While the Prescriptions is the earliest Chinese record devoted to diseases treated with drugs, the Shennong Herbal is the earliest record on Chinese drugs. This herbal, compiled about two thousand years ago, records 365 drugs, describing their sources, properties and uses as well as many cases of their incompatibilities. The drugs are divided according to properties into three categories: superior (120 drugs), medium (120 drugs) and inferior (125 drugs). Superior drugs are those considered at that time to be nontoxic, which could be safely taken in large amounts for extended periods; they are what we now know as tonics. Medium drugs are those that could be toxic or nontoxic, depending on usage. Inferior drugs are toxic, and are used for treating diseases and should not be used for extended periods.

Superior drugs include such well-known ones as ginseng, licorice, gandihuang (root of Rehmannia glutinosa Libosch.), huangqi (root of Astragalus spp.), huanglian (rhizome of Coptis spp.), wuweizi [fruit of Schisandra chinensis (Turcz.) Baill.], sesame seed, magnolia flower, lingzhi (Ganoderma spp.), fuling or poria [sclerotium of Poria cocos (Schw.) Wolf], Chinese date (fruit of Ziziphus jujuba Mill.), Job's tears [seed of Coix lacryma-jobi L. var. mayuen (Roman.) Stapf] and duzhong (bark of Eucommia ulmoides Oliv.).

 

Medium drugs include ginger, mahuang or ephedra herb (Ephedra spp.), danggui [root of Angelica sinensis (Oliv.) Diels], jixuecao or gotu kola [Centella asiatica (L.) Urb.], kuandonghua or coltsfoot flower (flower of Tussilaqo farfara L.), yinyanghuo (herb of Epimedium spp.), haizao (Sargassum spp.), hehuan (bark of Albizzia julibrissin Durazz.), gaoben, and zhuling or polyporus [sclerotium of Polyporus umbellatus (Pers.) Fries].

 

Inferior drugs include fuzi and wutou, which are lateral and main root respectively of aconite (Aconitum carmichaeli Debx.), rhubarb root (root and rhizome of Rheum spp.), baitouweng [root of Pulsatilla chinensis (Bge.) Regel], lianqiao or forsythia fruit [Forsythia suspensa (Thunb.) Vahl], qinghao, croton seed (fruit of Croton tiglium L.), guanzhong (rhizome of Dryopteris crassirhizoma Nakai and other ferns), and langdangzi or henbane seed (Hyoscyamus niger L.).

 

Many of the drugs in the Shennong Herbal are still being used today including all the ones listed above. Some of these uses have not changed after more than two thousand years and their rationale can be scientifically justified. For example, the use of haizao (Sargassum spp.) in the treatment of swelling of the neck (goiter) can be explained by its high content of iodine; the use of guanzhong (Dryopteris) in the treatment of intestinal worms certainly has its counterpart in the West, so does the use of langdangzi (henbane seed) as a muscle relaxant.