Gaboroquinones A and B and 4‘-O-Demethylknipholone-4‘-O-β-d-glucopyranoside, Phenylanthraquinones from the Roots of Bulbine frutescens

• Published in: Journal of natural products (Washington, D.C.) Vol. 65; no. 8; pp. 1117 - 1121
• Main Authors: ABEGAZ, Berhanu M., BEZABIH, Merhatibeb, MSUTA, Thomas, BRUN, Reto, MENCHE, Dirk, MüHLBACHER, Jörg, BRINGMANN, Gerhard
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2002; Glendale, AZ American Society of Pharmacognosy
• Subjects: Animals; Anthraquinones - chemistry; Anthraquinones - isolation & purification; Anthraquinones - pharmacology; Antimalarials - chemistry; Antimalarials - isolation & purification; Antimalarials - pharmacology; Biological and medical sciences; Botswana; Circular Dichroism; General pharmacology; Glucosides - chemistry; Glucosides - isolation & purification; Glucosides - pharmacology; Medical sciences; Molecular Conformation; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Plant Roots - chemistry; Plants, Medicinal - chemistry; Plasmodium falciparum - drug effects; Trypanocidal Agents - chemistry; Trypanocidal Agents - isolation & purification; Trypanocidal Agents - pharmacology; Trypanosoma - drug effects; Botswana; Africa; Antimalarial; Monocotyledones; Medicinal plant; Antiprotozoal agent; Plasmodium falciparum; Polyphenol; Folk medicine; Angiospermae; Parasiticid; Glycoside; Kinetoplastida; Protozoa; Apicomplexa; Anthraquinone derivatives; Aldose; Root; Pharmacognosy; Quinone; Glucoside; Tricyclic compound; Condensed benzenic compound; In vitro; Biological activity; Trypanosoma cruzi; Liliaceae; Ketophenols; Trypanosoma rhodesiense; Absolute configuration; Plant origin; Benzenic compound; Isolation; Spermatophyta; Structural analysis
• ISSN: 0163-3864; 1520-6025
• DOI: 10.1021/np0201218

The novel phenylanthraquinones 4'-O-demethylknipholone-4'-O-beta-D-glucopyranoside (2) and gaboroquinones A (3) and B (4) were isolated from the African medicinal plant Bulbine frutescens. Biaryl 2 represents the first phenylanthraquinone glucoside, while 3 and 4 are the first side-chain-hydroxylated phenylanthraquinones. Their constitutions were determined by spectroscopic analysis, in particular by HMBC, HMQC, and ROESY NMR investigations, and by chemical transformations. The axial configurations were elucidated chemically, by deglucosylation of 2 and by side-chain deoxygenation of 3 and 4 to give the known phenylanthraquinones 4'-O-demethylknipholone (5), isoknipholone (6), and knipholone (1), respectively, and chiroptically, by CD investigations. Compounds 2, 3, and 4 showed moderate to good antiplasmodial and antitrypanosomal activities in vitro.