Herb Root (根 gēn)

Zi Cao

Gromwell root · 紫草

Lithospermum erythrorhizon Sieb. et Zucc.; Arnebia euchroma (Royle) Johnst. · Radix Arnebiae seu Lithospermi

Also known as: Redroot Gromwell

Zi Cao (Gromwell root) plant

Images shown are for educational purposes only

Zi Cao (purple herb root) is a cooling herb traditionally used to clear heat from the blood and promote the healing of skin conditions. It is most commonly found in topical ointments for burns, eczema, rashes, and chronic sores, and is also taken internally for conditions involving blood heat such as dark-colored skin eruptions or purpura. First recorded in the Shen Nong Ben Cao Jing, it remains one of Chinese medicine's go-to herbs for skin health.

Category Heat-clearing herbs Herbs that clear Heat and cool the Blood (清热凉血药)
Therapeutic focus Skin Health Eczema and Dermatitis Relief Skin and Wound Care Detoxification

TCM Properties

Temperature

Cold

Taste

Sweet (甘 gān), Salty (咸 xián)

Channels entered

Heart, Liver

Parts used

Root (根 gēn)

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What This Herb Does

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

Therapeutic focus

In practical terms, Zi Cao is primarily used to support these areas of health:

Skin Health Eczema and Dermatitis Relief Skin and Wound Care Detoxification

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Zi Cao performs to restore balance in the body:

Cools the Blood Resolves Toxicity Vents Rashes Invigorates Blood and Dispels Stasis Moistens the Intestines and Unblocks the Bowels

How these actions work

'Cools the Blood' means Zi Cao clears Heat that has entered the Blood level, which in TCM is the deepest layer a fever-causing pathogen can reach. When Heat scorches the Blood, it can cause dark purple skin rashes, bleeding from the nose or gums, or blood in the urine. Zi Cao's cold nature and its affinity for the Heart and Liver channels (both closely linked to Blood circulation in TCM) make it well suited for these situations.

'Resolves toxins' refers to the herb's ability to counteract what TCM calls Heat toxins (热毒), which manifest as hot, red, swollen, or pus-filled skin lesions such as boils, abscesses, and infected sores. Zi Cao both clears the internal Heat driving these conditions and promotes healing of the affected tissue, which is why it is widely used in topical ointments for burns, eczema, and chronic ulcers.

'Vents rashes' (透疹) is a specialized action meaning it helps eruptive diseases like measles progress through to full expression. In TCM thinking, if a rash is 'stuck inside' and cannot break through to the skin surface, the toxin remains trapped and the illness worsens. Zi Cao encourages rashes to come out fully and turn a healthy red color rather than remaining dark purple, indicating that Blood Heat is being cleared.

'Invigorates the Blood' means Zi Cao gently promotes Blood circulation and helps resolve areas of stagnation. This complements its cooling action: it cools the Blood without causing it to congeal. This makes it useful for conditions where Blood Heat has led to both stagnation and bleeding, and is also why it appears in wound-healing ointments alongside Blood-moving herbs like Dang Gui.

'Moistens the intestines and unblocks the bowels' reflects a secondary action: in cases where Blood Heat leads to dry, constipated stools, Zi Cao's sweet, lubricating quality can gently ease bowel movements. This is not its primary use, but it is recognized in classical texts such as the Ben Cao Gang Mu, which notes that it "benefits the large intestine."

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Zi Cao is used to help correct these specific patterns.

Why Zi Cao addresses this pattern

Zi Cao is cold in nature, sweet and salty in taste, and enters the Heart and Liver channels, both of which govern Blood in TCM. This makes it highly targeted for Blood Heat, a pattern where excess Heat enters the Blood level and causes reckless movement of Blood out of the vessels. Zi Cao directly clears this Heat, cools the Blood, and simultaneously invigorates Blood circulation to prevent stagnation from forming as the Heat resolves. Its salty taste helps it penetrate into the Blood level where the pathology resides.

