Names: Rhizoma Dioscoreae Bulbiferae.  Dioscorea bulbifera L.  

Properties: Eliminates toxins, relieves swelling, reduces phlegm, cools blood, stops bleeding.

Function: Huang yao zi is effective in reducing swelling of the thyroid glands due to lack of iodine. It is also effective in reducing some of the swelling with unspecified causes.
Huang yao zi is effective in reducing swelling of the thyroid glands of animals caused by consuming a small amount of potassium thiocyanate.  It has no effect on the swelling of thyroid glands caused by the anti thyroid drugs  thiouracil (Tu) and Sod  Sulfadiazine

Huang yao zi can damage the tissues of liver and kidney. Short term usage can show the damaging effect on the liver. It takes long term usage to show the damage of kidneys.

Huang yao zi extract if effective for herpes infection of the retina.

Huang yao zi can inhibit the tumor S180 and the uterus neck tumor U14  of mice.

Its decoction has varying inhibiting effect on fungi that cause skin infections.

Modern Applications:

For tumors of different types: use huang yao zi, shan dou gen, bai yin in decoction
For swelling of thyroids: use huang yao zi, xia ku cao, kun bu in decoction
boils, snake bites, dog bites: use fresh or dry huang yao zi; make into powder and make into paste with vinegar. Apply externally.
For bleeding: vomiting blood, nose bleeding, menopausal bleeding, acute tonsillitis: combine with other herbs.

Chemical ingredients:

 the semi dry root contains:

22.5% of cane sugar
0.69% of reduce sugar
2.5% of starch
saponin
tanin
Dioscornin varies according to where it is produced, some product in certain localities do not contain any.
diosbulbin B
β-sitosterol

The whole plant contains:

diosbulbin A-H
D-sorbitol
2,4,6,-tetrahyroxy-9,10-dihydrophenanthrahe
2,4,5,6-tetrahydroxyphenanthrene

Dosage:  9 to 15 g. For external use: smash or grind and extract juice to apply to affected areas. 

Cautions: The roots of huang yao and ling yu zi (the pearly sprouts under the leaves) contain toxin. Over- consumption can cause burning sensation of the mouth and tongue, dripping of saliva, nausea, vomiting, abdominal pain, diarrhea, constriction of pupils; if serious, cardiac paralysis, difficulty in breathing, coma and death.

Antidode: empty stomach, promote diarrhea, take egg white, or arrow root (ge gen) starch porridge,  and activated carbon; drink cane sugar solution, or intra venous feeding of glucose solution. Taking mug bean soup or boil gang mei 250 grams with 5 bowls of water and simmer till 2 bowls and use as tea.

The roots of huang yao is toxic to the liver.