Herb Leaf (叶 yè)

Da Qing Ye

Isatis leaf · 大青叶

Isatis indigotica Fort. · Folium Isatidis

Also known as: Woad leaf, Indigo leaf, Lán Yè (蓝叶),

Da Qing Ye (Isatis leaf) plant

Images shown are for educational purposes only

Da Qing Ye (Isatis leaf) is a powerful cooling herb used in Chinese medicine to fight infections, reduce high fevers, and calm inflammatory skin conditions like rashes and sore throats. It is most commonly used during acute febrile illnesses such as influenza, mumps, and viral infections. Because it is very cold in nature, it is not suitable for people with weak digestion or cold constitutions.

Category Heat-clearing herbs Herbs that clear Heat and resolve Toxicity (清热解毒药)
Therapeutic focus Immune Support Fever Management Skin Health Throat Health

TCM Properties

Temperature

Cold

Taste

Bitter (苦 kǔ), Salty (咸 xián)

Channels entered

Heart, Stomach, Liver

Parts used

Leaf (叶 yè)

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What This Herb Does

Every herb has a specific set of actions — here's what Da Qing Ye does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Da Qing Ye is primarily used to support these areas of health:

Immune Support Fever Management Skin Health Throat Health

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Da Qing Ye performs to restore balance in the body:

Clears Heat and Resolves Toxicity Cools the Blood Cools the Blood and Resolves Macules Benefits the Throat

How these actions work

'Clears Heat and resolves toxins' means Da Qing Ye strongly counteracts infectious and inflammatory conditions caused by Heat and toxic pathogens. Its bitter, cold nature makes it especially effective against high fevers from epidemic diseases, viral infections like influenza and encephalitis, and bacterial infections. It targets the Heart and Stomach channels, where toxic Heat commonly accumulates during acute febrile illness.

'Cools the Blood' means the herb enters the Blood level and calms pathological Heat that has penetrated deeply into the bloodstream. When Heat invades the Blood, it can cause the blood to move recklessly, leading to nosebleeds, vomiting blood, or skin rashes (macules). Da Qing Ye's cold, slightly salty nature allows it to reach the Blood level and clear this deep-seated Heat. 'Reduces macules' (消斑) is closely related: when Heat toxins enter the Blood and damage the vessels, dark purplish spots appear on the skin. Da Qing Ye addresses the root cause by clearing the Heat and cooling the Blood so these rashes can resolve.

'Benefits the throat' refers to its ability to drain fire and toxins from the Heart and Stomach channels that flare upward, causing sore throat, swollen tonsils, and mouth ulcers. It is commonly combined with herbs like Xuan Shen (Scrophularia) and Huang Lian (Coptis) for these conditions.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Da Qing Ye is used to help correct these specific patterns.

Why Da Qing Ye addresses this pattern

When epidemic or warm-disease pathogens penetrate deeply into the Blood level, they cause high fever, delirium, and the eruption of dark purplish macules on the skin. Da Qing Ye is bitter, salty, and cold, which gives it a direct affinity for the Blood level through the Heart and Stomach channels. Its strong Heat-clearing and toxin-resolving actions address the root pathogenic Heat, while its Blood-cooling property calms the reckless movement of Blood that causes bleeding and macules. Classical sources describe it as a key herb for 'warm-toxin macules' (温毒发斑), frequently combined with Water Buffalo Horn (Shui Niu Jiao) and Xuan Shen to clear both Qi-level and Blood-level Heat simultaneously.

A practitioner would look for one or more of these signs

Skin Rashes

Dark purplish macules from Heat entering the Blood

High Fever

Persistent high fever unresponsive to sweating methods

Nosebleeds

Nosebleeds or vomiting blood from Heat forcing Blood out of vessels

Delirium

Delirium or restless agitation from Heat disturbing the Heart

Commonly Used For

These are conditions where Da Qing Ye is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Heart and Stomach Fire Blazing

TCM Interpretation

In TCM, influenza is understood as an invasion by epidemic Wind-Heat or warm-toxin pathogens (温毒). In milder cases, the pathogen stays at the body's surface level, causing fever, chills, sore throat, and headache. In more severe cases, the Heat toxin penetrates deeper, generating intense interior Heat that manifests as high sustained fever, severe sore throat, intense thirst, and restlessness. The pathogen primarily attacks through the Lung and Stomach systems, and when the toxic Heat is strong, it can progress into the nutritive (营 yíng) and Blood levels, causing deeper symptoms.

