高周波酸素プラズマによる低温灰化の生薬学的研究への応用 : センナ葉およびツバキの葉の灰化組織中のシュウ酸カルシウムの観察

抄録

Plant tissues are completely ashed at ordinary temperature by very reactive oxygen stream excited in a high-frequency electromagnetic field under a low pressure, preserving mineral microstructures precisely identical with the original tissue matrices. Microscopic examinations of the mineral structures of the ashed tissues readily suggested their valuable contribution to plant taxonomical and morphological studies, as well as in identification of original plants for crude drugs. Systematic studies on mineral microstructures of medicinal plants were taken up and, as the first step, leaves of Cassia angustifolia VAHL and Camelia japonica L., both involving calcium oxalate crystals, were examined through surface and cross-sectional views of the ashed tissues. The results thereby obtained are summarized as follows, in comparison with the conventional Molisch's high temperature ashing method. 1) The low-temperature ashing preserves the mineral microstructures better than the high temperature ashing method and crystals in the ashed tissues retain their original location and shape. 2) Calcium oxalate crystals forming both clustered and solitary bodies are non-reactive with the oxygen plasma so that their geometric constitutions and optical properties of the crystals can be studied well in the ashed tissues, while with the high-temperature ashing the calcium oxalate crystals are considerably destroyed by thermal decomposition during ignition. 3) Cell membrane, nuclei, chloroplasts, leucoplasts, and some other small grains are ashed as they were in the original tissues, suggesting that certain mineral constituents were present in these materials.