Bioassay-guided isolation, identification of compounds from Origanum rotundifolium and investigation of their antiproliferative and antioxidant activities.

CONTEXT: Origanum (Lamiaceae) has been used in food and pharmaceutical industries. OBJECTIVE: Isolation and identification of bioactive compounds from Origanum rotundifolium Boiss. and investigation of their antiproliferative and antioxidant activities. MATERIALS AND METHODS: The aerial part of O. rotundifolium was dried and powdered (1.0 kg ±2.0 g) then extracted with hexane, ethyl acetate, methanol and water. Solvent (3 × 1 L) was used for each extraction for a week at room temperature. The aqueous extract was partitioned with ethyl acetate (3 × 1 L) to yield the water/EtOAc extract subjected to chromatography to isolate the active compounds. The structures of isolated compounds were elucidated by 1 D, 2 D NMR and LC-TOF/MS. RESULTS: Apigenin (1), ferulic acid (2), vitexin (3), caprolactam (4), rosmarinic acid (5), and globoidnan A (6) were isolated and identified. Globoidnan A (6), vitexin (3), and rosmarinic acid (5) revealed the excellent DPPH• scavenging effect with IC50 values of 22.4, 31.4, 47.2 µM, respectively. Vitexin (3) (IC50 3.6), globoidnan A (6) (IC50 4.6), apigenin (1) (IC50 8.9) and ferulic acid (2) exhibited more ABTS•+ activity than standard Trolox (IC50 13.8 µg/mL). Vitexin (3) revealed the most antiproliferative activity against HeLa, HT29, C6 and Vero cells lines with IC50 values of 35.6, 32.5, 41.6, 46.7 (µM), respectively. DISCUSSION AND CONCLUSION: Globoidnan A (6) has the most antioxidant effects on all assays. This has to do with the chemical structure of the compound bearing the acidic protons. Vitexin (3) could be a promising anticancer agent.