Lithospermi Radix, the dried root of Lithospermum erythrorhizon, is an important pharmacopoeial crude drug and is traditionally used as a purple dye. The plant is currently cultivated in the northern part of Japan, for a stable supply. However, the lower survival rate of cultivated plants and their lower content of naphtoquinone (shikonin) derivatives than those of wild plants are vital issues that need to be resolved. In the present study, we established experimental cultivation plots in Taketa City, a typical semi-mountainous area in Oita Prefecture. Four test areas, in a rain shelter or open field (S or O area) in the presence or absence of plastic mulch (M or MN area), were examined. Plants seedlings were cultivated between March and December. After the harvest, shoot length, stem diameter, the numbers of aerial branches and underground parts, and root length were measured. In a quality evaluation, diethyl ether-soluble extract and shikonin derivative contents were analyzed. The aerial parts of plants cultivated in the S area as well as the underground parts of plants cultivated in the M area were significantly larger in size. The yield of diethyl ether extract and shikonin derivative contents from Lithospermi Radix prepared from plants cultivated in the S area were significantly higher than from those in the O area. In conclusion, cultivation using rain shelter and plastic mulch was beneficial for growth and shikonin derivative contents in plants.
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