Chinese Name : 细辛
Latin Name : Herba Asari
This herb is the entire plant of Asarum heterotropoides Fr. Schmidt var Mandshuricum (Maxim.) Kitag. (bei xi xin) and A, sieboldii Miq. (hua xi xin) of the family Aristolochiaceae. It is mainly grown in the regions of northern China, and the Fujian and Zhejiang provinces of central China, where it is harvested in summer or autumn, dried in the shade, cut into segments, and used unprocessed.
Asarum has traditionally been used as an emetic, expectorant, and diuretic, and for rheumatic affections and epilepsy. Today, it is used mainly for common colds, arthritis, chronic bronchitis, bronchial asthma, chronic rhinitis, nasosinusitis, toothache, gingivitis, neurovascular headache, and cancer pain.
Use of Asarum Herb in TCM
Pungent in taste and warm, and slightly toxic, it acts on the lung and kidney meridians.
Effects, Medicinal Uses, and Combinations
- Disperses Wind–Cold exopathogens and relieves colds, stuffy nose, neurovascular headache, and severe toothache. Asarum herb is prescribed with notopterygium root (qiang huo), atractylodes, dahurian angelica root, cnidium, dried rehmannia, scutellaria, licorice root, and siler (fang feng), as in Jiu Wei Qiang Huo Tang.
- Relieves arthralgia (Wind-Cold-Damp Bi-syndrome): to treat rheumatic joint pain, asarum herb is dispensed with pubescent angelica root, siler, and large-leaf gentian root, as in Du Huo Ji Sheng Tang (R-58).
- Alleviates sinus disorders: to treat stuffy nose, rhinitis, or nasosinusitis, asarum herb is combined in a decoction with magnolia flower, xanthium fruit, and dahurian angelica root (bai zhi).
In a decocton of 1.5 to 3 g, or 0.5 to 2 g if taken orally in powdered form, or applied externally as needed for tooth pain. This herb is potent. Avoid overdose, particularly when using the powdered form.
People with a headache due to yin deficiency, or coughs caused by Heat in the lungs should avoid this herb.
Side Effects and Toxicity
The classical Chinese materia medica describes asarum herb as “slightly toxic”. The alcohol extract showed more toxicity than the water decoction, indicating that the volatile oil of the herb is more potent and toxic. The extract acted as an anesthetic in frogs, mice, and rabbits. It showed stimulation followed by inhibition and it also blocked the sciatic nerve pain sensation in frogs. Other inhibitory effects reflexes, followed by death due to respiratory paralysis. The LD50 value of the decoction of A. sieboldii was 12.375 g/kg (intragastric) and 0.77 g/kg (intravenous) in mice.
Asarum heterotropoides (bei xi xin) contains about 3 percent volatile oil. Its main ingredients are methyl eugenol, safrole, beta-pinene, eucarvone, sabinene, elemicin, estragole, and t-caryophyllene. Asarum sieboldii (hua xi xin) contains about 1.9 percent volatile oil. Its main ingredients are methyl eugenol, eucarvone, elemicin, sabiaene, alpha-hydroxy-p-cymen, asarylketone, cineol, and l-asarinin.
The herb’s volatile oil is antipyretic, sedative, analgesic, and antihistaminic.
- Asarum’s volatile oil produced significant CNS depression. Sleep was induced in mice five minutes after administering the medication. Oral administration of 0.5 ml/kg of the oil showed analgesic activity in rabbits against pain induced by electrical stimulation of dental nerves. Its analgesic effect was also observed in mice.
- The herb’s volatile oil reduced the body temperature of healthy animals. Intragastric administration of the volatile oil reduced fever in rabbits induced by exposure to heat, typhoid vaccine, or tetrahydrogen-b-naphtylamine.
- Asarum’s volatile oil was stimulating at a low dose and inhibitory at higher doses on an isolated frog heart, stopping the heart at the diastolic phase. The alcohol extract of liao xi xin showed stimulation in the isolated hearts of rabbits and guinea pigs, suggesting a positive inotropic and chronotropic effect.
- Antihistaminic action. Methyleugenol inhibited histamine-induced contractions in an isolated guinea pig ileum.