Adelfo Reyes-Ramírez

Bioassay-Guided Isolation of an Anti-Ulcer Compound, Tagitinin C, from Tithonia diversifolia: Role of Nitric Oxide, Prostaglandins and Sulfhydryls

Tithonia diversifolia is a medicinal plant from the Municipality of Suchiapa, Chiapas, Mexico, that according to local folk medicine is considered useful in the treatment of gastric ulcers. The aim of the present study was to investigate the gastroprotective activity of T. diversifolia by using an ethanol-induced gastric ulcer experimental model in male Wistar rats. The results showed that T. diversifolia had gastroprotective activity, and that the dichloromethane extract had the highest protective activity (close to 90% when using doses between 10 to 100 mg/kg), and that further the compound tagitinin C isolated from this extract was the main active gastroprotective agent. Rats treated with tagitinin C suspended in Tween 80 at 1, 3, 10 and 30 mg/kg showed 37.7, 70.1, 100, and 100% gastroprotection, respectively. The effect elicited by tagitinin C (30 mg/kg) was not attenuated by pretreatment with either NG-nitro-L-arginine methyl ester (70 mg/kg, i.p.), a nitric oxide (NO) synthase inhibitor, N-ethylmaleimide (10 mg/kg, s.c.), a blocker of sulfhydryl groups, or indomethacin (10 mg/kg, s.c.), a blocker of prostaglandin synthesis, which suggests that the gastroprotective mechanism of action of this sesquiterpene lactone does not involve NO, sulfhydryl groups or prostaglandins.

Gastroprotection of Suaveolol, Isolated from Hyptis suaveolens, against Ethanol-Induced Gastric Lesions in Wistar Rats: Role of Prostaglandins, Nitric Oxide and Sulfhydryls

Hyptis suaveolens is a medicinal plant that is, according to traditional medicine, considered useful in the treatment of gastric ulcers. Although its gastroprotective activity was reported, the active compounds have not been identified. Therefore, the aim of the present study was to identify at least one active compound potentially responsible for the gastroprotective activity of H. suaveolens by using a bioassay guided study with an ethanol-induced gastric ulcer experimental model in rats. The results show that the hexane extract had protective activity (close to 70% when using doses between 10 and 100 mg/kg), and that the compound suaveolol, isolated from this extract, was one of the active gastroprotective agents. This is the first report about the gastroprotective activity of suaveolol. Rats treated with this compound at 3, 10, 30 and 100 mg/kg showed 12.6, 21.3, 39.6 and 70.2% gastroprotection respectively. The effect elicited by suaveolol (at 100 mg/kg) was attenuated by pretreatment with either NG-nitro-L-arginine methyl ester (70 mg/kg, i.p.), a nitric oxide (NO) synthase inhibitor, indomethacin (10 mg/kg, s.c.), a blocker of prostaglandin synthesis, or N-ethylmaleimide (10 mg/kg, s.c.), a blocker of sulfhydryl groups. This suggests that the gastroprotective mechanism of action of this compound involves NO, prostaglandins and sulfhydryl groups.

Anticonvulsant Effect of Annona diversifolia Saff. and Palmitone on Penicillin‐induced Convulsive Activity. A Behavioral and EEG Study in Rats

Summary:  Purpose: To evaluate hypnotic and anticonvulsant activities of Annona diversifolia Saff. and palmitone by using behavior and electroencephalographic (EEG) analysis in an experimental model of focal seizures in rats.

Synthesis, docking study and relaxant effect of 2-alkyl and 2-naphthylchromones on rat aorta and guinea-pig trachea through phosphodiesterase inhibition

Chromone (4), which form the base structure of various flavonoids isolated as natural products, is capable of relaxing smooth muscle. This is relevant to the treatment of high blood pressure, asthma and chronic obstructive pulmonary disease. The former disorder involves the contraction of vascular smooth muscle (VSM), and the latter two bronchoconstriction of airway smooth muscle (ASM). One of the principal mechanisms by which flavonoids relax muscle tissue is the inhibition of phosphodiesterases (PDEs), present in both VSM and ASM. Therefore, a study was designed to analyze the structure-activity relationship of chromone derivatives in vaso- and bronchorelaxation through the inhibition of PDE. Docking studies showed that these chromones bind at the catalytic site of PDEs. Consequently, we synthesized analogs of chromones substituted at position C-2 with alkyl and naphthyl groups. These compounds were synthesized from 2-hydroxyacetophenone and acyl chlorides in the presence of DBU and pyridine, modifying the methodology reported for the synthesis of 3-acylchromones by changing the reaction temperature from 80 to 30°C and using methylene chloride as solvent, yielding the corresponding phenolic esters 10a-10h. These compounds were cyclized with an equivalent of DBU, pyridine as solvent, and heated at reflux temperature, yielding the chromones 11a-11h. Evaluation of the vasorelaxant effect of 4, 11a-11h on rat aorta demonstrated that potency decreases with branched alkyl groups. Whereas the EC50 of compound 11d (substituted by an n-hexyl group) was 8.64±0.39 μM, that of 11f (substituted by an isobutyl group) was 14.58±0.64 μM. Contrarily, the effectiveness of the compound is directly proportional to the length of the alkyl chain, as evidenced by the increase in maximal effect of compound 11c versus 11d (66% versus 100%) and 11e versus 11f (60% versus 96%). With an aromatic group like naphthyl as the C-2 substituent, the effectiveness was only 43%. All compounds tested on guinea pig trachea showed less than 55% effectiveness. Compounds 4, 11a-11h were evaluated as PDE inhibitors in vitro, with 11d showing the greatest effect (73%), corroborating the importance of a long alkyl chain, which inhibits the decomposition of cGMP. Docking studies showed that the compound 11d was selective for the inhibition of PDE-5.