A practitioner would look for one or more of these signs

Skin Rashes

Dark purple or purplish-black rashes that are not bright red

Nosebleeds

Nosebleeds or bleeding gums from blood heat

Blood in Urine

Blood in the urine due to heat forcing blood out of the vessels

Purpura

Purpura or subcutaneous bleeding spots

Commonly Used For

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

Arises from: Heat Toxin Affecting the Skin Blood Heat

TCM Interpretation

TCM views eczema primarily as a condition involving Dampness and Heat in the Blood and skin. When internal Heat combines with Dampness, it pushes outward to the skin surface, producing red, itchy, weeping lesions. In acute flare-ups, Blood Heat is often the dominant factor, causing intense redness and burning sensation. Over time, Blood stagnation may develop alongside the Heat, leading to thickened, darkened skin in chronic cases. The Heart governs Blood and the Liver stores Blood, so both organs are implicated when Blood Heat manifests on the skin.

Why Zi Cao Helps

Zi Cao directly cools Blood Heat through its cold nature and its affinity for the Heart and Liver channels, addressing the root driver of inflammatory eczema. Its toxin-resolving action tackles the Heat-Dampness that produces weeping lesions. Unlike purely bitter cold herbs that can be harsh on digestion, Zi Cao's sweet taste makes it relatively gentle. Topically, Zi Cao oil preparations create a protective barrier over inflamed skin while the herb's active compounds (particularly shikonin and its derivatives) provide anti-inflammatory and antimicrobial effects, promoting tissue repair.

Also commonly used for

Measles

Used to help the rash express fully and to reduce severity

Keratitis

Including diaper dermatitis in infants

Ulcer

Chronic non-healing ulcers; used in ointment form

Viral Hepatitis

Clinical reports of use in both acute and chronic hepatitis

Psoriasis

Extracts of Zi Cao used for plaque psoriasis

Constipation

Constipation due to blood heat with dry stools

Acne

Topical use for heat-type acne and facial sores

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

Sweet (甘 gān), Salty (咸 xián)

Channels Entered

Heart Liver

Parts Used

Root (根 gēn)

Dosage & Preparation

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

Standard dosage

5–10g

Maximum dosage

Up to 15g in decoction for acute Blood-Heat conditions, under practitioner supervision. Historical case reports describe doses of 30–60g for severe thrombocytopenic purpura, but such high doses caused diarrhea and should only be used in monitored clinical settings.

Dosage notes

Standard dose of 5–10g is used for cooling Blood and resolving toxins in rashes and skin conditions. For facilitating measles eruption, 3–5g is often sufficient, typically combined with Cicadae Periostracum (Chan Tui) and Arctii Fructus (Niu Bang Zi). Higher doses toward 10–15g may be used for Blood-Heat patterns with purpura or bleeding. The herb has a mild laxative effect that becomes more pronounced at higher doses. For topical use (burns, eczema, dermatitis), the herb is infused in vegetable oil (typically sesame oil) at various concentrations (2–40%) and applied directly. External use has no strict dosage ceiling.

Processing Methods

In TCM, the same herb can be prepared in different ways to change its effects — here's how processing alters what Zi Cao does

Processing method

Steamed with beeswax: per the Lei Gong Pao Zhi Lun method, for every jin (500g) of Zi Cao, 60g of beeswax is melted in water, mixed with the herb, and steamed until the water evaporates. The root tips and fibrous lateral hairs are then removed before slicing.

How it changes properties

The beeswax processing moderates the herb's cold nature slightly and enhances its moistening, lubricating quality. This makes the processed form better suited for topical applications and gentler on the digestive system when taken internally. The core Blood-cooling and toxin-resolving actions are preserved but the likelihood of causing loose stools is reduced.

When to use this form

When Zi Cao is intended for internal use in patients with weaker digestion who might not tolerate the raw herb's strongly cold nature, or when preparing ointment bases where the waxy processing aids in smooth blending with oils.

