Alkanna

Alkanna (Alkanna tinctoria): A Comprehensive Reference

1. Identity, Taxonomy, and Natural Source

Alkanna tinctoria, the dyer's alkanet or simply alkanet, is a herbaceous flowering plant in the borage family Boraginaceae. The plant is also known as dyers' bugloss, orchanet, Spanish bugloss, or Languedoc bugloss. In South Asian trade, the root is sold under the name ratanjot — a trade name applied to multiple species in the Boraginaceae family with red-pigmented roots, including Alkanna tinctoria and certain Onosma species such as Onosma hispidum. Additional synonyms and common names recorded in the scientific and commercial literature include Anchusa tinctoria, Alkannawurzel, Alkermeswurzel, Racine d'alcanna, Racine d'orcanette, Radix anchusea, Rote ochsenzungenwurzel, and Schminkwurzel.

Alkanna tinctoria Tausch (syn. Anchusa tuberculata (Forssk.) Meikle), commonly known as alkanet or dyers' alkanet, is a perennial herbaceous plant distributed in Asia Minor and in Southern Europe, especially in the Mediterranean region. A hardy perennial, Alkanna tinctoria thrives in dry, rocky soils and Mediterranean climates, growing up to 50 cm tall, with hairy, lance-shaped leaves and small blue-purple flowers. The root is blackish outside, blue-red inside, with a whitish core. It is native to the Mediterranean region; A. tinctoria has 30 chromosomes and is regarded as a dysploid at the tetraploid level (4x + 2).

Common Forms and Preparations

• The dyestuff in the roots is insoluble in water but can be extracted using alcohol or other organic solvents such as oils.
• It is used to colour some cheeses and low-quality wines; powdered and mixed with oil, the alkanet root is used as a wood stain.
• In Australia, alkannin is approved for use as a food colouring; in the European Union, it is designated E103, but its approval for use has been withdrawn. It has been used as a colorant for products such as lipstick.
• Root extracts are prepared as oil-infusions, ethanolic extracts, ointments, and topical creams. Recent innovations in drug delivery systems, such as chitosan-based nanoparticles and electrospun nanofibers, have enhanced the efficacy of A. tinctoria extracts in wound healing applications.
• Today, alkanna root is used almost exclusively as a cosmetic dye. Orally, it has been used for diarrhea and gastric ulcers. Traditionally, topical alkanna root has been used to treat skin wounds and diseases.

2. Traditional and Historical Uses

The root produces a fine red colouring material, which has been used as a dye in the Mediterranean region since antiquity. The plant's name derives from the Greek "anchousa," meaning "paint," underscoring its longstanding role in coloring practices.

Alkanna tinctoria was well-known to the ancient Greeks and Romans, who referred to it as "alkanet." Dioscorides, the 1st-century physician, mentioned it in his pharmacopeia for treating skin afflictions and dyeing wool. Ancient Romans employed the dye to color fatty cosmetics, sweets, and wines, enhancing their aesthetic appeal in daily life and trade.

During the 17th century, French women used ointments infused with alkanet to color their faces, though the tint was noted to fade rapidly, highlighting its role in ephemeral beauty rituals. Artisans also mixed the powdered root with oil to stain wood like mahogany and marble in flesh tones, contributing to decorative arts and furniture making.

Ancient Greek and Roman physicians used alkanna root for its purported healing properties, applying it externally to aid wound healing, soothe burns, and reduce inflammation. Its emollient and astringent qualities made it a popular choice in ointments and poultices for skin ailments. In traditional Middle Eastern and South Asian medicine, alkanna root was often incorporated into balms and salves to treat minor cuts, abrasions, and even eczema. The plant's anti-inflammatory and antimicrobial properties contributed to its reputation as a soothing agent for various skin conditions.

Traditionally, root decoctions have been employed to treat skin wounds, abscesses, diarrhea, and inflammations, with topical applications used for bruises and ulcers. It is also said that the root is effective in the treatment of eye complaints, stomach pain, bronchitis, and other problems. The well-known Kashmiri dish Rogan Josh gets its distinctive burgundy color from the use of alkanet root, also known as Ratanjot, in traditional Indian cuisine.

