4720-09-6

Fructus Rhododendri (ba li ma) is the dried fruit of Rhododendron molle (Bl.) G. Don (yánɡ zhí zhú), mainly distributed in the Jiangsu, Hubei, and Jiangxi Provinces of China .
“Compendium of Materia Medica” recorded that Rhododendron molle (Bl.) G. Don (yánɡ zhí zhú) can be used to treat waist pain, arm pain, and poisoning. It is effective at lowering blood pressure and slowing the heart rate, but a large dosage can cause death . Rhomotoxin’s formulations include injection and tablet. Side effects include a burning sensation, numbness, dizziness, dry mouth, nausea, vomiting, vertigo, chest tightness, slow heartbeat, and low blood pressure. In addition, pregnant women should use it with caution.

Appearance: white crystalline or powder. Solubility: soluble in water, acetone, and chloroform, almost insoluble in diethyl ether or petroleum ether. Melting point: 265–268 °C. Specific optical rotation: ?50 to ?60°.

Because rhomotoxin can slow down heart rhythm and blood pressure, Deng Dao ji et al. from the First Affiliated Hospital of Wuhan Medical College researched Fructus Rhododendri in the early 1970s. They extracted the crystallization from fruits and obtained preliminary results by animal testing and clinical application .
Rhomotoxin is a white needle crystal that is extracted from the dried fruit of Rhododendron molle (Bl.) G. Don (yánɡ zhí zhú). Its biological activity is closely related to three-dimensional specificity and hydrophobicity. 5β-hydroxyl, 6β- hydroxyl, and, especially, the 2,3-epoxy groups can affect its biological activity .
Rhomotoxin was acetylated to obtain monoacetate (Japanese Rhododendron II). The melting points of rhomotoxin and Japanese Rhododendron III are identical (284–286 °C). IR and Rf of silica gel thin layer chromatography are identical. Therefore, rhomotoxin is Japanese Rhododendron III .

ChEBI: A tetracyclic diterpenoid that is grayanotoxane in which the pro-R hydrogen at position 14 is substituted by an acetoxy group and in which the 3beta-, 5-, 6beta-, 10-, and 16- positions are su stituted by hydroxy groups.

The pharmacological effects of rhomotoxin are mainly displayed in three aspects: (1) analgesic effect: the suspension, infusion, and alcohol made of rhomotoxin fruit have an analgesic effect in mice ; (2) effects on cardiovascular system: the resting heart rate is a bad prognostic indicator of hypertension and other cardiovascular diseases. Rhomotoxin can reduce the resting heart rate; (3) kidney protection: rhomotoxin promotes good blood pressure and a slow heart rate and provides kidney protection. Its mechanism may be related to a reduction in the content of angiotensin II (Ang II), increasing endothelial nitric oxide synthase (eNOS) content, and slowing heart rate .
The plasma concentration of mice decreased rapidly over time following intravenous injection of rhomotoxin; there was no residue after 6 h. Rhomotoxin is rapidly distributed to various organs through the blood circulation and reaches a peak within 5–15 min. The gallbladder (including bile) contained the highest amount, followed by the liver and kidneys. It affects, in order, the gallbladder (including bile), liver, kidney, thyroid, stomach, adrenal gland, heart, lungs, and brain. Rhomotoxin is excreted mainly by the kidney and digestive tract. More prototype drugs are in the urine than in the stool. Rhomotoxin has a stimulating effect on the stomach. A certain amount of rhomotoxin also entered the thyroid and adrenal glands. A very small amount was found in brain tissue, demonstratinge that rhomotoxin does not easily pass through the blood-brain barrier. Plasma dialysis showed that the plasma protein binding rate of rhomotoxin can reach as high as 60% in 30 min .

Rhomotoxin acts as an antihypertensive drug, and it is able to lower the blood pressure in patients with severe hypertension. Its pharmacological effects are related to parasympathetic function. Large-dosage-induced low blood pressure can be restored with ephedrine. Its antihypertensive effect lasts for 0.5–1 h. If blood pressure has not dropped to a satisfactory level, rhomotoxin must not have been added because an excessive drop in blood pressure would lead to shock. Oral administration with aluminum hydroxide can reduce rhomotoxin-induced stomach discomfort. Intramuscular injection can also cause local pain. In addition, procaine reduces its antihypertensive effect. Secondary hypertension and malignant hypertension patients should use it with caution, critical and dying patients should be disabled (including, for example, severe heart failure, cardiomyopathy, atrioventricular block, and severe ventricular arrhythmias).

Poison by subcutaneous,parenteral, intravenous and intraperitoneal routes. Whenheated to decomposition it emits acrid smoke and fumes.