Activity of the new quinolone WCK 771 against pneumococci.

The activity of WCK 771, a new experimental quinolone being developed to overcome quinolone resistance in staphylococci, against quinolone-susceptible and -resistant pneumococci was determined. Comparative activities of ciprofloxacin, levofloxacin, gatifloxacin, moxifloxacin, clinafloxacin, vancomycin, linezolid, amoxycillin, cefuroxime, azithromycin and clarithromycin were determined with MIC and time-kill experiments. Animal experiments were also performed to test the in-vivo anti-pneumococcal activity of WCK 771 compared to levofloxacin. WCK 771 MIC50/90 values for 300 quinolone-susceptible Streptococcus pneumoniae isolates (108 penicillin-susceptible, 92 penicillin-intermediate and 100 penicillin-resistant) were 0.5/0.5 mg/L; the MICs of beta-lactams and macrolides rose with those of penicillin G, and all isolates were susceptible to vancomycin and linezolid. WCK 771 MIC50/90 values for 25 quinolone-resistant pneumococcal isolates were 4/8 mg/L, compared to 0.5/1 mg/L for clinafloxacin, 2/4 mg/L for gatifloxacin and moxifloxacin, 8/16 mg/L for levofloxacin, and 16/>32 mg/L for ciprofloxacin. Time-kill studies showed that WCK 771 was bactericidal against pneumococci after 24 h at 4 x MIC, as were the other quinolones tested. Animal model studies showed that WCK 771 had efficacy comparable to that of levofloxacin, by both the oral and subcutaneous routes, for systemic infection caused by three quinolone-susceptible isolates of pneumococci. Overall, WCK 771 was potent both in vivo and in vitro against quinolone-susceptible, but not quinolone-resistant, S. pneumoniae, regardless of penicillin susceptibility.

Retarded development of exoerythrocytic stages of the rodent malaria parasite Plasmodium berghei in human hepatoma cells by extracts from Dioncophyllaceae and Ancistrocladaceae species.

Retarded development of exoerythrocytic stages of the rodent malaria parasite Plasmodium berghei in human hepatoma cells by extracts from Dioncophyllaceae and Ancistrocladaceae species. International Journal for Parasitology 27: 29-32. Naphthylisoquinoline alkaloid-containing extracts (10 micrograms ml-1) of species belonging to the Dioncophyllaceae and the Ancistrocladaceae, 2 small tropical plant families, display pronounced in vitro activities against exoerythrocytic stages of Plasmodium berghei (Anka), developing in human hepatoma cells (Hep G2). The highest activities were obtained with CH2Cl2 root and bark extracts, and a CH2Cl2/NH3 leaf extract from Triphyophyllum peltatum, a CH2Cl2/NH3 root extract from Ancistrocladus abbreviatus, and a CH2Cl2 leaf extract from A. tectorius. The degrees of growth inhibition ranged within 27.7-70.0%. The commercially available drug primaquine diphosphate (25 micrograms ml-1) caused a comparable effect (62.1%) in the same test system.

Chonemorphine, stigmasterol, and ecdysterone: steroids isolated through bioassay-directed plant screening programs.

In a bioassay-directed screening programme of plants for the identification of active constituents the following steroids were isolated. Chonemorphine was identified as the antiamoebic and antitrichomonad principle of Chonemorpha fragrans. Stigmasterol from Coleus forskohlii and ecdysterone from Diploclisia glaucescens were inactive constituents isolated during the process of purifying the active principles of the plants. D. glaucescens roots are a high-yielding source (0.5% of the dry root weight) of ecdysterone.

Cardiovascular effects of new water-soluble derivatives of forskolin.

A series of 6- and 7-aminoacyl derivatives of 7-deacetylforskolin was prepared to provide water-soluble derivatives of the potent cardioactive diterpenoid forskolin. The compounds were evaluated for positive inotropic and blood pressure lowering properties in pharmacological models. Several derivatives displayed potent positive inotropic activity in guinea pig atria (EC50 = 0.16-3.0 micrograms/mL). In the most active compounds, the amino moiety of the aminoacyl chain corresponded to a cyclic amine, and the acyl moiety to a C2-C4 alkanoyl group. In vivo biological evaluation led to the selection of 6-(piperidinoacetyl)-7-deacetylforskolin hydrochloride (49) as a candidate for clinical development.

