Huang Ya Zi, also known as Huang Yao Gen or Mu Yao Zi, is a tuber of the Dioscoreaceae plant Huang Du. After digging out the tuber, remove the stems and leaves, wash off the soil, and cut it into slices about 1-1.5 cm thick. It can be dried and used as medicine. It has a neutral nature and a bitter taste, and has the effects of cooling blood, reducing heat, dissolving nodules, and detoxifying. It is used to treat conditions such as hematemesis, epistaxis, throat bi, goiter, boils, and scrofula. In the market, the tubers of Polygonaceae plants such as Maomai Liao and Yi Liao (Buckwheat Seven) and the tubers of Menispermaceae plants such as Gui Deng Qing are often sold as fake Huang Ya Zi. The following are the distinguishing characteristics between genuine Huang Ya Zi and the fake Gui Deng Qing:
1. Genuine Huang Ya Zi has a faint scent and a bitter taste, while the fake has a slightly astringent taste.
2. Genuine Huang Ya Zi has a firm and brittle texture, easy to break, while the fake has a harder texture and is not as easy to break as the genuine.
3. The cross-sections are different: the cross-section of genuine Huang Ya Zi is light yellow to yellow-brown, smooth or with granular unevenness, while the fake has a light reddish-brown cross-section with numerous crystals, densely distributed dot-like protrusions, which are more obvious near the edge.
4. Distinguishing from the appearance: Genuine Huang Ya Zi is round or round-shaped slices, varying in size, with a diameter of about 3-7 cm and a thickness of 0.8-1.5 cm. The surface is dark brown with wrinkles, densely covered with short and small supporting roots and yellow-white circular supporting root scars. Some parts of the cork peel off, revealing a light yellow and smooth central column. Gui Deng Qing is mostly diagonally cut into elongated or horizontally cut into round slices, with a diameter of about 2.5-5 cm and a thickness of about 0.3-0.6 cm. Compared with genuine Huang Ya Zi, the slices are small and thin. The outer skin is gray-brown, and the edges are often curled. Sometimes, yellow-brown scales can be seen.
