Ban Lan Gen (Woad Root or Isatis Root)

Chinese Herb Actions

Chinese Herb Dosage

• What is the typical dosage of Ban Lan Gen?

  Roughly 15–30 g in decoction, a notably larger range than many herbs, reflecting its cold, heat-clearing nature and common use during febrile/epidemic illness. It is also widely sold as a prepared granule or powder (“Banlangen” preparations) for home use in China, taken at manufacturer-directed doses rather than raw decoction.

  Source: Sacred Lotus sources & references; cross-referenced against multiple online sources and standard materia medica ranges. Reference only — not a prescription.

Chinese Herb Contraindications & Cautions

• Are there cautions for Ban Lan Gen?

  Ban Lan Gen is not appropriate for patients without heat-toxin (“fire toxin”) signs, or for those with a weak constitution, since its bitter, cold nature can injure Spleen/Stomach yang and provoke digestive upset (loose stools, poor appetite, cold sensations) if used inappropriately or for too long, particularly in patients who are already cold or deficient.

  • Not for patients without fire-toxin/heat signs — using a strongly cold, toxin-clearing herb without a heat pattern present is traditionally discouraged.
  • Weak constitution / Spleen-Stomach deficiency — caution with prolonged use, given the bitter-cold nature.

  Source: Sacred Lotus sources & references; cross-referenced against multiple online sources and materia medica consensus. Traditional-use framing; not medical advice.

Herb-Drug Interactions

• No well-established clinical herb–drug interactions are documented for Ban Lan Gen. Given its widespread over-the-counter use in China for cold/flu-type symptoms, general caution about combining it with other cold/antiviral medications (to avoid redundant or additive effects) is a reasonable precaution rather than a demonstrated interaction. (Flagged for practitioner confirmation.)

Western / Biomedical Research

Chinese Herb Clinical Studies & Research

Provided as research context — a summary of published biomedical study, not a therapeutic or medical claim.

• Is there modern research on Ban Lan Gen (Isatis indigotica root)?

  Yes — a substantial body of laboratory and computational research supports antiviral and anti-inflammatory activity, but we could not verify large, high-quality human clinical trials specific to the root for common cold or influenza. Isatis indigotica root contains alkaloids, organic acids, flavonoids, lignans, and other compounds under active study.

  • Anti-influenza compound (in vitro) — clemastanin B, a lignan isolated from the root, inhibited multiple human (H1N1, H3N2, influenza B) and avian (H6N2, H7N3, H9N2) influenza strains in cell culture, acting early in the viral replication cycle without readily inducing resistance. Laboratory research, not a clinical trial.
  • SARS-CoV-2 main-protease inhibition (computational) — molecular docking/dynamics studies identified root polyphenols (sinigrin, hesperetin) as potential inhibitors of the SARS-CoV-2 main protease, comparable in modeled stability to reference antivirals. Computational prediction only, not laboratory or clinical proof.
  • Broad pharmacology review — a 2021 review summarizes antiviral, antibacterial, immunoregulatory, anti-inflammatory, and cholagogic (bile-promoting) effects across Isatis indigotica’s leaves and roots, and traditional clinical use for influenza, mumps (parotitis), and viral hepatitis, while noting most supporting data are preclinical.

  Overall, Ban Lan Gen has one of the deepest laboratory antiviral-research profiles among common Chinese herbs, but the leap from cell-culture/computational findings to proven clinical benefit in humans has not been established in what we could verify — treat the traditional throat/heat-toxin use as the primary basis for use, with research as supporting context.

  Sources: PMID 23403777 (International Journal of Molecular Medicine, 2013 — clemastanin B anti-influenza, in vitro); PMID 33292085 (Journal of Biomolecular Structure and Dynamics, 2022 — SARS-CoV-2 protease docking, computational); PMID 33779758 (Journal of Pharmacy and Pharmacology, 2021 — phytochemistry/pharmacology review). Research context, not a therapeutic claim.

Chinese Herb Notes

• What is the difference between Ban Lan Gen, Da Qing Ye, and Qing Dai?

  All three come from the same or closely related Isatis/woad plants and are commonly confused, but they are three distinct parts/preparations with different traditional emphases.

  • Ban Lan Gen (Radix Isatidis) — the root; emphasized for clearing heat-toxin and benefiting the throat.
  • Da Qing Ye (Folium Isatidis / Folium Daqingye) — the leaf of the same plant; traditionally considered stronger for cooling the blood and treating blood-heat rashes/macules, with less emphasis on the throat.
  • Qing Dai (Indigo Naturalis) — a processed indigo pigment/powder extracted from the leaves of Isatis and related indigo-yielding plants (e.g. Baphicacanthus/Strobilanthes cusia); used topically and internally for heat-toxin, blood-heat, and certain skin/liver-fire patterns, and is a distinct pharmaceutical preparation rather than a raw plant part.

  Because English common names (“woad,” “Isatis”) and pinyin are easy to conflate across these three, always check whether a source is referring to the root, the leaf, or the processed indigo powder before comparing dosage or indications.

  Source: Sacred Lotus sources & references; cross-referenced against multiple online sources and materia medica consensus on Isatis-derived herbs.