Sheng‐Chu Kuo

As part of our continuing search for potential anticancer candidates among 2-phenyl-4-quinolones and 2-phenyl-4-quinazolinones, two series of 6,7,2',3',4',5'-substituted 2-phenyl-4-quinazolinones and 6,2',3',4',5'-substituted 2,3-dihydro-2-phenyl-4-quinazolinones were synthesized and evaluated for cytotoxicity and as inhibitors of tubulin polymerization. In general, a good correlation was found between the two activities. Five of the 6-substituted heterocyclic 2-phenyl-4-quinozolinones (37-51) showed significant cytotoxicity against a panel of human tumor cell lines with EC(50) values in the low micromolar to nanomolar concentration ranges. Compound 38 was the most potent of these compounds, as well as the most potent inhibitor of tubulin polymerization in this series. The activity of 38 was in the same range as those of the antimitotic natural products, colchicine, podophyllotoxin, and combretastatin A-4. Substituted 2-phenyl-4-quinazolinones and 2, 3-dihydro-2-phenyl-4-quinazolinones also displayed highly selective cytotoxicity against the ovarian cancer 1A9 and P-gp resistant KB-VIN cell lines.

1. Our previous study demonstrated that YC-1, a derivative of benzylindazole, is a novel activator of soluble guanylate cyclase (sGC) in rabbit platelets. This work investigated whether the antiplatelet effect of YC-1 was mediated by a nitric oxide (NO)/sGC/cyclic GMP pathway in human platelets. 2. In human washed platelets, YC-1 inhibited platelet aggregation and ATP released induced by U46619 (2 microM), collagen (10 micro ml(-1)) and thrombin (0.1 u ml(-1)) in a concentration-dependent manner with IC50 values of (microM) 2.1 +/- 0.03, 11.7 +/- 2.1 and 59.3 +/- 7.1, respectively. 3. In a 30,000 g supernatant fraction from human platelet homogenate, YC-1 (5-100 microM) increased sGC activity in a concentration-dependent manner. At the same concentration-range, YC-1 elevated cyclic GMP levels markedly, but only slightly elevated cyclic AMP levels in the intact platelets. 4. MY-5445, a selective inhibitor of cyclic GMP phosphodiesterase, potentiated the increases in cyclic GMP caused by YC-1, and shifted the concentration-anti-aggregation curve of YC-1 to the left. In contrast, HL-725, a selective inhibitor of cyclic AMP phosphodiesterase, did not affect either the increases in cyclic nucleotides or the anti-aggregatory effect caused by YC-1. 5. Methylene blue, an inhibitor of sGC, blocked the increases of cyclic GMP caused by YC-1, and attenuated markedly the anti-aggregatory effect of YC-1. The adenylate cyclase inhibitor, 2',5'-dideoxyadenosine (DDA) did not affect YC-1-induced inhibition of platelet aggregation. 6. Haemoglobin, which binds NO, prevented the activation of sGC and anti-aggregatory effect caused by sodium nitroprusside, but did not affect YC-1 response. 7. These results would suggest that YC-1 activates sGC of human platelets by a NO-dependent mechanism, and exerts its antiplatelet effects through the sGC/cyclic GMP pathway.

Development of anti-severe acute respiratory syndrome associated coronavirus (SARS-CoV) agents is pivotal to prevent the reemergence of the life-threatening disease, SARS. In this study, more than 200 extracts from Chinese medicinal herbs were evaluated for anti-SARS-CoV activities using a cell-based assay that measured SARS-CoV-induced cytopathogenic effect (CPE) in vitro on Vero E6 cells. Six herbal extracts, one each from Gentianae Radix ( lóng dǎn; the dried rhizome of Gentiana scabra), Dioscoreae Rhizoma ( shān yào; the tuber of Dioscorea batatas), Cassiae Semen ( jué míng zǐ; the dried seed of Cassia tora) and Loranthi Ramus ( sāng jì shēng; the dried stem, with leaf of Taxillus chinensis) (designated as GSH, DBM, CTH and TCH, respectively), and two from Rhizoma Cibotii ( gǒu jǐ; the dried rhizome of Cibotium barometz) (designated as CBE and CBM), were found to be potent inhibitors of SARS-CoV at concentrations between 25 and 200 μg/ml. The concentrations of the six extracts needed to inhibit 50% of Vero E6 cell proliferation (CC50) and 50% of viral replication (EC50) were determined. The resulting selective index values (SI = CC50/EC50) of the most effective extracts CBE, GSH, DBM, CTH and TCH were > 59.4, > 57.5, > 62.1, > 59.4, and > 92.9, respectively. Among these extracts, CBM and DBM also showed significant inhibition of SARS-CoV 3CL protease activity with IC50 values of 39 μg/ml and 44 μg/ml, respectively. Our findings suggest that these six herbal extracts may have potential as candidates for future development of anti-SARS therapeutics.AbbreviationsSARS,severe acute respiratory syndromeCoV,coronavirusCPE,cytopathogenic effectTCM,traditional Chinese medicine.

Two new triterpenoids, lucidenic acid N (1) and methyl lucidenate F (2), together with four known compounds, lucidenic acid A, lucidenolactone, lucidenic acid C, and ganoderic acid E, were isolated from the dried fruiting bodies of Ganoderma lucidum. Their structures were elucidated by spectral and chemical transformation studies. Among them, lucidenic acid N (1), lucidenic acid A, and ganoderic acid E showed significant cytotoxic activity against Hep G2, Hep G2,2,15, and P-388 tumor cells.