Effect of the time of extraction on the potency and allergenic composition of the extract of Parietaria officinalis pollen.

Five Parietaria officinalis pollen extracts were obtained after respective 0.5, 4, 16, 48, 96 h of extraction in 0.0125 M NH4HCO3 pH 8.7 containing 0.05% NaN3 and 5.7 X 10(-4) M phenylmethylsulphonylfluoride. Conductivity, pH, absorption coefficient at 280 and 360 nm and content in protein and carbohydrates were determined in the extracts. Allergenic potency, evaluated by RAST inhibition was higher for the shorter-time extracts. The allergenic composition of the extracts was analyzed by a combination of gel filtration of the extracts and RAST inhibition of the eluted fractions: low molecular weight allergens were recovered only in longer-time extracts.