Effects of aqueous extract of Casearia sylvestris (Flacourtiaceae) on actions of snake and bee venoms and on activity of phospholipases A2

The crude aqueous extract from the leaves of Casearia sylvestris, a plant found in Brazilian open pastures, was assayed for its ability to inhibit phospholipase A(2) (PLA(2)) activity and some biological activities of bee and several snake venoms, and of a number of isolated PLA(2)s. The extract induced partial inhibition of the PLA(2) activity of venoms containing class I, II and III PLA(2)s. When tested against the purified toxins, it showed the highest efficacy against class II PLA(2)s from viperid venoms, being relatively ineffective against the class I PLA(2) pseudexin. In addition, C. sylvestris extract significantly inhibited the myotoxic activity of four Bothrops crude venoms and nine purified myotoxic PLA(2)s, including Lys-49 and Asp-49 variants. The extract was able to inhibit the anticoagulant activity of several isolated PLA(2)s, with the exception of pseudexin. Moreover, it partially reduced the edema-inducing activity of B. moojeni and B. jararacussu venoms, as well as of myotoxins MjTX-II and BthTX-I. The extract also prolonged the survival time of mice injected with lethal doses of several snake venoms and neutralized the lethal effect induced by several purified PLA(2) myotoxins. It is concluded that C. sylvestris constitutes a rich source of PLA(2) inhibitors. (C) 2000 Elsevier Science Inc. All rights reserved.