Why Da Qing Ye Helps

Da Qing Ye's strong Heat-clearing and toxin-resolving properties directly address the epidemic toxic Heat that drives influenza. Its bitter, cold nature powerfully drains the excess Heat from the Heart and Stomach channels, reducing fever and relieving sore throat. When combined with herbs like Jin Yin Hua (Honeysuckle) and Lian Qiao (Forsythia) for surface-level symptoms, or with Shui Niu Jiao (Water Buffalo Horn) and Xuan Shen for deeper Blood-level Heat, it provides coverage across multiple stages of the illness. Modern pharmacological research shows that isatis leaf extracts have demonstrated antiviral and antipyretic activity, lending biomedical support to its traditional use.

Also commonly used for

Lumps

Epidemic parotitis with swelling and pain

Encephalitis

Epidemic encephalitis B with high fever and delirium

Pneumonia

Acute pneumonia with high fever and cough

Mouth Ulcers

Recurrent oral ulceration from Heat toxins

Erysipelas

Skin erysipelas (丹毒) with redness, heat, and swelling

Dysentery

Acute bacterial dysentery with bloody stools and fever

Tonsillitis

Acute tonsillitis with sore throat and fever

Skin Rashes

Measles or febrile rashes with deep red or purplish color

Herb Properties

Every herb has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Cold

Taste

Bitter (苦 kǔ), Salty (咸 xián)

Channels Entered

Heart Stomach Liver

Parts Used

Leaf (叶 yè)

Dosage & Preparation

These are general dosage guidelines for Da Qing Ye — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

9-15g (dried herb); 30-60g (fresh herb)

Maximum dosage

Up to 30g of dried herb in severe acute Heat-toxin conditions; up to 60g when using fresh leaves (typically juiced or decocted), under practitioner supervision.

Dosage notes

The standard dose of 9-15g is used for most Heat-clearing purposes in dried decoction form. For more severe conditions such as high fever with skin eruptions (wen du fa ban), epidemic parotitis, or acute throat infections, doses toward the upper end (15g) or slightly above may be used. When fresh leaves are available (particularly in summer and autumn), the fresh herb is preferred for acute conditions at 30-60g, often juiced and taken directly. For prevention during epidemics, Da Qing Ye can be decocted at moderate doses (around 15g) and taken over several days. Because of its bitter cold nature, the dosage and duration should be kept to the minimum effective amount to avoid damaging digestion.

Common Herb Pairs

These ingredients are traditionally combined with Da Qing Ye for enhanced therapeutic effect

Ban Lan Gen
Ban Lan Gen 1:1 (Da Qing Ye 15g : Ban Lan Gen 15g)

Da Qing Ye (leaf) and Ban Lan Gen (root) come from the same Isatis plant but have complementary strengths. The leaf excels at cooling the Blood and clearing macules, while the root is stronger at resolving toxins and soothing the throat. Together they provide a comprehensive attack on epidemic Heat toxins at both the Qi and Blood levels.

When to use: Epidemic febrile diseases with both high fever and severe sore throat, such as influenza, mumps, or encephalitis where Heat toxins are intense.

Zhi Zi
Zhi Zi 2:1 (Da Qing Ye 15g : Zhi Zi 9g)

Zhi Zi (Gardenia fruit) clears Heat from the Triple Burner and drains fire downward through the urine, while Da Qing Ye clears Heart and Stomach fire-toxins and cools the Blood. Together they clear Heat at both the Qi and Blood levels and from multiple organ systems simultaneously, amplifying each other's Heat-clearing and detoxifying effects.

When to use: High fever with irritability, dark skin macules, and jaundice from intense Heat toxins, as seen in the classical Xi Jiao Da Qing Tang.

Xuan Shen
Xuan Shen 1:1 (Da Qing Ye 15g : Xuan Shen 15g)

Xuan Shen (Scrophularia root) nourishes Yin, clears deficiency-Heat, resolves toxins, and reduces swelling. Da Qing Ye clears excess Heat toxins and cools the Blood. Together they address both the excess toxic Heat and the Yin damage it causes, making their combined effect stronger for sore throat with Heat and swelling, and for macules from Blood-level Heat.

When to use: Warm-disease with sore throat, high fever, and developing macules where both toxin clearance and Yin protection are needed.

