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Tongcao has tiny holes and is open at both ends, hence the name Tongcao, which is now referred to as Muxiong. The Tongcao of today is the same as the ancient Tongtuomu. In the Song Dynasty, the Materia Medica mixed them together, causing confusion between names and realities. Now they have been separated.
《Herbaceous Section – Climbing Plants from the Compendium of Materia Medica》
From the above text, it is clear that in the Ming Dynasty “Compendium of Materia Medica” (本草綱目) written by Li Shizhen, the differences in the sources of the two similarly named medicinal materials, “Tongcao” and “Mutong,” are clearly pointed out.
According to the fourth edition of the Taiwan Pharmacopoeia, Mutong (木通) is described as follows: Mutong refers to the dried stems of plants from the Lardizabalaceae family. It includes: Five-leaf Mutong (Akebia quinata (Thunb.) Decne) Three-leaf Mutong (Akebia trifoliata (Thunb.) Koidz. White Mutong (Akebia trifoliata (Thunb.) Koidz. var. australis (Diels) Rehder) The dried stems are used in traditional medicine. Another plant, Clematis montana Buch.-Ham. ex DC. (known as Chuanmutong or Mountain Clematis) and Clematis armandii Franch. (known as Small Mutong), from the Ranunculaceae family, is also used. A banned variety is Guanmutong (關木通), which comes from Aristolochia manshuriensis Kom. (a member of the Aristolochiaceae family). It contains Aristolochic acid, which can cause kidney failure if used improperly, and is therefore not available on the market. Mutong is typically harvested in autumn. The stems are cut, the outer skin is removed, and then the finer branches are stripped away before being dried in the shade. Both Mutong and Tongcao (通草) are commonly used for their diuretic and lactogenic properties. Due to the shared term “通” (meaning “to pass through”), historical herbal texts sometimes confuse these two herbs. Mutong is usually produced in Jiangsu, Zhejiang, and Jiangxi, while Three-leaf Mutong is primarily from Zhejiang, and White Mutong is from Sichuan, Hubei, Hunan, Yunnan, and Jiangxi. Taiwan’s Hsinchu region also cultivates Tongcao. Mutong may also be known as Dingweng, Fuzhi, Dingfu, and Wangweng. The medicinal slices are typically round, oval, or irregularly shaped, with a gray-brown exterior. The cross-section shows radial arrangement, with a smaller or sometimes hollow pith. It has a faint odor and a slightly bitter and astringent taste. Chuanmutong (川木通) slices are yellowish-white, with a small pith, occasional hollowness, radial纹理, and裂隙, and usually have a shed outer skin with uneven edges.
According to the fourth edition of the Taiwan Pharmacopoeia, Mutong (木通) is characterized by its bitter and cold nature. It is associated with the Small Intestine and Bladder meridians and has the primary functions of promoting diuresis, clearing heart fire, and stimulating lactation. Due to its pronounced diuretic effects, it is commonly used. However, due to its frequent use, there are often cases of confusion with other herbs. Here are some common types and their distinguishing features: Sweet Mutong (甘木通): This is the dried leaves of the Clematis species, commonly known as Silk Clematis. The medicinal part is the leaf, differing from the typical vine stem structure, making it relatively easy to identify. Xinjiang Mutong (新疆木通): This refers to the dried stems of Clematis orientalis, known for its long cylindrical shape with swollen nodes, rough brown-yellow skin, and brittle texture. The smell is faint and the taste is slightly bitter. Dull-Toothed Clematis (鈍齒鐵線蓮): This is the dried stem of Clematis flammula. It is cylindrical with a yellow-brown or yellowish-brown surface, six longitudinal grooves, and swollen nodes. The texture is hard and not easily broken. The cross-section is yellow-white with numerous small holes, and the pith is small and white. The smell is faint, and the taste is mild. Wild Quince (野木瓜): This is the dried stem of the Passiflora species. The stem is cylindrical with a gray-brown surface and rough longitudinal striations. The cork layer often falls off, revealing fibrous bundles and loose, white ring-shaped central pith. The wood is broad and yellow-white or light brown, with dense rays and a small or sometimes hollow pith. The smell is faint and the taste is slightly bitter and astringent.
Small Clematis (小木通): The dried stem of Clematis armandii. The stem is long and cylindrical, with a brown-yellow or yellow-brown surface. The outer skin is easily separable from the wood, showing side branch and leaf scars. It is hard and not easily broken, with a yellow-white cross-section, thin bark, broad wood, and radial arrangement of rays. The central pith is small and white. The smell is faint, and the taste is slightly bitter. Clematis montana (綉球藤): The dried stem of Clematis montana. The surface is gray-black with a cross-section showing gray-white wood composed of various-sized, radially arranged wood sections. It is similar in appearance to Small Clematis but can be distinguished by specific features. Additionally, there have been instances of Mutong being adulterated with weight-increasing powders to artificially increase its mass. Such adulterated Mutong can be identified by its pale brown or yellow-white bark (normal Mutong is brown-yellow), white wood (normal Mutong is yellow-white), and irregular, brittle slices often showing bright spots under magnification.
Mukutong is a commonly used Chinese medicinal herb. However, due to its long history of use and variations in usage practices, confusion can arise. To ensure the safety of medicinal use, the government not only sets standards for sulfur dioxide but also imposes limits on heavy metals such as arsenic, cadmium, mercury, and lead. This helps ensure safety in usage, allowing the public to use the herb with confidence.
Image provided by Professor Zhang Xianzhe’s ‘Authentic Medicinal Materials Atlas’