Identification of phytoconstituents and in-vitro evaluation of the putative anticataractogenic effect of an ethanolic root extract of Leucas aspera

Abstract

Modern herbal medicine has played a significant role in treating oxidative stress and related complications. In the present investigation, gas chromatography-mass spectrometric analysis of ethanolic extracts of the leaf and of the root of Leucas aspera (L. aspera) (Willd.) Link separately showed the presence of various phytoconstituents; major components have already been reported to possess various biological, including antioxidant, activities. Of the two extracts analyzed, the root extract exhibited more potential antioxidant activity than did the leaf extract. Since this finding correlated with more perceptible amounts of antioxidant components being detected in the ethanolic extract of L. aspera root, the root extract was evaluated for possible anticataractogenic potential in cultured Wistar rat lenses. Following incubation of Wistar rat lenses for 24h at 37°C in Dulbecco's modified Eagle's medium (DMEM), gross morphological examination revealed that none of the eight lenses incubated in DMEM alone (Group I) exhibited any opacification (Grade 0), whereas all eight lenses incubated in DMEM that contained sodium selenite (100μM selenite/ml of DMEM) (Group II) exhibited thick opacification (Grade +++). In contrast, only one out of eight lenses incubated in DMEM containing sodium selenite (100μM selenite/ml of DMEM) and simultaneously exposed to the L. aspera root extract (300μg/ml of DMEM) (Group III) exhibited a slight degree of opacification (Grade +) after 24h incubation, while the remaining seven lenses did not show any opacification (Grade 0). The mean activities of catalase, superoxide dismutase, glutathione peroxidase and glutathione-S-transferase and the mean level of reduced glutathione were all significantly (p<0.05) higher in Group III lenses than the mean values in Group II lenses. The mean concentration of malondialdehyde in Group III lenses was significantly (p<0.05) lower than that in Group II lenses. Further, significantly (p<0.05) lower mean mRNA transcript levels of the genes encoding αA- and βB1-crystallins, as well as significantly lower mean levels of the αA- and βB1-crystallin proteins themselves, were observed in Group II lenses. However, in Group III lenses, the mean mRNA transcript levels of the crystallin genes, and the mean protein levels, were essentially similar to those noted in normal control (Group I) lenses. The results of the present study suggest that in selenite-challenged Wistar rat lenses simultaneously exposed to an ethanolic extract of L. aspera root, lenticular opacification was prevented by mean activities of enzymatic antioxidants, mean levels of reduced glutathione and malondialdehyde mean expression levels of genes encoding αA- and βB1-crystallins, and mean levels of the crystallin proteins themselves, being maintained at near normal levels. Further studies are required to confirm whether the ethanolic extract of the root of L. aspera can be developed for pharmacological management of cataract.

Keywords: Antioxidants; Cataract; Crystallin; GC–MS analysis; Leucas aspera; Phytoconstituents.