Sang Hoon Jung

SYNTHESIS OF FLAVONOIDS AND THEIR EFFECTS ON ALDOSE REDUCTASE AND SORBITOL ACCUMULATION IN STREPTOZOTOCIN-INDUCED DIABETIC RAT TISSUES

Aldose reductase, the key enzyme of the polyol pathway, and oxidative stress are known to play important roles in the complications of diabetes. A drug with potent inhibition of aldose reductase and oxidative stress, therefore, would be a most promising drug for the prevention of diabetic complications. The purpose of this study was to develop new compounds with these dual‐effects through synthesis of chalcone derivatives and by examining the structure‐activity relationships on the inhibition of rat lens aldose reductase as well as on antioxidant effects. A series of 35 flavonoid derivatives were synthesized by Wingets condensation, oxidation, and reduction of appropriate acetophenones with appropriate benzaldehydes. The inhibitory activity of these derivatives on rat lens aldose reductase and their antioxidant effects, measured using Cu2+ chelation and radical scavenging activities on 1,1‐diphenyl‐picrylhydrazyl in‐vitro, were evaluated. Their effect on sorbitol accumulation in the red blood cells, lenses and sciatic nerves of streptozotocin‐induced diabetic rats was also estimated. Among the new flavonoid derivatives synthesized, those with the 2′,4′‐dihydroxyl groups in the A ring such as 2,4,2′,4′‐tetrahydroxychalcone (22), 2,2′,4′‐trihydroxychalcone (11), 2′,4′‐dihydroxy‐2,4‐dimethylchalcone (21) and 3,4,2′,4′‐tetrahydroxychalcone (18) were found to possess the highest rat lens aldose reductase inhibitory activity in‐vitro, their IC50 values (concentration of inhibitors giving 50% inhibition of enzyme activity) being 1.6 times 10−7, 3.8 times 10−7, 4.0 times 10−7 and 4.6 times 10−7 M, respectively. All of the chalcones tested except 3, 18, 23 with o‐dihydroxy or hydroquinone moiety showed a weak free radical scavenging activity. In the in‐vivo experiments, however, compound 18 with o‐dihydroxy moiety in the B ring showed the strongest inhibitory activity in the accumulation of sorbitol in the tissues. It also showed the strongest activity in transition metal chelation and free radical scavenging activity. Of the 35 4,2′‐dihydroxyl and 2′,4′‐dihydroxyl derivatives of flavonoid synthesized, including chalcone, flavone, flavanone, flavonol and dihydrochalcone, some chalcone derivatives synthesized were found to possess aldose reductase inhibition and antioxidant activities in‐vitro as well as inhibition in the accumulation of sorbitol in the tissues in‐vivo. 3,4,2′,4′‐Tetrahydroxychalcone (18, butein) was the most promising compound for the prevention or treatment of diabetic complications.

Anti-tumor activities of decursinol angelate and decursin from Angelica gigas

Thein vivo anti-tumor activities of decursinol angelate (1) and decursin (2) isolated from the roots ofAngelica gigas were investigated. These two compounds, when administered consecutively for 9 days at 50 and 100 mg/kg i.p. in mice, caused a significant increase in the life span and a significant decrease in the tumor weight and volume of mice inoculated with Sarcoma-180 tumor cells. These results suggest that decursinol angelate (1) and decursin (2) fromA. gigas have anti-tumor activities.

Anti-oxidant activities of fucosterol from the marine algae Pelvetia siliquosa.

The anti-oxidant activities of fucosterol isolated from the marine algaePelvetia siliquosa were investigated. Fucosterol exhibited a significant decrease in serum transaminase activities elevated by hepatic damage induced by CCI4-intoxication in rats. Fucosterol inhibited the sGOT and sGPT activities by 25.57 and 63.16%, respectively. Fucosterol showed the increase in the anti-oxidant enzymes such as hepatic cytosolic superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-px) activities by 33.89, 21.56 and 39.24%, respectively, in CCI4-intoxicated rats. These results suggest that fucosterol possess not only the anti-oxidant, but also the hepatoprotective activities in rats.

