Indole alkoloids from Nauclea officinalis with weak antimalarial activity

Five indole alkaloids (naucleofficines A-E) were isolated from the stems (with bark) of Nauclea officinalis: (E)-2-(1-beta-D-glucopyranosyloxybut-2-en-2-yl)-3-(hydroxymethyl)-6,7-dihydro-indolo[2,3-a]quinolizin-4(12H)-one (1), (E)-1-propenyl-12-beta-D-glueopyranosyloxy-2,7,8 -trihydro-indolo[2,3-a]pyran [3,4-g]quinolizin-4,5 (13H)-dione (2), (E)-2-(1-hydroxybut-2-en-2-yl)-11-beta-D-glucopyranosyloxy-6,7-dihydro-indolo[2,3-a]quinolizin-4(12H)-one (3), (E)-1-propenyl-4-hydroxy-2,4a, 7,8,1 3b, 14,14a-hepthydro-(4 alpha,4a beta, 13b alpha, 14a beta)indolo [2, 3a]pyran[3,4-g]quinolizin-5(13H)-one(4)and1-(1-hydroxyethyl)-10-hydroxy-7,8-dihydro-indolo[2,3-a]pirydine[3,4-g]quinolizin-5(13H)one (10-hydroxyangustoline) (5), together with two known compounds, naucleidinal (6) and angustoline (7). All of the structures of the seven compounds above were elucidated by spectroscopic methods including use of 1D- and 2 D-NMR spectroscopic analyses. Compounds 2 and 3 are rare examples of monoterpene indole alkaloids with a glucopyranosyloxy group attached to position C-12. In vitro activity screening of the above seven compounds showed weak to moderate inhibitory activity against Plasmodium falciparum. (C) 2008 Elsevier Ltd. All rights reserved.