to that of essential oils obtained by direct hydrodistillation.