Common Herb Pairs

These ingredients are traditionally combined with Zi Cao for enhanced therapeutic effect

Dang Gui
Dang Gui Zi Cao 6g : Dang Gui 15-30g (Dang Gui predominates in ointment formulas)

Zi Cao cools Blood and resolves toxins while Dang Gui nourishes and invigorates Blood. Together they clear Heat from the Blood without leaving it depleted, and strongly promote tissue regeneration. This pairing forms the core of the famous Zi Yun Gao (Purple Cloud Ointment) used for burns, wounds, and chronic ulcers.

When to use: Burns, scalds, chronic non-healing sores, and skin lesions where both Heat toxins and Blood stasis impede wound healing.

Niu Bang Zi
Niu Bang Zi 1:2 (Zi Cao 5g : Niu Bang Zi 10g)

Both herbs resolve toxins and help vent rashes, but through complementary mechanisms. Zi Cao works at the Blood level to cool Blood Heat and push the rash outward, while Niu Bang Zi works at the Qi level to disperse Wind-Heat and clear the throat. Together they address incomplete rash eruption from both the Qi and Blood levels simultaneously.

When to use: Measles or other eruptive febrile diseases where the rash fails to emerge fully, especially with accompanying sore throat and fever.

Chi Shao
Chi Shao 1:1 (equal doses, typically 10g each)

Both herbs cool the Blood, but Chi Shao also clears Liver Fire and disperses Blood stasis more strongly. Together they powerfully clear Blood Heat toxins and resolve the dark, purple discoloration of rashes and purpura. Zi Cao contributes its rash-venting ability while Chi Shao adds stronger stasis-dispersing action.

When to use: Blood Heat with severe dark purple rashes, purpura, or warm-disease rashes (温病发斑) where the spots are purple-black rather than bright red.

Chan Tui
Chan Tui 2:1 (Zi Cao 10g : Chan Tui 5g)

Chan Tui (cicada moulting) disperses Wind and vents rashes from the exterior, while Zi Cao cools Blood and vents rashes from the Blood level. Together they clear both the Wind and Heat components of eruptive skin diseases, making the rash come out smoothly.

When to use: Measles or allergic rashes with itching, where both Wind and Blood Heat are involved. Also for allergic purpura.

Key Formulas

These well-known formulas feature Zi Cao in a prominent role

Sheng Ji Yu Hong Gao 生肌玉红膏 Assistant

This famous wound-healing ointment from Chen Shigong's Wai Ke Zheng Zong (1617) showcases Zi Cao's topical skin-healing properties. Zi Cao contributes its Blood-cooling and toxin-resolving actions to help regenerate tissue in chronic ulcers and sores that will not close. The formula demonstrates how Zi Cao works synergistically with Blood-nourishing herbs like Dang Gui in an oil medium for external application.

Comparable Ingredients

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

Mu Dan Pi
Zi Cao vs Mu Dan Pi

Both cool the Blood and invigorate Blood circulation, but Mu Dan Pi (Moutan bark) more strongly clears deficiency-type Heat (steaming bone disorder) and resolves Blood stasis from deeper organ levels, particularly the Liver. Zi Cao is more specialized for skin conditions: it has a unique rash-venting action (透疹) and stronger topical wound-healing properties that Mu Dan Pi lacks. For Blood Heat manifesting as skin rashes, burns, or eczema, Zi Cao is preferred. For Blood Heat with menstrual irregularity or deep-level steaming bone Heat, Mu Dan Pi is the better choice.

Chi Shao
Zi Cao vs Chi Shao

Both are cold, enter the Liver channel, and cool Blood Heat. However, Chi Shao (red peony root) more strongly clears Liver Fire, disperses Blood stasis, and alleviates pain, making it more suitable for conditions with obvious stasis and pain such as abdominal masses or traumatic injury. Zi Cao is better for Blood Heat manifesting on the skin surface because of its toxin-resolving and rash-venting actions. For skin eruptions, purpura, and topical wound healing, Zi Cao is the primary choice; they are often paired together for severe Blood Heat rashes.