Shu Di Huang
Shu Di Huang 1:2 (Da Qing Ye 15g : Sheng Di Huang 30g)

Sheng Di Huang (raw Rehmannia) is a premier Blood-cooling and Yin-nourishing herb, while Da Qing Ye excels at clearing Heat toxins. Together they powerfully cool the Blood, stop bleeding caused by Heat, and clear the toxins driving the fever, while Sheng Di Huang protects the Yin fluids that Heat tends to damage.

When to use: Heat deeply entered into the Blood level with bleeding (nosebleeds, blood in urine), dark purplish macules, and a deep crimson tongue.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Ban Lan Gen
Da Qing Ye vs Ban Lan Gen

Both come from the same Isatis plant and share Heat-clearing, toxin-resolving actions. However, Da Qing Ye (the leaf) is stronger at cooling the Blood and clearing macules, making it more suitable when Heat has entered the Blood level and caused skin eruptions or bleeding. Ban Lan Gen (the root) is stronger at resolving toxins and soothing the throat, making it the preferred choice for severe sore throat, swollen glands, and 'Big Head Plague' (大头瘟). A classical teaching notes: the leaf disperses (散), while the root descends (降).

Qing Dai
Da Qing Ye vs Qing Dai

Qing Dai (Natural Indigo) is a processed powder derived from Da Qing Ye and related plants. It shares similar Heat-clearing and Blood-cooling properties, but is additionally effective at clearing Liver fire, calming convulsions, and treating Lung-Heat cough with bloody phlegm. Qing Dai is typically used externally for mouth and throat inflammation, or internally as pills and powders (not decoctions), while Da Qing Ye is the standard decoction herb.

Jin Yin Hua
Da Qing Ye vs Jin Yin Hua

Both are major Heat-clearing and toxin-resolving herbs. Jin Yin Hua (Honeysuckle flower) is lighter and more aromatic, excelling at clearing Wind-Heat at the surface level and treating carbuncles and sores. Da Qing Ye is heavier and colder, with a specific ability to cool the Blood and clear macules when Heat has penetrated deeper into the Blood level. For surface-level infections, Jin Yin Hua is preferred; for deep Blood-level Heat with macules, Da Qing Ye is more appropriate.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Da Qing Ye

Historically, multiple plant species from different families were all used as "Da Qing Ye" in different regions of China, which creates a significant identification challenge. The modern Chinese Pharmacopoeia recognises only the leaf of Isatis indigotica (Song Lan, Brassicaceae) as the official source. Common substitutes and regional alternatives include: 1. Liao Lan (蓼蓝, Polygonum tinctorium, Polygonaceae): leaves formerly used as Da Qing Ye in northeastern China, Hebei, and Tianjin. Distinguishable by its smaller, elliptical leaves (3-10 cm), a flat leaf stalk with a membranous sheath clasping the stem, and a slightly unpleasant odour. Now sold separately as "Liao Da Qing Ye." 2. Ma Lan (马蓝, Baphicacanthus cusia, Acanthaceae): leaves used in southern provinces (Fujian, Guangdong, Guangxi, Sichuan). Identified by elliptical to obovate-oblong leaves with fine serrated margins, dark green to brownish-black colour when dried, and square-shaped stems. 3. Lu Bian Qing / Da Qing Mu (路边青, Clerodendron cyrtophyllum, Verbenaceae): formerly used in Hunan, Hubei, and Jiangxi. Distinguished by larger, paper-textured leaves that are brownish-yellow to brownish-red on the upper surface. These substitutes have different chemical profiles and may not be equivalent in clinical effect.

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any herb.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Da Qing Ye

Non-toxic

Da Qing Ye is classified as non-toxic in the Chinese Pharmacopoeia and has a long history of safe use at standard doses. No specific toxic components requiring special precautions have been identified at typical medicinal dosages. One isolated case report described a patient who developed hematuria (blood in urine) after receiving an injection of Da Qing Ye (from the Clerodendron cyrtophyllum source), which resolved after discontinuing the preparation. This was associated with an injectable preparation rather than standard oral decoction use. The herb's strongly cold nature means the main safety concern is damage to digestive function from overuse or use in patients without genuine Heat patterns, rather than chemical toxicity.

