Synthesis and pharmacological evaluation of novel heterotricyclic acylhydrazone derivatives, designed as PAF antagonists

This paper describes the synthesis and the antiplatelet properties of new heterotricyclic N-acylhydrazone derivatives (7a-e), structurally analogous to known hetrazepinic PAF antagonists, exploring molecular hybridization as a tool for molecular designing. The synthetic route employed to access compounds (7a-e) used, as starting material, the previously described methyl 3-hydroxy-8-methyl-6-phenyl-6H-pyrazolo[3,4-b]thieno[2, 3-d]pyridine-2-carboxylate derivative. The results from inhibitory effects of these novel acylhydrazone derivatives (7a-e) upon PAF-induced platelet aggregation, indicated that all compounds present a significant antithrombotic profile.

Anti-inflammatory and analgesic activities of the latex containing triterpenes from Himatanthus sucuuba

Some triterpenes and iridoids were previously isolated from the stem bark of Himatanthus sucuuba. The latex from Himatanthus sucuuba is used in popular amazonian medicine as an anti-inflammatory remedy. Fractions of the latex were pharmacologically evaluated with a view to verify this popular use in the carrageenan-induced rat paw edema and in the acetic acid-induced mouse constriction tests. The hexane fraction inhibited the edema formation by 35.9% at a dose of 200 mg/kg (p.o.) but no activity was observed at 100 mg/kg (p.o.). The triterpenes present in the hexane fraction were identified as lupeol acetate, alpha-amyrin and lupeol cinnamates. The fraction containing only cinnamates inhibited the edema and the abdominal constrictions by 50-40% and 57.9%, respectively, at 100 mg/kg (p.o.). Among all the fractions studied, the fraction containing only cinnamates showed the greatest anti-inflammatory activity which suggests that these compounds were responsible for the previously described activity of the crude extract.

Synthesis and analgesic activity of novel N-acylarylhydrazones and isosters, derived from natural safrole

Anew series of antinociceptive compounds belonging to the N-acylarylhydrazone (NAH) class were synthesized from natural safrole (7). The most analgesic derivative represented by 10f, [(4'-N,N-dimethylaminobenzylidene-3-(3', 4'-methylenedioxyphenyl)propionylhydrazine], was more potent than dipyrone and indomethacin, used as standards. The NAH compounds described herein were structurally planned by molecular hybridization and classical bioisosterism strategies on previously reported analgesic NAH in order to identify the pharmacophoric contribution of the N-acylarylhydrazone moiety and investigate the structure-activity relationship (SAR) in these series.

Synthesis and pharmacological evaluation of a new class of bicyclic phospholipids, designed as platelet activating factor antagonists

(+/-)-3-Alkoxymethyl-(2-oxabicyclo[3.3.0]octane)-5-yl-methyl-phosp horyl- ethyl-pyridinium [alkyl chain = methyl (5a) and (5b), allyl (6a) and (6b), n-propyl (7a) and (7b) and n-hexyl (8a) and (8b)] derivatives, structurally designed as conformationally restricted platelet activating factor (PAF) antagonists were synthesized in 12-26% overall yield, using ethyl (+/-)-3-hydroxymethyl-5-(2-oxabicyclo [3.3.0] octane) carboxylate (13a,b) as key intermediate. The anti-platelet profile of the new derivatives was evaluated in a PAF-induced aggregation model in rabbit platelet-rich plasma; only compound 8a exhibited a modest activity.

New pyrazolylhydrazone derivatives as inhibitors of platelet aggregation

A series of 5-pyrazolylhydrazone derivatives was designed to be mixed hybrid isosteres of both BW755C and CBS-1108, which belong to the class of dual cyclo-oxygenase and 5-lipoxygenase inhibitors. Some derivatives of this series inhibit the in-vitro platelet aggregation of citrated platelet-rich rabbit plasma induced by ADP (5 microM), collagen (5 micrograms mL-1) and arachidonic acid (100 microM). The structure-activity relationships of this class of compounds were determined from these results. When ADP is used as the aggregation inducer, the presence of free oxygenated substituents at the p-position in the phenyl subunit of the hydrazone moiety favours inhibitory activity; p-methoxyformylbenzene-5-(1-phenyl-3-methyl-4-nitropyrazolyl )hydrazone (100 microM), which has a methoxy group at this position was the most active with 62.8% inhibition of aggregation. In contrast, substitution in the aryl ring does not affect the aggregation induced by collagen, whereas the non-substituted compound, formylbenzene-5-(1-phenyl-3-methyl-4-nitropyrazolyl)hydra zon e, showed similar activity to those of substituted derivatives. In the arachidonic acid assays, the presence of an aryl ring linked to the hydrazone moiety, with an adequate electronic density at the ring due to the nature of its substituents, is an important structural requirement for inhibitory activity.