Changbae Jin

Neuroprotective effects of antioxidative flavonoids, quercetin, (+)-dihydroquercetin and quercetin 3-methyl ether, isolated from Opuntia ficus-indica var. saboten.

The flavonoids quercetin, (+)-dihydroquercetin, and quercetin 3-methyl ether were isolated from the ethyl acetate fractions of the fruits and stems of Opuntia ficus-indica var. saboten. In the present study, we evaluated their protective effects against oxidative neuronal injuries induced in primary cultured rat cortical cells and their antioxidant activities by using three different cell-free bioassays. Quercetin was found to inhibit H(2)O(2)- or xanthine (X)/xanthine oxidase (XO)-induced oxidative neuronal cell injury, with an estimated IC(50) of 4-5 micro g/ml. However, it was no more protective at concentrations of 30 micro g/ml and above. (+)-Dihydroquercetin concentration-dependently inhibited oxidative neuronal injuries, but it was less potent than quercetin. On the other hand, quercetin 3-methyl ether potently and dramatically inhibited H(2)O(2)- and X/XO-induced neuronal injuries, with IC(50) values of 0.6 and 0.7 micro g/ml, respectively. All three principles markedly inhibited lipid peroxidation and scavenged 1,1-diphenyl-2-picrylhydrazyl free radicals. In addition, quercetin and quercetin 3-methyl ether were shown to inhibit XO activity in vitro, with respective IC(50) values of 10.67 and 42.01 micro g/ml. These results indicate that quercetin, (+)-dihydroquercetin, and quercetin 3-methyl ether are the active antioxidant principles in the fruits and stems of Opuntia ficus-indica var. saboten exhibiting neuroprotective actions against the oxidative injuries induced in cortical cell cultures. Furthermore, quercetin 3-methyl ether appears to be the most potent neuroprotectant of the three flavonoids isolated from this plant.

Caffeic acid phenethyl ester inhibits nitric oxide synthase gene expression and enzyme activity

Since nitric oxide (NO) synthesized by inducible nitric oxide synthase (iNOS) has been known to be involved in inflammatory and autoimmune-mediated tissue destruction, modulation of NO synthesis or action represents a new approach to the treatment of inflammatory and autoimmune diseases. Caffeic acid phenethyl ester (CAPE), an active component of honeybee propolis, has been identified to show anti-inflammatory, anti-viral and anti-cancer activities. The present study, therefore, examined effects of CAPE on iNOS expression and activity of iNOS enzyme itself. Treatment of RAW 264.7 cells with CAPE significantly inhibited NO production and iNOS protein expression induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma). CAPE also inhibited iNOS mRNA expression and nuclear factor-kappa B (NF-kappaB) binding activity in a concentration-dependent manner. Furthermore, transfection of RAW 264.7 cells with iNOS promoter linked to a chloramphenicol acetyltransferase reporter gene, revealed that CAPE inhibited the iNOS promoter activity induced by LPS plus IFN-gamma through the NF-kappaB sites of the iNOS promoter. In addition, CAPE directly interfered with the catalytic activity of murine recombinant iNOS enzyme. These results suggest that CAPE may exert its anti-inflammatory effect by inhibiting the iNOS gene expression at the transcriptional level through the suppression of NF-kappaB activation, and by directly inhibiting the catalytic activity of iNOS.

Anti-angiogenic, antioxidant and xanthine oxidase inhibition activities of the mushroom Phellinus linteus.

Fruiting bodies of Phellinus linteus were extracted with 70% ethanol at room temperature. The Phellinus linteus extract (PL) showed strong anti-angiogenic activity, which was detected using the chick embryo chorioallantoic membrane (CAM) assay. The in vitro antioxidant activities of PL were evaluated using two different bioassays. PL was comparable to Vitamin C in scavenging the stable free radical 1,1-diphenyl-2-picrylhyrazyl (DPPH). It also inhibited lipid peroxidation (LPO) in a concentration-dependent manner. These results suggest that antioxidant and anti-angiogenic activities of Phellinus linteus would be partly responsible for its anti-tumor effect.

Constituents of the stems and fruits of Opuntia ficus-indica var. saboten

From the stems and fruits ofOpuntia ficus-indica var.saboten, eight flavonoids, kaempferol (1), quercetin (2), kaempferol 3-methyl ether (3), quercetin 3-methyl ether (4), narcissin (5), (+)-dihydrokaempferol (aromadendrin,6), (+)-dihydroquercetin (taxifolin,7), eriodictyol (8), and two terpenoids, (6S,9S)-3-oxo-α-ionol-|β-D-glucopyranoside (9) and corchoionoside C (10) were isolated and identified by means of chemical and spectroscopic. Among these isolates, compounds3–5 and8–10 were reported for the first time from the stems and fruits of O.ficusindica var.saboten.

Structure-Related Inhibition of Human Hepatic Caffeine N3-Demethylation by Naturally Occurring Flavonoids

The effects of flavonoids on caffeine N3-demethylation, a marker activity of CYP1A2, in human liver microsomes were investigated to elucidate the inhibition mechanism and the structure-activity relationship. Caffeine N3-demethylase activity was inhibited by the presence of various flavonoids, whose structures seem to be closely related to the degree of inhibition. Among twenty-one compounds tested, the most active was chrysin with an IC50 value of 0.2 microM. Others had IC50 values ranging from 1 to more than 500 microM. Kinetic analysis revealed that the mechanism of inhibition varied among the flavonoids. The inhibitory effect was postulated to be governed by factors such as the number of hydroxyl groups and glycosylation of these free hydroxyl groups. An increase in the number of free hydroxyl groups reduced the inhibitory effect on P450 activity. Analysis of the quantitative structure-activity relationship (QSAR) showed that the volume to surface area ratio was the most effective factor on the inhibition of caffeine N3-demethylation, and the electron densities on the C3 and C4 atoms exercised significant influence on the inhibitory effect. The calculated inhibitory effect of flavonoids on CYP1A2 activity was highly correlated with the antimutagenicity of flavonoids in 2-amino-3,4-dimethylimidazo[4,5-flquinoline (MelQ)-induced umu response.

