Rhamnus Nakaharai Research Articles

A new anthraquinone glycoside from Rhamnus nakaharai and anti-tyrosinase effect of 6-methoxysorigenin

In continual study on the heartwood of Rhamnus nakaharai, a new alaternin-8-O-glucoside, namely 1,2,6,8-tetrahydroxy-3-methylanthraquinone-8-O-β-glucopyranoside (1), together with some known compounds were further isolated and characterised by 1-D, 2-D NMR and other spectral evidences. The free radical scavenging and antityrosinase activities of the isolates, including alaternin (1a), emodin (2a), emodin-8-O-β-glucopyranoside (2), 6-methoxysorigenin-8-O-β-glucopyranoside (3) and 6-methoxysorigenin (3a) were tested. Alaternin (1a) exhibited to be mild DPPH radical scavenger with half as potent as vitamin C, while both alaternin (1a) and emodin-8-O-β-glucopyranoside (2) exhibited stronger SOD-like activity than that of BHA. 6-Methoxysorigenin (3a), a reported potential antioxidant, and its 8-O-glucoside (3) both performed significant inhibitory effect on mushroom tyrosinase with about twice as potent as kojic acid, the positive control.

Two novel carbonic acid esters conjugated with oligophenyl glucosides from Rhamnus nakaharai

Two novel carbonic acid esters conjugated with oligomeric phenyl glycosides have been isolated and characterized from the wood of Rhamnus nakaharai. The structures are characterized as 5,7-dihydroxyphthalide 5- O-β-[6- O-{3″-methoxy-4″- O-β-[6‴- O-(4⁗- O-carboxy-3⁗,5⁗-dimethoxy)phenyl]glucopyranosyl}phenyl]glucopyranoside ( 1) and 6- O-{3′-methoxy-4′- O-β-[6″- O-(3‴-mercapto-5‴-methoxy-4‴- O-methylcarboxy)phenyl]glucopyranosyl}phenyl β-glucopyranose ( 2), namely, rhamnakoside A ( 1) and B ( 2), all by NMR and other spectral methods, respectively. They could be a novel case of phase II detoxification products and biogenetic diversity in plant kingdom.

Antioxidative Effects of 6-Methoxysorigenin and Its Derivatives from Rhamnus nakaharai

In the search for potential antioxidants, the naphthalenic compounds, 6-methoxysorigenin (2) and its glycosides [i.e. 6-methoxysorigenin-8-O-glucoside (3), alpha-sorinin (4), and 6-methoxysorigenin-8-rutinoside (5)] isolated from Rhamnus nakaharai together with two acylates (peracetate and perpropionate) of 2 were evaluated for antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH), metal chelating, and electron spin resonance (ESR) assays as well as anti-lipid peroxidation assay. The results showed that 2 possesses the most potent DPPH radical scavenging, metal chelating, and anti-lipid peroxidation activities with IC50 values of 3.48, 615.90, and 5.95 microg/ml, respectively. The glycosides 3, 4, and 5 showed decreasing antioxidant activity that was related to an increased substitution at 1,8-dihydroxyl with sugar molecules. This suggests the importance of 1,8-dihydroxyl of 2 in the antioxidative effect. The iron chelation result could further explain the main cause of increasing antioxidant activity in 2. The acylates of 2 (2a peracetate and 2b perpropionate), although lacking a free hydroxyl, also exhibited significant anti-lipid peroxidation effect. ESR results further demonstrated that 2 possesses strong antioxidant activities. Taken together, this study shows that 2 is a potent antioxidant and may also be used for designing new iron chelators for clinical applications.

Mechanisms of suppression of nitric oxide production by 3- O-methylquercetin in RAW 264.7 cells

Rhamnus nakaharai Hayata (Rhamnaceae) is used as a folk medicine in Taiwan for treating constipation, inflammation, tumors, and asthma. 3- O-Methylquercetin (3-MQ), a main constituent of the plant, has been reported to have potential for use in the treatment of asthma. The mechanisms of anti-inflammation of 3-MQ are still unclear. Nitric oxide (NO) production induced by lipopolysaccharide (LPS) through iNOS expression in RAW 264.7 cells, a mouse macrophage cell line, may reflect the degree of inflammation and may provide a measure for assessing the effect of drugs on the inflammatory process. Therefore, we were interested in investigating the mechanisms of suppression of NO production by 3-MQ in RAW 264.7 cells. 3-MQ (1–10 μM) concentration-dependently inhibited LPS (100 ng/mL)-induced NO production in RAW 264.7 cells. The IC 50 value was calculated to be 4.23 μM. 3-MQ (1–10 μM) significantly and concentration-dependently inhibited LPS (100 ng/mL)-induced iNOS protein and mRNA expressions in cells. The IC 50 values were calculated to be 4.36 and 6.53 μM, respectively. There was no significant difference among these three IC 50 values of 3-MQ. In conclusion, 3-MQ may exert its anti-inflammatory effect through the inhibition of iNOS DNA transcription.

