Carlina: Benefits, Side Effects and Dosage

Carlina is a genus of flowering plants in the Asteraceae family, with Carlina acaulis and Carlina acanthifolia being the most studied species. Traditionally used in European folk medicine, Carlina roots and leaves have been applied for digestive and skin disorders, and modern science is beginning to uncover their complex phytochemistry and potential health benefits. However, as with many botanical remedies, Carlina's effects are a balance of potent bioactivity and considerations for safety. In this article, we explore the evidence-based benefits, possible side effects, and guidance on dosage for Carlina.

Benefits of Carlina

Carlina has gained attention for its diverse therapeutic properties, ranging from antimicrobial and antioxidant to anti-inflammatory and even anticancer effects. As scientific research delves deeper, Carlina’s traditional uses are being validated and new applications are emerging.

Benefit	Main Evidence	Active Constituents	Source(s)
Antimicrobial	Effective against bacteria and fungi	Carlina oxide, essential oil	1 3
Anti-inflammatory	Reduces inflammation in animal models	Essential oil	1
Antioxidant	Inhibits lipid peroxidation, scavenges radicals	Carlina oxide, phenolic acids	1 5
Gastroprotective	Protects against gastric ulcers	Root essential oil	1
Anticancer	Inhibits proliferation, induces apoptosis in melanoma cells	Triterpenes, phenolic acids	4

Table 1: Key Benefits of Carlina

Antimicrobial Properties

Carlina essential oils, especially those derived from roots, exhibit significant antimicrobial activity. Laboratory studies have shown these extracts are especially effective against Gram-positive bacteria such as Streptococcus pyogenes, Enterococcus faecalis, and Bacillus subtilis, as well as the fungus Candida albicans 1 3. The antimicrobial action is largely attributed to carlina oxide, a natural polyacetylene compound present in high amounts in Carlina roots 3.

• Broader spectrum: Activity extends to some Gram-negative bacteria and additional fungi, though the strongest effects are against Gram-positive strains 1 3.
• Potential application: May offer alternatives for topical or digestive system infections.

Anti-inflammatory Effects

Carlina root essential oil has demonstrated strong anti-inflammatory activity in animal studies. In rat models, oral or topical application of the oil reduced swelling in a dose-dependent manner, with effects comparable to the pharmaceutical anti-inflammatory, indomethacin 1. This validates the plant’s traditional use for inflammatory skin and digestive conditions.

Antioxidant Activity

Carlina’s antioxidant effects are significant and dose-dependent. The essential oil and extracts reduce lipid peroxidation (a marker of oxidative stress) and neutralize free radicals such as DPPH and hydroxyl radicals 1 5. These antioxidant properties are due to both carlina oxide and phenolic acids like chlorogenic acid and 3,5-di-caffeoylquinic acid 5.

• Cultivation matters: Field-grown plants tend to have higher carlina oxide content, while hydroponic systems yield comparable levels of other antioxidants 5.

Gastroprotective (Anti-ulcer) Potential

Carlina root essential oil displayed protective effects in animal models of gastric ulcer. In rats exposed to ethanol-induced gastric injury, the oil reduced ulcer formation in a dose-dependent manner, indicating a potential role in protecting the stomach lining 1.

Anticancer and Antiproliferative Effects

Recent studies have shown that extracts from Carlina leaves and roots can inhibit the growth of human melanoma cells in vitro 4. Leaf extracts, in particular, induce apoptosis (programmed cell death) in cancer cells and inhibit proliferation-related signaling pathways, such as ERK1/2 phosphorylation 4. The active compounds responsible are likely triterpenes and phenolic acids found in the extracts.

Side Effects of Carlina

While Carlina offers several promising health benefits, it is important to be aware of its potential side effects. The same bioactive compounds that confer therapeutic effects can also pose toxicity risks if not properly managed.

Side Effect	Severity/Observations	Compound(s) Involved	Source(s)
Cytotoxicity	Toxic to normal and cancer cells in vitro	Carlina oxide	6
Acute toxicity	High doses affect liver, kidney, stomach in rats	Essential oil (carlina oxide)	7
Neurological signs	Only at very high doses in animals	Essential oil	7
Selective cytotoxicity	Normal fibroblasts less sensitive than cancer cells	Leaf extracts	4

Table 2: Main Side Effects and Safety Concerns

Cytotoxicity and Toxicity of Carlina Oxide

Carlina oxide, the main polyacetylene in Carlina root essential oil, has been identified as the key compound responsible for both the antimicrobial and cytotoxic effects of Carlina. In vitro studies show that carlina oxide induces apoptosis and necrosis not only in melanoma cells but also in normal human fibroblasts 6. Moreover, it modulates important cellular pathways, such as decreasing AKT and ERK1/2 activity and altering PD-L1 expression 6.

