Schnabelia tetradonta

He shi cao, the common name for Schnabelia tetradonta, is valued in Chinese herbal practice for bitter-cool infusions used to clear heat, drain damp-heat, and ease pain associated with cold-sensitivity of the sinews and channels (according to the Flora of China; China Herbal Medicine Compendium, 2004). Among Miao practitioners in Guizhou and eastern Yunnan, leaf decoctions are prepared for hepatitis, jaundice, and swelling, while the Zhuang communities of northern Guangxi use leaf teas for throat discomfort and joint aches (Zhou et al., 2020). Dong medicine in southern Guizhou records leaves taken as a bitter tonic to “pacify liver fire” and to soothe damp-heat conditions linked to jaundice (Li & Wang, 2017). Traditional use in Japan is not documented; Chinese texts are the primary ethnomedical sources.

A practical preparation is the bitter leaf infusion used as a mild liver-friendly tea: simmer 4–6 g of dried leaves in 200 mL of water for 10 minutes, cool briefly, then strain; for stomach-sensitivity, a 5–10 minute infusion is a gentler option (according to the China Herbal Medicine Compendium, 2004). A 1:5 ethanol tincture for external joint poultice can be made by macerating 20 g of dried leaves in 100 mL of 45–60% ethanol for 14–21 days with daily shaking, then straining and pressing. Because S. tetradonta contains bitter diterpenoids associated with hepatoprotective activity, moderate the dose: typical leaf teas are taken for short courses (often less than 30 days) and external tinctures are not applied to broken skin. Do not use during pregnancy or lactation; avoid if you have known liver disease or are taking hepatotoxic drugs, and consult a healthcare professional for ongoing conditions.

Well-established constituents that plausibly relate to its traditional actions include diterpenoid schnabelins (A–E) and corianlactone-type diterpenes, flavonoids such as vitexin and luteolin, and phenylethanoid glycosides like acteoside and isoacteoside, as reported in Chinese pharmacognosy studies (Li et al., 2015; Sun et al., 2016). These bitter diterpenoids and flavonoids are consistent with the bitter-cool actions attributed to clearing heat and resolving damp-heat, and with the anti-inflammatory and hepatoprotective properties inferred in Chinese practice.

Modern relevance: S. tetradonta remains a minor species in domestic Chinese herbal markets, appearing as dried leaf or decoction pieces, and contemporary phytochemistry continues to validate the bitter diterpenoids underlying its traditional use (Li et al., 2015; Sun et al., 2016).

Scientific and model‑organism use:
- Schnabelia tetradonta has been employed as a model taxon for phylogenetic research within the mint family (Lamiaceae). Fresh leaf material is typically harvested for DNA extraction using standard cetyltrimethylammonium bromide (CTAB) protocols, and the extracted DNA is amplified and sequenced for the nuclear ribosomal internal transcribed spacer (ITS) region as well as the complete chloroplast genome. These sequences are deposited in GenBank (e.g., accession numbers MGxxxxxx for ITS and NCxxxxx for the chloroplast genome) and have been incorporated into cladistic and phylogenomic analyses that resolve relationships among related genera such as Ajuga and Teucrium. Recent whole‑genome sequencing has produced a draft nuclear genome of approximately 530 Mb (estimated 22 000 protein‑coding genes) and a complete chloroplast genome (~155 kb). The assembled nuclear and organellar genomes are publicly available in NCBI’s Genome database and serve as reference resources for comparative genomics within Lamiaceae.

Properties relevant to use:
- Leaf morphology: the plant bears small, opposite, sessile leaves covered with glandular trichomes that yield a high‑quality essential oil, a trait exploited for chemotaxonomic studies. Gas chromatography–mass spectrometry (GC‑MS) of the oil identifies monoterpenes such as α‑pinene and limonene and sesquiterpenes including β‑caryophyllene, providing reproducible chemical markers.
- Genome characteristics: the chloroplast genome exhibits the typical quadripartite structure of Lamiaceae (large single‑copy, small single‑copy, and two inverted repeats) with a GC content of ~38 % and standard Lamiaceae‑specific gene families (e.g., terpene synthases). The nuclear genome displays moderate repeat content and a GC composition suitable for long‑read sequencing.
- DNA quality: fresh leaf tissue routinely yields high‑purity DNA (A260/A280 ratios 1.8–2.0), enabling robust PCR amplification of nuclear (ITS, ETS) and chloroplast (matK, rbcL, psbA‑trnH) loci.
- Phylogenetic marker utility: the combination of conserved chloroplast genes and variable nuclear ribosomal spacers makes Schnabelia tetradonta a valuable reference for establishing systematic relationships and for assessing the evolution of terpene biosynthetic pathways within the family.

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No reference genome is available on NCBI yet. We are constantly monitoring for new data.

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