Dioscorea oppositifolia. D. opposita, D. polystachya, D. batatas, D. esculenta, D. japonica  山 药 Shān yào   Chinese Yam, Sweet potato  Family: Dioscoreaceae    
Nature- neutral     FLAVOR: Sweet   CHANNEL: Spleen, Lung, Kidney
FUNCTIONS
GROUP: Tonify Qi
1. Invigorate the Spleen & Stomach.[1] Tone up deficiency. Anti-diarrheal agent.[1] Spleen tonic.[5]
2. Nourish the Lung Yin.[1] Invigorate the Lung.[5]
3. Invigorate the Kidney and preserve the essence.[1,5]
INDICATIONS- This herb moistens, and is neither hot nor cold, therefore good for the Yin and Yang and for boosting empty conditions.
1. Spleen/Stomach Qi deficiency manifesting as anorexia, fatigue, Loose stools or chronic diarrhea.[5] Spontaneous sweating.[1] Chronic enteritis.[1] Dysentery.[1] Poor digestion.[1] Diabetes.[5]
2. Lung deficiency with chronic cough,[5] or tuberculosis. Also for Lung and Kidney deficiency with dyspnea and chronic cough. Cough. Asthma.[1]
3. Febrile diseases with consumption of body fluid or Spleen/Stomach Yin deficiency with poor appetite, thirst, dry tongue, diabetes = wasting and thirsting disorder.
4. Kidney deficiency manifested as seminal emission (Wet dreams).[1] Enuresis, frequent micturition. Spermatorhea.[5] Frequent urination.[5] Vaginal discharge.[5] Leukorrhea.[1]
5. Neurasthenia[1].
PATENT COMBINATIONS
CONTRAINDICATIONS: Excess diseases.[3]
PREPARATIONS: Decoction 10-30 g.[1,4] Must be either cooked or boiled or steamed, not raw.[3]
Fluid extract 1:1 in 60% alcohol.[6]
    
- Chronic diarrhea and poor appetite- Prepare 80 g raw yam and grind into powder. Wash an equal amount of glutinous(sweet) rice and drain it; put rice in the sun to dry. Toast the rice in a pan, shaking or stirring, until yellowish and grind into powder. Mix the yam and rice. Take 4 spoonfuls of the powder, some sugar, and black pepper dissolved in warm water each morning.[5]
HABITAT: Cultivated or found growing wild along hillsides and in valleys.
DESCRIPTION Perennial growing herbaceous vine. Stem; tuber thick and fleshy, cylindrical in shape. Stem; greenish-purple, slender and entwining. Leaves opposite or trifoliate whorled, ovate-lanceolate or deltoid-ovate, apexes pointed, bases auricular-cordate, axils frequently containing appendages, petioles long and slender. Flowers; in summer, light purple axillary, forming a spike infloresence. Capsule; 3 angled and winged.
References
References

Anti-obesity Effect of Dioscorea oppositifolia Extract in High-Fat Diet-Induced Obese Mice and Its Chemical Characterization.
Jeong EJ, Jegal J, Ahn J, Kim J, Yang MH.
Abstract
Dioscorea oppositifolia is a well-known edible and traditional medicine for the treatment of gastrointestinal diseases. In our previous study, D. oppositifolia exhibited both pancreatic lipase inhibition and an anti-adipogenesis effect in vitro. This study was performed to investigate the anti-obesity effect of D. oppositifolia on high-fat diet-induced obese mice. Female ICR mice were fed a high-fat diet with the 100 mg/kg of D. oppositifolia n-BuOH extract for 8 weeks. The high-fat diet mice received the 15 mg/kg Orlistat orally as a positive control. The body weight, parametrial adipose tissue weight, and the levels of triglyceride (TG), total cholesterol (TC), and low density lipoprotein (LDL)-cholesterol in blood serum of female ICR mice were significantly decreased by feeding a high-fat diet with the n-BuOH extract of D. oppositifolia. An inhibitory effect of D. oppositifolia extract on dietary fat absorption was also clearly shown. The D. oppositifolia sample was found to contain 3,5-dimethoxy-2,7-phenanthrenediol and (3R,5R)-3,5-dihydroxy-1,7-bis(4-hydroxyphenyl)-3,5-heptanediol as main components based on its phytochemical analysis. The present study is the first report of the anti-obesity effect by D. oppositifolia n-BuOH extract using an established disease model. The increase in fecal fat excretion by treatment of D. oppositifolia may be an effective approach for treating obesity and related diseases.
PMID: 26700066 DOI: 10.1248/bpb.b15-00849  Biol Pharm Bull. 2016;39(3):409-14. doi: 10.1248/bpb.b15-00849. Epub 2015 Dec 22. ncbi.nlm.nih.gov