Shu Di Huang
Zi Cao vs Shu Di Huang

Both are cold and cool the Blood, but Sheng Di Huang (raw Rehmannia) also strongly nourishes Yin and generates fluids, making it the first choice when Blood Heat is accompanied by Yin Deficiency with dry mouth, a red tongue with little coating, and wasting Heat. Zi Cao does not nourish Yin. Instead, it has specialized skin-directed actions (venting rashes, resolving skin toxins, topical wound healing) that Sheng Di Huang does not possess. For Blood Heat with Yin damage, use Sheng Di Huang; for Blood Heat with skin manifestations, use Zi Cao.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Zi Cao

The three official Pharmacopoeia sources (Arnebia euchroma, Lithospermum erythrorhizon, and Arnebia guttata) are distinct species sometimes confused with each other. Xinjiang Zi Cao has multiple branching divisions at the root head with soft herbaceous stems bearing fine hairs, while Inner Mongolia Zi Cao has fewer branches and more woody stem remnants. Imported material from Central Asian countries (Afghanistan, Pakistan, Iran) is common in the market and may include species closely related to but not identical with the official Arnebia euchroma. These imports are often difficult to distinguish by appearance alone and may have significantly lower shikonin content. Dian Zi Cao (Onosma paniculatum), found in Yunnan and Guizhou, is sometimes encountered as a regional substitute but is not an official Pharmacopoeia source. A key authentication test: genuine Zi Cao should readily stain the fingers a deep purple-red colour when handled. Material that does not stain or stains weakly may be adulterated, substituted, or degraded. Chemical assay for L-shikonin content (minimum 0.80%) provides definitive quality verification.

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

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Zi Cao

Non-toxic

Zi Cao is classified as non-toxic at standard oral doses. However, animal toxicology studies have shown that concentrated Xinjiang Zi Cao preparations can cause adverse effects at high doses: in mice fed a 30% Zi Cao feed mixture, body weight dropped about 30% within one week, and 40% mortality was observed within 15 days. In rabbits given 5g/kg root powder by oral gavage, deep purple urine, proteinuria, haematuria, and diarrhea appeared after 3 days, resolving 2 days after discontinuation. The naphthoquinone pigment shikonin has an intraperitoneal LD50 of approximately 20 mg/kg in mice. At standard decoction doses (5–10g), these toxic effects are not observed. The herb has a notable laxative effect that may cause loose stools even at normal doses, which is a pharmacological action rather than toxicity per se.

Contraindications

Situations where Zi Cao should not be used or requires extra caution

Caution

Spleen and Stomach deficiency cold with loose stools or diarrhea. Zi Cao is cold in nature and can further injure the Spleen Yang and worsen digestive weakness. The classical text Ben Cao Jing Shu specifically warns against use when there is diarrhea, poor appetite, and clear urination.

Caution

Rashes that have already fully erupted and are spreading. Zi Cao's action of venting rashes outward (tou zhen) is only appropriate when the rash has not yet fully surfaced. Once eruptions are complete, its use is unnecessary and may worsen the condition.

Avoid

Pregnancy, particularly during the first trimester. Zi Cao has demonstrated anti-fertility and anti-gonadotropic effects in pharmacological studies, including suppression of the oestrous cycle and inhibition of pituitary gonadotropin release. It should be avoided or used with great caution during pregnancy.

Caution

Qi deficiency patterns without Blood Heat. Zi Cao's cold nature and Blood-cooling action can damage Qi if the underlying pattern does not involve genuine Heat or toxin in the Blood level. The Ben Cao Jing Shu warns that in pox rashes with Qi deficiency, weak Spleen and Stomach, and poor appetite, this herb is prohibited.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Contraindicated during pregnancy. Pharmacological studies have demonstrated significant anti-fertility and anti-gonadotropic effects. In animal studies, oral administration of Zi Cao suppressed the oestrous cycle in mice, significantly reduced ovarian weight, and inhibited pituitary gonadotropin secretion (particularly luteinising hormone). These effects reversed upon cessation of the herb. European species of Lithospermum have also shown suppression of pituitary gonadotropin release. Given these reproductive effects and the herb's Blood-moving properties, Zi Cao should not be used during pregnancy.