Anti-oxidant activities of the extracts from the herbs of Artemisia apiacea.

The anti-oxidant activities of the various fractions from the herbs of Artemisia apiacea were investigated. The n-hexane and n-butanol fractions were found to cause significant free radical scavenging effects on DPPH, their scavenging potencies as indicated in IC(50) values, being 230.1 and 183.7 microg/ml, respectively. The n-butanol fraction exhibited a significant decrease in serum transaminase activities elevated by hepatic damage induced by CCl(4)-intoxication in rats. All fractions tested exhibited a lipid peroxidation causing a significant decrease in MDA production in TBA-reactant assay. The n-butanol fraction was the strongest in the increase in the anti-oxidant enzymes such as hepatic cytosolic superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-px) activities in CCl(4)-intoxicated rats. These results suggest that the herbs of A. apiacea possess not only the anti-oxidant, but also the activities in CCl(4)-intoxicated rats. Especially, the n-butanol extract was found to cause significant increases in the rat liver cytosolic SOD, catalase, GSH-px activities as well as a significant decrease in the MDA production.

Anti-oxidant activities ofacanthopanax senticosus stems and their lignan components

The antioxidant activities ofAcanthopanax senticosus stems were evaluated in CCI4-intoxicated rats. Then-butanol fraction from the water extract of the stems, when pretreated orally at 200 mg/kg/day for 7 consecutive days in rats, was demonstrated to exhibit significant increases in antioxidant enzyme activities such as hepatic cytosolic superoxide dismutase, catalase and glutathione peroxidase by 30.31, 19.82 and 155%, respectively. Then-butanol fraction whereas showed a significant inhibition of serum GPT activity (65.79% inhibition) elevated with hepatic damage induced by CCI4-intoxication. Eleutheroside B, a lignan component, isolated from then-butanol fraction was found to cause a moderate free radical scavenging effect on DPPH, its scavenging potency as indicated in IC50 value, being 58.5 μM. These results suggested that the stems ofA. senticosus possess not only antioxidant but also hepatoprotective activities.

ISOFLAVONOIDS FROM THE RHIZOMES OF BELAMCANDA CHINENSIS AND THEIR EFFECTS ON ALDOSE REDUCTASE AND SORBITOL ACCUMULATION IN STREPTOZOTOCIN INDUCED DIABETIC RAT TISSUES

Aldose reductase, the key enzyme of the polyol pathway, is known to play important roles in the diabetic complication. The inhibitors of aldose reductase, therefore, would be potential agents for the prevention of diabetic complications. To evaluate active principles for the inhibition of aldose reductase from the rhizomes ofBelamcanda chinensis, twelve phenolic compounds were isolated and tested for their effects on rat lens aldose reductase. As a result, isoflavones such as tectorigenin, irigenin and their glucosides were found to show a strong aldose reductase inhibition. Tectoridin and tectorigenin, exhibited the highest aldose reductase inhibitory potency, their IC50 values, being 1.08x 10-6 M and 1.12 x 10-6 M, respectively, for DL-glyceraldehyde as a substrate. Both compounds, when administered orally at 100 mg/kg for 10 consecutive days to streptozotocin-induced diabetic rats, caused a significant inhibition of sorbitol accumulation in the tissues such as lens, sciatic nerves and red blood cells. Tectorigenin showed a stronger inhibitory activity than tectoridin. From these results, it is suggested that tectorigenin is attributed to be a promising compound for the prevention and/or treatment of diabetic complications.

Antioxidant activities of isoflavones from the rhizomes ofbelamcanda chinensis on carbon tetrachloride-lnduced hepatic injury in rats

The present study was carried out to clarify whether tectorigenin and tectoridin isolated from the rhizomes ofBelamcanda chinensis (Iridaceae) inhibit hepatic damage induced by carbon tetrachloride (CCI+4)-intoxication in rats by the experimental methodsin vitro andin vivo. Tectorigenin and tectoridin exhibited a significant decrease in serum transaminase activities elevated by hepatic damage induced by CCI4-intoxication in rats, as well as in a lipid peroxidation causing a significant decrease in malondialdehyde (MDA) production by thiobarbituric acid (TBA)-reactant assay. Both compounds also showed strong increase in the antioxidant enzymes such as hepatic cytosolic superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-px) activities in CCI4-intoxicated rats. These results suggested that tectorigenin and tectoridin isolated from the rhizomes ofB. chinensis possess not only the antioxidative, but also the hepatoprotective activities in CCI4-intoxicated rats.