Ethanol extract of propolis inhibits nitric oxide synthase gene expression and enzyme activity.

Propolis obtained from honeybee hives has been used in Oriental folk medicine as an anti-inflammatory, anti-carcinogenic, or immunomodulatory agent. However, the molecular basis for anti-inflammatory properties of propolis has not yet been established. Since nitric oxide (NO) synthesized by inducible nitric oxide synthase (iNOS) has been known to be involved in inflammatory and autoimmune-mediated tissue destruction, modulation of NO synthesis or action represents a new approach to the treatment of inflammatory and autoimmune diseases. The present study, therefore, examined effects of ethanol extract of propolis (EEP) on iNOS expression and activity of iNOS enzyme itself. Treatment of RAW 264.7 cells with EEP significantly inhibited NO production and iNOS protein expression induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma). EEP also inhibited iNOS mRNA expression and nuclear factor-kappa B (NF-kappaB) binding activity in a concentration-dependent manner. Furthermore, transfection of RAW 264.7 cells with iNOS promoter linked to a chloramphenicol acetyltransferase (CAT) reporter gene, revealed that EEP inhibited the iNOS promoter activity induced by LPS plus IFN-gamma through the NF-kappaB sites of the iNOS promoter. In addition, EEP directly interfered with the catalytic activity of murine recombinant iNOS enzyme. These results suggest that EEP may exert its anti-inflammatory effect by inhibiting the iNOS gene expression via action on the NF-kappaB sites in the iNOS promoter and by directly inhibiting the catalytic activity of iNOS.

Inhibition of angiogenesis by propolis

Propolis, obtained from honeybee hives, has been used in Oriental folk medicine as an antiinflammatory, anti-carcinogenic, and immunomodulatory agent. There is considerable evidence suggesting that angiogenesis and chronic inflammation are codependent. Blockage of angiogenesis results in an anti-inflammatory effect. Ethanol (EEP) and ether extracts of propolis (REP), and caffeic acid phenethyl ester (CAPE), an active component of propolis, were examined for their anti-angiogenic activities using the chick embryo chorioallantoic membrane (CAM), and the calf pulmonary arterial endothelial (CPAE) cell proliferation, assays. The presence of EEP, REP and CAPE inhibited angiogenesis in the CAM assay and the proliferation of CPAE cells. The results suggest that anti-angiogenic activities of EEP, REP and CAPE are also responsible for their anti-inflammatory effect.

Synthesis of tyrosinase inhibitory (4-oxo-4H-pyran-2-yl)acrylic acid ester derivatives

Melanogenesis is a physiological process that results in the production of melanin pigment. However, excessive accumulations of epidermal pigmentation can cause various hyperpigmentary disorders such as, melasma and age spots. Kojic acid and hydroxylated cinnamic acid derivatives are known to inhibit tyrosinase, a key component of melanin biosynthesis. Pyronyl-acrylic acid esters 3a-i, which share structural features of kojic acid and hydroxylated cinnamic acid, were prepared and their abilities to inhibit tyrosinase and melanin production were evaluated. Of the esters synthesized, 3e and 3h, which derived from diethylene glycol moieties were found to inhibit melanin production by ca. 20% at 20 microg/ml, whereas kojic acid at 200 microg/ml inhibited melanin production by 15.8%.

Antioxidant caffeic acid derivatives from leaves ofparthenocissus tricuspidata

Five caffeic acid derivatives; methyl ester of caffeoylglycolic acid (1), dimethyl ester of caffeoyltartaric acid (2), dimethyl ester of caffeoyltartronic acid (3), monomethyl ester of caffeoyltartronic acid (4), methyl ester of caffeic acid (5), and some other secondary metabolites including; quercetin, quercetin 3-O-β-D-glucuronide methyl ester, kaempferol, 3,5,7,4′-O-tetramethylkaempferol, β-sitosterol glucoside, 2α-hydroxyursolic acid and 2,24-dihydroxyursolic acid, have been isolated and characterized. All the isolated compounds were characterized with the help of NMR spectroscopy and mass spectrometry. Structure of compound3 was also confirmed by a single X-ray crystallographic technique. Isolates were evaluated for antioxidant activities and most of the tested compounds were found to be potent in DPPH free radical scavenging (IC50 = 4.56–14.17 μg/mL) and superoxide anion scavenging (IC50= 0.58–7.39 μg/mL) assays.

A new epicatechin gallate and calpain inhibitory activity from Orostachys japonicus

Calpains are calcium-dependent proteases that cleave a variety of intracellular substrates. The overactivation of mu-calpain is associated with a wide range of disease conditions. To search for calpain inhibitors from natural products, the phytochemical constituents of the ethyl acetate fraction of the whole plant of Orostachys japonicus (Crassulaceae) were studied. The various chromatographic separation of this fraction led to the isolation of a new tannin, (-)-epicatechin 5-gallate (1) along with 9 known compounds. Their structures were elucidated by spectroscopic and chemical analyses. Among them, (-)-epicatechin 5-gallate (1) and kaempferol (9) exhibited moderate inhibitory activity against mu-calpain with IC(50) values of 18.0+/-2.9 and 15.4+/-2.0 microg/ml, respectively.