Antiallergic effect of an aqueous leaf extract of Pistia stratiotes in murine model of ovalbumin-induced allergic conjunctivitis.

AIM: The aim was to investigate the antiallergic effect of an aqueous leaf extract of Pistia stratiotes (ALPS) in a murine model of ovalbumin (OVA)-induced allergic conjunctivitis (AC). MATERIALS AND METHODS: Prior to topical challenge (instillation of 1.5 mg OVA in 10 µL phosphate buffered saline into their conjunctival sacs) to induce AC, groups of sensitized Imprinting Control Region mice (injected IP, on day 1 and 7, with 0.2 ml solution of 100 µg OVA and 0.01 mg aluminum hydroxide in phosphate buffered saline), were treated with 5 mg/kg cetirizine, 10, 50 or 100 mg/kg of ALPS, or 2 ml/kg normal saline per os. Conjunctival redness, lid edema, tearing and lid scratching (clinical symptoms of AC) were scored. Serum OVA specific immunoglobulins were determined using ELISA. Histopathological assessment of the conjunctival mucosal tissue was conducted. The extract was screened for secondary plant metabolites. RESULTS: Pretreatment with the extract significantly (P ≤ 0.05-0.01) and dose-dependently reduced the scores for clinical symptoms, which were marked in vehicle-pretreated mice. Pretreatment also lowered (P ≤ 0.01-0.001) serum OVA specific immunoglobulins. Mast cell infiltration and degranulation in conjunctival stroma (measured by an inflammatory score) in histopathological studies was also significantly low (P ≤ 0.05-0.01) on pretreatment. CONCLUSION: The ALPS exhibited interesting antiallergic activity and hence could be useful in managing AC.