Suppression of tumor growth by a new glycosaminoglycan isolated from the African giant snail Achatina fulica

Acharan sulfate is a new type of glycosaminoglycan from the giant African snail, Achatina fulica. Acharan sulfate, which has a primary repeating disaccharide structure of alpha-D-N-acetylglucosaminyl-2-O-sulfo-alpha-L-iduronic acid, was studied as a potential antitumor agent in both in vivo and in vitro assays. The antiangiogenic activity of acharan sulfate was evaluated in the chorioallantoic membrane assay and by measuring its effect on the proliferation of calf pulmonary artery endothelial cells. In vivo, a matrigel plug assay showed that acharan sulfate suppressed basic fibroblast growth factor (bFGF)-stimulated angiogenesis and lowered the hemoglobin (Hb) content inside the plug. Acharan sulfate was administered s.c. at two doses for 15 days to C57BL/6 mice implanted with murine Lewis lung carcinoma in the back. It was also administered i.p. to ICR mice bearing sarcoma 180 at a dose of 30 mg/kg. Subcutaneous injection of acharan sulfate at doses of 10 and 30 mg/kg decreased tumor weight and tumor volume by 40% without toxicity or resistance. Intraperitoneal injection of acharan sulfate also decreased tumor weight and volume by 40% in sarcoma 180-bearing mice. These results suggest that the antitumor activity of acharan sulfate may be related to the inhibition of angiogenesis.

Antiinflammatory activity of hyperin from Acanthopanax chiisanensis roots.

The chloroform and the ethyl acetate fractions from the roots of Acanthopanax chiisanensis exhibited a significant inhibition of prostaglandin E2 (PGE2) production in rat peritoneal macrophages stimulated by the protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA). Hyperin was isolated as an active principle from the ethyl acetate fraction. It suppressed not only PGE2 production but also nitric oxide (NO) productionin vitro in a concentration dependent manner, their IC50, being 24.3 and 32.9 μM, respectively. Hyperin also caused a significant inhibition of increase in acetic acid-induced vascular permeability in micein vivo.

Inhibition of prostaglandin E2 production by 2'-hydroxychalcone derivatives and the mechanism of action

The effects of 14 synthetic 2′‐hydroxychalcone derivatives on prostaglandin E2 (PGE2) production in rat peritoneal macrophages stimulated by the protein kinase C activator, 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), were examined to clarify the structure‐activity relationship. 2′,4‐Dihydroxy‐4′‐methoxychalcone (compound 3), 2′,4‐dihydroxy‐6′‐methoxychalcone (compound 8) and 2′‐hydroxy‐4′‐methoxychalcone (compound 9) suppressed PGE2 production more potently than the other compounds. The IC50 (50 % Inhibitory concentration) value for compounds 3, 8 and 9 was calculated to be 3 μ. The activity of cyclooxygenase (COX)‐1 was inhibited slightly by compound 9, but that of COX‐2 was not inhibited. At concentrations that inhibited the production of PGE2, compound 9 had no effect on the release of radioactivity from [3H]arachidonic acid‐labelled macrophages stimulated by TPA. Western‐blot analysis revealed that the induction of COX‐2 protein by TPA was inhibited by compound 9 in parallel with the inhibition of PGE2 production. Compounds 3 and 8 had similar effects. These findings suggest that 4′‐methoxyl and 6′‐methoxyl groups are required for the expression of more potent inhibitory activity against PGE2 production, and that the inhibition of PGE2 production by these 2′‐hydroxychalcone derivatives is due to the inhibition of TPA‐induced COX‐2 protein expression.