The effect of propolis extract in experimental chemical corneal injury

To investigate the effect of propolis, a natural resin produced by honeybees, in the treatment of alkali-injured rabbit eyes.

A corneal alkali burn was induced by applying filter paper immersed in 1 N NaOH on the central axis of the right corneas of 24 rabbits for 30 s. The animals were divided into three treatment groups: group 1 (control) was given 0.3% tobramycin and phosphate-buffered solution; group 2 was treated with antibiotic coverage and topical 1% ethanolic extract of propolis; group 3 received antibiotic coverage and topical 1% dexamethasone. The dexamethasone-treated group was maintained as the positive control. Drugs were instilled 4 times a day for 7 days. The corneal inflammation was evaluated by calculating the average inflammatory index obtained from clinical observation of the ciliary hyperemia, central and peripheral corneal edema at 24 h, 48 h, on day 5 and day 7, before sacrificing the animals. Then, the corneas underwent routine histological examination.

The effects of dexamethasone and propolis on healing of injured corneas were similar (p>0.05) and significantly better than controls at 24 h (p<0.01, p< 0.05, respectively), and on day 7 (p<0.05) with respect to the inflammatory index. On histological observation, inflammatory cell infiltration was lower as compared to control in both the dexamethasone and propolis groups (p<0.001) and similar with each other (p>0.05).

Our study shows that propolis has an anti-inflammatory effect comparable to dexamethasone in chemical corneal injury.