The ability of low levels of elevated ozone to change the growth and phytochemical constituents of a medicinal plant Andrographis paniculata (Burm. f.) Nees.

Ground-level ozone (O) is well recognized as a secondary air pollutant with detrimental effects on plant growth and biochemistry. In a field study, Andrographis paniculata (King of Bitter) was exposed to ambient O and elevated O (AO + 20 ppb) at three growth stages [45, 90, and 135 days after treatment, (DAT)] using open-top chambers. Elevated O stress negatively impacted plant growth, increased cell damage, and induced foliar injuries. However, elevated O also boosted antioxidant production such as proline, phenol, and enzymatic antioxidants, as well as certain secondary metabolites such as tannins, phytosterols, saponins, and alkaloids. This may enhance the plant's medicinal properties, including compounds limonene dioxide, phytol, palmitic acid, and androstadiene. While, certain metabolites like Citronellol, Khusenol, and tocopherol displayed an adverse reaction under elevated O exposure. The novel detection of acrodiene, squalene, and neophytadiene under O stress emphasizes their medicinal significance. Notably, an important bioactive compound andrographolide in A. paniculata showed increased synthesis under elevated O at 45 and 90 DAT, suggesting that O exposure could enhance the plant's pharmaceutical value.