Rosmarinic acid, a new snake venom phospholipase A 2 inhibitor from Cordia verbenacea (Boraginaceae): antiserum action potentiation and molecular interaction

Abstract

Many plants are used in traditional medicine as active agents against various effects induced by snakebite. The methanolic extract from Cordia verbenacea (Cv) significantly inhibited paw edema induced by Bothrops jararacussu snake venom and by its main basic phospholipase A 2 homologs, namely bothropstoxins I and II (BthTXs). The active component was isolated by chromatography on Sephadex LH-20 and by RP-HPLC on a C18 column and identified as rosmarinic acid (Cv-RA). Rosmarinic acid is an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid [2- O-cafeoil-3-(3,4-di-hydroxy-phenyl)- R-lactic acid]. This is the first report of RA in the species C. verbenacea (‘baleeira’, ‘whaler’) and of its anti-inflammatory and antimyotoxic properties against snake venoms and isolated toxins. RA inhibited the edema and myotoxic activity induced by the basic PLA 2s BthTX-I and BthTX-II. It was, however, less efficient to inhibit the PLA 2 activity of BthTX-II and, still less, the PLA 2 and edema-inducing activities of the acidic isoform BthA-I-PLA 2 from the same venom, showing therefore a higher inhibitory activity upon basic PLA 2s. RA also inhibited most of the myotoxic and partially the edema-inducing effects of both basic PLA 2s, thus reinforcing the idea of dissociation between the catalytic and pharmacological domains. The pure compound potentiated the ability of the commercial equine polyvalent antivenom in neutralizing lethal and myotoxic effects of the crude venom and of isolated PLA 2s in experimental models. CD data presented here suggest that, after binding, no significant conformation changes occur either in the Cv-RA or in the target PLA 2. A possible model for the interaction of rosmarinic acid with Lys49-PLA 2 BthTX-I is proposed.