Isolation and structural elucidation of coumarins from Micromelum falcatum (Rutaceae)
Micromelum falcatum Tanaka (Rutaceae) is a small tree growing in Southeastern Asia  showing protective and therapeutic effects against cold and rheumatoid arthritis according to the traditional medicine of China . The leaves of the plant, collected in Cambodia, after drying and pulverization (20gr) were extracted successively with CH2Cl2 (200ml x 3), MeOH (200ml x 3) and H2O (200ml x 3). In parallel, a protocol using NH3 and extraction (150gr) with EtOAc and MeOH was followed for focused isolation of alkaloids . All the resulted extracts were evaluated qualitatively using a novel HPLC-DAD method. The analytical profiling revealed the presence of coumarins as the major class of constituents in both CH2Cl2 and EtOAc extracts before and after the alkalization. The HPLC-DAD method was transferred to semi-preparative scale and was used for the isolation of the detected coumarins. Nine known and two new coumarins, microfalcrin (1) and microcoumaririn (2) were isolated. Three among them, micromarin A, B and C were isolated for the first time from Micromelum falcatum. The identification of the isolated compounds was performed by HRMS and NMR (1 &2D) spectroscopy.
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