What is the use of the “blue” in Isatis root?

As a common household medicine for clearing away heat and detoxifying, cooling blood and relieving sore throat, Isatis root has accompanied generations of people growing up. Despite this, many people don't actually know much about Isatis root. **Is Isatis root the root of Isatis? What is Isatis? What is the use of "blue"? **To clarify these questions, we must first talk about "blue".

1. Extract dyes to make pigments

There is a kind of plant that was first used by people to extract indigo dye, which was used for dyeing clothes or making cyanine, a pigment for Chinese paintings. It is indigo grass, or "indigo" for short.

Lan is a pictophonetic character. The grass head represents the meaning, and the lower half "jian" represents the pronunciation (similar pronunciation). The first Chinese character dictionary in my country, "Shuowen Jiezi", explains that "lan is the grass used to dye blue." More than 2,000 years ago, the ancients knew that the liquid soaked in indigo grass could be extracted into a cyan color, which was darker than blue, and was called indigo (dark blue, also called indigo). "Blue is derived from indigo, but it is bluer than indigo." Xun Kuang, an educator in the late Warring States period, wrote in "Encouraging Learning". From this, we can get a familiar idiom "青出蓝而胜于蓝", which is used to describe students who surpass their teachers or later generations who are better than their predecessors.

The indigo made from indigo grass is rich, bright and dignified. It is not easy to fade when dyed into clothes. It has been loved by people for thousands of years. During the dyeing process, the working people of my country use dyeing water, drawing and other techniques, and then according to the humidity, degree of oxidation and other factors, make the cloth surface change accordingly, making it look extremely beautiful. Clothes and fabrics unearthed before the Tang Dynasty in recent years can all show the flavor of indigo at that time. With the development of science and technology, fiber fabrics and finished products printed and dyed with indigo grass will become more and more popular among modern people and become an important part of fashion.

Hakka blue shirt dyed with indigo grass Source: Zhanggong Release Network

The beauty of indigo is found in poems of all dynasties. "I have been picking indigo all morning, but I cannot fill even one bag." In the poem "Picking Green" in the Book of Songs, the indigo girl misses her lover and cannot complete her task every day. "At sunrise, the river flowers are redder than fire, and in spring, the river water is as green as blue." In the eyes of the poet Bai Juyi, the river water in spring is like indigo. "Singing and drinking indigo wine, how many people are there in the world?" The free-spirited Lan Caihe improvised lyrics, blending the fairy spirit into wine and poetry...

At the same time, the indigo plant used as a dye also inspired the ancients, so indigo became the main raw material for Chinese painting pigments. Indigo, also known as indigo flower, is the indigo in Chinese painting pigments, containing green and blue. It turns out that the liquid made from indigo is originally green, and turns blue after contact with oxygen in the air.

What else can indigo be used for besides dye and pigment?

2. Five blues are commonly used as medicine

Ancient people began to use indigo to dye cloth and paint. As research deepened, it was discovered that there are many types of indigo, which can be eaten and used as medicine. Farmers were the first to discover that the roots, stems, and leaves of indigo are edible. They called the leaves of indigo leaves Daqingye and put them on the table. Some rural people in Yunnan and Guizhou now have the habit of eating indigo and Daqingye: either cooking soup, stir-frying, or pickling them into pickles to eat with rice.

Finding Chinese medicine from food is the wisdom of our ancients. After research, ancient medical scientists divided blue grass into five categories, namely Isatis indigofera, Polygonum tinctorium, Indigofera wu, Indigofera sibiricum and Indigofera sibiricum. "There are five kinds of indigo, each with its main treatment," Li Shizhen wrote in "Compendium of Materia Medica".

Indigo, also known as "blue" or "indigo", is a plant of the genus Polygonum in the family Polygonaceae. Its flowers are light red and its leaves contain a lot of blue juice. It grows in the north and south of China, mostly in the wild by the gullies or in the wet valleys, and is planted in a small part of the south. Before the Wei and Jin Dynasties, people used indigo to refer specifically to indigo grass (because people had not yet discovered other types). "Indigo comes from indigo, but it is bluer than indigo", and the "indigo" here refers to indigo. Indigo has the effects of detoxification, antipyretic and bactericidal.

Wulan is actually the indigofera tinctoria that grows in the Jianghai Plain in the lower reaches of the Yangtze River. Because the area belonged to the Wu Kingdom in ancient times, it was named Wulan. After the Qing Dynasty, Wulan was combined with indigofera tinctoria and was no longer listed separately.

