Ya Zhi Cao
StarCommelina communis L.
Traditionally used for
- Nose & throat
- Cough & breathing
- Colds & fever
- Digestion
- Urinary & fluids
- Mood & calm
- Skin
Cautions & contraindications
- Diabetes
☯ TCM Properties
Cools Heat, drains Fire and slightly resolves toxicity and cools the Blood; Clears Heat, facilitates urination and unblocks painful urinary dysfunction
Traditional Chinese Uses
Ya Zhi Cao (Herba Commelinae, the aerial parts of Commelina communis, the common dayflower) is a sweet, bland, cold heat-clearing herb entering the Lung, Stomach and Small Intestine (and Bladder) channels. It clears Heat and drains Fire while resolving toxicity, and is used for the high fever, thirst, and irritability of warm-febrile disease, for Wind-Heat colds, and for hot, swollen, painful sore throat, where fresh material or expressed juice is favored.
Because it is bland and draining, it also promotes urination and unblocks painful, hot, dribbling urinary dysfunction (lin syndrome) and relieves edema, especially damp-heat patterns. It slightly cools the Blood as well, aiding hot swollen sores and carbuncles, which the pounded fresh herb can dress externally. Typical dose is 15-30 g dried, or 30-60 g fresh. Its cold, draining nature is used cautiously in Spleen-Stomach cold-deficiency.
Western Herbalism Properties
Relationships
Full-screen graph →Click a node for details · double-click to expand it · Ctrl/⌘ + scroll or two fingers to zoom and pan.
Botanical Description
Ya Zhi Cao is the dried aerial parts of Commelina communis L. (Commelinaceae), the common dayflower, an annual herb of moist disturbed ground throughout China, Korea, Japan, and now widely naturalized in temperate regions. Stems are decumbent and rooting at lower nodes, 20 to 60 cm long, bearing alternate lanceolate to ovate-lanceolate sheathing leaves. The distinctive flowers, enclosed in folded spathe-like bracts, open for a single morning and have two showy upper bright blue petals and one inconspicuous lower white petal, the source of a natural blue dye historically used in Japanese woodblock printing. In traditional Chinese medicine the herb is sweet, slightly bitter, and cold, entering the Lung, Stomach, and Small Intestine channels; it clears heat, resolves toxicity, and promotes urination, and is used for febrile illness with thirst, sore throat, edema with painful urination, carbuncles, and snakebite.
Active Constituents
1-Deoxynojirimycin (DNJ)
Piperidine iminosugar alkaloidConcentration: a content limit of not less than 0.056 percent of the dried herb has been proposed on the basis of a 57-batch UPLC survey covering 23 Chinese provinces and regions; total alkaloid content fell in the order North China, Northeast, Northwest, East, Southwest, Central, South China
The best-characterised constituent and the compound proposed as the quality marker for this drug. It is a potent alpha-glucosidase inhibitor, the same enzymatic target as acarbose and miglitol, isolated from the herb by bioassay-directed fractionation. It is the pharmacological basis for the traditional use of the plant in diabetes and the reason the herb has real potential to interact with glucose-lowering therapy.
2,5-Dihydroxymethyl-3,4-dihydroxypyrrolidine (DMDP)
Pyrrolidine iminosugar alkaloidIsolated together with the piperidine iminosugars from a methanolic extract that showed potent alpha-glucosidase inhibition. Contributes to the same carbohydrate-digestion-blocking effect.
alpha-Homonojirimycin
Piperidine iminosugar alkaloidBoth an alpha-glucosidase inhibitor and the single compound shown to carry the herb's antiviral effect: purified alpha-homonojirimycin from Commelina communis was protective against influenza virus infection in mice, which locates the activity of the crude total alkaloid fraction in a defined molecule.
7-O-beta-D-Glucopyranosyl-alpha-homonojirimycin
Iminosugar glycosideGlucosylated congener isolated in the same alpha-glucosidase-directed fractionation. Reported here for completeness; no separate pharmacology has been established for it.
1-Deoxymannojirimycin
Piperidine iminosugar alkaloidConcentration: quantified routinely alongside DNJ in the multi-province UPLC survey of the herb
Iminosugar of the mannose series, quantified as one of the four alkaloid quality indicators for the herb along with DNJ, norharman and harman.
Norharman and harman
beta-Carboline alkaloidsConcentration: quantified as two of the four alkaloid markers in the 57-batch UPLC survey, with content varying markedly by geographical origin
These are the constituents that give the herb a plausible central pharmacology rather than a purely metabolic one, and they are the basis of the theoretical monoamine oxidase caution recorded below. They are present at low levels relative to the iminosugars.
Flavone C-glycosides (orientin, isoorientin, vitexin, isovitexin)
Flavone C-glycosidesThe characteristic flavonoid class of the aerial parts and the likely contributors to the antioxidant activity attributed to the genus. No dose-defining activity has been established for them in this species.
Commelinin (a malonylawobanin and flavocommelin magnesium complex)
MetalloanthocyaninThe blue pigment of the flower and a classic of plant colour chemistry, but of no known medicinal relevance. Listed because it is what makes the plant recognisable in the field and hence a useful identity check on the crude drug.
