Inhibition of aldose reductase by herbs extracts and natural substances and their role in prevention of cataracts REV CUBANA PLANT MED 2005;10(3-4) Laboratorio de bioquímica: Escuela de Farmacia. Universidad de Puerto Rico, San Juan, Puerto Rico Laboratorio de productos naturales: Escuela de Farmacia. Universidad de Puerto Rico, San Juan, Puerto Rico Inhibition of aldose reductase by herbs extracts and natural substances and their role in prevention of cataracts Dr. Ángel Guzmán 1 and Dr. Ricardo O. Guerrero 2 Summary Cataractogenesis is a common complication that occurs in diabetes mellitus. Aldose reductase is a lens enzyme probably involved in the development of this eye problem. The purpose of this investigation was to screen plant extracts for aldose reductase inhibitors (ARI) and to investigate their possible influence in diabetic cataractogenesis prevention. 13 plants and 3 natural products were randomly selected for our experiment. The 19 extracts originated from plant material which was extracted with ethanol, water and DCM, and assessed for inhibitors of aldose reductase. This enzyme was isolated from bovine lenses homogenates. The enzyme was incubated in a reaction mixture containing 50 mM Na-phosphate buffer (pH 6.2), NADPH, 400 mM LiSO 4 and dl-glyceraldehyde. A spectrophotometrical assay was performed in which NADP is produced and its absorption read at 340 nm. Eugenia borinquensis, Mangifera indica, Eucalyptus deglupta, and Syzygium malaccense were among the best inhibitors. Normal and diabetic Sprague Dawley rats were used to evaluate the in vivo effect of E. deglupta, M. indica, and E. borinquensis in cataractogenesis prevention. All of these extracts had preventive effects on the formation of cataracts. It is concluded that further investigation to explain the above findings is necessary. Perhaps the next step will include an activity monitored isolation of the effective principles. Future investigation will ince the isolation of the active principles in these extracts. Key words: Puerto Rico, plant extracts, aldose reductase inhibition, cataractogenesis prevention. A cataract is the opacity of the lens that produces painless gradual loss of vision. Acquired cataracts may result from trauma, radiation or metabolic disorders. It may be produced in several conditions such as hyperglycemia, galactosemia, hypocalcaemia and diabetes mellitus. 1 Aldose reductase (AR), the key enzyme of the polyol pathway, is known to play important roles in diabetic complications. The inhibitors of aldose reductase, therefore, would be potential agents in the prevention of one of these complications, namely, the development of cataracts. Through the years, medicinal plants have been the focus of many investigations for the search of aldose reductase inhibitors (ARI). Ueda et al. 2 studying the leaves of Myrciaria dubia found ellagic acid and two of its derivatives as potent ARI. Three flavonoids isolated from Brickellia arguta by Rosler et al., 3 showed anti- cataract activity in rats. Some Chinese herbs have also been investigated as source of ARI with a fluorometric assay. 4 Kohda et al. 5 discovered acteoside, an active ARI phenolic glycoside from a 70 % acetone extract of Monochasma savatierii. Perillosides A and C were found to be excellent ARI. These monoterpene glycosides were isolated from the leaves of Perilla frutescens. The investigators 6 attempted to establish a relationship