Place of origin: Rhizoma Alismatis is mainly planted in several provinces such as Fujian, Sichuan and Jiangxi. It is also planted in Guangdong, Guangxi, Hubei and Hunan provinces ^[1]. Jian ‘ou County of Fujian Province is the famous hometown of Rhizoma Alismatis in China, whose Rhizoma Alismatis produced is listed as genuine medicinal materials ^[2][3].

For the resistance to cold and delight in sunlight, Rhizoma Alismatis can be grown well under warm and humid condition, which is generally planted in the areas below 800 meters above sea level. The average annual temperature in its planting area is in the range of 17-26°C. Rhizoma Alismatis is usually planted in paddy fields rich in organic matter with slightly viscous soil.

Rhizoma Alismatis is a tuber, whose shape is spherical, elliptic or oval, 2-7 cm in length and 2-6 cm in diameter. The surface, with the color of yellowish-white or yellowish-brown, has irregular transverse circular shallow furrows and many marks of fibrous roots with fine bulges, and nodular bud marks can be occasionally found on the bottom. The texture is solid. The cross section is powdery with the color of yellow – white. It has a slight odor and slight bitter taste ^[1].

The application of Rhizoma Alismatis has a very long history in China, firstly recorded in Wei Feng, The Book of Poetry^[4], which indicated that Rhizoma alismatis was one of the common medcines used from the early stage of Spring and Autumn Period. In Variorum of Shennong’s Classic of Materia Medica, Rhizoma Alismatis was listed as the top grade. Its properties and effects were recorded that “It had sweet taste and cold nature; it is non-toxic. It could mainly treat the disorders, such as wind-cold and dampness, difficult lactation and promoting urination, in order to nourish five organs, invigorate Qi, and strengthen the body. Long-term treatment could improve hearing and vision, get full easily, prolong life, reduce body weight, and gain color “^[6]. Various aspects of Rhizoma Alismatis were described in detail in the books of traditional herbal medicines in the past dynasties, such as morphological characteristics, distribution area, harvesting period, processing and preparation, compatibility and application. Rhizoma Alismatis drink was one of the traditional Chinese medicine prescriptions in the Internal Canon of Medicine, in which the discussion on the compatibility and usage of Rhizoma Alismatis has been become a reference case for various doctors ^[4].

Rhizoma Alismatis can mainly treat the disorders including difficult urination, heat stranguria, difficulty and pain in micturition, swelling, and dizziness due to phlegm and sputum, which is especially suitable for the patient with damp-heat in lower JIAO ^[7]. For difficult urination and swelling, Rhizoma Alismatis is usually associated with Ramulus Cinnamomi, Poria cocos and Polyporus umbellatus. For spermatorrhea and deficiency of kidney-Yin, Rhizoma Alismatis can be compatible with Rehmannia glutinosa, Cortex moutan, Rhizoma anemarrhenae and Cortex Phellodendri, such as Liuwei Dihuang Pill. It was recorded in Synopsis of Golden Chamber that “If the patient is with diaphragm fluid retention under the heart, he will feel faint and dizzy, then Rhizoma Alismatis decoction could main treat him.” The symptoms involved include palpitation, chest distress, dizziness and nausea, which are similar to those of hypertension mentioned in modern medicine. In modern Traditional Chinese Medicine, Rhizoma Alismatis has been used in the clinical treatment of hypertension, hyperlipidemia, fatty liver, and coronary heart disease ^[1].

1. Terpenoids

The cholesterol-lowering effects of Rhizoma Alismatis extract was studied since the late 1960s. In 1970, Japanese scientists found that oral administration of Rhizoma Alismatis extract reduced cholesterol levels in plasma and liver through animal experiments. Triterpenoids were the main components in Rhizoma Alismatis extract ^[10]. The studies showed that, the lipid-lowering components in Rhizoma Alismatis were mainly Ali-B, Ali-B 23-acetate and Ali-C 23-acetate ^[8], which could increase the expression level of FXR in hepatocytes and activate BSEP signal pathway in the liver ^[9], showing significant liver-protection ability. In addition, Ali-A 24-acetate could reduce lipid deposition in the liver by blocking the expression of the related genes ^[11]. Furthermore, abnormal purine metabolism caused hyperuricemia thus leading to hypertension. It was found that Rhizoma Alismatis may prevent the elevation of blood pressure or hypertension by improving purine metabolism. Secondly, in terms of glycerophospholipid metabolism, Rhizoma Alismatis could significantly reduce LDL level and help the body recover lipid metabolism to protect the function of vascular endothelium ^[13].