A rapid and sensitive bioassay involving cultured rat glioma cells to screen for substances capable of elevating intracellular cyclic AMP concentration.

Cultured rat glioma (ASK) cells are morphologically converted from a spindle to an astrocyte form when treated with dibutyryl cAMP. This morphologic transformation is discernible by light microscopy and can be visually quantitated. As described herein, dose-dependent astrocyte generation was demonstrated by treatment of confluent monolayers with forskolin [1], a compound known to activate adenylate cyclase, and the potency of four forskolin derivatives was found to correlate with previously established biologic potential. Neither a crude ginseng extract nor purified ginsenosides were active in the process, but supplementation of the otherwise inactive ginseng extract with 1 demonstrated 50% of the cells were morphologically converted to the astrocyte form at a concentration of approximately 0.0008%. Retinoic acid was also active in this test system; the morphologic transformation was reversed on treatment with colchicine, and intracellular cAMP concentration was elevated approximately 10-fold. Evaluation of 15 retinoids established a general correlation between the activity in this system and other systems reported in the literature. Thus, the astrocyte formation assay appears to provide several advantages that make it attractive as a screen for the detection or evaluation of substances capable of elevating intracellular cAMP concentration. In addition to technical ease, the procedure is rapid, sensitive, and relatively inexpensive.

Stimulation of adenylate cyclase by water-soluble analogues of forskolin.

Analogues of forskolin that are more soluble in water than forskolin have been synthesized and tested for their ability to interact with adenylate cyclase. These analogues are esterified with various heterocyclic amino acids at the 6 beta-hydroxyl position of forskolin or at the 6 beta-hydroxyl or 7 beta-hydroxyl position of 7-desacetyl forskolin. Analogues were tested for their ability to activate rat brain adenylate cyclase, activate detergent-solubilized rat brain adenylate cyclase, increase cyclic AMP in intact S49 wild-type cells, and inhibit the binding of 3H-forskolin to rat brain membranes. Forskolin activated rat brain adenylate cyclase with an EC50 of 4 microM and increased cyclic AMP in intact S49 cells with an EC50 of 5 microM. Analogues esterified at the 7 beta-hydroxyl position had EC50 values that ranged from 4 microM to 15 microM for activating adenylate cyclase in membranes and solubilized preparations, and for increasing cyclic AMP in S49 cells. Analogues esterified at the 6 beta-hydroxyl position with no acyl group at the 7 beta-hydroxyl position were generally less potent than the corresponding 7-acyl analogues with EC50 values that ranged from 30 microM to 100 microM. Interestingly, the diacyl analogues of forskolin containing an acetate group at the 7 beta-hydroxyl position and esterified with heterocyclic amino acids at the 6 beta-hydroxyl position were very potent at stimulating adenylate cyclase, with EC50 values that ranged from 1 microM to 25 microM. The 7-acyl analogues and the 6,7-diacyl analogues inhibited the binding of 3H-forskolin to rat brain membranes with IC50 values that ranged from 20 microM to 70 microM, while the 6-acyl analogues had much higher IC50 values that ranged from 100 nM to 375 nM. Aqueous solutions of forskolin were also produced by dissolving forskolin in solutions of hydroxypropyl-gamma-cyclodextrin. These aqueous solutions of forskolin were equipotent with alcoholic solutions of forskolin in stimulating adenylate cyclase. In conclusion, water-soluble derivatives of forskolin may be useful for increasing cyclic AMP in broken cell preparations or in intact cell preparations where the presence of organic solvents, which are necessary to solubilize forskolin, are detrimental. Alternatively, aqueous solutions of forskolin can be produced by dissolving forskolin in solutions of hydroxypropyl-gamma-cyclodextrin.

Trequinsin, a potent new antihypertensive vasodilator in the series of 2-(arylimino)-3-alkyl-9,10-dimethoxy-3,4,6,7-tetrahydro-2H-py rim ido [6,1-a]isoquinolin-4-ones.