Suppressive Effects of 3-O-Methylquercetin on Ovalbumin-Induced Airway Hyperresponsiveness

Rhamnus nakaharai Hayata (Rhamnaceae) has been used as a folk medicine in Taiwan for treating constipation, inflammation, tumors, and asthma. 3-O-Methylquercetin (3-MQ), a main constituent of the plant, has been reported to inhibit total cAMP- and cGMP-phosphodiesterase (PDE) of guinea pig trachealis at low concentrations. 3-MQ has been also reported to more selectively inhibit PDE3 than PDE4 with a low K(m) value. Therefore we were interested in investigating its suppressive effects on ovalbumin (OVA)-induced airway hyperresponsiveness in vivo and in vitro. 3-MQ (3-30 micromol/kg, i. p.) significantly suppressed the enhanced pause (Penh) value induced by aerosolized methacholine (50 mg/mL) in sensitized mice after secondary allergen challenge. 3-MQ (3-30 micromol/kg, i. p.) also significantly suppressed total inflammatory cells, macrophages, neutrophils, and eosinophils, but not lymphocytes. In addition, 3-MQ (3 micromol/kg, i. p.) significantly decreased the secretion of TNF-alpha, and at the highest dose (30 micromol/kg, i. p.) even decreased the secretions of IL-4, IL-5, and TNF-alpha. 3-MQ (1-10 microM) as well as Ro 20-1724 (3-30 microM), a selective PDE4 inhibitor, significantly attenuated OVA (100 microg/mL)-induced contractions. 3-MQ (30 microM) as well as milrinone (1-10 microM), a selective PDE3 inhibitor, significantly enhanced baseline contractions in isolated guinea pig left and right atria. However, neither 3-MQ nor milrinone significantly affected baseline beating rate in the right atria. 3-MQ (3-30 micromol/kg, i. p.) did not significantly affect systolic pressure in conscious mice. In conclusion, 3-MQ has both anti-inflammatory and bronchodilating effects, and has the potential for use in the treatment of asthma at a dose without affecting blood pressure.

3-O-methylquercetin more selectively inhibits phosphodiesterase subtype 3.

Rhamnus nakaharai Hayata (Rhamnaceae), has been used as a folk medicine in Taiwan for treating constipation, inflammation, tumors and asthma. 3-O-methylquercetin (3-MQ), a main constituent of the plant, has been reported to inhibit total cAMP- and cGMP-phosphodiesterase (PDE) of guinea pig trachealis. Therefore we were interested in investigating the inhibitory effect of 3-MQ on various PDE isozymes from guinea pig lungs and hearts. Isolated guinea pig lungs and hearts were homogenized and centrifuged. The supernatant was chromatographed over a column of Q-sepharose, and eluted with various concentrations of NaCl. In the following order, PDE subtypes 1, 5, 2, 4 from lungs, and 3 from hearts were separated. The IC 50 values of 3-MQ on these isozymes were 31.9, 86.9, 18.6, 28.5 and 1.6 microM, respectively. 3-MQ (10-100 microM) non-competitively inhibited PDE2, but competitively inhibited PDE4. 3-MQ (1-10 microM) also competitively inhibited PDE3. However, 3-MQ (10-100 microM) did not competitively inhibit PDE1 and 5, although it had a tendency to competitively inhibit PDE1 at concentrations of 10 - 30 microM. The present results showed that K i value of 3-MQ was similar to that of milrinone in PDE3, and was not significantly different from that of Ro 20 - 1724 in PDE4, respectively. In conclusion, 3-MQ was revealed to be a selective and competitive PDE3/PDE4 inhibitor, although its inhibitory effect on PDE4 was not potent. Therefore, 3-MQ may have a potential in the treatment of asthma beside its antiviral activity.