Because of the production of alkannin pigment (a naphthoquinone), the roots of the plant have a long history in the food industry for coloring confectionery and wines and as food additives, as well as in cosmetics as natural dyes.

3. Phytochemistry: Key Constituents and Active Compounds

3.1 Naphthoquinones: Alkannin and Shikonin

The roots of A. tinctoria contain bioactive naphthoquinones, primarily alkannin and shikonin, along with their derivatives, which exhibit notable antimicrobial, anti-inflammatory, and wound-healing activities. The plant is well-known for its large quantity of naphthoquinone enantiomers, specifically alkannin and shikonin (A/S). These compounds offer various pharmaceutical applications and find use in cosmetics, food supplements, and natural dyes.

Alkannin and shikonin are enantiomers — mirror-image molecules sharing the same molecular formula but different chirality. The main phytochemical components of A. tinctoria roots that are responsible for its biological activity are the naphthoquinones alkannin, shikonin, and their derivatives: acetylalkannin, angelylalkannin, 5-methoxyangenylalkannin, acetylshikonin, dimethylacrylalkannin, naphtharzin, arnebifuranone, shikalkin, alkanfuranol, and alkandiol.

In analyses of Alkanna species collected from several regions of Greece regarding their constituent hydroxynaphthoquinones, among which was A. tinctoria, the main hydroxynaphthoquinones were determined to be β,β-dimethylacrylalkannin, isovalerylalkannin, α-methyl-n-butylalkannin, and acetylalkannin.

3.2 Phenolic Compounds and Flavonoids

The plant's rich phytochemical profile includes terpenoids, flavonoids, and phenolic compounds that contribute to its antioxidant and anti-inflammatory properties. In addition, A. tinctoria contains flavonoids such as kaempferol and quercetin, which are renowned for their strong antioxidant and anti-inflammatory effects, aiding in cellular protection and reducing oxidative stress. Several phenolic metabolites such as luteolin-type flavonoids as well as caffeic acid derivatives have been reported.

3.3 Phytosterols and Fatty Acids

Alkanet root contains alkannin and shikonin, both of which are pigments purported to be wound healing and anti-inflammatory. It also contains phytosterols (beta-sitosterol, stigmasterol), and fatty acids (palmitic, stearic, and oleic).

3.4 Other Secondary Metabolites

The ethanolic extract contains diverse phytochemicals, including flavonoids, alkaloids, phenolic compounds, glycosides, terpenoids, saponins, proteins, sterols, carbohydrates, and resins. Ononitol (4-O-methyl-myo-inositol) has been found as the main compound in the aerial parts.

3.5 Pyrrolizidine Alkaloids

Three pyrrolizidine alkaloids were isolated from Alkanna tinctoria and their structures analysed by spectroscopic methods. One of them is new and the name dihydroxytriangularine has been proposed for it. The presence of pyrrolizidine alkaloids (PAs) is a defining toxicological feature of this plant, discussed further in the safety section.

4. Established Mechanisms of Action

4.1 Anti-inflammatory Mechanisms

Underlying anti-inflammatory mechanisms are related to the inhibition of the NF-κB signaling pathway and a decrease in the release of pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6. The anti-inflammatory capacity of shikonin is attributed to the regulation of immune cells, signaling pathways (e.g., TLR4/MyD88/NF-κB), and pro-inflammatory cytokines (e.g., TNF-α, IL-6).

4.2 Antitumor Mechanisms

Shikonin exerts antitumor effects by inducing multiple cell death modalities through caspase-3 activation, ROS generation, modulation of ATF3 expression, modulation of RIP1/RIP3 signaling, and activation of the BAX/caspase-3/GSDME pyroptosis axis. Furthermore, it suppresses tumor cell proliferation, inhibits metastasis, and blocks cell cycle progression by downregulating oncogenic c-Myc and MMP2 while upregulating the cell cycle inhibitor P21.

