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Dr. Da Zhen introduces ‘Di Gu Pi’ on the Traditional Chinese Medicine Channel.:
The clear dew is on the thorny shrubs. The virtuous gentleman, with his evident noble character, brings forth good virtues.
《Dew, Book of Songs》
In the “Book of Songs,” the wolfberry (枸杞) and sour jujube (酸棗) are used as metaphors for an open and honest gentleman. Both “wolfberry” and “jujube” are plants with thorns that can bear fruit, symbolizing the noble qualities of a gentleman—uprightness, brightness, sincerity, and loyalty. These plants are used to metaphorically represent people of great virtue, demonstrating the high regard ancient people had for the wolfberry
According to the fourth edition of the Taiwan Pharmacopoeia, Di Gu Pi (地骨皮) refers to the dried root bark of the Solanaceae plants Lycium chinense Mill. or Lycium barbarum L. Typically, the roots are harvested in early spring or late autumn, cleaned, and then the bark is stripped and dried for later use. The medicinal material often appears cylindrical with a grayish-yellow outer surface and irregular, easily scaling patterns. It is light and easily broken, with an uneven cross-section. It has a faint smell and a slightly sweet taste that turns bitter. The best quality is characterized by large, thick pieces without a woody core or impurities.
The “Shen Nong Ben Cao Jing” (Divine Farmer’s Classic of Materia Medica) from the Han dynasty records: “Goji berries grow in the plains of Changshan and other hills and valleys,” referring to the region around present-day Quyang in Hebei province. Shen Kuo of the Northern Song Dynasty noted in his “Mengxi Bitan” that “Goji berries grown in the extreme edge of Shaanxi are tall, over ten feet, with large, thornless stems several inches wide. The root bark is like houpu (Magnolia bark), sweet and superior to that from other places,” indicating that the root bark from Shaanxi, known as Di Gu Pi, is of high quality.
Li Shizhen’s “Ben Cao Gang Mu” (Compendium of Materia Medica) from the Ming dynasty also states: “In ancient times, goji berries and Di Gu Pi from Changshan were considered the best, but those from Shaanxi are now regarded as the finest, with those from Ganzhou being exceptional.” This further confirms the superior quality of Di Gu Pi from Shaanxi. Nowadays, it is also cultivated in Shanxi, Shandong, Shaanxi, and Inner Mongolia, and there are small-scale cultivations in Taiwan, although fruit production is rare there, and the leaves are primarily used as food.
The name “Di Gu Pi” first appeared in “Lei Gong Pao Zhi Lun” by Lei Xiao during the Wei, Jin, and Southern and Northern Dynasties periods. Due to its long history of use, it has many alternate names, such as goji root, Di Gu, Di Xian, Hong’erduo root, Gounai root bark, and Hongliu root bark. Because it sprouts in spring and its leaves are soft and thin like pomegranate leaves, it is colloquially known as “sweet vegetable” and thus also called “sweet tooth root.
In clinical practice, Di Gu Pi (地骨皮) in Traditional Chinese Medicine is primarily used to clear deficient heat and cool the blood. It is commonly employed to treat symptoms such as night sweats due to deficiency, feverish conditions from weakness, and cough or asthma due to lung heat. It is also used in common formulas like Xie Bai San and Qing Xin Lian Zi Yin.
Depending on the clinical purpose, Di Gu Pi is processed in different ways. The commonly used method involves removing impurities and residual woody core, then washing and drying the bark. Another method is salting the Di Gu Pi, where the clean bark is sprayed with a saline solution, mixed evenly, and then steamed or soaked.
In the pot, then stir-fry over low heat until it turns a deep brown color with slight charred spots, then remove and let it cool.
When purchasing Di Gu Pi (地骨皮), it’s important to be cautious of counterfeit materials. Common confusions include:
- Dry Root Bark of Verbena (大青): Sometimes labeled as “Land Bone Bark” or “Red Land Bone Bark” in Fujian, Zhejiang, and Guangxi regions. It has a yellow-brown outer surface with wrinkles and a yellow-white inner surface with fine vertical lines. The broken surface shows a light yellow-brown outer layer and a brownish inner layer, usually flat with a faint smell and a slightly bitter taste.
- Dry Bark of Muckle-leafed Wintergreen (毛葉探春): This bark appears cylindrical with a gray-yellow outer surface and irregular vertical cracks, and a brown-yellow inner surface with fine vertical lines. It is easily broken with an uneven cross-section. The outer layer is yellow to brown-yellow, with a faint aroma and a slightly bitter, astringent taste. It lacks the “white inner bark” feature found in Di Gu Pi. Muckle-leafed Wintergreen is used for invigorating blood and removing stasis, unlike Di Gu Pi’s function of clearing deficient heat and cooling the blood.
- Dry Root Bark of Rubiaceae Plant (毛烏口樹): Known as “White Land Bone Bark” in Zhejiang, causing confusion. Its appearance includes a gray-brown outer surface with slightly twisted vertical wrinkles and long horizontal pores, with a light yellow or gray-yellow inner surface and fine vertical lines. It is lightweight, brittle, and has a faint aroma with a slightly spicy and bitter taste.
- Dry Root Bark of Rutaceae Plant (香加皮): Its main identifying feature is a distinct aroma and a bitter taste.
- Dry Root Bark of Black Wolfberry (黑枸杞): This bark is easily flaked off, with an outer surface of yellow-brown and an inner surface of brownish color. It has a salty taste.
For powder forms, fluorescent observation methods can also be used for identification.
n summary, the identification of Di Gu Pi (地骨皮) primarily relies on the following principles:
“Soft Outer Bark”: Di Gu Pi has a soft and thick outer bark. It can be broken with a slight press from a fingernail.
“White Inner Layer”: The inner surface of Di Gu Pi is grayish-white, visible when broken. The white part of the inner layer should initially taste sweet and turn bitter after chewing for a few seconds.
No Special Aroma: Di Gu Pi should not have a distinct aroma. If it has any noticeable fragrance, it should be regarded with caution.
Common Di Gu Lu (地骨露) is made by steaming and boiling Di Gu Pi. The Taiwan Pharmacopoeia specifies the allowable limits for sulfur dioxide and heavy metals such as arsenic, cadmium, mercury, and lead to ensure consumer safety.
Image provided by Professor Zhang Xianzhe’s ‘Authentic Medicinal Material Atlas’ http://en.whatsintcm.com