Contraindications

Situations where Da Qing Ye should not be used or requires extra caution

Avoid

Spleen and Stomach deficiency-cold (脾胃虚寒): Da Qing Ye is bitter and very cold in nature. In people whose digestive system is already weak and cold, with symptoms such as loose stools, poor appetite, and abdominal cold pain, this herb can further damage the Spleen Yang and worsen digestive weakness.

Caution

Absence of true Heat or Fire toxin: This herb should not be used when there is no genuine excess Heat pattern. Using cold, bitter herbs in conditions without real Heat (such as deficiency-type low-grade fever or cold-type sore throat) can injure the body's Qi and Yang without therapeutic benefit.

Caution

Aspirin allergy or sensitivity: Da Qing Ye contains chemical compounds with structural similarities to salicylates. People with aspirin allergy may potentially experience allergic reactions including asthma attacks.

Caution

Known sensitivity to Isatis preparations: Rare cases of blood in the urine (hematuria) have been reported following injection of Da Qing Ye extract preparations. Oral decoction use carries lower risk, but any prior adverse reaction to Isatis products warrants caution.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

There is insufficient safety data on the use of Da Qing Ye during pregnancy. Its strongly cold and bitter nature poses a theoretical risk of damaging Spleen and Stomach Yang in the pregnant person, which could indirectly affect fetal nourishment. No specific teratogenic effects have been reported, but the herb is not considered an established safe choice during pregnancy. As a precaution, it should be avoided unless clearly indicated for an acute Heat-toxin condition and prescribed by a qualified practitioner.

Breastfeeding

No specific studies exist on the transfer of Da Qing Ye constituents into breast milk. Its bitter, cold nature could theoretically affect the infant's digestion if active compounds pass into breast milk, potentially causing loose stools in the nursing infant. Short-term use for acute febrile illness under practitioner guidance is likely acceptable, but prolonged use should be avoided during breastfeeding.

Children

Da Qing Ye is used in numerous paediatric Chinese patent medicines for childhood febrile illnesses (including children's cold preparations and fever-reducing oral liquids). Dosage should be reduced proportionally according to the child's age and body weight, typically one-third to one-half of the adult dose for school-age children. Because of its strongly cold nature, it should only be used short-term in children and only when a genuine Heat pattern is present. Prolonged use can easily damage the immature Spleen and Stomach, causing poor appetite and loose stools.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Da Qing Ye

No well-documented pharmaceutical drug interactions have been established for Da Qing Ye through rigorous clinical studies. However, the following theoretical considerations apply based on its known pharmacological properties:

  • Anticoagulant/antiplatelet medications: Da Qing Ye contains compounds with structural similarity to salicylates. Concurrent use with warfarin, aspirin, or other blood-thinning medications may theoretically increase bleeding risk, though this has not been confirmed in clinical studies.
  • Immunosuppressive medications: Given the demonstrated immunomodulatory effects of Isatis indigotica extracts (including enhancement of immune responses), there is a theoretical concern about interference with immunosuppressive therapy. Patients on such medications should exercise caution.

Dietary Advice

Foods and dietary considerations when taking Da Qing Ye

While taking Da Qing Ye, avoid cold, raw, and greasy foods that may further burden the Spleen and Stomach, since the herb itself is already very cold in nature. Favour easily digestible, warm foods (such as rice congee or light soups) to support digestion during treatment. Avoid spicy, fried, or heavily seasoned foods if being used for Heat-toxin conditions, as these can aggravate the underlying Heat.

Botanical Description

Physical characteristics and morphology of the Da Qing Ye source plant

Isatis indigotica Fort. (Chinese woad) is a biennial herbaceous plant in the Brassicaceae (Cruciferae, or mustard) family. In its first year, the plant forms a basal rosette of leaves close to the ground. The leaves are oblong to inversely lance-shaped, 5 to 20 cm long and 2 to 6 cm wide, with a glaucous blue-green surface and blunt tips. The leaf base narrows and extends down the stalk in a wing-like fashion. The stalk itself is 4 to 10 cm long and pale brownish-yellow.

In the second year, the plant sends up an erect flowering stem that can reach 40 to 100 cm, branching in the upper portion. The small flowers are yellowish-white with four petals, arranged in racemes. The fruits are short, flattened, oblong pods (siliques) that hang downward on slender stalks and have winged edges. The root is the source of the famous herb Ban Lan Gen (Isatidis Radix). The plant grows well in temperate climates across much of China, preferring well-drained soils, and is widely cultivated. Historically, the plant was also one of China's primary sources of natural indigo dye.

