Rare ellagic acid sulphate derivatives from the rhizome of Geum rivale L.-structure, cytotoxicity, and validated HPLC-PDA assay

Abstract

Two rare sulphate ellagic acid derivatives were isolated from the rhizome of Geum rivale L. in three simple steps. Their structures were identified by comprehensive NMR studies (1H NMR, 13C NMR, 1H-1H COSY, HMBC, HSQC) as 3, 3'-dimethoxy-4-sulphoxyellagic acid potassium salt (1) and 3, 3', 4'-trimethoxy-4-sulphoxyellagic acid potassium salt (2). Subsequently, a new precise (RSD < 2.6%), accurate (recoveries in the range of 96.5-98.7%), and sensitive (LODs in the range of 0.15-0.16 μg/mL) HPLC-PDA procedure was developed for the simultaneous quantification of compounds 1 and 2 in plant material. The rhizome of G. rivale proved to be a good source of both compounds, with the content of 2.94 ± 0.03 and 5.45 ± 0.03 mg/g dw respectively, whereas at most, trace amounts were detected in related plant materials (aerial parts of G. rivale, rhizome and aerial parts of G. urbanum). The cytotoxicity of isolated compounds tested on human leukaemia (promyelocytic HL-60 and lymphoblastic NALM-6) and melanoma (WM 115) cell lines with IC50 values in the range of 306.4-473.8 μM was demonstrated to be lower than that of ellagic acid (IC50 = 62.3-300.6 μM).