Antiplasmodial activity of Punica granatum L. fruit rind.
OBJECTIVE
Sun-dried rind of the immature fruit of Punica granatum L. (Punicaceae) (Pg) is presently used as a herbal formulation (OMARIA) in Orissa, India, for the therapy and prophylaxis of malaria. The aims of this study were (i) to assess in vitro the antiplasmodial activity of the methanolic extract, of a tannin enriched fraction and of compounds/metabolites of the antimalarial plant, (ii) to estimate the curative efficacy of the Pg extracts and (iii) to explore the mechanism of action of the antiplasmodial compounds. Urolithins, the ellagitannin metabolites, were also investigated for antiplasmodial activity.


METHODS
Chloroquine-susceptible (D10) and -resistant (W2) strains of Pf were used for in vitro studies and the rodent malaria model Plasmodium berghei-BALB/c mice was used for in vivo assessments. Recombinant plasmepsins 2 and 4 were used to investigate the interference of Pg compounds with the metabolism of haemoglobin by malaria parasites.


RESULTS
The Pg methanolic extract (Pg-MeOH) inhibited parasite growth in vitro with a IC(50) of 4.5 and 2.8 microg/ml, for D10 and W2 strain, respectively. The activity was found to be associated to the fraction enriched with tannins (Pg-FET, IC(50) 2.9 and 1.5 microg/ml) in which punicalagins (29.1%), punicalins, ellagic acid (13.4%) and its glycoside could be identified. Plasmepsin 2 was inhibited by Pg-MeOH extract and by Pg-FET (IC(50) 7.3 and 3.0 microg/ml), which could partly explain the antiparasitic effect. On the contrary, urolithins were inactive. Both Pg-MeOH extract and Pg-FET did not show any in vivo efficacy in the murine model.


CONCLUSIONS
The in vitro studies support the use of Pg as antimalarial remedy. Possible explanations for the negative in vivo results are discussed.
Dell'Agli
Mario
M
Department of Pharmacological Sciences, University of Camerino, Italy. mario.dellagli@unimi.it
Galli
Germana V
GV
Corbett
Yolanda
Y
Taramelli
Donatella
D
Lucantoni
Leonardo
L
Habluetzel
Annette
A
Maschi
Omar
O
Caruso
Donatella
D
Giavarini
Flavio
F
Romeo
Sergio
S
Bhattacharya
Deepak
D
Bosisio
Enrica
E
D000818:Animals; D000962:Antimalarials / Q000494:pharmacology* / Q000627:therapeutic use; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors*; D004195:Disease Models, Animal; D004610:Ellagic Acid / Q000494:pharmacology* / Q000627:therapeutic use; D005638:Fruit; D006454:Hemoglobins / Q000378:metabolism; D047348:Hydrolyzable Tannins / Q000494:pharmacology* / Q000627:therapeutic use; D029561:Lythraceae / Q000737:chemistry*; D008288:Malaria / Q000188:drug therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008517:Phytotherapy; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D010962:Plasmodium berghei / Q000187:drug effects; D010963:Plasmodium falciparum / Q000187:drug effects; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors*
D000962:Antimalarials; D006454:Hemoglobins; D047348:Hydrolyzable Tannins; D010936:Plant Extracts; D015800:Protozoan Proteins; D004610:Ellagic Acid; D016282:Aspartic Acid Endopeptidases; C100637:plasmepsin II