Premna: A Plant That Makes "Tofu" and Also Sets Bones, Stops Pain and Bleeding

There is a plant whose leaves are rich in nutrients and pectin and can be made into a tofu-like food, making it very popular among common people. Its botanical name is Premna microphylla (doufu chai). As the name suggests, it is a shrub like firewood, and the leaves of this "firewood" can be made into tofu.

The tofu made from Premna leaves is also called immortal tofu (shenxian doufu). It is a traditional snack in areas such as Xichuan (Henan), Jiangxi, Guilin (Guangxi), Hunan, Guizhou, Lu'an (Anhui), and Shaanxi. Immortal tofu closely resembles ordinary tofu, except that its color is a natural green; it has a slippery texture and a cool, refreshing taste—astringent with a hint of sweetness and a long aftertaste.

Premna microphylla belongs to the Verbenaceae family and is widely distributed across northern, southern, central, and southwestern China. Besides making tofu, folk medicine uses it to treat traumatic injuries, rheumatic bone pain, and unexplained swellings and toxins. Premna microphylla has many subspecies and many aliases.

One type called banjiu zhan is the root or stem of Premna puberula (whose leaves smell like underarm odor, hence the name) and Premna fulva, both Verbenaceae. In Guizhou it is also called immortal tofu bush; in Guangxi it is called die-da wang (traumatism king) or zhan gu (battle bone)—a name that already indicates it is an excellent herb for treating traumatic injuries in Guangxi and elsewhere. Folk medicine uses its stems, leaves, and roots to treat rheumatic arthritis, impotence, and menstrual irregularity. The leaves of banjiu zhan can also treat edema, in which case they are made into tofu and eaten. Its leaves also treat unexplained toxic sores, taken internally or pounded into a paste for external application; crushed leaves applied externally also treat burns and scalds. In some places banjiu zhan is also called banjiu tree.

Another, called da chou huangjing, is the root and leaf of Premna subcordata (Verbenaceae), also aliased as banjiu ye. It clears heat and resolves toxicity, activates blood and stops pain; it is used mainly for dysentery, welling abscesses and sores, scrofula, dysmenorrhea, hernia, and traumatic bleeding. It may be decocted for internal use, soaked in wine, or crushed fresh for external application. Taken as a decoction, the dose is 5–30g. For external use the dose is not fixed; it is pounded and applied to welling abscesses, sores, or scrofula. Folk medicine also uses da chou huangjing for women's dysmenorrhea: as recorded in Wanxian Traditional Chinese Medicine, 15g of da chou huangjing root and 6g of fennel, stir-fried with vinegar and soaked in wine, taken internally, treats dysmenorrhea.

In the Simao region of Yunnan there is a local medicinal herb called bone-setting tree, the root or stem bark of Premna straminipes, also aliased as lei wutong. According to Yunnan Chinese Herbal Medicine, Premna straminipes sets bones, stops bleeding, and relieves pain; it is used for traumatic injuries, bone fractures, external bleeding, and rheumatic bone pain. It may be decocted internally at 15–30g, soaked in medicinal wine, or crushed fresh and applied to the affected area.

In the Mengzi region of Yunnan there is also a herb called jin-gu-san (bone-strengthening powder, also called jie-gu-san), the root of nettle-leaved Premna or Premna mengziensis (Verbenaceae). It expels wind-dampness, activates blood and unblocks the vessels, relieves pain, and stops bleeding. It is used for wind-cold-damp bi, soreness of the sinews and bones, stomach pain with vomiting of blood, vasculitis, and lower back pain.

The various Premna species from different regions differ slightly but belong to different varieties of the same plant. Besides those mentioned above, other varieties may exist in some places. Premna grows in mountainous areas at different altitudes and varies in height; plants growing in sunny spots differ slightly from those in shade. However, the main medicinal actions of this plant do not differ greatly.

Premna is a medicinal and edible plant with very few side effects. Extracts of Premna root act on non-specific immunity in vivo by enhancing macrophage phagocytosis, inhibiting PGE2 production, and reducing swelling of inflamed tissue; they also promote T-lymphocyte proliferation to exert specific immune effects, thereby producing an anti-inflammatory action. Stem extracts also have marked anti-inflammatory, analgesic, and microcirculation-improving effects, and protect the sciatic nerve and soft-tissue injury. These effects may be related to its flavonoid compounds. Compound Premna Liniment is a Chinese patent medicine made from Premna that reduces swelling, relieves pain, fights inflammation, and enhances immunity. Jiangu Injection is also a Premna preparation used to treat common orthopedic diseases such as hypertrophic spondylitis, rheumatoid arthritis, and frozen shoulder.

The author recently met a family member of a patient from Hunan, who reported having traced folk cases in some part of Hunan where Premna was used to treat liver cancer, effectively prolonging patients' lives and improving their quality of life. However, research data on Premna for cancer is scarce. Still, given its hemostatic and analgesic effects, it is believed that Premna may have adjunctive therapeutic value in various tumors.