Research has emphasized the importance of antitumor activity in apoptosis, necroptosis, and immunogenic cell death, and has expounded the relationship of antitumor activity and naphthoquinone scaffold that can generate ROS and alkylating agent. The antitumor mechanisms of naturally-occurring shikonin, alkannin, and their derivatives are divided into the direct interaction involved in alkylating agent — covalently binding the DNA and protein — as well as the indirect interaction mediated by ROS, nonspecifically influencing the mitochondria or multiple signal pathways.

In 1998, Plyta and colleagues discovered that alkannin and naphthoquinones both act as inhibitors of DNA topoisomerase I (TOPO I). Shikonin and its enantiomeric analogue alkannin are prevailing natural lead compounds in the drug discovery and development of anticancer agents. Despite having numerous biological effects, the most important activity reported for shikonin derivatives is the antitumor effect, which is exerted through various mechanisms such as induction of apoptosis and autophagy.

4.3 Antioxidant Mechanisms

A. tinctoria exhibited the strongest antioxidant activity (211 mgTE/g extract in DPPH and 366 mgTE/g extract in ABTS), probably due to its high total phenolic (53.3 mgGAE/g extract) and flavonoid (20.8 mgRE/g extract) content. This provides robust evidence of Alkanna tinctoria's phytochemical richness and pharmacological potential, reinforcing its traditional medicinal applications. The ethanolic extract's high yield and diverse bioactive constituents, including shikonin derivatives and polyphenols, underpin its potent antioxidant activity, as demonstrated by DPPH (88.98% inhibition, IC₅₀ = 196.8 µg/mL), hydrogen peroxide scavenging (49.36% inhibition, IC₅₀ = 20.3 µg/mL), and reducing power assays.

4.4 Wound-Healing Mechanisms

Mechanistic insights highlight alkannin's role in promoting angiogenesis and collagen synthesis, alongside shikonin's modulation of NF-κB and MAPK pathways. The naphthoquinone enantiomers alkannin and shikonin have been shown to exhibit strong antioxidant, wound-healing, antimicrobial, and anti-inflammatory properties, and extensive recent research has adequately established their antitumor properties, indicating the applications of these metabolites as active ingredients in several pharmaceutical and cosmetic preparations.

5. Scientific Evidence by Area of Use

5.1 Wound Healing — Skin Graft Donor Sites

A prospective, randomized, placebo-controlled clinical trial was conducted to compare the healing effectiveness of Alkanna tinctoria (L.) Tausch with standard dressing on wound healing at the donor site after removal of the skin graft. Enrolled patients were randomly allocated to receive topical A. tinctoria extract ointment (20%) or standard dressing (dressing with base ointment) daily. Wound healing was assessed using the Bates-Jensen assessment tool at the 2nd and 4th weeks after intervention.

Decreases in wound score were significantly greater in the A. tinctoria group compared with the placebo group (P <0.05). The surface areas of graft donor sites in the A. tinctoria group were significantly reduced as compared with the control group at day 28 of the intervention (P <0.05). The proportion of patients in the A. tinctoria group achieving complete wound healing within 2 to 4 weeks was 50% and 96.66%, respectively, significantly higher than in patients receiving standard care: 0% and 23.3%, respectively. No adverse effects were seen in either group treated with herbal and placebo ointments.

Evidence assessment: This is a single randomized, blinded, placebo-controlled trial, published in BMC Complementary and Alternative Medicine (2017). While results are statistically significant and favourable, replication by independent research groups and larger trials are needed before definitive conclusions can be drawn.

5.2 Wound Healing — Burn Injuries

Gümüş and Özlü (2017) conducted an experimental study to assess the effect of a mixture containing beeswax, olive oil, and Alkanna tinctoria Tausch on epithelization initiation time, pain scores, and hospitalization duration. The study enrolled 31 second-degree burn patients in the treatment group and 33 in the control group. The results revealed earlier epithelization in the treated group (3.00 ± 0.85 days) when compared to the control group (6.90 ± 1.77 days) with routine treatment (a mixture of nitrofurazone and rifamycin). Patients using the mixture had a reduced hospitalization duration of 8.22 days compared to 14.42 days in controls. Furthermore, whereas infections occurred in 6.1% of control group wound cultures, no infections occurred in experimental group wound cultures.

