Benefits
Cough support studied with a standardized herbal combination
The main human cough evidence comes from a fixed oral solution that pairs vasaka leaf with echinacea and eleuthero. In two randomized trials in adults with respiratory infections, this combination eased cough, doing better than placebo in one trial and better than a standard cough medicine in the other. Because it is a three-herb product, the effect cannot be credited to vasaka on its own.
Expectorant and mucus-thinning activity of its alkaloids
In animal tests the alkaloids vasicine and vasicinone increased watery airway secretions, the action behind vasaka's traditional use for loosening chest mucus. The widely used mucus-thinning medicines bromhexine and ambroxol were developed from vasicine. These are laboratory and animal findings, not outcomes measured in people taking the herb.
Bronchodilator activity seen in laboratory airway models
In guinea-pig airways the alkaloids vasicine, vasicinone and deoxyvasicine delayed chemically triggered airway tightening, partly comparable to a standard airway medicine at the highest dose tested. This work used alkaloids from a related plant source rather than vasaka itself, and the effect has not been measured in human breathing.
Oral leaf extract evaluated in a 14-day clinical study
In an open-label study in adults with mild COVID-19, a vasaka leaf extract taken for 14 days was followed by recovery in all participants, shifts in several blood markers, and no reported adverse effects. The study had no placebo group, so the changes cannot be attributed to the extract, and it did not test cough or breathing.
Mechanism of action
Vasicine and vasicinone, the characteristic alkaloids
Vasaka leaf contains the quinazoline alkaloids vasicine (also called peganine) and vasicinone. Vasicine is the chemical parent of the mucolytic medicines bromhexine and ambroxol, which is why the herb is linked with thinning and clearing airway mucus.
Expectorant and bronchodilator actions in the airway (lab and animal)
In animal airway studies these alkaloids raised the volume of watery airway secretions and relaxed bronchial smooth muscle, delaying chemically induced airway tightening. This is the proposed basis of the traditional expectorant and anti-cough reputation; the same actions have not been confirmed in people.
Cough-suppressing activity in animal cough models
In mouse and guinea-pig models where cough was triggered by irritant chemicals, the alkaloids lowered cough frequency and lengthened the time before coughing started, approaching a reference cough medicine at the highest dose. These are animal data only.
Clinical trials
Randomized, double-blind, placebo-controlled, parallel-group trial comparing a fixed oral solution of Justicia adhatoda leaf, Echinacea purpurea root and Eleutherococcus senticosus root (KanJang, 30 mL/day standardized to vasicine) with placebo and with the drug bromhexine over 5 days (Barth et al. 2015, Phytomedicine).
177 adults aged 18 to 65 with uncomplicated upper respiratory infection (common cold).
Both the herbal combination and bromhexine relieved cough more than placebo, measured as the change in cough frequency. On the third and fourth days the combination group improved somewhat faster than the bromhexine or placebo groups, and tolerability was good. Because the product also contains echinacea and eleuthero, the result cannot be attributed to vasaka alone.
Randomized trial of the same fixed combination (KanJang) of Echinacea purpurea, Adhatoda vasica and Eleutherococcus senticosus, compared double-blind with an echinacea-plus-eleuthero mixture and open-label with the drug bromhexine, in acute respiratory infection (Narimanian et al. 2005, Phytomedicine).
Adults with non-complicated acute respiratory tract infection.
Cough severity and frequency, mucus clearance, nasal congestion and general feeling of sickness improved more with the full combination than with the standard treatment, and recovery was about two days shorter than with the standard treatment. No adverse reactions were reported. As a multi-herb product, the trial does not isolate vasaka's contribution.
Randomized, open-label, three-armed study of oral herbal extracts for 14 days: Adhatoda vasica 500 mg, Tinospora cordifolia 500 mg, or both at 250 mg each; primary outcomes were symptoms, vital signs and viral clearance (Verma et al. 2023, Eur J Med Res).
150 adults aged 19 to 65 with no-to-mild COVID-19 enrolled; 136 completed.
All participants in the three arms recovered and none reported adverse effects from the herbs. The combined Adhatoda-plus-Tinospora arm cleared the virus a little sooner than either herb alone, and several blood markers shifted in the Adhatoda group. With no placebo arm and an open-label design, the changes cannot be attributed to the extract, and cough was not the focus.
Laboratory and animal study of the quinazoline alkaloids vasicine, deoxyvasicine and vasicinone (isolated here from Peganum harmala, the same alkaloids that occur in vasaka), tested for antitussive, expectorant and bronchodilating activity (Liu et al. 2015, Phytomedicine). No human participants.
Mouse and guinea-pig cough, airway-secretion and bronchoconstriction models; oral doses of 5, 15 and 45 mg/kg.
The alkaloids cut cough frequency and lengthened cough latency, approaching codeine at the highest dose; increased airway mucus secretion in a phenol-red test; and prolonged the time to chemically induced airway tightening in guinea pigs. These are animal findings with isolated alkaloids, not a test of vasaka in people.
Early clinical trial of Adhatoda vasica (vasa) syrup in patients with non-ulcer dyspepsia (amlapitta), an Ayurvedic hyperacidity complaint; uncontrolled (Chaturvedi et al. 1983, Anc Sci Life).
Patients with non-ulcer dyspepsia and hyperacidity.
The syrup was reported to lower total and free stomach acid in people with hyperacidity, with results the authors called hopeful. This is the main stand-alone human report on the leaf, but it is small, decades old, uncontrolled, and about digestion rather than breathing.