Mechanisms of relaxant action of 3-O-methylquercetin in isolated guinea pig trachea.

We investigated the mechanisms of action of 3-O-methylquercetin (3-MQ), isolated from Rhamnus nakaharai (Hayata) Hayata (Rhamnaceae) which is used as a folk medicine for treating constipation, inflammation, tumors and asthma in Taiwan. The tension changes of tracheal segments were isometrically recorded on a polygraph. 3-MQ concentration-dependently relaxed histamine (30 microM)-, carbachol (0.2 microM)- and KCl (30 mM)-induced precontractions, and inhibited cumulative histamine-, and carbachol-induced contractions in a non-competitive manner. 3-MQ also concentration-dependently and non-competitively inhibited cumulative Ca(2+)-induced contractions in depolarized (K(+), 60 mM) guinea-pig trachealis. The nifedipine (10 microM)-remaining tension of histamine (30 microM)-induced precontraction was further relaxed by 3-MQ, suggesting that no matter whether VDCCs were blocked or not, 3-MQ may have other mechanisms of relaxant action. The relaxant effect of 3-MQ was unaffected by the removal of epithelium or by the presence of propranolol (1 microM), 2',5'-dideoxyadenosine (10 microM), methylene blue (25 microM), glibenclamide (10 microM), N(omega)-nitro-L-arginine (20 microM), or alpha-chymotrypsin (1 U/ml). However, 3-MQ (7.5 - 15 microM) and IBMX (3 - 6 microM), a positive control, produced parallel and leftward shifts of the concentration-response curve of forskoline (0.01 - 3 microM) or nitroprusside (0.01 - 30 microM). 3-MQ or IBMX at various concentrations (10 - 300 microM) concentration-dependently and significantly inhibited cAMP- and cGMP-PDE activities of the trachealis. The IC50 values of 3-MQ were estimated to be 13.8 and 14.3 microM, respectively. The inhibitory effects of 3-MQ on both enzyme activities were not significantly different from those of IBMX, a non-selective PDE inhibitor. The above results reveal that the mechanisms of relaxant action of 3-MQ may be due to its inhibitory effects on both PDE activities and its subsequent reducing effect on [Ca(2+)]i of the trachealis.3-MQ:3-O-methylquercetinIBMX:3-isobutyl-1-methylxanthineVDCCs:voltage dependent calcium channelscAMP:adenosine 3',5'-cyclic monophosphatecGMP:guanosine 3',5'-cyclic monophosphatePDE:phosphodiesteraseWe investigated the mechanisms of action of 3-O-methylquercetin (3-MQ), isolated from Rhamnus nakaharai (Hayata) Hayata (Rhamnaceae) which is used as a folk medicine for treating constipation, inflammation, tumors and asthma in Taiwan. The tension changes of tracheal segments were isometrically recorded on a polygraph. 3-MQ concentration-dependently relaxed histamine (30 microM)-, carbachol (0.2 microM)- and KCl (30 mM)-induced precontractions, and inhibited cumulative histamine-, and carbachol-induced contractions in a non-competitive manner. 3-MQ also concentration-dependently and non-competitively inhibited cumulative Ca(2+)-induced contractions in depolarized (K(+), 60 mM) guinea-pig trachealis. The nifedipine (10 microM)-remaining tension of histamine (30 microM)-induced precontraction was further relaxed by 3-MQ, suggesting that no matter whether VDCCs were blocked or not, 3-MQ may have other mechanisms of relaxant action. The relaxant effect of 3-MQ was unaffected by the removal of epithelium or by the presence of propranolol (1 microM), 2',5'-dideoxyadenosine (10 microM), methylene blue (25 microM), glibenclamide (10 microM), N(omega)-nitro-L-arginine (20 microM), or alpha-chymotrypsin (1 U/ml). However, 3-MQ (7.5 - 15 microM) and IBMX (3 - 6 microM), a positive control, produced parallel and leftward shifts of the concentration-response curve of forskoline (0.01 - 3 microM) or nitroprusside (0.01 - 30 microM). 3-MQ or IBMX at various concentrations (10 - 300 microM) concentration-dependently and significantly inhibited cAMP- and cGMP-PDE activities of the trachealis. The IC50 values of 3-MQ were estimated to be 13.8 and 14.3 microM, respectively. The inhibitory effects of 3-MQ on both enzyme activities were not significantly different from those of IBMX, a non-selective PDE inhibitor. The above results reveal that the mechanisms of relaxant action of 3-MQ may be due to its inhibitory effects on both PDE activities and its subsequent reducing effect on [Ca(2+)]i of the trachealis.3-MQ:3-O-methylquercetinIBMX:3-isobutyl-1-methylxanthineVDCCs:voltage dependent calcium channelscAMP:adenosine 3',5'-cyclic monophosphatecGMP:guanosine 3',5'-cyclic monophosphatePDE:phosphodiesterase