Evidence assessment: This study was conducted in a controlled hospital setting (Complement Ther Med, 2017), but it tested a combination preparation — beeswax, olive oil, and A. tinctoria — not A. tinctoria extract alone. The relative contribution of each component cannot be isolated from these results, limiting conclusions about A. tinctoria specifically.

5.3 Antimicrobial Activity

All four bacteria tested in a 2015 PMC-published study — including A. baumannii, E. coli, P. aeruginosa, and S. aureus — were categorized as multi-drug resistant (MDR). All four extracts showed potential activity against S. aureus compared to the positive control antibiotic (Imipenem). Among the four extracts of Alkanna tinctoria leaves, the aqueous extract showed best activity against A. baumannii (10 ± 3 mm), P. aeruginosa (12 ± 0.5 mm), and S. aureus (14 ± 0.5 mm). The MICs and MBCs results also showed quantitative concentration of plant extracts required to inhibit or kill MDR bacteria.

Evidence assessment: All antimicrobial data reported are in vitro (laboratory, not clinical human studies). Translating these findings to clinical infection management requires further preclinical and human studies.

5.4 Antioxidant Activity

Alkanna root has demonstrated radical scavenging activity, suggesting potential antiaging effects; however, clinical trial information is lacking. Studies focused on the phytochemical investigation and pharmacological activities of methanolic extracts of Alkanna tinctoria have examined antioxidant scavenging using DPPH, ABTS free radicals, and hydrogen peroxide assays. All published antioxidant results for A. tinctoria are from in vitro or laboratory assays, not from human clinical trials.

5.5 Anticancer Potential

Modern research has shown many traditional applications while discovering new therapeutic potentials, particularly in cancer treatment and diabetic wound management. Research to seek active compounds against human colorectal cancer from the root of Alkanna tinctoria led to the isolation of two naphthoquinones, alkannin and angelylalkannin, that showed significant inhibitory effects on the cancer cells.

Studies in cell lines have demonstrated that shikonin significantly inhibited the activity of colorectal cancer cells in a time- and dose-dependent manner. Flow cytometry and western blot results indicated that shikonin induced cell apoptosis by down-regulating BCL-2 and activating caspase-3/9 and the cleavage of PARP. Shikonin inhibits proliferation of colorectal cancer cells through the activation of ROS-mediated ER stress. In vivo results showed that shikonin effectively inhibited tumor growth in HCT-116 and HCT-15 xenograft models. In conclusion, shikonin inhibited the proliferation of colorectal cancer cells in vitro and in vivo and warrants future investigation.

Furthermore, shikonin inhibits PD-L1 expression through the NF-κB/STAT3 and NF-κB/CSN5 pathways, and mediates tumor immunomodulation as a result.

Evidence assessment: Despite a substantial and growing body of in vitro and animal model data, clinical trials and toxicity profiling remain scarce. No published human clinical trials specifically testing alkannin or A. tinctoria root extract as a cancer treatment have been identified in peer-reviewed literature. Evidence remains at the preclinical stage.

5.6 Additional Pharmacological Potential

Apart from the pharmacological activities described above, alkannin/shikonin and their derivatives also possess therapeutic potential against phytogenotoxicity, bronchial asthma, peptic ulcer, spasmogenicity, atherosclerosis, inflammatory diseases, ischemic heart diseases, cataract, hepatotoxicity, and impotency. These indications are largely derived from in vitro and animal studies; human evidence is absent or minimal.

6. Body Systems and Health Areas Associated with Alkanna

• Integumentary system (skin and wound healing): The strongest body of evidence, including two human clinical studies (skin graft donor sites and burn injuries), along with extensive traditional use.
• Immune and inflammatory systems: Anti-inflammatory activity demonstrated in vitro and in animal models via NF-κB, TLR4/MyD88, and cytokine modulation pathways.
• Oncology (investigational): Preclinical evidence in colorectal, pancreatic, hepatocellular, and hematological cancer cell lines; no clinical data.
• Gastrointestinal system: Orally, alkanna root has been used for diarrhea and gastric ulcers in traditional contexts, but no clinical trial evidence supports these indications.
• Antimicrobial / infectious disease: In vitro data against MDR pathogens; no clinical evidence.
• Cardiovascular system: Shikonin and alkannin derivatives have been investigated in the context of atherosclerosis and ischemic heart disease in preclinical models only.