Sourcing & Harvesting

Where Da Qing Ye is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Summer and autumn, harvested in 2 to 3 rounds: first around mid-June, second in late July, and third in September to October. In northern China, typically harvested twice (early July and late October).

Primary growing regions

Widely cultivated across China. Major production regions include Jiangsu, Anhui, and Hebei provinces, which are considered the primary sources for the Chinese Pharmacopoeia-standard herb (from Isatis indigotica). Additional important production areas include Henan, Shandong, Heilongjiang, and Gansu. Historically, different botanical sources of Da Qing Ye came from different regions: the leaves of Ma Lan (Baphicacanthus cusia) were produced mainly in southern provinces such as Fujian, Guangdong, and Guangxi, while Liao Lan (Polygonum tinctorium) leaves came from Hebei and Tianjin. In the modern Chinese Pharmacopoeia, only the leaf of Isatis indigotica is the official source.

Quality indicators

Good quality Da Qing Ye leaves should be large, intact (not excessively broken), and dark greyish-green in colour on the upper surface. When flattened, complete leaves are oblong to inversely lance-shaped, 5 to 20 cm long, with the leaf base narrowing into a winged stalk. The texture should be brittle and crisp. The aroma is faint, and the taste should be slightly sour, bitter, and astringent. Leaves that are green and large are considered best quality. Avoid material that is excessively brown, mouldy, or consisting mainly of broken fragments and stalks.

Classical Texts

Key passages from the classical Chinese medical texts that describe Da Qing Ye and its therapeutic uses

Ben Cao Gang Mu (本草纲目) by Li Shizhen

Original: 「主热毒痢，黄疸，喉痹，丹毒。蓝叶汁，解斑蝥、芫青、樗鸡、朱砂、砒石毒。」

Translation: "Treats Heat-toxin dysentery, jaundice, throat obstruction (severe sore throat), and erysipelas (red skin lesions). The juice of the Lan leaf can resolve the toxicity of blister beetles, green cantharis, ailanthus chicken (Huechys), cinnabar, and arsenic."

Ben Cao Jing Shu (本草经疏)

Original: 「甄权云大青味甘，能去大热，治温疫寒热。盖大寒兼苦，其能解散邪热明矣。经曰：大热之气，寒以取之，此之谓也。时行热毒，头痛大热口疮，为胃家实热之证，此药乃对病之良药也。」

Translation: "Zhen Quan says Da Qing is sweet in flavour, able to eliminate great Heat, and treats the alternating chill and fever of epidemic warm diseases. Being greatly cold and also bitter, its ability to disperse pathogenic Heat is clear. The classics say: 'Great Heat is taken by Cold' - this is exactly what it means. For epidemic Heat toxin with headache, high fever, and mouth sores, which is a pattern of Stomach excess Heat, this herb is the ideal medicine."

Ben Cao Zheng (本草正) by Zhang Jiebin

Original: 「治瘟疫热毒发斑，风热斑疹，痈疡肿痛，除烦渴，止鼻衄，吐血……凡以热兼毒者，皆宜蓝叶捣汁用之。」

Translation: "Treats epidemic Heat-toxin eruptions with macules, wind-Heat rashes, abscesses and swelling pain, eliminates vexation and thirst, stops nosebleed and vomiting of blood... In all cases where Heat is combined with toxin, the pressed juice of the Lan leaf is suitable."

Ming Yi Bie Lu (名医别录)

Original: 「疗时气头痛，大热，口疮。蓝叶汁，杀百药毒，解狼毒、射罔毒。」

Translation: "Treats seasonal epidemic headache, great fever, and mouth sores. The juice of the Lan leaf neutralises hundreds of drug toxins, and resolves Wolfsbane and Aconite poisoning."

Historical Context

The history and evolution of Da Qing Ye's use in Chinese medicine over the centuries

The medicinal use of "Lan" (indigo-producing plants) in China dates back to the Shen Nong Ben Cao Jing (Divine Farmer's Classic of Materia Medica), where the seeds were recorded under the name "Lan Shi" (蓝实) as a top-grade herb. The name "Da Qing Ye" first appeared in the Ming Yi Bie Lu (Supplementary Records of Famous Physicians). Li Shizhen explained the etymology in the Ben Cao Gang Mu: the plant was called "Da Qing" (meaning "great blue-green") because its stems and leaves are all a deep blue-green colour.

