An-Rong Lee

Antioxidative and Anti-Inflammatory Activities of Polyhydroxyflavonoids of Scutellaria baicalensis GEORGI

The active ingredients of ‘golden root’ of Scutellaria baicalensis GEORGI (Huang-Qin), a valuable traditional Chinese medicine, are polyhydroxyflavonoids, namely baicalein, oroxylin A and wogonin. With the objective of overcoming their poor solubility and to investigate their structure and activity relationships, baicaleinyl 7-O-sulfate was prepared, and extensive comparative antioxidative and anti-inflammatory tests were conducted. All the polyhydroxyflavonoids exhibited significant antioxidative and free-radical scavenging activities. In respect of their nitric oxide (NO) inhibition, wogonin was superior to all the other flavonoids, while oroxylin A was most potent in the inhibition of lipid peroxidation. Wogonin proved to be the most potent (82.9% inhibition, p<0.05) in its anti-inflammatory activity against carrageenan-induced rat hind paw edema. There was a correlation between the in-vivo anti-inflammatory activity and the in-vitro antioxidative activities.

Synthesis of baicalein derivatives as potential anti‐aggregatory and anti‐inflammatory agents

The direct acylation of trimethoxyphenol (1) with substituted cinnamoyl chlorides followed by Fries rearrangement and cyclization afforded a practical route for the synthesis of novel baicalein derivatives 4 functionalized on the B‐ring in good overall yields. In the methylthiazoletetrazolium bromide (MTT) assay, none of the synthetic polyhydroxyflavonoids were cytotoxic at concentrations up to 200 μm on lipopolysaccharide (LPS)‐activated murine RAW 264.7 macrophages over 24 h, while in the same cells they significantly inhibited NO production. Among the derivatives, 4d (IC50 = 46.1 ± 0.3 μm) was found to exhibit the most potent activity compared with N‐nitro‐L‐arginine methyl ester (L‐NAME, IC50 > 300 μm). Compounds 4b, 4e, 4f, 4h and 4i remarkably inhibited platelet aggregation induced by arachidonic acid and collagen in rabbit washed platelets compared with aspirin. Analysis of their structure‐activity relationships indicated that, in the structural modification on the B‐ring of baicalein (4a), introduction of appropriate electro‐withdrawing substituents such as 2‐CI (4b), 4‐CI (4d), and 4‐phenyl (4i) notably increased the potency on the inhibition of LPS‐activated NO production and arachidonic acid‐ and collagen‐induced aggregation. Baicalein itself was equally effective in the inhibition of LPS‐activated NO production and collagen‐induced aggregation but less active against arachidonic acid‐induced aggregation. Our in‐vitro results suggested that by appropriate structural modification of baicalein it may be possible to develop novel therapeutic agents against platelet‐aggregation and inflammation.

Ionic mechanisms responsible for the antiarrhythmic action of dehydroevodiamine in guinea-pig isolated cardiomyocytes.

1 Dehydroevodiamine alkaloid (DeHE), an active ingredient of a Chinese herbal medicine Wu‐Chu‐Yu (Evodiae frutus), has been shown to decrease aterial blood pressure in experimental animals and prolong action potential duration in cardiac cells. The aim of the present study was to explore the ionic basis of its possible antiarrhythmic effects. 2 Guinea‐pig atrial and ventricular myocytes were isolated enzymatically and the ionic currents were recorded under whole‐cell patch‐clamp with single suction pipettes. 3 DeHE at a concentration of 0.1 μm inhibited reversibly the time‐dependent outward K current (delayed rectifier, Ik) and the Na‐dependent inward current (INa). 4 In low‐K (1 mm) and high‐Ca (9 mm) solution, DeHE also depressed the delayed afterdepolarizations (DAD) and the transient inward current (Iti) induced by 2 μm strophanthidin. On the other hand, DeHE occasionally induced early afterdepolarizations and slow response action potentials at a depolarized level. 5 At higher concentrations (1 μm and above), the L‐type Ca current (ICa,L) was moderately inhibited. 6 The present findings indicate that DeHE may depress triggered arrhythmias in Ca‐overloaded guinea‐pig cardiac myocytes through its inhibitory actions on INa, Iti and, to a smaller extent, ICa. DeHE may also exert class III antiarrhythmic effect through a reduction of outward K currents (Ik) across the sarcolemma.

Differential inotropic effects of halothane and isoflurane in dog ventricular tissues

The differential effects of halothane (0.25-0.75%) and isoflurane (0.5-1.25%) on the electromechanical activity of canine ventricular tissues were compared in vitro. In Purkinje fibres, halothane but not isoflurane could induce an initial increase of contractile force which was not blocked by diltiazem or propranolol. In ventricular muscles, halothane decreased the resting state contraction more markedly than isoflurane. The results suggest that halothane induces a greater negative inotropy than isoflurane through a differential alteration of intracellular Ca2+ stores.