7. Dosage Forms and Reported Dosages

No recent clinical data justify human dosage recommendations for oral use of alkanna root. The following dosages have been reported specifically in published studies:

• Topical ointment for wound healing (skin graft donor site): Patients were randomly allocated to receive topical A. tinctoria extract ointment at a concentration of 20%, applied daily.
• Topical mixture for burn injuries: The mixture was prepared by adding 30 g of beeswax to 1,000 mL of medical olive oil brought to boiling point (200–210 °C), and then, after its complete melting, 50 g of Alkanna tinctoria was added and heated for 5 minutes. Afterwards, the mixture was filtered and dispensed into bottles which were then sterilised.
• Cosmetic topical concentration limit: After reviewing all the available evidence, the Cosmetic Ingredient Review (CIR) Expert Panel recommended alkanet root as safe when used at ≤2% concentration in cosmetic products.

8. Safety Considerations

8.1 Pyrrolizidine Alkaloids (PAs): Core Toxicological Concern

Alkanet root contains pyrrolizidine alkaloids (PAs), which are compounds known for their hepatotoxicity — causing liver damage — when used in high doses and over prolonged exposure. Most PAs are toxic to both livestock and humans, often accidentally administered through the consumption of medicinal plants and PA-contaminated products, such as milk, honey, medicinal plant teas, and beverages. The types of toxicity caused by these alkaloids include hepatotoxicity, pneumotoxicity, and genotoxicity.

It is generally considered that PAs exhibit hepatotoxicity via their activated metabolite, pyrrolic ester, which is catalysed by the hepatic cytochrome P450 (CYP450) enzyme system. The pyrrolizidine alkaloid components in alkanna root may cause liver and/or lung toxicity. The most hepatotoxic pyrrolizidine alkaloids include the cyclic diesters, such as retrorsine and senecionine. Fulvine and monocrotaline have been implicated in causing liver and pulmonary toxicities. Specifically, pyrrolizidine alkaloids cause liver cell enlargement, disturbances in liver cell metabolism with functional losses, and fatty degeneration in the liver.

A study in 2014 found PAs detected in the human bloodstream after cosmetic use. Alkanna root may cause acute liver failure, cirrhosis, pneumonitis, pulmonary hypertension, or heart failure.

8.2 Oral Use

When taken by mouth, there is considerable concern about using alkanna as medicine, because it naturally contains harmful chemicals called pyrrolizidine alkaloids (PAs), which can harm the liver. These chemicals can block blood flow in the veins in the liver and cause liver damage. If products meet certain purity standards, they can be labelled "hepatotoxic PA-free," but there is not enough information to know if it is safe to take hepatotoxic PA-free alkanna by mouth.

8.3 Topical Use

There is considerable concern about using alkanna as topical medicine, because it naturally contains harmful chemicals called pyrrolizidine alkaloids. These chemicals can harm the liver. Applying alkanna preparations that contain these chemicals to broken skin is considered likely unsafe.

8.4 Pregnancy and Lactation

During pregnancy, alkanna preparations that contain hepatotoxic pyrrolizidine alkaloids might cause birth defects as well as liver damage. There is insufficient information to know whether it is safe to use hepatotoxic PA-free preparations during pregnancy. It is also considered unsafe to use alkanna during breast-feeding. Hepatotoxic PAs can pass into breast milk and harm the nursing infant. There is not enough information to know whether hepatotoxic PA-free preparations are safe during breast-feeding.

8.5 Pre-existing Liver Disease

Alkanna contains chemicals called hepatotoxic pyrrolizidine alkaloids. These chemicals harm the liver, making existing liver disease worse.

