Di Yu

Anticoagulant and antiplatelet medications: Di Yu has demonstrated hemostatic (blood-clotting) effects in pharmacological studies, including shortening bleeding time and promoting platelet aggregation via its tannin content. This may theoretically oppose the effects of anticoagulants (e.g. warfarin, heparin) and antiplatelet drugs (e.g. aspirin, clopidogrel). If a patient is on such medications, the concurrent use of Di Yu should be discussed with their prescribing physician.

Iron supplements and iron-containing preparations: The high tannin content of Di Yu (approximately 17%) can form insoluble complexes with iron and other metal ions, potentially reducing the absorption of iron supplements. These should be taken at different times.

Alkaloid-containing medications: Tannins may also bind to and precipitate alkaloid compounds, potentially reducing the bioavailability of alkaloid-based pharmaceuticals if taken concurrently.

Hepatotoxic drugs: Although Di Yu itself is not considered toxic, in situations where large amounts of tannins may be absorbed (particularly via large-area topical burn application), there is a theoretical concern about additive hepatic burden when combined with other hepatotoxic drugs.

Sanguisorba officinalis L. (Great Burnet) is a clump-forming, rhizomatous herbaceous perennial of the Rosaceae (rose) family. It typically grows 30 to 100 cm tall, with erect, slender stems that are sometimes tinged reddish and are sparsely branched toward the top. The leaves are mostly basal, odd-pinnately compound with 7 to 25 leaflets. Each leaflet is ovate to oblong, 1.5 to 3 cm long, with serrated margins, a rounded to heart-shaped base, and a medium green colour.

The flowers appear from June to September in dense, terminal, shortly cylindrical spikes 1 to 2.5 cm long. Individual flowers are small with four dark maroon to purple-red sepals (petals are absent) and four stamens with thickened filaments. The plant grows naturally in wet meadows, moist grasslands, hillside pastures, marshes, stream banks, and forest margins across the temperate regions of Europe, northern Asia, and parts of North America. The medicinal root and rhizome are thick, woody, and irregularly spindle-shaped, with a dark greyish-brown exterior and a pink to pale yellow interior.

Di Yu was first recorded in the Shen Nong Ben Cao Jing (circa Han Dynasty), classified in the middle grade of medicinals. Its name literally means "earth elm" because, as Tao Hongjing (陶弘景) of the Southern Dynasties explained, its leaves resemble elm leaves and the plant initially spreads along the ground (初生布地). He also noted its flower-heads are dark purplish-black, resembling fermented soybeans (豉), hence its alternative name Yu Chi (玉豉, "jade soybeans"). Li Shizhen in the Ben Cao Gang Mu cited an alchemical text that called it Suan Zhe (酸赭, "sour ochre"), noting its sour taste and reddish-brown colour.

A particularly important clinical insight attributed to Li Shizhen is the differential use of different parts of the root: the upper section (shang jie) is charred for stopping bleeding, while the root tip (shao) is used raw for moving Blood. This distinction between the hemostatic and the Blood-moving properties of different root sections became a well-known teaching point in later Materia Medica literature. The herb also has a long history in burn treatment, reflected in the folk saying "家有地榆皮，不怕烫伤皮" ("If your home has Di Yu bark, you need not fear scalded skin"). The Latin genus name Sanguisorba itself reflects the herb's hemostatic reputation, deriving from Latin sanguis (blood) and sorbeo (to soak up).

Over the centuries, understanding of Di Yu evolved from its early broad indications (wounds, sweating, vaginal discharge) to a more focused role as a cooler of Blood Heat in the lower body, particularly for intestinal bleeding, bloody dysentery, hemorrhoidal bleeding, and burns. Modern clinical practice has further expanded its use to include ulcerative colitis, eczema, and as an adjunct in chemotherapy-induced leukopenia (via Di Yu Sheng Bai Pian).