• In vivo evidence: In zebrafish, carlina oxide displayed high toxicity, with an LC50 (lethal concentration for 50% of organisms) of just 10.13 µg/mL after 96 hours of exposure 6.
• Implication: Therapeutic products derived from Carlina should be thoroughly purified to remove carlina oxide to avoid toxic effects 6.

Organ Toxicity in Animal Models

Acute toxicity studies in mammals (rats) indicate that while lower, practical doses of Carlina essential oil are generally safe, very high doses (1000 mg/kg) produce modest neurological symptoms and moderate effects on the stomach, liver, and kidney 7.

• Reassuringly, doses closer to those expected in practical use (such as in eco-friendly pesticides or traditional remedies) did not cause observable adverse effects in rats 7.
• However, caution is needed to avoid excessive dosing or use of unstandardized extracts.

Selective Cytotoxicity and Safety Profile

Leaf extracts from Carlina species have shown selective cytotoxicity—being more toxic to melanoma cells than to normal fibroblasts at equivalent doses 4. This suggests some degree of therapeutic window, but does not eliminate the risk to healthy cells at higher concentrations.

• No caspase activity (an indicator of apoptosis) was observed in normal fibroblasts at moderate doses, but higher concentrations did increase proliferation in some cell types 4.

Other Considerations

• Allergic reactions: As with all plant-based products, allergic responses are possible, though not specifically documented in the available studies.
• Traditional use: Historical use as a skin remedy and antiparasitic agent underscores the need for caution and modern safety evaluation 6.

Dosage of Carlina

Determining the correct dosage of Carlina is challenging, as standardized preparations are not widely available and most research is preclinical. However, studies provide some guidance on effective and safe concentrations.

Preparation/Use	Effective Dose Range	Safety Considerations	Source(s)
Essential oil (root)	10–100 mg/kg (animal studies)	Dose-dependent toxicity (avoid high doses)	1 7
Leaf/root extracts	100–300 μg/mL (cell studies)	Watch for cytotoxicity at high doses	4 6
Carlina oxide (isolated)	Not recommended (toxic)	Should be removed from extracts	6

Table 3: Dosage Ranges and Recommendations

Animal and In Vitro Dosage

• Essential oil (root): In animal models, doses between 10 and 100 mg/kg have demonstrated anti-inflammatory, antimicrobial, and gastroprotective effects 1. Toxicity was only noted at the highest end or above, particularly in sensitive species 7.
• Leaf/root extracts: In cell culture assays, concentrations up to 100 μg/mL for leaves and up to 300 μg/mL for roots were effective for antiproliferative and cytotoxic effects against melanoma cells 4. However, higher concentrations may affect normal cells as well 4 6.

Human Dosage Considerations

• No standardized human dose: There is currently no established safe or effective dose for Carlina products in humans. Traditional use often involved topical application or teas, but amounts were not standardized.
• Carlina oxide caution: Given the demonstrated toxicity of carlina oxide, it is recommended that any therapeutic or supplement product based on Carlina should be thoroughly purified to remove this compound 6.
• Product variability: The concentration of active compounds such as carlina oxide, triterpenes, and phenolic acids varies widely depending on cultivation method and plant part used 5. Field-grown roots have higher carlina oxide, while hydroponic or soil-grown leaves may have higher antioxidants 5.

Practical Recommendations

• Seek standardized extracts: If considering Carlina-based products, look for those that are standardized for low or absent carlina oxide content.
• Start low, monitor: For topical use, start with diluted preparations and monitor for irritation or allergy.
• Medical supervision: Consult a healthcare professional before using Carlina, especially for internal use or if you have underlying health conditions.

Conclusion

Carlina is a plant with a rich history in traditional medicine and a growing body of scientific evidence supporting its diverse health benefits. However, its potent bioactive compounds, especially carlina oxide, require careful attention to safety and dosing. Here are the main points to remember:

• Significant benefits: Antimicrobial, anti-inflammatory, antioxidant, gastroprotective, and anticancer activities have been demonstrated in preclinical studies 1 3 4 5.
• Key constituents: Carlina oxide, triterpenes, and phenolic acids are responsible for most of the observed effects 1 3 4 5.
• Toxicity risk: Carlina oxide is cytotoxic to both cancer and normal cells and shows high in vivo toxicity; products should be purified and doses carefully managed 6 7.
• Dosage uncertainty: No standardized human dose exists; most evidence is from animal and cell studies. Use only standardized and well-characterized extracts 1 4 5 6 7.
• Professional advice: Always consult a healthcare provider before using Carlina-based products, especially internally.

Carlina represents a promising botanical with multiple potential applications, but more research and rigorous safety standards are needed before it can be recommended for widespread therapeutic use.