Diterpene Alkaloids from the Roots of Aconitum moldavicum and Assessment of Na_v 1.2 Sodium Channel Activity of Aconitum Alkaloids

Abstract

A new aconitane alkaloid, 1-O-demethylswatinine (1), was isolated from the root of Aconitum moldavicum together with the known compounds cammaconine (2), columbianine (3), swatinine (4), gigactonine (5), delcosine (6), lycoctonine (7), and ajacine (8). The structures were established by means of HRESIMS, 1D and 2D NMR spectroscopy, including ¹H-¹H COSY, NOESY, HSQC, and HMBC experiments, resulting in complete ¹H-NMR chemical shift assignments for 1–4. The effects of the isolated compounds 4–8, together with eighteen other Aconitum diterpene and norditerpene alkaloids with different skeletal types and substitution patterns, were studied on Na_v 1.2 channels by the whole-cell patch clamp technique, using the QPatch-16 automated patch clamp system. Pyroaconitine, ajacine, septentriodine, and delectinine demonstrated significant Na_v 1.2 channel inhibition (57–42 %) at 10 µM concentration; several other compounds (acovulparine, acotoxicine, hetisinone, 14-benzoylaconine-8-O-palmitate, aconitine, and lycoctonine) exerted moderate inhibitory activity (30–22 %), while the rest of the tested alkaloids were considered to be inactive. On the basis of these results and by exhaustive comparison of data of previously published computerized QSAR studies on diterpene alkaloids, certain conclusions on the structure-activity relationships of Aconitum alkaloids concerning Na_v 1.2 channel inhibitory activity are proposed.

Key words

Aconitum moldavicum - Ranunculaceae - aconitine - norditerpene alkaloids - Na_v 1.2 sodium channel inhibitory activity

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