The plant has a remarkable dual identity in Chinese civilisation, serving both as a vital medicine and as the primary source of indigo dye. The famous line from Xunzi's "Exhortation to Learning" (劝学篇), "Blue is extracted from the indigo plant, yet it is bluer than indigo" (青出于蓝而胜于蓝), refers to these same plants. As early as the Spring and Autumn period, indigo extracted from "Lan" plants was used for dyeing textiles, an industry that flourished for centuries.

Originally, several different plant species were all used as sources of Da Qing Ye, including Isatis indigotica (Song Lan), Polygonum tinctorium (Liao Lan), Baphicacanthus cusia (Ma Lan), and Clerodendron cyrtophyllum (Lu Bian Qing). Over time, Isatis indigotica became the dominant cultivated species due to its greater yield and stronger pharmacological effects, and the 2020 Chinese Pharmacopoeia now recognises only this species as the official source. The leaves (Da Qing Ye), root (Ban Lan Gen), and the processed indigo pigment from the leaves (Qing Dai) are all important medicines, each with slightly different therapeutic emphases despite their shared origin.

Modern Research

4 published studies investigating the pharmacological effects or clinical outcomes of Da Qing Ye

1

Review: Phytochemistry, pharmacological activities, and clinical applications of Isatis indigotica (2021)

Li J, Huang G, Ye M, et al. Isatis indigotica: a review of phytochemistry, pharmacological activities and clinical applications. Journal of Pharmacy and Pharmacology, 2021, 73(9), 1157-1171.

A comprehensive review summarizing that Isatis indigotica contains alkaloids, organic acids, flavonoids, lignans, nucleosides, amino acids, and steroids. The review found that the plant demonstrates antiviral activity against influenza, hepatitis B, mumps, herpes simplex, and other viruses, along with antibacterial, immunoregulatory, anti-inflammatory, and bile-secretion-promoting effects. Clinically, preparations are frequently used for viral influenza, parotitis, and viral hepatitis.

PubMed
2

Preclinical study: Indirubin from Isatis indigotica reduces H1N1 susceptibility via MAVS signaling (2018)

Luo Z, Liu LF, Wang XH, et al. Indirubin, a bisindole alkaloid from Isatis indigotica, reduces H1N1 susceptibility in stressed mice by regulating MAVS signaling. Frontiers in Pharmacology, 2019, 10, 78.

This animal study found that indirubin, a key alkaloid from Isatis indigotica, reduced susceptibility to H1N1 influenza virus in restraint-stressed mice. Indirubin lowered mortality, alleviated lung damage, and promoted interferon-beta production through the mitochondrial antiviral signaling (MAVS) pathway. The compound also reduced pro-inflammatory cytokine levels in lung tissue.

PubMed
3

Preclinical study: Antiviral activity of Isatis indigotica extract and indirubin against Japanese Encephalitis Virus (2012)

Chang SJ, Chang YC, Lu KZ, Tsou YY, Lin CW. Antiviral activity of Isatis indigotica extract and its derived indirubin against Japanese encephalitis virus. Evidence-Based Complementary and Alternative Medicine, 2012, 2012, 925830.

This in vitro and in vivo study tested Isatis indigotica extracts and their marker compounds (indigo and indirubin) against Japanese Encephalitis Virus (JEV). The methanol extract, indigo, and indirubin all showed concentration-dependent inhibition of JEV replication in cell culture, with relatively low cytotoxicity. Mouse protection experiments also demonstrated improved survival rates after JEV challenge.

PubMed
4

Clinical trial: Effect of indigowood root extract on radiation-induced oral mucositis (2009)

You WC, Hsieh CC, Huang JT. Effect of extracts from indigowood root (Isatis indigotica Fort.) on immune responses in radiation-induced mucositis. Journal of Alternative and Complementary Medicine, 2009, 15(7), 771-778.

A small randomised clinical trial of 20 head and neck cancer patients receiving radiotherapy. The group using Isatis indigotica root preparation (gargled and swallowed) experienced significantly reduced severity of radiation mucositis, anorexia, and swallowing difficulty compared to controls. Serum interleukin-6 levels were significantly lower in the treatment group, supporting the anti-inflammatory mechanism.

PubMed

Research on individual TCM herbs is growing but still limited by Western clinical trial standards. These studies provide emerging evidence and should be considered alongside practitioner expertise.