L-Tetrahydropalmatine

The roots of Stephania rotunda furnish this alkaloid which forms colourless plates when crystallized from EtOH. It is laevorotatory with [α]²³_D - 262° (EtOH) and gives a crystalline hydrochloride with m.p. 258-9°C (dec.) and the methiodide which decomposes at that same temperature. Three methoxyl groups and one methyl group are present.

Appearance: off-white solid, odorless, tasteless, and turns yellow under light and heat. It should be protected from light and air. Solubility: this product is usually dissolved in chloroform, slightly soluble in ethanol or ether, insoluble in water, and soluble in dilute sulfuric acid. Melting point: 141–144?°C. Specific optical rotation: ?290 to –300°.

From the 1920s, many researchers have focused on the alkaloid compounds contained in the Yan Hu Suo and extracted more than 30 different kinds of alkaloids. Among them Rotundine is one of the most important active compounds and has been successfully applied in clinical practice.
Tetrahydropalmatine (THP) was firstly discovered by Zhao Chenggu, a famous medicinal phytochemist in China. He isolated 13 kinds of alkaloids and identified the structure of 6 of them. In 1936, Huang Minglong, a famous organic chemist, proved THP is a racemate. From 1933, Wang Jingxi and Lu Zihui began to study the pharmacological effects of THP and found that THP could induce catalepsy in animals. Rotundine is a levo-THP and obtained from the resolution of DL-THP during 1959–1964. From 1956 to 1965, the famous Chinese neuropharmacologist, Jin Guozhang, identified Rotundine as the main effective component in Yan Hu Suo and further studied its underlying mechanisms. He also found that Stephania contains abundant L-THP, which could become the source of clinical medication.
In 1965, Rotundine was recorded in the textbooks of pharmacology. After over 20?years of clinical practices, people have proved that Rotundine has reliable efficacy and low side effect. In 1977, Rotundine was recorded in the Chinese Pharmacopoeia. In 1979, THP achieved a full synthesis, and currently Rotundine is mainly produced by artificial synthesis. From 1980, the study on the mechanisms of Rotundine made great progress. The analgesic effect of Rotundine has nothing to do with opioid receptors or prostaglandins. Rotundine does not belong to narcotic analgesics and antipyretic analgesics. Further, Rotundine has been found to have no affinity with M-cholinergic receptor and GABA system in the brain. But it has affinity to dopamine receptors. The exact mechanisms and pharmacology effects of Rotundine still need more research.

1. Pain induced by gastrointestinal and hepatobiliary disorders, menstrual pain, and pain after childbirth.
2. Mild trauma and postoperative pain
3. Headache insomnia and spasmodic cough.
4. There is a report about the usage of Rotundine in arrhythmia caused by I–III hypertension and other diseases.
5. The hypnotic effect of Rotundine happens in 15?min after administration and then appears after 2?h. Because the analgesic effect happens at the same time, Rotundine is particularly suitable for insomnia patients with pain.
6. Side effects: drowsiness, dizziness, fatigue, and nausea. Large dose of Rotundine can inhibit the respiratory center and may cause extrapyramidal symptoms.

Crystallise it from MeOH or EtOH by addition of water [see Kametani & Ihara J Chem Soc (C) 530 1967, Bradsher & Dutta J Org Chem 26 2231 1961]. When crystallised from Me2CO/Et2O, it has m 142o. The hydrate has m 115o(effervescence). The picrate has m 188o(dec) (from aqueous EtOH). [Bradsher & Datta J Org Chem 26 2231 1961, Beilstein 21 II 196, 21 III/IV 2769.]

Kondo, Matsuno., J. Pharm. Soc., Japan, 64, (9A), 28 (1944)