Effect of repeated administration of Annona diversifolia Saff. (ilama) extracts and palmitone on rat amygdala kindling

Annonas are consumed as fresh fruits, but, because of their effects on the central nervous system, are also used in folk medicine. The effect on rat amygdala kindling of repeated administration of Annona diversifolia hexane (100mg/kg IP or PO) and ethanol (100mg/kg, PO) leaf extracts and palmitone (10mg/kg, IP) was determined. Electrographic and/or behavioral changes were monitored during kindling-induced seizures 60minutes after treatments. Antiepileptic efficacy was evaluated with respect to afterdischarge (AD) duration, spike frequency, and/or behavioral seizure activity. Oral administration of both extracts significantly decreased spike frequency, whereas intraperitoneally administered hexane extract and palmitone only reduced AD duration. Hexane extract and palmitone exhibited anticonvulsant properties and delayed establishment of a kindling state as observed with diazepam (0.3mg/kg IP). These results reinforce the anticonvulsant properties of this plant, and palmitone and other constituents are responsible for the pharmacological effects.

Synthesis, biological evaluation, and docking studies of gigantol analogs as calmodulin inhibitors.

Several analogs of gigantol (1) were synthesized to evaluate their effect on the complexes Ca(2+)-calmodulin (CaM) and Ca(2+)-CaM-CaM sensitive phosphodiesterase 1 (PDE1). The compounds belong to four structural groups including, 1,2-diphenylethanes (2-11), diphenylmethanes (13-15), 1,3-diphenylpropenones (16-18), and 1,3-diphenylpropanes (20-22). In vitro enzymatic studies showed that all compounds except 11 inhibited the complex Ca(2+)-CaM-PDE1 with IC(50) values ranging from 9 to 146 μM. On the other hand, all analogs but 11, 12 and 15 quenched the extrinsic fluorescence of the CaM biosensor hCaM-M124C-mBBr to different extent, then revealing different affinities to CaM; their affinity constants (K(m)) values were in the range of 3-80 μM. Molecular modeling studies indicated that all these compounds bound to CaM at the same site that the classical inhibitors trifluoperazine (TFP) and chlorpromazine (CPZ). Some of these analogs could be worthy candidates for developing new anti-tumor, local anesthetics, antidepressants, antipsychotic, or smooth muscle relaxant drugs, with anti-CaM properties due to their good affinity to CaM and the straightforwardness of their synthesis. In addition they could be valuable tools for the study of Ca(2+)-CaM functions.

Palmitone prevents pentylenetetrazole-caused neuronal damage in the CA3 hippocampal region of prepubertal rats

Palmitone is a secondary metabolite of polyketide origin extracted from leaves of Annona diversifolia Saff. (Annonaceae). We found that palmitone possesses anticonvulsant properties against penicillin-, 4-AP-, and pentylenetetrazole (PTZ)-caused seizure in adult animals. Some convulsants as PTZ cause neuronal damage in different brain regions such as the CA3 hippocampal region. Our objective was to evaluate if palmitone protects against PTZ-caused seizures and hippocampal neuronal damage in prepubertal rats. We used 32 prepubertal Wistar rats (30-35 days old) divided into four groups of 8 animals; group I was the control group, group II received a single PTZ dose of 50mg/kg ip, group III received a single palmitone dose of 50mg/kg ip, and group IV received a palmitone dose of 50mg/kg ip plus a PTZ dose of 50mg/kg ip. Ten days after administration, the animals were killed using pentobarbital anesthesia (35 mg/kg). The brains were removed and were embedded in paraffin. Coronal cuts of 7 microm were obtained from -2.8 to -3.3 from Bregma. Each section was stained with cresyl violet-eosin. We evaluated the number of normal and abnormal neurons in the CA3 hippocampal region in a 10,000 microm(2) section. It was observed that palmitone did not prevent the PTZ-caused seizure but palmitone prevents the PTZ-caused neuronal damage in the CA3 hippocampal region.