• Korean Journal of Medicinal Crop Science
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• v.20 no.4
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• pp.222-230
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• 2012

We evaluated the inhibitory effects of extracts and components of Geranium thunbergii on aldose reductase (AR) and galactitol formation in rat lenses with high levels of galactose as a part of our ongoing search of natural sources for therapeutic and preventive agents for diabetic complications. The inhibitory effects of water, methanol and ethanol extracts of G. thunbergii on rat lens AR (RLAR) were determined. Comparing inhibitory effects of various solvent extracts, ethanol extract showed RLAR inhibitory activity ($IC_{50}$ values, 5.24 and $6.39{\mu}g/m{\ell}$, respectively). The ethanol extract was fractionated to chloroform, ethyl acetate and water. Of these, the ethyl acetate fraction from ethanol extract of G. thunbergii exhibited RLAR inhibitory activity ($IC_{50}$ value, $2.64{\mu}g/m{\ell}$). In order to identify the bioactive components of ethyl acetate soluble fraction of ethanol extract from G. thunbergii, eight compounds, namely gallic acid (1), protocatechuic acid (2), p-hydroxybenzoic acid (3), brevifolin carboxylic acid (4), geraniin (5), ellagic acid (6), kaempferol-3-O-arabinofuranosyl-7-O-rhamnopyranoside (7), kaempferitrin (8) were isolated. The isolates were subjected to in vitro bioassays to evaluate their inhibitory activity on RLAR and galactitol formation in rat lenses. The ellagic tannins (5, 6) and flavonoid (7) exhibited strong inhibitory effects on RLAR. Also, these three compounds (5, 6 and 7) suppressed galactitol accumulation in rat lens under high galactose conditions, demonstrating the potential to prevent galactitol accumulation exo vivo. These results suggest that the extracts and components of G. thunbergii are a promising agent in the prevention or treatment of diabetic complications.

• Archives of Pharmacal Research
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• v.17 no.5
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• pp.331-336
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• 1994

The ether extract from the roots of angelica clahurica was found to inhibit bovine lens aldose reductase (BLAR0 activity in vitro by 100% at 100.mu.g/ml. Systematic fractionation of the ether soluble fraction and subsequent active frctions monitorede by bioassy led to isolation of four furanocoumarins, isoimperatorin (I0, imperatorin (II), ter-O-methyl byakangelicin (III) and byakangelicin (IV), among which compound III and IV were identified as potential AR inhibitors, their $IC_{50}$ values being $2.8{\mu}M{\;}and{\;}6.2{\mu}M$, respectively. Galactosemic cataract formation tors, in rats treated with 40 g/kg/day of galactose was blocked almost completely throughout the exeprimental periods up to 44 days by i.p. administrations of byakangelicin (IV) at 50 mg/kg/day. In coincidence with the inhibitory action on cataract formation, the galactitol accumulation in rats treated with byakangelicin (IV) was found to be markedly prevented by approximately 80.5% compared to those of the contro. These results indicate that byakangelicin (IV), as a main principle of this plant, possesses high potential for a clinically useful drug of the future which prevents and/or improves sugar cataract as well as diabetic complications.

• Korean Journal of Pharmacognosy
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• v.25 no.1
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• pp.41-46
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• 1994

The ether, ethylacetate and n-butanol soluble fractions from the roots of Scutellaria baicalensis showed a significant inhibition of lens aldose reductase (AR) activity in vitro. During systematic fractionation of the active fractions, 7 flavonoids were isolated and compared their inhibitory activities against rat AR using DL-glyceraldehyde as a substrate, among which baicalin (VII) was found to exhibit the most potent inhibitory activity. Baicalin (VII) and wogonin-7-O-glucuronide (VI), with repeated treatments (30 mg/kg/day, i.p.) throughout the experimental periods caused a significant suppression of cataract formation induced by galactose (40 g/kg/day) as well as the decrease of galactitol accumulation in the rat lens. The flavonoids also exhibited a significant inhibition of sorbitol accumulation in the lenses of diabetic rats induced by streptozotocin (STZ).

• Proceedings of the Korean Society of Applied Pharmacology
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• 1998.11a
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• pp.184-184
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• 1998

Aldose reductase(AR), a rate-limiting enzyme in the polyol pathway, has been demonstrated to cause the intracellular accumulation of sorbitol or galactitol and hence to play key roles not only in the cataract formation in the lens but also in the pathogenesis of diabetic complications such as neuropathy, retinopathy and nephropathy, etc. In a series of investigations to evaluate potential AR inhibitors from medicinal plants, we have shown that some hot water extracts exhibited a significant inhibition of a significant inhibition of bovine lens AR in vitro. Among active plants, the roots of Angelica dahuria (Umbelliferae) were shown to have relatively potent AR inhibitory activity. Systematic fractionation of the ether soluble fraction monitored by bioassay led to isolation of two furanocoumarins, byakangelicin(I) and ter-O-methyl byakangelicin( II), were identified as potential AR inhibitors, their $IC_{50}$ values being 6.2 M and 2.8 M, respectively.