1. Zulu Medicinal Plants: An Inventory; University of Natal Press, Pietermaritzburg, 1996, p. 137.
2. Gaboroquinones A and B and 4‘-O-Demethylknipholone-4‘-O-β-d-glucopyranoside, Phenylanthraquinones from the Roots of Bulbine frutescens
3. The first 6′-O-sulfated phenylanthraquinones: isolation from Bulbine frutescens, structural elucidation, enantiomeric purity, and partial synthesis
4. The absolute axial configurations of knipholone and knipholone anthrone by TDDFT and DFT/MRCI CD calculations: a revision
5. Isoknipholone obtained in this work occurred as a 85:15 (P/M) enantiomeric mixture (Supporting Information, Figure S1) in comparison to a sample previously isolated from the same plant (52:48, P/M).[3] The absolute configuration of isoknipholone anthrone had as yet not been established, which is, in part, due to the fact that the parent isoknipholone available was a nearly racemic mixture (52:48, P/M).[3] Thus, reduction of the now available P-enriched sample of isoknipholone (85:15, P/M) to isoknipholone anthrone allowed establishment of the absolute configuration by HPLC-CD analysis on a chiral phase, revealing isoknipholone anthrone to be P-configured (Supporting Information, Figure S2).