Indigofera is a perennial shrub of the genus Indigofera of the family Acanthaceae. It blooms small lavender flowers and mainly grows in southern regions such as Yunnan, Guizhou, and Sichuan. Its roots, leaves, and stems can all be used as medicine, with the effects of clearing away heat and detoxifying, sterilizing and anti-inflammatory, preventing infectious diseases such as influenza, and treating wind-heat colds, tonsillitis, and snake bites. Indigofera is bitter and cold in nature. Taking too much can cause nausea, vomiting, skin allergies, chest tightness, and shortness of breath. Indigofera is generally grown in humid areas at an altitude of 400 to 500 meters. It is usually dug in spring or autumn, and the stems and leaves are used to process Indigo. The roots are washed and dried in the sun or oven. Indigofera has become a herb that makes many farmers in mountainous areas rich.

It is worth mentioning that Malan is not the same as the "Malan" that rural children sang when skipping rubber ropes in the 1970s and 1980s. "Kick a shuttlecock three times, Malan blooms twenty-one, twenty-five-six, twenty-five-seven, twenty-eight, twenty-nine, thirty-one..." The Malan in the ballad is also known as Malin, Malian, and Zhu Yingtai Flower. It is a plant of the genus Iris in the family Iridaceae. It has bright blue, white, snow-green and other colorful flowers, and is mainly used for viewing.

The gorgeous amaranth image source: China Plant Library Indigofera indigofera, also known as Sophora japonica, wild Sophora japonica, etc., is distributed in Taiwan, Hainan and other places. It is a good medicine for clearing away heat and detoxification, removing blood stasis and stopping bleeding. Compared with other blue grasses, the biggest feature of Indigofera indigofera is that it can prevent Japanese encephalitis.

Wood blueprint source: China Plant Library

Compared with Polygonum, Indigofera tinctoria, Indigofera tinctoria and Indigofera tinctoria, Isatis indigotica is much more famous.

3. Northern and Southern Isatis Indigo Plants are a good anti-toxic medicine

As a biennial herbaceous plant of the genus Isatis in the family Cruciferae, Isatis indigotica is native to the Yellow River Basin in the south of China and the Heilongjiang River Basin in the north. Its flowers are yellow. The name Isatis indigotica comes from "white cabbage". Cabbage is a general term for cabbage, including oil cabbage and Chinese cabbage. Isatis indigotica is very similar to oil cabbage (i.e. rapeseed), so it is very popular among people. Isatis indigotica has several other names, including Chinese blue, tea blue, and plate blue.

Image source of Isatis indigofera: Chinese Plant Library

Isatis? Could it be the original ingredient of Isatis root?

The answer is both yes and no.

Because there are two types of isatis root, namely southern isatis root and northern isatis root. Northern isatis root is the root of woad, while southern isatis root is the root of indigofera. In fact, it is more appropriate to call isatis root or indigofera root.

From the composition of the raw materials, we can know that the northern isatis root contains the antibacterial ingredient mustard glycoside, which is mainly used to clear away heat and detoxify, and has an inhibitory effect on Gram-negative bacteria and parotid virus ; the southern isatis root does not contain mustard glycoside, and is mainly used for exogenous fever, sore throat, ecchymosis on the body surface, dark purple tongue, throat ulcers, etc. Although the northern and southern isatis roots can eliminate heat and toxins in the body, there is a difference in the dosage of the two . The northern isatis root is usually used by adults at a time of 15 grams, while the southern isatis root is usually used by adults at a time of between 10-30 grams.

In fact, in modern times, people have not had a deep understanding of the raw material "Isatis indigotica", and most of them confuse Isatis indigotica, Indigofera tinctoria, Polygonum tinctoria, etc. For a period of time after liberation, pharmacies only supplied Isatis indigotica (actually Northern Isatis indigotica). In 1995, the "Chinese Pharmacopoeia" added the "Southern Isatis indigotica" entry for "Indigofera tinctoria", which distinguished the two plants. At the same time, there was also a special medicine for "Southern Isatis indigotica" on the market.

References:

1. The paper "Research Progress on Pharmacological Effects and Clinical Application of Radix Isatidis", author Chen Min, Chen Xiaofeng, Gu Zhenlun, "Chinese Wild Plant Resources" No. 21

2. The paper "Study on the Biological Characteristics of Isatis indigotica (Radix Isatidis)", author Du Peixin, Zhang Danyan, "Journal of Guangzhou University of Traditional Chinese Medicine", issue 4, 2008

3. The chapter "Isatis indigotica" in the book "Chinese Herbal Medicine Atlas"

4. Book "Shuowen Jiezi", published by Zhonghua Book Company in 2017

5. The article "Learn a Chinese herbal medicine every day - Isatis root (with pictures)" is from the Medical Knowledge Treasure Network

6. The article "Dye Plants: Better Than Blue - Indigofera" from the official website of Xi'an Botanical Garden

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Author: Wei Deyong, member of Shenzhen Writers Association, Guangdong Editor: Guru