Morin hydrate: a better protector than purpurogallin of corneal endothelial cell damage induced by xanthine oxidase and SIN-1

Abstract

PURPOSE. Free radicals are responsible for tissue injury in corneal preservation and transplantation. Morin hydrate, a flavonoid from Brazil wood, has been shown to be cytoprotective in several types of cells. The aim of this study was to investigate the effectiveness of morin hydrate on rabbit corneal endothelial cells against damage induced by oxyradicals and nitric oxide. METHODS. Corneal endothelial cell cultures were prepared from New Zealand white rabbits, using standard microcarrier technique. Two free-radical-generating systems were used – 17 IU/L xanthine oxidase/1 mM hypoxanthine and 5 mM 3-morpho-linosydnonimine- N-ethylcarbamide (SIN-1, a nitric oxide-donating agent). RESULTS. Over 95% of cultured corneal endothelial cells necrosed within 3.6 ± 1.5 min after exposure to xanthine oxidase/ hypoxanthine. Adding morin hydrate delayed cell necrosis to 5.8 ± 0.3 min (0.25 mM morin hydrate), 13.3 ± 5.0 min (0.5 mM), and 41.5 ± 8.6 min (1.0 mM). Exposed to nitric oxide generated by SIN-1, cells necrosed by 9.5 ± 2.5 min, versus 14.1 ± 1.3 min (0.25 mM morin hydrate), 27.2 ± 2.0 min (0.5 mM), and 43.3 ± 5.4 min (1.0 mM). Morin hydrate significantly prolonged survival of cells compared to equimolar concentrations of purpurogallin, Trolox, or ascorbate (P < 0.01). CONCLUSION. This study demonstrates that morin hydrate behaves as a broad-spectrum antioxidant: it scavenges not only xanthine oxidase/hypoxanthine-generated oxyradicals, but also nonenzymatic, nitrogen-derived radicals, better than those above mentioned antioxidants. This property of morin hydrate may help prevent free radical damage in corneal preservation solutions.