Diverse biological effects of the ajwain oil from Iranian Trachyspermum ammi

Trachyspermum ammi (Apiaceae) is a plant with a good reputation in the traditional Persian and Ajurvedic medicine. The hydrodistilled essential oil from the fruits of T. ammi, known as ‘ajwain oil’, is used in countries like Iraq, Iran, Afghanistan, Pakistan, and India in the preparation of curry, to flavor several foods, as preservative, and in perfumery. At therapeutic level, ajwain oil is employed in the treatment of gastrointestinal ailments, lack of appetite and bronchial problems. In the present work, the essential oil of T. ammi growing in Iran was analysed by GC-FID and GC-MS showing thymol (67.4%), p-cymene (17.9%) and γ-terpinene (11.3%) as the major constituents. Afterwards, we investigated the biological effects displayed by ajwain oil, namely the antimicrobial and antioxidant activity, the cytotoxicity on tumor cells, and the induction of lymphocyte proliferation. In addition, the inhibition on nicotinate mononucleotide adenylyltransferase (NadD), which is a promising new target for developing novel antibiotics, was evaluated. The antimicrobial effects of ajwain oil, measured by the agar disc diffusion method, were relevant, with inhibition zones higher than those of reference antibiotics, especially on S. aureus and C. albicans (34.7 and 54.3 mm, respectively). This effect was not due to the enzymatic inhibition on NadD. The ajwain oil exhibited a considerable dose-dependent inhibition on the ABTS radical cation, with an IC50 value of 22.4 µg/mL. MTT assay revealed that ajwain oil is particularly cytotoxic on colon carcinoma cells, with a IC50 value of 9.6 µg/mL. Finally, PBMC proliferation assay revealed some role for the ajwain oil within the network of interactions of the cells of the immune system.