Inhibiting Activities of the Secondary Metabolites of Phlomis brunneogaleata against Parasitic Protozoa and Plasmodial Enoyl-ACP Reductase, a Crucial Enzyme in Fatty Acid Biosynthesis.

Kirmizibekmez H, Calis I, Perozzo R, Brun R, Donmez AA, Linden A, Ruedi P, Tasdemir D.

Department of Pharmacognosy, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey.

Anti-plasmodial activity-guided fractionation of Phlomis brunneogaleata (Lamiaceae) led to the isolation of two new metabolites, the iridoid glycoside, brunneogaleatoside and a new pyrrolidinium derivative (2 S,4 R)-2-carboxy-4-( E)- p-coumaroyloxy-1,1-dimethylpyrrolidinium inner salt [(2 S,4 R)-1,1-dimethyl-4-( E)- p-coumaroyloxyproline inner salt]. Moreover, a known iridoid glycoside, ipolamiide, six known phenylethanoid glycosides, verbascoside, isoverbascoside, forsythoside B, echinacoside, glucopyranosyl-(1-->G (i)-6)-martynoside and integrifolioside B, two flavone glycosides, luteolin 7- O-beta- D-glucopyranoside ( 10) and chrysoeriol 7- O-beta- D-glucopyranoside ( 11), a lignan glycoside liriodendrin, an acetophenone glycoside 4-hydroxyacetophenone 4- O-(6'- O-beta- D-apiofuranosyl)-beta- D-glucopyranoside and three caffeic acid esters, chlorogenic acid, 3- O-caffeoylquinic acid methyl ester and 5- O-caffeoylshikimic acid were isolated. The structures of the pure compounds were elucidated by means of spectroscopic methods (UV, IR, MS, 1D and 2D NMR, [alpha] (D)) and X-ray crystallography. Compounds 10 and 11 were determined to be the major anti-malarial principles of the crude extract (IC (50) values of 2.4 and 5.9 microg/mL, respectively). They also exhibited significant leishmanicidal activity (IC (50) = 1.1 and 4.1 microg/mL, respectively). The inhibitory potential of the pure metabolites against plasmodial enoyl-ACP reductase (FabI), which is the key regulator of type II fatty acid synthases (FAS-II) in P. falciparum, was also assessed. Compound 10 showed promising FabI inhibiting effect (IC (50) = 10 microg/mL) and appears to be the first anti-malarial natural product targeting FabI of P. falciparum. Abbreviations. ACP:Acyl Carrier Protein CC:Column Chromatography FabI:Enoyl-Acyl Carrier Protein Reductase FAS-I:Type I Fatty Acid Synthase System FAS-II:Type II Fatty Acid Synthase System MPLC:Medium Pressure Liquid Chromatography