Three new indole alkaloids (1-3), named grandilodines A-C, and five known ones were obtained from the Malayan Kopsia grandifolia. The structures were established using NMR and MS analyses and, in the case of 1 and 2, were confirmed by X-ray diffraction analyses. Alkaloids 1, 3, and lapidilectine B (8) were found to reverse multidrug resistance in vincristine-resistant KB cells.
Three new Lycopodium alkaloids comprising two lycodine-type alkaloids (1, 2) and one fawcettimine alkaloid (3), in addition to 16 known alkaloids, were isolated from Lycopodium platyrhizoma. The structures of these alkaloids were elucidated based on analysis of their NMR and MS data. Lycoplatyrine A (1) represents an unusual lycodine-piperidine adduct. The structures and absolute configurations of lycoplanine D (hydroxy-des- N-methyl-α-obscurine, 10) and lycogladine H (11) were confirmed by X-ray diffraction analysis.
A methanol extract of the stem bark of the Malayan Alstonia penangiana provided seven new bisindole alkaloids, comprising six macroline-sarpagine alkaloids (angustilongines E-K, 1-6) and one macroline-pleiocarpamine bisindole alkaloid (angustilongine L, 7). Analysis of the spectroscopic data (NMR and MS) of these compounds led to the proposed structures of these alkaloids. The macroline-sarpagine alkaloids (1-6) showed in vitro growth inhibitory activity against a panel of human cancer cell lines, inclusive of KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, HT-29, HCT 116, and A549 cells (IC50 values: 0.02-9.0 μM).
The stem of Stephanotis floribunda afforded a new cyclic pentapeptide stephanotic acid (1), possessing a novel 6-(leucin-3'-yl) tryptophan skeleton. The structure of 1 was assigned on the basis of extensive NMR experiments and a chemical reaction and shown to be closely related to the bicyclic octapeptide moroidin (3), a toxin from Laportea moroides.
Two new resveratrol tetramers, hopeaphenol A (1) and isohopeaphenol A (2), along with the known vaticaphenol A (3), were isolated from the stem bark of Vatica oblongifolia ssp. oblongifolia through bioassay-guided fractionation. The structures and their relative stereochemistry were determined by spectroscopic techniques. Compounds 1 and 3 demonstrated moderate activity against methicillin-resistant Staphylococcus aureus and Mycobacterium smegmatis.
A new dichlorinated pulvinic acid derivative, methyl-3',5'-dichloro-4,4'-di-O-methylatromentate, was isolated from the fruiting body of a Scleroderma sp. The structure was determined using spectroscopic methods, and an X-ray analysis was carried out for confirmation of the structure. Compound was found to display moderate antimicrobial activity against Bacillus subtilis.