Breastfeeding

Caution advised. While there are no specific classical prohibitions against use during breastfeeding, the herb's demonstrated anti-gonadotropic activity and effects on pituitary hormone secretion raise theoretical concerns about potential transfer through breast milk and possible effects on lactation. Additionally, the cold nature of the herb could affect the nursing infant's digestion. Use during breastfeeding should only occur under professional guidance and at conservative doses.

Children

Zi Cao has a long history of use in paediatric medicine, particularly for facilitating measles eruption and treating infantile eczema. Classical paediatric texts such as the Xiao Er Yao Zheng Zhi Jue feature Zi Cao prominently. Dosage for children should be reduced proportionally by age and body weight, typically one-third to one-half of the adult dose. Topical Zi Cao oil preparations are widely used for nappy rash and infantile dermatitis and are generally well tolerated. Internal use in infants should be cautious due to the herb's cold nature and laxative tendency, which can easily disturb the immature digestive system. The Ben Cao Jing Shu specifically warns against internal use in children with Spleen deficiency, poor appetite, diarrhea, or clear copious urination.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Zi Cao

Anticoagulant and antiplatelet medications: Zi Cao has demonstrated effects on blood coagulation and platelet function. Its active component shikonin may theoretically potentiate the effects of warfarin, heparin, aspirin, and other anticoagulants or antiplatelets. Concurrent use warrants monitoring of coagulation parameters.

Hormonal contraceptives and fertility treatments: The herb's well-documented anti-gonadotropic and anti-fertility effects may interfere with hormonal therapies including oral contraceptives, hormone replacement therapy, or fertility medications. The mechanism involves suppression of pituitary gonadotropin (especially LH) release.

Cytochrome P450 substrates: Shikonin has been shown to enhance certain CYP450 metabolic enzymes. This may alter the metabolism and blood levels of drugs processed through these pathways, though the clinical significance at standard herbal doses is not well established.

Dietary Advice

Foods and dietary considerations when taking Zi Cao

Avoid cold, raw, greasy, and hard-to-digest foods while taking Zi Cao internally, as these can compound the herb's cold nature and exacerbate its tendency to loosen the stools. Light, easily digestible, warm foods are preferable. Since the herb is often used for Heat conditions with skin rashes, it is also advisable to avoid spicy, fried, and heavily seasoned foods that may aggravate Heat in the Blood.

Botanical Description

Physical characteristics and morphology of the Zi Cao source plant

Zi Cao refers to the dried root of plants in the Boraginaceae family. The Chinese Pharmacopoeia recognises three source species: Arnebia euchroma (Royle) Johnst. (Xinjiang Zi Cao, "soft" Zi Cao), Lithospermum erythrorhizon Sieb. et Zucc. ("hard" Zi Cao), and Arnebia guttata Bunge (Inner Mongolia Zi Cao).

Lithospermum erythrorhizon is a perennial herb growing 50–90 cm tall, with an erect stem covered in coarse stiff hairs. The leaves are alternate, lanceolate to ovate-lanceolate, 3–8 cm long, rough-textured on both surfaces. Small white tubular flowers appear in terminal scorpioid cyme clusters from June to August, producing smooth, shiny, greyish-white nutlets. The medicinal root is thick, conical, somewhat twisted, and distinctly purple-red due to high concentrations of naphthoquinone pigments (shikonin and its derivatives).

