Inhibitory effect of triterpenes from Crataegus pinatifida on HIV-I protease.

The methanol extracts of the leaves of Crataegus pinnatifida showed potent inhibitory activities against HIV-1 protease at a concentration of 100 micrograms/ml. The subsequent fractionation and isolation of the extract gave two active compounds. Their structures were identified as uvaol (1) and ursolic acid (2) by spectral data. These active compounds inhibit HIV-1 protease with IC50 values of 5.5 and 8.0 microM, respectively.     

Inhibition of viral proteases by Zingiberaceae extracts and flavones isolated from Kaempferia parviflora

In order to identify novel lead compounds with antiviral effect, methanol and aqueous extracts of eight medicinal plants in the Zingiberaceae family were screened for inhibition of proteases from human immunodeficiency virus type 1 (HIV-1), hepatitis C virus (HCV) and human cytomegalovirus (HCMV). In general, the methanol extracts inhibited the enzymes more effectively than the aqueous extracts. HIV-1 protease was strongly inhibited by the methanol extract of Alpinia galanga. This extract also inhibited HCV and HCMV proteases, but to a lower degree. HCV protease was most efficiently inhibited by the extracts from Zingiber officinale, with little difference between the aqueous and the methanol extracts. Many of the methanol extracts inhibited HCMV protease, but the aqueous extracts showed weak inhibition. In a first endeavor to identify the active constituents, eight flavones were isolated from the black rhizomes of Kaempferia parviflora. The most effective inhibitors, 5-hydroxy-7-methoxyflavone and 5,7-dimethoxyflavone, inhibited HIV-1 protease with IC50 values of 19 microM. Moreover, 5-hydroxy-3,7-dimethoxyflavone inhibited HCV protease and HCMV protease with IC50 values of 190 and 250 microM, respectively.     

L-696,474, a novel cytochalasin as an inhibitor of HIV-1 protease. III. Biological activity.

L-696,474, an inhibitor of the HIV-1 protease, was discovered in extracts of the fungal culture Hypoxylon fragiforme (MF5511; ATCC 20995). L-696,474 is a novel cytochalasin with a molecular weight of 477 and an empirical formula of C30H39NO4. L-696,474 inhibited HIV-1 protease activity with an IC50 of 3 microM and the mode of inhibition was competitive with respect to substrate (apparent Ki = 1 microM). Furthermore, L-696,474 was not a slow-binding inhibitor. The inhibition due to L-696,474 was also independent of the HIV-1 protease concentration. L-696,474 was inactive against pepsin, another aspartyl protease; stromelysin, a zinc-metalloproteinase; papain, a cysteine-specific protease or human leucocyte elastase, a serine-specific protease. Two other novel cytochalasins (L-697,318 and L-696,475) isolated from the same culture were inactive against the HIV-1 protease. Commercially available cytochalasins B, C, D, E, F, H and J were inactive while cytochalasin A was as active as L-696,474 against the HIV-1 protease.     

白藜芦醇衍生物体外抗HIV-1活性的初步研究

目的:检测白藜芦醇衍生物IFB-1和IFB-9的体外抗HIV-1活性,并对其进行抗HIV-1作用机制的初步研究。方法:采用MTT比色法检测白藜芦醇衍生物IFB-1和IFB-9的细胞毒性;细胞病变法检测化合物对HIV-1急性感染的抑制活性;采用HIV-1 p24抗原ELISA方法检测临床分离株HIV-1KM018在PBMC中复制的抑制实验;采用细胞病变法检测HIV-1感染和未感染细胞之间的融合;采用HIV-1重组逆转录酶活性抑制实验,HIV-1重组蛋白酶活性抑制实验以及直接杀病毒实验来研究化合物体外抗HIV-1机制。结果:白藜芦醇衍生物IFB-1和IFB-9对HIV-1IIIB诱导的合胞体形成抑制的选择指数分别为16.16和230.27;IFB-1和IFB-9均能抑制p24抗原的产生,EC50s分别为14.51和0.23μg.mL-1,也能抑制HIV-1KM018在PBMC中的复制。IFB-1和IFB-9对感染细胞与未感染细胞融合有较好的抑制,但对病毒逆转录酶和蛋白酶体外活性没有抑制作用,也不能直接杀死HIV-1病毒。结论:白藜芦醇衍生物IFB-1和IFB-9具有抗HIV-1活性,其作用机制可能为抑制病毒进入细胞。     

cis-fumagillin, a new methionine aminopeptidase (type 2) inhibitor produced by Penicillium sp. F2757

