A Sulphonoglycolipid from the Fern Polypodium decumanum and its Effect on the Platelet Activating-factor Receptor in Human Neutrophils

The South American fern Polypodium decumanum, traditional name calaguala, has documented clinical use in oral treatment of skin disorders, including psoriasis. The inflammatory mediator platelet‐activating factor (PAF), has been implicated in the pathogenesis of psoriasis. A constituent of a calaguala extract has been shown to have inhibitory activity in a PAF‐induced exocytosis model in human neutrophils. The compound was identified as the sulphoquinovosyl diacylglycerol 1,2‐di‐O‐palmitoyl‐3‐O‐(6‐sulpho‐α‐d‐quinovopyranosyl)‐glycerol by spectroscopic means. When subsequently studied in an in‐vitro model for [3H]PAF binding in neutrophils from man the compound caused dose‐dependent displacement of [3H]PAF from its receptor with an IC50 value of 2 μm. It is suggested that the compound acts through PAF receptor antagonism in intact human neutrophils.