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From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P-configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells.

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Other bioactive products U 1300Joziknipholones A and B: The First Dimeric Phenylanthraquinones, from the Roots of Bulbine frutescens. -The absolute stereostructures of the title dimers (I) are unambiguously established by application of an improved method for the reductive cleavage into the monomeric phenylanthraquinone and phenylanthrone units. Joziknipholone A possess the P-configuration at both axes of these units, whereas in joziknipholone B the anthrone unit is P-configurated and the anthraquinone unit is M-configurated. Both compounds exhibit good antimalarial activities and low antitumoral activities. -(BRINGMANN*, G.; MUTANYATTA-COMAR, J.; MAKSIMENKA, K.; WANJOHI, J. M.; HEYDENREICH, M.; BRUN, R.; MUELLER, W. E. G.; PETER, M. G.; MIDIWO, J. O.; YENESEW, A.; Chem. Eur.

Two novel compounds, alienusolin, a 4α-deoxyphorbol ester (1), crotonimide C, a glutarimide alkaloid derivative (2), and ten known compounds, julocrotine (3), crotepoxide (4), monodeacetyl crotepoxide (5), dideacetylcrotepoxide, (6), β-senepoxide (7), α-senepoxide (8), (+)-(2S,3R-diacetoxy-1-benzoyloxymethylenecyclohex-4,6-diene (9), benzyl benzoate (10), acetyl aleuritolic (11), and 24-ethylcholesta-4,22-dien-3-one (12) were isolated from the Kenyan Croton alienus. The structures of the compounds were determined using NMR, GCMS, and HRESIMS studies.