Series of 3-substituted-9,10-dimethoxy-3,4,6,7-tetrahydro-2H-pyrimido [6,1-a]isoquinoline-2,4-diones and 2-substituted-9,10-dimethoxy-6,7-dihydro-4H-pyrimido [6,1-a]isoquinolin-4-ones were synthesized and tested for blood pressure lowering properties in anesthetized normotensive cats and conscious spontaneously hypertensive rats. Several compounds in the 2-(arylamino)-9,10-dimethoxy-6,7-dihydro-4H-pyrimido [6,1-a]isoquinolin-4-one series display a high order of activity. The most active compounds are the alkyl derivatives of the 2-mesitylamino/2-mesitylimino tautomeric forms. The 2-(mesitylimino)-3-methyl analogue trequinsin is a potent antihypertensive agent and displays a hemodynamic profile characteristic of an arteriolar dilator. It is also a potent inhibitor of both cAMP phosphodiesterase and platelet aggregation.

Quantitative Determination of Forskolin by TLC and HPLC.

Thin layer chromatographic (TLC) and high pressure liquid chromatographic (HPLC) methods for quantitative determination of forskolin, a novel positive inotropic, antihypertensive, platelet aggregation inhibitory and adenylate cyclase stimulating agent are described. Both methods are suitable for the routine assay of pharmaceutical preparations containing forskolin. The HPLC method is also efficiently used for the assay of forskolin containing plant materials. A comparative evaluation is made of the two chromatographic methods with a previously reported gas liquid chromatographic method to determine forskolin.

The antihypertensive and positive inotropic diterpene forskolin: effects of structural modifications on its activity.

Four naturally occurring analogues of forskolin were isolated. Forty-nine semisynthetic derivatives were prepared, incorporating structural alterations at the 1-, 6-, 7-, 9-, 11-, and 14/15-positions. Blood pressure lowering properties of 53 compounds were assessed in anesthetized normotensive cats and of 31 compounds in conscious spontaneously hypertensive (SH) rats. The positive inotropic properties of 25 compounds were investigated in an isolated guinea pig atrial preparation. Forskolin was unique among the compounds in its hypotensive activity in cats and in its positive inotropic properties. Although several derivatives displayed oral antihypertensive activity in the SH rats, none was significantly more potent than forskolin. The optimal structural requirements for activity are apparent, since they are found in forskolin itself.

Structure-activity relationships for activation of adenylate cyclase by the diterpene forskolin and its derivatives.

Forskolin (7 beta-acetoxy-8,13-epoxy-1 alpha, 6 beta, 9 alpha-trihydroxylabd-14-en-11-one), a diterpene from the Indian plant Coleus forskohlii, activates cyclic AMP generating systems in a number of mammalian tissues in a rapid and reversible fashion. Derivatives of forskolin have been tested for their ability to stimulate membrane adenylate cyclase from rat brain and rabbit heart, as well as cyclic AMP generation in guinea pig brain vesicular preparations, a model system for intact cells. Derivatives at the 6 beta- and 7 beta-hydroxy functions retain activity, but none have greater activity than that of forskolin. Reduction of the 11-keto function affords an active 11 beta-hydroxy derivative. Reduction of the 14,15-vinyl (alpha) substituent reduces activity, while epoxidation abolishes activity. Derivatization or lack of the 1 alpha- and 9 alpha-hydroxy functions results in a marked reduction in activity, emphasizing the importance of the alpha aspect of the molecule. However, the 1 alpha, 6 beta-di-O-acetyl derivative does retain activity. None of the inactive derivatives, which include the 14,15-epoxy, the 1,9-dideoxy, and the 1,6-diketo derivatives, antagonize the stimulatory effects of forskolin.

GLC method for assay of forskolin, a novel positive inotropic and blood pressure-lowering agent.

A GLC method for the quantitative determination of forskolin, a novel positive inotropic and blood pressure-lowering agent, is described. This method is simple, rapid, and sensitive and is suitable for the routine assay of plant materials and pharmaceutical preparations containing forskolin.