Antiprotozoal activity of Buxus sempervirens and activity-guided isolation of O-tigloylcyclovirobuxeine-B as the main constituent active against Plasmodium falciparum.
Buxus sempervirens L. (European Box, Buxaceae) has been used in ethnomedicine to treat malaria. In the course of our screening of plant extracts for antiprotozoal activity, a CH2Cl2 extract from leaves of B. sempervirens showed selective in vitro activity against Plasmodium falciparum (IC50 = 2.79 vs. 20.2 µg/mL for cytotoxicity against L6 rat cells). Separation of the extract by acid/base extraction into a basic and a neutral non-polar fraction led to a much more active and even more selective fraction with alkaloids while the fraction of non-polar neutral constituents was markedly less active than the crude extract. Thus, the activity of the crude extract could clearly be attributed to alkaloid constituents. Identification of the main triterpene-alkaloids and characterization of the complex pattern of this alkaloid fraction was performed by UHPLC/+ESI-QTOF-MS analyses. ESI-MS/MS target-guided larger scale preparative separation of the alkaloid fraction was performed by 'spiral coil-countercurrent chromatography'. From the most active subfraction, the cycloartane alkaloid O-tigloylcyclovirobuxeine-B was isolated and evaluated for antiplasmodial activity which yielded an IC50 of 0.455 µg/mL (cytotoxicity against L6 rat cells: IC50 = 9.38 µg/mL). O-tigloylcyclovirobuxeine-B is thus most significantly responsible for the high potency of the crude extract.
Institut für Pharmazeutische Biologie und Phytochemie (IPBP), University of Münster, Pharma Campus, Corrensstraße 48, D-48149 Münster, Germany. julia.althaus@uni-muenster.de.
Julia B
JB
Althaus
Institut für Lebensmittelchemie, Technische Universität Braunschweig, Schleinitzstraße 20, D-38106 Braunschweig, Germany. g.jerz@tu-bs.de.
Gerold
G
Jerz
Institut für Lebensmittelchemie, Technische Universität Braunschweig, Schleinitzstraße 20, D-38106 Braunschweig, Germany. p.winterhalter@tu-bs.de.
Peter
P
Winterhalter
Swiss Tropical and Public Health Institute (Swiss TPH), Socinstraße 57, CH-4002 Basel, Switzerland. Marcel.Kaiser@unibas.ch.
Marcel
M
Kaiser
Swiss Tropical and Public Health Institute (Swiss TPH), Socinstraße 57, CH-4002 Basel, Switzerland. Reto.Brun@unibas.ch.
Reto
R
Brun
Institut für Pharmazeutische Biologie und Phytochemie (IPBP), University of Münster, Pharma Campus, Corrensstraße 48, D-48149 Münster, Germany. thomschm@uni-muenster.de.
Thomas J
TJ
Schmidt
D000470:Alkaloids / Q000008:administration & dosage* / Q000737:chemistry; D000818:Animals; D000981:Antiprotozoal Agents / Q000008:administration & dosage* / Q000737:chemistry; D031235:Buxus / Q000737:chemistry; D006801:Humans; D008288:Malaria / Q000188:drug therapy* / Q000469:parasitology; D021261:Parasitic Sensitivity Tests; D010936:Plant Extracts / Q000008:administration & dosage* / Q000737:chemistry; D010963:Plasmodium falciparum / Q000187:drug effects; D051381:Rats; D053719:Tandem Mass Spectrometry; D014315:Triterpenes / Q000737:chemistry*
D000470:Alkaloids; D000981:Antiprotozoal Agents; C000593603:O-tigloylcyclovirobuxeine-B; D010936:Plant Extracts; D014315:Triterpenes