Valorization of six Nepeta species by assessing the antioxidant potential, phytochemical composition and bioactivity of their extracts in cell cultures

Six Nepeta spp. (N. cataria, N. racemosa, N. sibirica, N. nuda, N. melissifolia, and N. grandifiora) were evaluated for their bioactivities and phytochemical composition. The herbs were extracted with acetone, methanol and water; and the antioxidant capacity was determined using several in vitro assays. The content of total phenolics in the extracts was up to 669.0 mg/g, while their recovery from dry plant material was up to 241.2 mg/g of gallic acid equivalents. Among 29 identified compounds, the chlorogenic, ferulic and rosmarinic acids were the most abundant constituents. The cytotoxicity and cellular antioxidant activity was tested in Caco-2 cells. The selected extracts with highest antioxidant capacity were evaluated for their antiproliferative activity in human colon carcinoma HT29 cells. Only N. melissifolia extract showed cytotoxicity after 48 h of incubation at > 6.98 mg/mL. The best antiproliferative activity after 24/48 h of incubation demonstrated the extract of N. nude with the ED50 of 7.5 and 2.75 mg/mL, respectively.