Abstract
Searching for effective and safe aldose reductase (AR) inhibitor agent is a major thrust area in the mainstream of anti-cataractogenic research. This study was set up to investigate the in vitro aldose reductase inhibitory (ARI) activity of fractions of methanolic extract of Chromolaena odorata leaves, on partially purified AR from goat lens, for potential use in the development of anticataractogenic agent. The phyto-constituents of the leaves were screened in aqueous and methanolic extracts and the free radical scavenging activities of the fractions were evaluated. The kinetics of the enzyme in the presence of fractions of the leaves was then compared. Phenol, flavonoid, alkaloid, saponin, terpenoid, quinones and phlobatannins were detected in both extracts. All the fractions inhibited AR in an uncompetitive manner, showing a reduced V max and Km when compared with glyceraldehyde. ARI activity was found to be the highest with aqueous fraction (IC50, 0.22 ± 0.01 mg/ml). All other fractions showed mild to moderate AR inhibition capacity, while it was found to be the lowest within hexane fraction (IC50, 1.20 ± 0.10 mg/ml). All the fractions showed free radical scavenging activity and metal chelating activity. The study confirmed the ARI and antioxidant capacity of Chromolaena odorata which may be due to its phenolic constituents, indicating that the plant may serve as a base for the development of anticataract agent.
Highlights
The use of medicinal plants, plant extracts or plantderived pure chemicals to treat human ailments is an important alternative therapeutic approach (Patwardhan et al, 2004)
The first enzyme, aldose reductase (AR), reduces glucose to sorbitol with the aid of its co-factor NADPH; the second enzyme, sorbitol dehydrogenase (SDH), with its co-factor NAD+, converts sorbitol to fructose
The results showed that the phenolic acids present and complex mixtures of lipophilic flavonoid aglycones are major and powerful antioxidants that protect cultured skin cells against oxidative damage (Phan et al, 2001)
Summary
The use of medicinal plants, plant extracts or plantderived pure chemicals to treat human ailments is an important alternative therapeutic approach (Patwardhan et al, 2004). A systematic search for useful bioactivities from medicinal plants is considered to be a rational approach in nutraceutical and drug research (Akinmoladun et al, 2007). Aldose reductase (ALR2; AR; EC 1.1.1.21) is a key enzyme in the polyol pathway that controls the conversion of glucose to sorbitol. The polyol pathway is usually a twostep metabolic process through which glucose is reduced to sorbitol, which is further converted to fructose. The first enzyme, aldose reductase (AR), reduces glucose to sorbitol with the aid of its co-factor NADPH; the second enzyme, sorbitol dehydrogenase (SDH), with its co-factor NAD+, converts sorbitol to fructose. The AR enzyme is found in almost all mammalian cells, but is richer in organs such as the lens, retina and sciatic nerves, which are affected by diabetic complications
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