New thymol derivatives and cytotoxic constituents from the root of Eupatorium cannabinum ssp. asiaticum

Two new thymol (=5-methyl-2-(1-methylethyl)phenol) derivatives, 8,10-didehydro-9-(3-methylbutanoyl)thymol 3-O-tiglate (1) and 9-O-angeloyl-8-methoxythymol 3-O-isobutyrate (2), were isolated from the root of Eupatorium cannabinum ssp. asiaticum, together with six known compounds, 3-8. The structures of 1 and 2 were determined through extensive 1D/2D-NMR and MS analyses. Among the isolates, 9-acetoxy-8,10-epoxythymol 3-O-tiglate (3) was the most cytotoxic, with IC50 values of 0.02±0.01, 1.02±0.07, and 1.36±0.12 μg/ml, respectively, against DLD-1, CCRF-CEM, and HL-60 cell lines. In addition, 10-acetoxy-9-O-angeloyl-8-hydroxythymol (4) and eupatobenzofuran (6) exhibited cytotoxicities, with IC50 values of 1.14±0.16 and 2.63±0.22, and 7.63±0.94 and 2.31±0.14 μg/ml, respectively, against DLD-1 and CCRF-CEM cell lines.