Abstract:

Taraxacum mongolicum is an important medicinal and edible perennial herb. T. grypodon is widely distributed in Linzhi, Tibet. The research aims to study the contents of flavonoids, polysaccharides, tannins, lignin and other chemical components in the roots and leaves of T. grypodon at different growth periods, which are closely related to its medicinal and edible quality, and provide important guiding significance for the efficient utilization of dandelions resources in Tibet. Taking the whole herb of T. grypodon at different growth stages distributed in four areas of Linzhi as the research materials, contents of total flavonoids, polysaccharides, tannins and lignin in the leaves and roots were measured and analyzed respectively. The results showed that: (1) The flavonoid content in the leaves was 72.83-162.93 mg/g, and that in the roots was 12.73-34.32 mg/g. The flavonoid content in the leaves was significantly higher than that in the roots (P<0.05). The flavonoids mainly accumulated in the leaves and showed significant changes with the growth period. (2) The total sugar content of leaves at different growth stages was 26.26-81.09 mg/g, and that in the roots was 243.08-528.08 mg/g. The total sugar content in the roots was significantly higher than that in the leaves (P<0.05), and the change trends of the total sugar content in the roots and leaves were opposite under different growth periods. (3) The reducing sugar content in the leaves was 13.73-63.38 mg/g, while that in the roots was 44.61-122.2 mg/g, which was significantly higher than that in the leaves. (4) The polysaccharide content in the leaves was 12.53-35.56 mg/g, with no significant difference at different growth stages. The polysaccharide content in the roots was 141.35-483.46 mg/g, which was significantly higher than that in the leaves. (5) The tannin content in the leaves was 18.99-49.74 mg/g, and that in the roots was 6.35-16.88 mg/g. The tannin content in leaves was significantly higher than that in the roots (P<0.05), and there were significant differences in the tannin content at different growth stages. (6) The lignin content in the leaves was 58.68-104.93 mg/g, and that in the roots was 72.90-139.92 mg/g. The lignin content in the roots was higher than that in the leaves, but the difference was not significant. Therefore, flavonoids and tannins of T. grypodon in Linzhi mainly accumulate in the leaves, and the leaves are its main medicinal tissues. The change rules of flavonoids and tannins contents are similar at different growth periods of the plants. On the contrary, saccharides mainly accumulate in the root tissues, and the contents of total sugar, reducing sugar, and polysaccharide are all the lowest during the fruiting stage. Lignin content in the leaves is less than 10%, and there is little difference at different growth stages. T. grypodon is a superior medicinal and edible plant resource with high flavonoid and polysaccharide content, but low tannin and lignin content. In order to maximize the economic effect, the leaf and root tissues should be collected separately according to demand during harvest.

Key words: Linzhi of Tibet, Taraxacum grypodon, flavonoid, polysaccharides, tannin, lignin, medicinal and edible herb