⚠ Drug Interactions
Acarbose, miglitol and voglibose (alpha-glucosidase inhibitors)
This is a same-target overlap, not a speculative one. Bioassay-directed fractionation of Commelina communis isolated five compounds acting on alpha-glucosidase: DMDP, 1-deoxymannojirimycin, 1-deoxynojirimycin, alpha-homonojirimycin and its 7-O-glucoside. DNJ is the same iminosugar pharmacophore that acarbose and miglitol exploit. A herb dose therefore adds to the prescribed inhibitor at the same enzyme, and the classic dose-limiting adverse effects of that class are additive.
Clinical note: Expect the gastrointestinal effects of the prescribed inhibitor to worsen. Introduce the herb at the low end of the dose range and warn the patient before they attribute the symptoms to the drug and stop it.
Insulin, sulfonylureas and glinides
The herb's iminosugar alkaloids blunt the postprandial glucose rise by inhibiting alpha-glucosidase, and the plant's traditional use for diabetes is explicitly attributed to them. Where the patient is on a drug that supplies insulin independently of the meal, flattening the glucose curve shifts the balance toward hypoglycaemia. No human pharmacodynamic study of the herb with these drugs was found, so the size of the effect is not quantified.
Clinical note: Advise capillary glucose monitoring for at least two weeks after starting or changing the dose. Note that hypoglycaemia occurring while an alpha-glucosidase inhibitor is on board should be treated with glucose, not sucrose, since disaccharide breakdown is what is being inhibited.
Monoamine oxidase inhibitors and serotonergic drugs (SSRIs, SNRIs, triptans, tramadol)
Norharman and harman have been quantified in Commelina communis as two of its four marker alkaloids. These beta-carbolines are known reversible inhibitors of monoamine oxidase A. Their concentration in the crude herb is low relative to the iminosugars, no pharmacokinetic study of them from this herb exists, and no clinical case of a monoaminergic reaction attributed to Ya Zhi Cao was found. This entry exists so a practitioner meeting an unexplained serotonergic presentation has the constituent on record, not because a reaction should be expected.
Clinical note: No action needed for ordinary use. In a patient on an irreversible MAOI, prefer another heat-clearing diuretic herb, on the general principle of not adding an unquantified MAO-active constituent to that background.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 15–30 g | Daily | — | — | 中国药典 2020 monograph 【鸭跖草】【用法与用量】15～30g。外用适量。 【性味与归经】甘、淡，寒。归肺、胃、小肠经。 — Matched to ChP by romanised drug name (pinyin 'Ya Zhi Cao' → 鸭跖草); the romanisation is unique across all 649 ChP monographs, and the match was cross-checked against this record's own TCM temperature. Quoted verbatim. |
Evidence Tier
Moderate evidence · 4 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
0
In vitro / animal
4
4 verified · 0 unverified
Show 4 studies
- α-Glucosidase Inhibitors fromCommelina communis
- Protective effect of homonojirimycin from Commelina communis (dayflower) on influenza virus infection in mice
- Anti-influenza-virus activity of total alkaloids from Commelina communis L.
- Effect of total alkaloids from Commelina communis L. on lung damage by influenza virus infection
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
α-Glucosidase Inhibitors fromCommelina communis
The source study for this herb's antidiabetic pharmacology. A methanolic extract of Commelina communis showed potent alpha-glucosidase inhibition, and bioassay-directed fractionation isolated one pyrrolidine alkaloid, DMDP, and four piperidine alkaloids: 1-deoxymannojirimycin, 1-deoxynojirimycin, alpha-homonojirimycin and 7-O-beta-D-glucopyranosyl-alpha-homonojirimycin. All five were identified from this species for the first time, supporting the traditional use of the plant in diabetes.
Protective effect of homonojirimycin from Commelina communis (dayflower) on influenza virus infection in mice
Narrows the herb's antiviral effect to a single compound. Purified homonojirimycin from Commelina communis was protective against influenza virus infection in mice, which means the activity of the crude total alkaloid fraction is attributable to a defined iminosugar rather than to an uncharacterised mixture.
Anti-influenza-virus activity of total alkaloids from Commelina communis L.
Total alkaloids from Commelina communis showed anti-influenza-virus activity, establishing the alkaloid fraction rather than the flavonoids or the anthocyanin as the antiviral fraction of the herb.
Effect of total alkaloids from Commelina communis L. on lung damage by influenza virus infection
Follow-up from the same group examining the effect of the total alkaloid fraction on lung damage caused by influenza virus infection, extending the finding from viral activity to host tissue injury.
⚠ Safety & Contraindications
- Diabetes
Contraindications
Its use is cautious in patients with deficiency or weakness of the spleen and stomach. And if use, the dosage should be decreased.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 37–43.
Historical Texts
Ben Cao Shi Yi (Gleanings from the Materia Medica), Chen Cangqi
Tang dynasty, circa 739 CEReferences
- Dagne A, Yihunie W, Nibret G, Tegegne BA. The genus Commelina: Focus on distribution, morphology, traditional medicinal uses, phytochemistry, and Ethno-pharmacological activities: An updated literature review . Heliyon (2024) [DOI]
- Fu BR, Zhuo WJ, Huang XX, Lu PC, He X, Ji RF. [Quality evaluation of Commelina communis medicinal materials from different origins based on content of four alkaloid components combined with chemometrics]. . Zhongguo Zhong Yao Za Zhi (China Journal of Chinese Materia Medica) (2025) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
📝 Notes
Public notes from the community and your own private notes on Ya Zhi Cao.
No notes yet.