Zinc Sulphadiazines: Novel Topical Antimicrobial Agents for Burns

Two new zinc sulphadiazine (Zn(SD)2)‐amine complexes, zinc sulphadiazine‐methylamine (Zn(SD)2(CH3NH2)2) and zinc sulphadiazine‐ethylenediamine (Zn(SD)2(C2H8N2)3·H2O), were prepared and compared with silver sulphadiazine (AgSD). The compounds were readily obtained by reaction of zinc nitrate hexahydrate with sulphadiazine or its salt in methylamine and ethylenediamine, respectively.

Synthesis and radical scavenging of novel magnolol derivatives

We have investigated the developdment of potential antioxidants based on magnolol, a naturally occurring biphenolic obtained from the bark of Magnolia officinalis. A series of aminomethylated derivatives of magnolol were synthesized under the aromatic Mannich reaction. In‐vitro testing for diphenyl‐p‐picrylhydrazyl (DPPH) scavenging and chemiluminescence assays in whole cell models revealed that the pyrrolidyl‐containing magnolols (2b (5,5′‐diallyl‐3‐(pyrrolidin‐1‐ylmethyl)‐biphenyl‐2,2′‐diol), 3a (5,5′‐diallyl‐3,3′‐bis‐(pyrrolidin‐1‐ylmethyl)‐biphenyl‐2,2′‐diol) and 4c (5,5′‐diallyl‐3‐(morphorin‐4‐ylmethyl)‐3′‐(pyrrolidin‐1‐ylmethyl)‐biphenyl‐2,2′‐diol)) displayed promising free radical scavenging effects as compared with magnolol. The results from compound 4c indicated that the naturally occurring component was suitable to be a lead compound toward promising antioxidants.

Synthesis of 5,6,7-trimethoxyflavone as a key intermediate for the preparation of baicalein

Approaches towards the preparation of 5,6,7-trimethoxyflavone (8), a key intermediate for the synthesis of baicalein, are discussed. Of the synthetic routes, the most efficient was accomplished by direct Fries acylation of trimethoxyphenol (1) with cinnamoyl chloride followed by oxidative cyclization of the resulting chalcone 6 with I 2 /DMSO in good overall yields (70%). Demethylation of 8 using 47% HBr/AcOH readily produced baicalein. The chalcone 6 could also be prepared by Claisen-Schmidt condensation of acetophenone 2 with benzaldehyde catalyzed in alkali.

Novel Daidzein Analogs and Their in Vitro Anti-Influenza Activities

A series of novel isoflavonoids were synthesized based on structural modifications of daidzein, an active ingredient of traditional Chinese medicine (TCM) and evaluated for their anti‐influenza activity, in vitro, against H1N1 Tamiflu‐resistant (H1N1 TR) virus in the MDCK cell line. Among them, 4‐oxo‐4H‐1‐benzopyran‐8‐carbaldehydes 11a–11g were most promising, and they demonstrated better activities and selectivities comparable to those the reference ribarivin, a nucleoside antiviral agent. 3‐(4‐Bromophenyl)‐7‐hydroxy‐4‐oxo‐4H‐1‐benzopyran‐8‐carboxaldehyde (11c) displayed the best inhibitory activity (EC50, 29.0 μM) and selectivity index (SI>10.3). Analysis of the structureactivity relationships (SAR) indicated that both the non‐naturally‐occurring Br‐substituted B‐ring and appropriate CHO and OH groups on the A‐ring might be critical for the activity and selectivity against H1N1 TR influenza viruses.

The novel compound MP407 inhibits platelet aggregation through cyclic AMP-dependent processes

Abstract Platelet hyperactivity plays a critical role for initiating several vascular diseases such as atherothrombosis. Therefore, development of effective antiplatelet agents is necessary for ameliorating platelet‐related diseases. In this study, we investigated the effects of the new synthesized compound, MP407 on platelet aggregation and further elucidated the underlying mechanisms. Our results demonstrated that MP407 dose‐dependently inhibited collagen‐induced platelet aggregation, thromboxane B2 (TXB2) production, intracellular Ca2+ mobilization, platelet membrane GPIIb/IIIa expression, and the phosphorylation of Akt, GSK3&bgr;, p38MAPK, and phospho (Ser) PKC substrate (p47). Moreover, MP407 is able to increase the cyclic AMP formation both in resting and activated platelets. However, blocking cyclic AMP formation with 2′5′‐ddAdo, an inhibitor of adenylate cyclase, greatly reversed the antiplatelet activity of MP407 and related platelet‐activating pathways. MP407 also enhanced VASP phosphorylation at Ser157 in collagen‐stimulated platelets, which was attenuated by addition of 2′5′‐ddAdo. Therefore, the antiplatelet activity of MP407 may be modulated by cyclic AMP‐dependent regulation of Akt, GSK3&bgr;, p38MAPK and VASP phosphorylation. Notably, treatment with MP407 markedly reduced the pulmonary thrombosis and the numbers of paralysis and death in mice induced by ADP injection, but did not affect the bleeding time. Taken together, MP407 may be a potential candidate or lead compound for developing novel antiplatelet or antithrombotic agents for platelet hyperactivity‐triggered disease therapy.