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In ancient times, there was a physician named Du Zhong who went into the mountains to gather herbs. By chance, he noticed that when the bark of this particular tree was broken, many white threads appeared, making it difficult to snap, much like the “sinews and bones” of a human body. He pondered: If humans consumed the “sinews and bones” of this tree, wouldn’t their own sinews and bones become as strong as the tree? After trying it for a few days, he felt invigorated and his waist and legs felt much lighter. After consuming it for a period of time, he not only became physically fit and his hair turned black, but he also ascended to immortality and became a celestial being.
This legend narrates the distinctive characteristics of this herbal medicine and its clinical efficacy, hence the alternative name “Si Xian” for this herb.
According to the fourth edition of the Taiwan Pharmacopoeia, Du Zhong (Eucommia ulmoides Oliv.) is the dried bark of the Eucommia tree. It is typically harvested from the Qingming to the summer solstice period by scraping off the bark. The harvested bark has its outer layer, full of impurities, fungi, or moss, removed. This outer layer, referred to as “coarse bark,” is the exfoliating layer outside the cork cambium in botanical terms. After removal, the bark is “sweated” until the inner bark turns purplish-brown and is then dried for future use. It is mainly produced in Sichuan, Guizhou, Yunnan, and Shaanxi. The variety produced in Sichuan is known as “Chuan Du Zhong,” traditionally regarded as high quality, particularly from Tongjiang County. Recently, Tongjiang has also started cultivating silver ear mushrooms with notable success. Another variety produced in Shaanxi and Hubei is traditionally called “Han Du Zhong.” Taiwan began cultivating Eucommia around 1975, resulting in a significant production volume.
Eucommia ulmoides typically exhibits a ‘plate-like’ appearance. This is characteristic of medicinal herbs derived from the bark of woody plants. When the bark is peeled from the tree trunk and dried, it doesn’t shrink or curl, resulting in wide, flat, or thick pieces. The herb is usually grayish-brown or light brown in color, with a rough texture and is easily breakable. It has a slightly bitter taste. High-quality Eucommia typically has thick bark, large, intact pieces, numerous white, sticky fibers when broken, and a dark purple inner surface. The unique characteristic of Eucommia is the presence of these white, gummy fibers, often referred to as ‘gum silk’, which can be observed when any part of the plant, including the bark, leaves, or seeds, is broken.
The Shen Nong Ben Cao Jing (Divine Farmer’s Materia Medica) states: “Pungent in taste, neutral in nature. Primarily treats pain in the loins and spine, replenishes the middle jiao, benefits essence and qi, strengthens the sinews and bones, invigorates the will, eliminates itching and dampness in the perineum, and clears residual urine.” Therefore, in addition to alleviating pain in the loins and spine, it also has the effect of strengthening the sinews and bones.
Depending on different clinical needs, there are various processing methods for Eucommia ulmoides. One common method is to produce salted Eucommia. Clean Eucommia pieces are mixed with saline solution, allowed to moisten, and then placed in a pan. Clean sand is first heated in the pan over high heat until it feels loose, and then the moistened Eucommia pieces are added and stir-fried until the gummy fibers break and the surface turns black. It is then immediately cooled, the sand is sieved out, and the product is set aside for later use. Another preparation is charred Eucommia. Clean Eucommia is placed in a hot pan and stir-fried over medium heat until the surface is black and the interior is brown. A small amount of water is then sprayed on to extinguish any flames, and the product is removed and allowed to cool completely before being collected. However, there have been instances where processed Eucommia found in the market is not prepared properly, such as the presence of white gummy fibers or the use of charcoal to artificially darken the entire herb. In such cases, the black charcoal powder can be easily rubbed off with a hand. Therefore, care should be taken when selecting Eucommia, as a darker color does not necessarily indicate better quality.
In China, there are several adulterants such as Euonymus alatus, Euonymus phellomanus, Euonymus bungeanus, and Euonymus sieboldianus from the Celastraceae family. These plants also produce white, gummy fibers when their bark is broken, leading to confusion with genuine Eucommia ulmoides. Another adulterant is Euonymus japonicus, also known as ‘large-leaved boxwood’ or ‘zhengmu pi’. Its outer surface is grayish-brown or grayish-brown, and the fracture surface has dense, silvery-white gummy fibers. However, these fibers have poor elasticity and break at around 3 mm, serving as a key distinguishing feature. In Guangxi, China, there are records of a medicinal plant called ‘Du Zhong Teng’. The bark, when the outer layer is removed, is reddish-brown, and the inner surface is also reddish-brown. It also produces white, gummy fibers when broken and is therefore called ‘red Eucommia’. It’s important to distinguish it from genuine Eucommia when using it. In Taiwan, Eucommia is a popular health food, and the government has set standards for sulfur dioxide as well as heavy metals such as arsenic, cadmium, mercury, and lead. Therefore, consumers can purchase Eucommia with confidence.
Image provided by Professor Zhang Xian-zhe, Authentic Medicinal Material Atlas http://en.whatsintcm.com“