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Methanolic extracts of Plantago species as 12-lipoxygenase inhibitors
Lipoxygenases are a family of enzymes involved in a variety of human diseases like inflammation, asthma, artherosclerosis and cancer . 12-Lipoxygenase (12-LO), followed by peroxidase, catalyzes the oxidation of arachidonic acid to yield 12-hydroxy-5,8,10,14-eicosatetraenoate (12-HETE). The 12-HETE is preferentially formed in platelets, but its overexpression is noticed in different tumor cells, and its influence on inducing angiogenesis and metastasis in prostate, pancreatic, breast and lung cancer has been acknowledged . Several medicinal plants with natural products having 12-LO inhibitory activity are known , but there are no reports on the Plantago species. The aim of this study was to examine 12-LO inhibitory activity of methanolic extracts from seven Plantago species (P. maior L., P. media L., P. lanceolata L., P. holosteum Scop., P. coronopus L., P. schwarzenbergiana Schur., P. maritima L.) collected from five different locations in Serbia.
In vitro 12-LO assay was performed using human platelets (1.25×109, viable, but outdated for medical treatment), stimulated by ionophore A23187 and Ca2+. The extracts, dissolved in DMSO, were added to final concentration of 2mg/ml. The 12-LO product 12-HETE was quantified by RP-HPLC/MS/MS, after the addition of prostaglandin B2 as internal standard. All extracts showed inhibitory activity ranged from 16% (P. schwarzenbergiana, locality Padej) to above 70% (P. maior, P. media, P. lanceolata and P. coronopus). Quercetin, a known inhibitor of 12-LO, expressed inhibitory activity of 82% at concentration of 40µg/ml.
In this study, we managed not only to optimize a method for in vitro 12-LO inhibitory activity , but also to introduce certain Plantago species as a possible new sources of natural 12-LO inhibitors.
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