8.6 Drug Interactions

Inducers of the CYP450 isoenzyme system, including rifampin, St. John's Wort, and phenobarbital, may increase the conversion of pyrrolizidine alkaloids to toxic metabolites.

8.7 Regulatory and Industry Guidance

The Cosmetic Ingredient Review Expert Panel (2007) published a final report on the safety assessment of Alkanna tinctoria root extract, Alkanna tinctoria seed oil, and alkannin in the International Journal of Toxicology, 26(Suppl 2), 47–56. Following this review, the CIR Expert Panel recommended alkanet root as safe when used at ≤2% concentration in cosmetic products.

Despite the plant's pharmacological promise, it remains underutilized due to several critical challenges, including variability in phytochemical content, lack of standardization protocols, insufficient clinical trials, and unresolved toxicity concerns.

9. Current Research Landscape and Limitations

In the time frame of 1969 to 2021, a total of 634 full-text reports on alkannin/shikonin are available in the PubMed database, of which 606 reports were published after 2000, showing the increasing research interest. The preponderance of this research, however, remains preclinical. The usage of A. tinctoria in modern therapeutic applications represents a successful bridge between traditional medicine and contemporary pharmaceutical research, though additional clinical studies are needed to fully establish its therapeutic efficacy.

Despite robust preclinical evidence, clinical trials and toxicity profiling remain scarce. This represents an advocacy for standardized extraction protocols, human studies, and regulatory integration to harness A. tinctoria's full therapeutic potential in evidence-based medicine.

References

• Kheiri A, et al. (2017). The effects of Alkanna tinctoria Tausch on split-thickness skin graft donor site management: a randomized, blinded placebo-controlled trial. BMC Complementary and Alternative Medicine. PMC.
• Phytochemical Profiling and Biological Assessment of the Aerial Parts from Three Mediterranean Alkanna Species (PMC, 2024).
• Metabolic Profiles, Genetic Diversity, and Genome Size of Bulgarian Population of Alkanna tinctoria (PMC, 2023).
• Pharmacological and analytical aspects of alkannin/shikonin and their derivatives: An update from 2008 to 2022 (PMC, 2022).
• Research progress in mechanism of anticancer action of shikonin targeting reactive oxygen species (PMC/Frontiers in Pharmacology, 2024).
• Recent Advances of Shikonin in the Molecular Mechanisms of Anticancer, Anti-Inflammation and Immunoregulation (PubMed, 2025).
• Advance in Anti-tumor Mechanisms of Shikonin, Alkannin and their Derivatives (PubMed, 2017).
• Khan UA, et al. (2015). Alkanna tinctoria leaves extracts: a prospective remedy against multidrug resistant human pathogenic bacteria. BMC Complementary and Alternative Medicine. PMC.
• Identification of Toxic Pyrrolizidine Alkaloids and Their Common Hepatotoxicity Mechanism (PMC, 2016).
• Shikonin induced Apoptosis Mediated by Endoplasmic Reticulum Stress in Colorectal Cancer Cells (PMC, 2022).
• Shikonin induces colorectal carcinoma cells apoptosis and autophagy by targeting galectin-1/JNK signaling axis (PMC, 2020).
• Shikonin induces ROS-based mitochondria-mediated apoptosis in colon cancer (PMC, 2018).
• Pyrrolizidine alkaloids from Alkanna tinctoria (ScienceDirect, 2001).
• Gümüş K, Özlü ZK. (2017). The effect of a beeswax, olive oil and Alkanna tinctoria (L.) Tausch mixture on burn injuries. Complement Ther Med. PubMed.
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• Alkanet Root (Alkanna tinctoria): Benefits, Safety, and Responsible Use — Botanical Formulations (2025). [References Cosmetic Ingredient Review Expert Panel, 2007; Lachenmeier et al., 2014].
• Rai A, et al. (2025). Phytochemical and pharmacological evaluation of Alkanna tinctoria. Chemistry Research Journal, 10(4):75–82.
• The Potential of Medicinal Plants and Natural Products in the Treatment of Burns and Sunburn — A Review (MDPI Pharmaceutics, 2023).