Gan Chan, also known as Toad or Boiled Shrimp Toad, is mentioned in the book "Ming Yi Bie Lu". It refers to the dried whole body of the Chinese common toad (Bufo bufo gargarizans Cantor) or the black-spotted toad (Bufo melanostictus Schneider) from the family Bufonidae. It is captured during the summer and autumn seasons. After capture, the toad's toad oil is scraped off, and then it is scalded to death with boiling water before being dried.
[Processing Method] 1. Gan Chan in "Xiao Er Yao Zheng Zhi Jue": "Remove the four legs and intestines, and wash them." Currently, the original medicinal material is taken, impurities and ashes are removed, and the head and claws are cut into small pieces.
2. Gan Chan in "Shu Ben Cao": "The diagram says to take it when it is sun-dried or fire-dried." "Wei Sheng Bao Jian": "Sun-dried, charred." "Ben Cao Gang Mu": "Nowadays, people all dry it in the wind, and yellow mud is used to cure it. It is baked and preserved for its therapeutic properties." Currently, sand is placed in a pot, heated with strong fire, and then clean dried toad pieces are added and stir-fried until they turn slightly dark yellow and start to foam. The sand is then sifted out and the mixture is left to cool.
[Characteristics of the Herbal Pieces] Gan Chan is irregularly shaped or in the form of slices. The surface is grayish-green or greenish-brown, with warts, and the inner surface is grayish-yellow, with visible bones and membranes. It has a slight fishy smell and a spicy taste. Processed Gan Chan has a charred yellow surface, a pale yellow interior, and bubble-like protrusions, with a spotted pattern. It is light and brittle. It has a slight fishy smell and a slight burnt odor.
[Processing Effects] Gan Chan is spicy, cool, and toxic. It enters the liver, spleen, and lung meridians. It has the functions of breaking up masses and promoting urination, detoxifying and killing parasites, and relieving pain. Fresh Gan Chan is mostly used externally for conditions such as sores, boils, and swollen lymph nodes, such as Toad Ointment (from "Sheng Ji Zong Lu"). Stir-frying with sand makes the texture loose, and the active ingredients are easily extracted during decoction. It also helps to improve the smell and taste, making it easier to take. It is used for pediatric malnutrition, yin ulcers, swollen feet, and malignant sores.
[Processing Research] In the Jin Dynasty, there was a method called "burning with ash" ("Zhou Hou Bei Ji Fang"). In the Song Dynasty, there were methods such as burning with ash, making it with wine and Ophiopogon, scorching, and grinding into juice ("Zheng Lei Ben Cao"). There were also methods such as making it into a paste ("Xiao Er Wei Sheng Zong Wei Lun Fang"), calcining with charcoal, making it with wine and honey, and making it with Coptis chinensis ("Tai Ping Sheng Hui Fang"), and making it with vinegar ("Chen Shi Xiao Er Bing Yuan Fang Lun"). In the Yuan Dynasty, there was a method called "charred" ("Wei Sheng Bao Jian"). In the Ming Dynasty, there were methods such as making it with croton and ginger ("Pu Ji Fang"), making it with vinegar ("Qi Xiao Liang Fang"), simmering ("Ben Cao Meng Quan"), making it with milk ("Lu Fu Jin Fang"), and pounding it into a paste ("Jing Yue Quan Shu"). In the Qing Dynasty, there was a method called "stir-frying with charcoal" ("Yi Zong Jin Jian"), and so on. Currently, there are more than 10 commonly used processing methods for Gan Chan.
The main active component in toad skin is Bufogenins, which are toxic. Studies have shown that when toad skin is scalded in hot water for a few minutes and then dried at 50-80°C, and then ground into fine powder, the content of Bufogenins in the toad skin changes. The content is slightly higher than that of fresh toad skin, indicating that Bufogenins are not destroyed during the scalding process and that it is possible for toxic components in the toad skin to hydrolyze into Bufogenins.
