The Expectorant and Antitussive Effects of Yingshanhong (Manshanhong, Rhododendron simsii)

It is again the season when Yingshanhong blooms. Most people admiring the red hillsides do not know that this beautiful flower is also an excellent medicinal herb. Yingshanhong—also called Manshanhong, Yingshanhong, and Kaoshanhong—is the plant Rhododendron simsii of the Ericaceae family; when it blooms, whole mountains turn red, hence the names “Red Hillside” (Manshanhong) and “Yingshanhong.”

Manshanhong tablets, made from an extract of the leaves, are a common Chinese patent medicine for cough and excessive sputum, used for productive cough from bronchitis, cor pulmonale, or other causes; they are less effective for cough and sputum due to emphysema. It has also been reported that Manshanhong works only for productive cough and has little anti-asthmatic effect, so it is not very effective for asthma.

Modern pharmacology shows that oral or intraperitoneal preparations of Manshanhong’s ethanol or water extracts and its volatile oil all have antitussive action, which is central in origin. Manshanhong is especially effective for productive cough; the farrerol (Dujuan Su) it contains is the main expectorant component. Farrerol markedly promotes phenol-red excretion from the respiratory tract in mice, suggesting it acts directly on the respiratory mucosa; desmethylfarrerol also has good expectorant action. Foreign reports also note that Manshanhong extract can treat myocarditis and gastroenteritis; animal experiments confirm that Manshanhong extract lowers heart rate. Thus Manshanhong not only helps cough and sputum but also has some heart-rate-lowering effect.

Manshanhong has low toxicity. Taken as a decoction, an adult daily dose within 50 g causes essentially no adverse effects, but more than 100 g daily may harm the body. Its side effects are mainly dry mouth, nausea, vomiting, gastric discomfort, stomachache, poor appetite, diarrhea, dizziness, and headache. Those with hepatic or renal insufficiency who overdose may worsen their existing damage, so they should use it cautiously.

In Northeast China (especially around the Changbai Mountains), residents commonly steep Manshanhong in liquor to treat chronic bronchitis or bronchial asthma: use 60 g of coarsely ground Manshanhong leaves steeped in 500 g of white liquor for a week, then take 15–20 ml three times daily. Those who cannot drink alcohol may instead make a compound Ginseng-leaf syrup: 20 g dried Manshanhong leaves, 10 g Ginseng leaves, 10 g goji berries, prepared as syrup and taken daily; this treats chronic bronchitis and cor pulmonale. The most convenient option, however, is simply to take Manshanhong tablets.

If dried Manshanhong is included in a compound decoction, the adult dose per prescription should be kept to 10–30 g, reduced for children.