Arnebia euchroma is a shorter perennial (up to 50 cm) native to high-altitude regions of Central Asia. It has lance-shaped, hairy leaves and vivid reddish-purple funnel-shaped flowers blooming June through August. Its root is larger and softer than that of L. erythrorhizon, with a distinctively loose, layered bark that easily peels away in strips.

Sourcing & Harvesting

Where Zi Cao is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Spring or autumn. Cultivated plants are typically harvested in autumn (mid to late October) of the second year of growth. Wild material is collected in spring (April to May) or autumn (September to October).

Primary growing regions

Xinjiang Zi Cao (soft Zi Cao, Arnebia euchroma): Xinjiang and Tibet are the premier producing regions and recognised dao di (terroir) sources. Wild populations grow on the northern and southern slopes of the Tianshan Mountains and in western Tibet at high altitudes in cold, dry conditions. Xinjiang Zi Cao is now classified as a national second-level endangered species due to overharvesting. Hard Zi Cao (Lithospermum erythrorhizon): Historically distributed across northeast China (Liaoning, Jilin, Heilongjiang), as well as Hebei, Henan, Shanxi, Shaanxi, Gansu, Shandong, and several southern provinces. Wild resources of this species have been severely depleted and it is now rare in commerce. Inner Mongolia Zi Cao (Arnebia guttata): Found in Inner Mongolia, northern Hebei, Ningxia, and western Gansu. Imported material from Central Asian countries bordering Xinjiang also enters the market, though quality can be inconsistent.

Quality indicators

Soft Zi Cao (Xinjiang, Arnebia euchroma): Good quality roots are 7–20 cm long, 1–2.5 cm in diameter, with a vivid purple-red to purple-brown surface colour. The bark should be loose and layered, peeling away in strip-like sheets stacked 10 or more layers deep. The texture should be soft and light, breaking easily to reveal a small yellowish-white wood core. A distinctive aroma should be present, with a slightly bitter, astringent taste. Heavier purple colour throughout indicates higher shikonin content. Hard Zi Cao (Lithospermum erythrorhizon): Roots are conical, twisted, 7–14 cm long, 1–2 cm diameter, with a purple-red to purple-black rough surface with longitudinal striations. The bark is thin and easily shed. Texture is hard and brittle, snapping cleanly. Cross-section shows a deep purple bark layer and a larger greyish-yellow wood core. Taste is sour and sweet. For both types, the deeper and more intense the purple-red colour, the higher the quality. Roots should strongly stain the fingers purple when handled. Per the Chinese Pharmacopoeia, total hydroxynaphthoquinone pigment content (calculated as L-shikonin) must not be less than 0.80% (or 0.90% in some editions). Avoid material that is faded, overly woody, or lacking colour transfer to the fingers.

Classical Texts

Key passages from the classical Chinese medical texts that describe Zi Cao and its therapeutic uses

Shen Nong Ben Cao Jing (《神农本草经》)

Chinese: 主心腹邪气，五疸，补中益气，利九窍，通水道。

English: It governs pathogenic Qi in the chest and abdomen, the five types of jaundice, supplements the middle and boosts Qi, opens the nine orifices, and frees the water passages.

Ming Yi Bie Lu (《名医别录》)

Chinese: 疗腹肿胀满痛。以合膏，疗小儿疮及面齄。

English: It treats abdominal swelling, distension, fullness and pain. Made into an ointment, it treats children's sores and facial blemishes.

Ben Cao Gang Mu (《本草纲目》)

Chinese: 治斑疹、痘毒，活血凉血，利大肠。

English: It treats maculopapular rashes and pox toxins, invigorates and cools the Blood, and frees the Large Intestine.

Ben Cao Gang Mu (《本草纲目》) — on the name

Chinese: 紫草花紫，根紫，可以染紫，故名紫草。

English: The flowers of Zi Cao are purple, its root is purple, and it can be used to dye things purple, hence the name "Purple Herb."

