Antimalarial bioassay-guided fractionation of an EtOH extract of the root wood of Cryptocarya rigidifolia (Lauraceae) led to the isolation of the five new 5,6-dihydro-α-pyrones cryptorigidifoliols A-E (1-5) and the six bicyclic tetrahydro-α-pyrone derivatives cryptorigidifoliols F-K (6-11). The structure elucidations of all compounds were made on the basis of the interpretation of spectroscopic data and chemical derivatization, and the relative and absolute configurations were determined by NOESY, electronic circular dichroism (ECD), and (1)H NMR analysis of α-methoxyphenylacetyl (MPA) derivatives. The bicyclic tetrahydro-α-pyrone derivatives were identified as products of acid-catalyzed intramolecular Michael addition of the 5,6-dihydro-α-pyrones in the presence of silica gel.
View Article and Find Full Text PDFTen new neolignans including the 6'-oxo-8.1'-lignans cymosalignans A (1a), B (2), and C (3), an 8.O.
View Article and Find Full Text PDFPlant natural products have historically been very important to drug discovery and development, particularly in the anticancer field. This is illustrated by a discussion of the structures and activities of camptothecin and its analogues, paclitaxel (Taxol), the vinca alkaloids vinblastine and vincristine, and podophyllotoxin and its analogues. A description of the isolation of one new and three known cardenolides from the Madagascar plant Pentopetia androsaemifolia is then provided as an example of this approach to drug discovery.
View Article and Find Full Text PDFInvestigation of a Malagasy endemic plant identified as Symphonia pauciflora Baker (Clusiaceae) for antiproliferative activities against the A2780 ovarian cancer cell line led to the isolation of a new compound identified as 2-(3,3-dimethylallyl)-7-methoxy-l,5,6-trihydroxy-2",2"-dimethylpyrano(6",5":3,4) xanthone (1) and the two known guttiferones A (2) and I (3). The structure elucidation of 1 was based on the analysis of its 1D and 2D NMR and mass spectral data. Compound 1 showed good antiproliferative activity with an IC50 value of 3.
View Article and Find Full Text PDFFractionation of an antiplasmodial ethanolic extract from the aerial parts of Vitex cauliflora led to the isolation of the new labdane diterpene 1 together with the known triterpene uvaol. The structure of the new compound 1 was established as 3-oxo,15,17,18-triacetoxy-labda-7,13E-diene on the basis of spectroscopic data (1D and 2D NMR, MS).
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