Selective inhibition against the yeast MetAP2 (methionine aminopeptidase type 2) was detected in the fermentation broth of a fungus F2757 that was later identified as Penicillium janczewskii. A new compound cis-fumagillin methyl ester (1) was isolated from the diazomethane treated fermentation extracts together with the known compound fumagillin methyl ester (2). The cis-fumagillin methyl ester, a stereoisomer of fumagillin methyl ester at the C2'-C3' position of the aliphatic side chain, selectively inhibited growth of the map1 mutant yeast strain (MetAP1 deletion strain) at a concentration as low as 1 ng. However, the wild type yeast w303 and the mutant map2 (MetAP2 deleted) strains were resistant up to 10 microg of the compound. In enzyme experiments, compound 1 inhibited the MetAP2 with an IC50 value of 6.3 nM, but it did not inhibit the MetAP1 (IC50 >200 microM). Compound 2 also inhibited the MetAP2 with an IC50 value of 9.2 nM and 105 microM against MetAP1.     

Antiplasmodial activity of Cryptolepis sanguinolenta alkaloids from leaves and roots

The roots of Cryptolepis sanguinolenta have been investigated for their chemical composition since 1931 but so far no studies on the leaves have been reported although they are used in traditional medicine in Guinea-Bissau. Two new alkaloids identified as cryptolepinoic acid (1) and methyl cryptolepinoate (2) and the known alkaloids cryptolepine (4), hydroxycryptolepine (5/5a) and quindoline (6), were isolated from the ethanolic and chlorophormic leaf extracts. Aqueous and ethanolic extracts of the leaves and roots and seven alkaloids isolated from those extracts were tested in vitro against Plasmodium falciparum K1 (multidrug-resistant strain) and T996 (chloroquine-sensitive clone). All the extracts were shown to give 90% inhibition of P. falciparum K1 growth at concentrations < 23 micrograms/ml. Cryptolepine (4) was the most active alkaloid tested with IC50 values (0.23 microM to K1; 0.059 microM to T996) comparable with chloroquine (0.26 microM to K1; 0.019 microM to T996). The indolobenzazepine alkaloid cryptoheptine (7) was the second most active with IC50 values of 0.8 microM (K1) and 1.2 microM (T996). Cryptolepinoic acid (1) showed no significant activity while its ethyl ester derivative 3 was active against P. falciparum K1 (IC50 = 3.7 microM). All the indoloquinoline alkaloids showed cross-resistance with chloroquine but not the indolobenzazepine alkaloid 7. It was noticed that alkaloids with weakly basic characteristics were active whereas other structurally related alkaloids with different acid-base profiles were inactive. These observations are in agreement with the antimalarial mechanism of action for quinolines.     

Inhibitory activity of flavonoids and tannins against HIV-1 protease

Twenty-nine flavonoids and six hydrolyzable tannins were studied for their inhibitory activity against human immunodeficiency virus (HIV)-1 protease using fluorescence and HPLC assays. Among the flavonoids, flavones, flavanones, flavonols, catechols and chalcones, the flavonols were the most active category while flavanones and catechols displayed low activity. Quercetin was the most potent inhibitor of the target enzyme with an IC50 value of 58.8 microM, while butein and luteolin showed moderate activity. Of the hydrolyzable tannins tested, three ellagitannins which contain a hexahydroxvdiphenoyl (HHDP) unit linked to the O-3 and 0-6 positions of the sugar, were found to strongly inhibit HIV-1 protease. The IC50 values of corilagin and repandusinic acid on HIV-1 protease were 20.7 and 12.5 microM, respectively.     

Antioxidant effects of diarylheptanoid derivatives from Alnus japonica on human LDL oxidation

Two diarylheptanoids, oregonin (1) and hirsutanone (2), were isolated by bioassay-guided fractionation of the methanol extracts of the leaves of Alnus japonica Steud and their structures were elucidated from their spectroscopic data. Compounds 1 and 2 exhibited significant low-density lipoprotein (LDL)-antioxidant activities, e. g., thiobarbituric acid-reactive substances (TBARS) assay (1: IC50 = 3.2 microM, 2: IC50 = 1.5 microM), lag time (1 : 162 min, 2 : 230 min at 2.0 microM, control: 63 min), relative electrophoretic mobility (REM, inhibition of 1 : 71%, 2 : 75% at 10 microM), apoB-100 fragmentation (inhibition of 1 : 27.3%, 2 : 40.3% at 10 microM) and macrophage-mediated LDL oxidation (inhibition of 1 : 82%, 2 : 84% at 1 microM).