Historical Context

The history and evolution of Zi Cao's use in Chinese medicine over the centuries

Zi Cao is one of the oldest documented Chinese herbs, first recorded in the Shen Nong Ben Cao Jing (circa 1st–2nd century CE) under the names Zi Dan (紫丹) and Zi Yao (紫苭). The Er Ya, China's oldest dictionary (3rd century BCE), already lists it as Miao (藐) and Ci Cao (茈草). The name literally means "purple herb," reflecting the vivid purple-red colour of both its flowers and root.

For over two thousand years, Zi Cao served a dual purpose: as medicine and as one of the most prized natural dyes in East Asia. The root produces shikonin pigments that yield a deep purple-red colour, used to dye imperial silk and textiles in China, Korea, and Japan (where the plant is called murasaki, the Japanese word for purple). With the arrival of synthetic aniline dyes in the late 19th and early 20th centuries, demand for Zi Cao as a dye collapsed, and cultivated production declined sharply.

The traditional "hard" Zi Cao (L. erythrorhizon) was the original medicinal species used for over two millennia. However, wild resources were gradually exhausted. In the 1950s, "soft" Zi Cao from Xinjiang (Arnebia euchroma) was discovered and introduced into clinical use, entering the Chinese Pharmacopoeia as an official source species in 1977. This newer variety now dominates the market. Historically, the herb was especially valued in paediatric medicine for facilitating the eruption of measles and pox rashes, and numerous classical paediatric texts feature it prominently.

Modern Research

4 published studies investigating the pharmacological effects or clinical outcomes of Zi Cao

1

Comprehensive Review: Shikonin therapeutic actions, pharmacokinetics, toxicology, and clinical trials (2022)

Guo C, He J, Song X, et al. Phytomedicine. 2022; 96: 153918.

A systematic review covering research through August 2021, summarizing shikonin's broad pharmacological profile including anti-inflammatory, anti-cancer, cardiovascular protective, antimicrobial, analgesic, and anti-obesity effects. The review found these actions are mediated primarily through NF-kB, PI3K/Akt/MAPK, Akt/mTOR, and TGF-beta signalling pathways. It noted shikonin has poor oral bioavailability and few clinical trials to date, but pharmaceutical innovations like nanoparticles and liposomes are being developed to improve delivery.

PubMed
2

Review: Pharmacological properties and derivatives of shikonin (2019)

Sun Q, Gong T, Liu M, et al. Pharmacological Research. 2020; 159: 104983.

An updated review showing that shikonin exerts strong anticancer effects on various cancer types by inhibiting cell proliferation and migration, inducing apoptosis, triggering reactive oxygen species generation, suppressing exosome release, and activating anti-tumour immunity. The review also covered anti-inflammatory and wound-healing properties, and noted that some shikonin derivatives show stronger anticancer activity with lower toxicity than shikonin itself.

PubMed
3

Preclinical study: Shikonin as a selective IMPDH2 inhibitor targeting triple-negative breast cancer (2020)

Wang W, Wu Y, Chen S, et al. Phytomedicine. 2020; 79: 153338.

This study identified shikonin as a novel competitive inhibitor of the enzyme IMPDH2, which is overexpressed in triple-negative breast cancer. Shikonin effectively inhibited growth of human and murine TNBC cell lines in a dose-dependent manner, an effect that was reversed by supplementation with guanosine, confirming the mechanism of action through purine nucleotide synthesis blockade.

PubMed
4

Review: Shikonin and derivatives — Isolation, Chemistry, Biosynthesis, Pharmacology and Toxicology (2022)

Islam AAEH, Ibrahim A, et al. Frontiers in Pharmacology. 2022; 13: 905755.

A comprehensive review of shikonin's natural sources, diverse pharmacological activities (anticancer, antithrombotic, neuroprotective, antidiabetic, antiviral, anti-inflammatory, anti-gonadotropic, antioxidant, antimicrobial), toxicology data, biosynthetic pathways, and worldwide patents. The review highlighted shikonin's potential as a drug candidate while noting the need for further clinical development.

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.