(2S,3S,4R,2'R )-2-(2'-Hydroxytetracosanoylamino) octadecane-1,3,4-triol at concentration of 100 ug/mL shows selectively inhibitory activity against phospholipase A 2 (PLA 2) secreted from Crotalus adamenteus venom, but inactive against PLA 2 of bee venom