Gaboroquinones A and B and 4′-O-demethylknipholone-4′-O-β-D-glucopyranoside, phenylanthraquinones from the roots of Bulbine frutescens - Abegaz, B M; Bezabih, M; Msuta, T; Brun, R; Menche, D; Mühlbacher, J; Bringmann, G (J Nat Prod, 2002)