RESUMO
CONTEXT: The search for newer compounds against pathogenic species continues unabated due to drug resistance. Traditionally, Tagetes erecta Linn. (Compositae) has been used for the treatment of various parasitic and microbial diseases. OBJECTIVE: To evaluate the antioxidant activity of the ethanol extract of Tagetes erecta roots and its cytotoxicity against prostate and HeLa cancer cell lines followed by activity-guided isolation. MATERIALS AND METHODS: The antioxidant screening was carried out using diphenylpicrylhydrazyl (DPPH) radical scavenging assay with serial concentrations ranging from 2 to 100 µg/mL, and cytotoxicity was evaluated against prostate (PC-3) and HeLa cell lines using microculture tetrazolium test (MTT) assay with concentrations ranging from 500 to 1.89 µg/mL. Isolation of the ethanol extract was carried out using column chromatography whereby 21 isolates were obtained (T1-T21), and the most active isolate was subjected for characterization using ultraviolet (UV), infrared (IR), nuclear magnetic resonance (NMR), and mass spectroscopic techniques. RESULTS: The ethanol extract scavenged DPPH free radicals thereby exhibiting antioxidant activity with an IC50 of 35.9 µg/mL. In addition, the extract conferred noticeable cytotoxicity against the HeLa (LD50 of 164.28 µg/mL) and PC-3 cell lines (LD50 of 407.3 µg/mL). Among all the isolates, T3 showed antioxidant activity with IC50 of 11.56 µg/mL and cytotoxicity with LD50 of 12.5 µg/mL against HeLa and 30.25 µg/mL against PC-3 cell lines and was characterized as 2-ethynyl-5-(thiophen-2-yl) thiophene. DISCUSSION: The new thienyl compound (T3) exhibited profound antioxidant activity and cytotoxicity at relatively lower concentrations than the extract. CONCLUSION: The observations provide support for the ethnobotanical use of the plant.