Browsing by Author "Fayez, Shaimaa"

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    Ancistrobrevinium A, the first N-methylated, cationic naphthylisoquinoline alkaloid, from the tropical liana Ancistrocladus abbreviatus (Ancistrocladaceae)
    (Taylor and Francis Ltd., 2023-03-29T00:00:00) Tajuddeen, Nasir; Fayez, Shaimaa; Kushwaha, Prem Prakash; Feineis, Doris; Ak� Assi, Laurent; Kumar, Shashank; Bringmann, Gerhard
    Ancistrobrevinium A (1) is the first N-methylated and non-hydrogenated, and thus cationic naphthylisoquinoline alkaloid. It was discovered in the root bark extract of the phytochemically productive West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Its constitution was elucidated by HR-ESI-MS and 1D and 2D NMR. Due to the steric hindrance in the proximity of the linkage between the naphthalene and isoquinoline parts, the biaryl axis is rotationally hindered. It thus constitutes a stable element of chirality�the only one in the new alkaloid since, different from most other naphthylisoquinoline alkaloids, it has no stereogenic centers. The axial configuration of 1 was assigned by electronic circular dichroism (ECD) investigations, which gave a positive couplet, indicating a �positive chirality�, here corresponding to a P-configuration. Ancistrobrevinium A (1) showed a weak cytotoxic activity against A549 lung cancer cells (IC50 = 50.6 ?M). � 2023 Informa UK Limited, trading as Taylor & Francis Group.
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    Naphthylisoindolinone alkaloids: the first ring-contracted naphthylisoquinolines, from the tropical liana Ancistrocladus abbreviatus, with cytotoxic activity
    (Royal Society of Chemistry, 2022-10-12T00:00:00) Fayez, Shaimaa; Bruhn, Torsten; Feineis, Doris; Assi, Laurent Ak�; Kushwaha, Prem Prakash; Kumar, Shashank; Bringmann, Gerhard
    The West African liana Ancistrocladus abbreviatus is a rich source of structurally most diverse naphthylisoquinoline alkaloids. From its roots, a series of four novel representatives, named ancistrobrevolines A-D (14-17) have now been isolated, displaying an unprecedented heterocyclic ring system, where the usual isoquinoline entity is replaced by a ring-contracted isoindolinone part. Their constitutions were elucidated by 1D and 2D NMR and HR-ESI-MS. The absolute configurations at the chiral axis and at the stereogenic center were assigned by using experimental and computational electronic circular dichroism (ECD) investigations and a ruthenium-mediated oxidative degradation, respectively. For the biosynthetic origin of the isoindolinones from �normal� naphthyltetrahydroisoquinolines, a hypothetic pathway is presented. It involves oxidative decarboxylation steps leading to a ring contraction by a benzilic acid rearrangement. Ancistrobrevolines A (14) and B (15) were found to display moderate cytotoxic effects (up to 72%) against MCF-7 breast and A549 lung cancer cells and to reduce the formation of spheroids (mammospheres) in the breast cancer cell line. � 2022 The Royal Society of Chemistry.