2. Polysaccharides

Rhizoma Alismatis polysaccharides are mainly acid polysaccharides and glucan, such as PII, PIIIF and SI, which could enhance the activity of immune cells and antibodies ^[12]. In addition, Rhizoma Alismatis polysaccharide also shows antioxidant activity, especially scavenging activity on hydroxyl radical, which is very important for the organism to protect life system ^[14].

According to the processing method on Rhizoma Alismatis, the processing with wine was firstly recorded in Lei Gong’s Treatise on Preparation and Boiling of Materia Medica in Nan Dynasty. After Song, Yuan, Ming and Qing Dynasties, several methods were mentioned, including frying, steaming, simmering and frying with salt water. Nowadays, the frying method is mainly applied in Zhenjiang, Jiangsu and Zhejiang, the processing with wine is mainly used in Baoding area, and the frying with salt water method is applied in Beijing, Chongqing and Heilongjiang ^[5].

Raw Rhizoma Alismatis: Remove the impurities from Rhizoma Alismatis, separate them by size, slightly soak and wash, moisten and cut into thick slices, dry and sieve out the debris. The slice is yellowish-white, with many small holes. The rim is yellowish-white, with the marks of fibrous roots.

Fried Rhizoma Alismatis: Fry the bran in a hot pan over medium heat. When smoking, add the Rhizoma Alismatis slices (dried slices) in the pan. Stir them until the color of Rhizoma Alismatis turns yellow. Sift out the bran and cool the slices. Fried Rhizoma Alismatis has the color of yellow on the surface, with occasional burnt spots, and slight smell of burning.

Processed Rhizoma Alismatis with salt water: Take the clean slices of Rhizoma Alismatis, mix and moisten them with salt water. After the slices of Rhizoma Alismatis absorb salt water completely, heat them gently until the color turns pale yellow. Take them out, cool them, and sift out the debris. Salt-fried Rhizoma Alismatis has the color of pale yellow on the surface, with occasional burnt spots, and slightly salty smell.

Processed Rhizoma Alismatis with wine: Place the clean slices of Rhizoma Alismatis in hot pan (100°C), spray well with wine during frying, fry to dryness, take out and cool them. The color of the surface of processed Rhizoma Alismatis with wine is deepened.

After different processing, the efficacy of Rhizoma Alismatis may be enhanced or mitigated. Raw Rhizoma Alismatis is good at promoting urination and clearing heat. After fried with bran, the cold nature of Rhizoma Alismatis should be alleviated, which can be apt at eliminating dampness, harmonizing the spleen, ascending lucidity and descending turbidity. After fried with salt, the function of Rhizoma Alismatis on clearing heat can be increased to promote urination and injure Yin.

Rhizoma Alismatis is one of the common medicines used in Traditional Chinese Medicine (TCM). Rhizoma Alismatis was listed as the top grade in Variorum of Shennong’s Classic of Materia Medica, saying that “It has sweet taste and cold nature; it is non-toxic”. Rhizoma Alismatis is one of the herbal medicines that can be used in healthcare food announced by National Health Commission of the People’s Republic of China. Secondly, as for the usage of Rhizoma Alismatis, Chinese Materia Medica compiled by State Administration of Traditional Chinese Medicine has proposed that “Rhizoma Alismatis is forbidden to take by the patients with kidney deficiency and spermatorrhea without damp-heat syndrome”. It can also quote the description of Rhizoma Alismatis in Collective Notes to Canon of Materia Medica “Sea clam and clam are prohibited” ^[1].

The research group on Rhizoma Alismatis in Zhejiang Province studied clinical application of Rhizoma Alismatis since 1976. The preparation of Rhizoma Alismatis was applied to 193 patients with hyperlipemia, aged 27-65 years, whose therapeutic effect was compared with that of Clofibrate (one of drugs for hyperlipidemia). It was found that Rhizoma Alismatis could significantly reduce the levels of total cholesterol and triglyceride in the serum, especially the effect of lowering cholesterol was better. No obvious adverse symptoms were found ^[15].

Lu Zhizheng, TCM expert, believed that hyperlipidemia is associated with “Dampness”, “Turbidities”, “Phlegm” and “Stasis” mentioned in TCM theory ^[16]. Rhizoma Alismatis is an important herbal medicine to treat phlegm turbidities, which is used in many Chinese herbal medicine prescriptions in the clinical studies for treating hyperlipidemia to reduce phlegm turbidity.

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11. Zhou, Xuan, et al. “Alisol A 24-acetate isolated from the Alismatis Rhizoma improves hepatic lipid deposition in hyperlipidemic mice by ABCA1/ABCG1 pathway.” Journal of Nanoscience and Nanotechnology 19.9 (2019): 5496-5502.
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