Sweet Flag

Multiple long-term animal studies confirm β-asarone, the dominant compound in Acorus calamus (up to 80.6% of rhizome essential oil), causes intestinal tumors and organ damage with chronic exposure. Reviews (Sharma et al. 2020, Middha et al. 2026) and ex vivo/in vivo studies (Parashar et al. 2026) document dose-dependent toxicity, including complete mortality at higher oral doses in mice. A 2025 Ames test (Anantha Narayana & Mukne) found no mutagenicity under acute conditions, but long-term carcinogenicity remains established. The herb is banned or restricted in food in the US and other countries due to this risk.

In vitro, Acorus calamus essential oil (dominated by β-asarone at 80.6%) showed bactericidal activity against Gram-positive, Gram-negative bacteria and fungi, with Micrococcus luteus most susceptible at MBC 0.032 mg/mL (Joshi 2016). Leaf extracts also demonstrated antibacterial zones against Pseudomonas aeruginosa and Staphylococcus aureus exceeding standard antibiotics in vitro (Haran et al. 2024).

In a rodent model of depression, Vacha administration prevented stress-induced behavioral deficits in ambulation and rearing, demonstrating antidepressant effects through a mechanism distinct from typical 5-HT1A receptor sensitization (Tripathi & Singh 2010). A 2020 review confirmed antidepressant properties among the documented neurological effects of Acorus calamus in preclinical models.

In an animal Maximal Electro Shock seizure model, both raw and traditionally processed (Shodhana) Vacha rhizomes significantly decreased the duration of the tonic extensor phase, with the processed form showing additional reductions in convulsion and stupor phases (Bhat et al. 2012). A comprehensive 2020 review corroborated anticonvulsant activity as a well-documented effect of the herb in preclinical literature.

β-Asarone exhibited vasorelaxation in isolated rat mesenteric arteries at concentrations of 1-30 μg/mL through modulation of L-type voltage-dependent calcium channels (Parashar et al. 2026). A 2020 review also listed antihypertensive effects among the pharmacological properties documented in preclinical studies. However, dose-dependent toxicity limits translational potential.

In a rat model, oral Vacha benzene extract (ED50 of 10 mg) administered for 4 weeks significantly prevented stress-induced reductions in total and differential leukocyte counts, immunoglobulin content, and bone marrow cellularity (p < 0.001), while also preventing structural involution of lymphoid organs (Sarjan et al. 2017).

Two comprehensive reviews (Sharma et al. 2020; Middha et al. 2026) document neuroprotective effects of Acorus calamus active compounds through modulation of Nrf-2, NF-κB, PI3K/AKT, and Ras/MAPK signaling pathways in preclinical models, reducing oxidative stress associated with neurological dysfunction. Evidence remains limited to animal and in vitro studies with no direct human clinical trials on cognition.

In vitro studies demonstrated that Acorus calamus leaf extract exhibited significant free radical scavenging activity comparable to ascorbic acid in DPPH and hydrogen peroxide assays, with dose-dependent ferric ion reduction in the FRAP assay (Haran et al. 2024). A 2020 review also noted antioxidative properties among the documented pharmacological effects.