Narciindole A, the first representative of Amaryllidaceae alkaloids with an indol-3-ylmethanone framework, was isolated from bulbs of Narcissus pseudonarcissus (L.) cv. Carlton, together with carltonine D and carltonine E, which share the same unusual structural motif as dimeric carltonine C (reported in 2020), exhibiting atropisomerism. Unambiguous structure elucidations have been achieved by NMR spectroscopy, HRMS, and comparison with literature data of related alkaloids. Furthermore, the chirality of known alkaloids with a galanthindole biaryl core was revised using optical rotation. Last, but not least, a biosynthetic pathway for dimeric carltonine-type alkaloids was proposed. Unfortunately, in terms of biological activity, the isolated alkaloids showed only moderate inhibition of human acetylcholinesterase and/or butyrylcholinesterase.

ADINACO Research Group Department of Pharmacognosy and Pharmaceutical Botany Faculty of Pharmacy Charles University Heyrovskeho 1203 500 05 Hradec Kralove Czech Republic

ADINACO Research Group Department of Pharmacognosy and Pharmaceutical Botany Faculty of Pharmacy Charles University Heyrovskeho 1203 500 05 Hradec Kralove Czech Republic; Institute of Pharmaceutical Sciences University of Graz Beethovenstraße 8 8010 Graz Austria

Department of Bioorganic and Organic Chemistry Faculty of Pharmacy Charles University Heyrovskeho 1203 500 05 Hradec Kralove Czech Republic

Institute of Pharmaceutical Sciences University of Graz Beethovenstraße 8 8010 Graz Austria

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Carltonine-derived compounds for targeted butyrylcholinesterase inhibition