The Anticancer, Antibacterial, and Antihypertensive Effects of Maweilian
Maweilian is the root and rhizome of Thalictrum species such as T. glandulosissimum, T. tsao-oo, T. cultratum, and T. faberi of the buttercup family. Named for its horsetail-like shape and Coptis-like taste, it contains berberine (the main alkaloid of Coptis, or Huanglian). Maweilian is mainly distributed on China's Yunnan-Guizhou Plateau and in the Sichuan Basin.
Maweilian is not a commonly used herb; Li Shizhen did not include it in the Bencao Gangmu (Compendium of Materia Medica). The Qing-dynasty physician Zhao Xuemin included it in Gangmu Shiyi (Supplement to the Compendium), noting that it "is cold in nature but not harsh, bitter but milder, not as thick as Chuanlian (i.e., Coptis). It purges evil heat from between the skin membranes and fascia, and is used for childhood colds and in smallpox practice."
From this passage we can see that the ancients already recognized Maweilian's anti-inflammatory and antibacterial (heat-clearing and detoxifying) action, and used it for childhood colds, measles, and smallpox. TCM holds that Maweilian is bitter and cold, entering the Heart, Liver, and Large Intestine meridians; it clears heat and dries dampness, drains fire and resolves toxins. It treats damp-heat diarrhea, dysentery, jaundice, fever from colds, measles, boils and sores, red swollen painful eyes, and cancerous swellings.
Modern pharmacology finds Maweilian's chief action to be anticancer. The total alkaloids from different regional species—including thalictrine, hernandezine, thalicarpine, and isotthalicarpine—all show clear anticancer activity.
Animal experiments show that intraperitoneal injection of total Maweilian alkaloids at 40–80 mg/kg once daily for nine days extended the survival of mice inoculated with P388 lymphatic leukemia cells by 33.6–84.3%. Hernandezine injected intraperitoneally markedly inhibited P388, mouse sarcoma S180 (ascites type), and colon cancer C26; it prolonged survival of leukemic mice and achieved a 33.3% inhibition rate against solid colon tumors. In vitro, hernandezine also markedly inhibited mouse leukemia L1210 cells and human oral epidermal carcinoma KB cells.
In vitro, baicaline markedly inhibits human esophageal cancer cells, and thalicarpine significantly inhibits rat Walker carcinosarcoma W256, mouse Lewis lung carcinoma, mouse sarcoma S37, Ehrlich ascites carcinoma, and multiple sarcomas. Some scholars believe hernandezine's anticancer mechanism is blocking the transition of G1-phase cells into S phase.
These data show Maweilian has broad anticancer action: it extends cancer patients' survival and inhibits rapid cancer-cell growth. Its folk use for boils and swellings is therefore not without scientific basis.
Maweilian also has a broad antibacterial spectrum, inhibiting Staphylococcus aureus, Mycobacterium smegmatis, Candida albicans, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, dysentery bacilli, Salmonella septicaemiae, and Salmonella typhimurium. These organisms often cause dry mouth, scanty dark urine, mouth ulcers, and diarrhea, which TCM attributes to damp-heat pouring downward; hence Maweilian's reputation for clearing heat and drying dampness and treating fever, diarrhea, and abdominal pain. But Maweilian also inhibits beneficial flora such as Bifidobacterium, so overuse can disrupt gut flora and cause constipation or diarrhea.
Maweilian also has a fair antihypertensive effect, but it is not long-lasting; in animal experiments, excessive doses cause a precipitous, sometimes fatal drop in blood pressure, so we do not normally use it for hypertension. It has some toxicity, but serious side effects generally require very large doses; normal doses usually cause only constipation or diarrhea that resolves on stopping. Pregnant women should avoid it, and TCM also advises against it for those with spleen-stomach deficiency-cold.
Maweilian has some effect on acid regurgitation and stomach pain from excess stomach acid, much like Coptis. But its side effects are milder than Coptis's and it is less bitter, so it is sometimes used clinically as a substitute. Pairing Maweilian with Wuzhuyu (Evodia) treats stomach-heat pain and acid vomiting—essentially Danxi's Zuojin Wan with Maweilian replacing Coptis. Pairing it with Zhizi (Gardenia), Huangqin (Scutellaria), and Huangbai (Phellodendron) treats vexation, thirst, and diarrhea from febrile disease—Huanglian Jiedu Tang with Maweilian replacing Coptis. Maweilian is commonly used for damp-heat and warm-damp disorders.
The sores and swellings Maweilian treats are mostly of the heat-toxin type, so when used for cancerous lumps or furuncles it is often paired with other heat-clearing, toxin-resolving herbs such as Pugongying (Dandelion), Jinyinhua (Honeysuckle), Lianqiao (Forsythia), Zihuadiding (Viola), and Sheng Gancao (Raw Licorice).
The usual adult dose in decoction is 3–15 g, reduced for children. Maweilian is bitter and hard to drink, so the dried herb may also be ground finely and filled into empty capsules. Fresh or powdered Maweilian can be applied externally for red, swollen, hot, painful lesions.