Lens Aldose Reductase Inhibitory and Free Radical Scavenging Activity of Fractions of Chromolaena odorata (Siam Weed): Potential for Cataract Remediation

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.