What are the active medicinal properties of arnica?

Arnica montana, commonly known as arnica, mountain daisy, or wolf's bane, is a flowering plant in the family Asteraceae. It is native to the mountainous regions of Europe and Siberia. Arnica has been used in traditional medicine for centuries for its anti-inflammatory, analgesic, and wound-healing properties. The active medicinal properties of arnica are primarily attributed to the presence of various chemical compounds, including:

1. Sesquiterpene lactones: These compounds are responsible for many of arnica's therapeutic effects. They have anti-inflammatory, analgesic, and antimicrobial properties. The main sesquiterpene lactones in arnica include helenalin, dihydrohelenalin, and arnicin.

2. Flavonoids: These compounds are known for their antioxidant and anti-inflammatory properties. They help to protect cells from damage and reduce inflammation. The primary flavonoids in arnica include quercetin, luteolin, and kaempferol.

3. Triterpenes: These compounds have anti-inflammatory and wound-healing properties. They help to reduce swelling and promote tissue repair. The primary triterpenes in arnica include arnidiol and faradiol.

4. Essential oils: Arnica contains several essential oils, such as thymol, borneol, and cineole. These oils have antimicrobial, anti-inflammatory, and pain-relieving properties.

5. Coumarins: These compounds are known for their anticoagulant and anti-inflammatory properties. They help to improve blood circulation and reduce swelling. The primary coumarins in arnica include esculetin and umbelliferone.

6. Carotenoids: These compounds are precursors to vitamin A and have antioxidant and anti-inflammatory properties. They help to protect cells from damage and reduce inflammation. The main carotenoids in arnica include beta-carotene and lutein.

Arnica also contains other compounds, including polysaccharides, tannins, and minerals. These substances may also contribute to the plant's medicinal properties.

It is important to note that arnica should be used only for external applications and should not be ingested. Internal use of arnica can cause serious side effects, including nausea, vomiting, diarrhea, and seizures.