In vitro anti-inflammatory effects of quercetin 3-O-methyl ether and other constituents from Rhamnus species.

The anti-inflammatory activities of the isolated flavonoids, quercetin 3-O-methyl ether (1), kaempferol (2), and quercetin (3), of Rhamnus nakaharai, and anthraquinone, frangulin B (4), of Rhamnus formosana, were assessed in vitro by determining their inhibitory effects on the chemical mediators released from mast cells, neutrophils, macrophages, and microglial cells. Compounds 1 - 3 strongly inhibited the release of beta-glucuronidase and lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe/cytochalasin B (fMLP/CB). Compound 1 strongly inhibited superoxide anion formation in fMLP/CB or phorbol 12-myristate 13-acetate (PMA)-stimulated rat neutrophils. Compound 1 exhibited potent inhibitory effect on tumor-necrosis factor-alpha ( TNF-alpha) formation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells while 1 and 4 showed potent inhibitory effects on TNF-alpha formation in LPS/IFN-gamma (interferon-gamma)-stimulated murine microglial cell lines N9.

Novel Antiplatelet Naphthalene from Rhamnus nakaharai

A new naphthalene derivative, isotorachrysone [1], was isolated from the stem bark of Rhamnus nakaharai along with several known compounds. The antiplatelet effects of isotorachrysone [1], isotorachrysone peracetate [2], 6-methoxysorigenin [3], quercetin 3-O-methyl ether [4], and quercetin 3-O-methyl ether peracetate [5] were studied using washed rabbit platelets. Of the compounds tested, 1, 2, 4, and 5 showed potent antiplatelet effects on arachidonic acid (AA-) and collagen-induced platelet aggregation. Compound 5 also showed potent antiplatelet effects on platelet-activating factor-(PAF-) induced platelet aggregation. Isotorachrysone [1] and its peracetate [2] were also studied for antiplatelet activity in human platelet-rich plasma (PRP) and both showed potent inhibition of the secondary aggregation induced by epinephrine. The antiplatelet effects of 1 and 2 are due partially to an inhibitory effect on thromboxane formation.

Flavonol and Naphthalene Glycosides from Rhamnus nakaharai

A new naphrhalene glycoside and a new flavonol triglycoside have been isolated from the root bark of Rhammus nakahari. These compounds have been characterized a 6-methoxysorigenin-8-O-α-L-rhamnosyl (1→6)-glucoside [2] and kaempferol 3-O-[α-L-rhamnopyranosyl (1→4)-α-L-rhamnopyranosyl (1→6)]-β-D-galactopyranoside (kaempferol 3-isorhamninoside) [3]

Anthraquinone and naphthalene glycosides from Rhamnus nakaharai

A new anthraquinone glycoside and a new naphthalene glycoside have been isolated from the root bark of Rhamnus nakaharai. These compounds have been characterized as chrysophanol 8- O-xylosyl-(1 → 6)-glucoside and 2-acetyl-3-methyl-6-methoxynaphthalene-1,8-diol 8- O-xylosyl-(1 → 6)-glucoside, respectively.

Nakahalene and Cytotoxic principles of Formosan Rhamnus Species

A new naphthalene compound, named nakahalene, has been isolated from the root bark of Rhamnus nakaharai (Rhamnaceae) together with chrysophanol, physcion, emodin, rhamnocitrin, and kaempferol. Nakahalene has been characterized as 2-acetyl-3-methyl-6-methoxylnaphthalene-1,8-diol [4]. The cytotoxic effects of the isolated anthraquinones of Rhamnus formosana and Rhamnus nakaharai were investigated

Rhamnustrioside, a flavonol triglycoside from Rhamnus nakaharai

A new flavonol triglycoside, rhamnustrioside, has been isolated from the fresh fruits of Rhamnus nakaharai together with kaempferol. The structure