Rational Design, Synthesis and Evaluation of Indole Nitrogen Hybrids as Photosystem II Inhibitors.

We report the synthesis of twelve indole derivatives bearing nitro or amide groups via Fischer indole methodology followed by reduction/acetylation and amidation reactions. After thorough characterization, these indoles were subjected to a number of studies in order to evaluate their bioactive potential as photosynthesis and plant growth inhibitors. Firstly, these molecular hybrids were evaluated as photosystem II (PSII) inhibitors through chlorophyll a (Chl a) fluorescence measurement. In this study, 6-chloro-8-nitro-2,3,4,9-tetrahydro-1H-carbazole (15a) and 5-chloro-2,3-dimethyl-7-nitro-1H-indole (15b) showed the best results by reducing the phenomenological parameters of reaction centers ABS/RC, TR0 /RC and ET0 /RC of PSII. Electron chain blockage by these compounds may lead to diminished ATP synthesis and CO2 fixation which interrupt the plant development. The compounds 15a and 15b both act as postemergent herbicides, reducing the dry biomass of Ipomoea grandifolia and Senna alata weeds by an average of 40% and 37%, respectively, corroborating the fluorescence results. Additionally, the molecular docking study revealed that the presence of strong electron-withdrawing groups at the indole phenyl ring is important for the ligand's interaction with the binding pocket of protein D1 on PSII. The optimization of these molecular features is the goal of our research group in further understanding and development of new potent herbicides.

Comparative study of the chemical profile of the parotoid gland secretions from Rhaebo guttatus from different regions of the Brazilian Amazon.

Amphibian cutaneous secretion has great potential for bioprospection and is a great tool in the development of bioproducts. Thus, the objective of the present work was to evaluate the comparative study of the chemical profile parotoid gland secretions from Rhaebo guttatus collected in two distinct regions of the Brazilian Amazon. For this, the chemical composition of six methanolic extracts of this species were analyzed by Liquid Chromatography in UV and MS Detection Ultra-Chromatography Systems (UFLC-DAD-micrOTOF). All obtained chromatograms presented two distinct regions; one referring to the more hydrophilic molecules (alkaloids), while the other refers to the more hydrophobic compounds (steroids). The steroid region resembles all samples, regardless of where they were collected. In the alkaloid region, there was a standardized variation for the samples from the southern Brazilian Amazon, but the same was not true for the samples collected in the Amazon-Cerrado transition region. Thus, the data suggest that the environment and diet of R. guttatus may be important in alkaloid production, but do not influence steroid content. These results add new information about the poison of the toad R. guttatus and raises new questions to be further investigated, thus contributing to the knowledge of the anuran fauna of the Brazilian Amazon.

In vitro inhibition of protein glycation and advanced glycation end products formation by hydroethanolic extract and two fractions of Simaba trichilioides roots.

Long-term hyperglycemia maintenance is responsible for increased protein glycation and formation of advanced glycation end products (AGEs), both are associated with the onset of diabetes mellitus complications. Efforts have been made to discover new agents having antiglycation potential. The aim of this study was to investigate the effects of the hydroethanolic extract and the ethyl acetate and methanolic fractions of Simaba trichilioides roots on the formation of AGEs. In an in vitro model system of protein glycation, incubations with hydroethanolic extract, ethyl acetate or methanolic fractions of S. trichilioides decreased the fluorescent AGEs, and markers of tyrosine and tryptophan oxidation. Protein crosslinking was reduced in the presence of the ethyl acetate fraction of S. trichilioides. Simaba trichilioides roots seem to be a promising source of compounds having ability to prevent glycoxidation changes, with potential applications in complementary therapies for management of diabetic complications.

Synthesis and evaluation of indole derivatives as photosynthesis and plant growth inhibitors.

Indole derivatives were synthetized based on the Fischer indole methodology using different phenyl hydrazine hydrochlorides and either cyclohexanone or 2-butanone. The pre- and post-emergent herbicidal activities were evaluated against Ipomoea grandifolia. A carbazole, 6-chloro-2,3,4,9-tetrahydro-1H-carbazole (3b), decreased the PIabs parameter by 32% and increased the cross-section related parameters, indicating the inactivation of the reaction center on photosystem II. Compound 3b acts as a post-emergent herbicide prototype since dry biomass was reduced by 50%, corroborating the fluorescence results. Comparing instead with a germination experiment, 2,3,4,9-tetrahydro-1H-carbazole (3a) was found to be the most effective agent, inhibiting seed germination by 22% and decreasing root length by 50%. The tetrahydrocarbazoles showed better results than indole derivatives potentially due to the presence of methylene groups at structures, which increase the compounds' lipophilicity and may facilitate their access to the plant. In addition, electron withdrawing groups on the aromatic ring were found to correlate with increased herbicide activity. Further optimization of this series towards the development of herbicides is ongoing.

New compounds of Siolmatra brasiliensis and inhibition of in vitro protein glycation damage.

Twenty compounds were isolated from the hydroethanolic extract of the stems of Siolmatra brasiliensis, five flavonoids, two lignans, one glucosyl phytosterol, seven nor-cucurbitacins, one new phenolic derivative named siolmatrin (1) and four new dammarane-type saponins named siolmatrosides II-V (2-5), the structures of the compounds were assigned by means of 1D and 2D NMR experiments and HRESIMS of the natural compounds and some acetyl derivatives. The effects of the crude hydroethanolic extract (SbExt) and the ethyl acetate fraction (SbEtAc) of Siolmatra brasiliensis stems on the formation of advanced glycation end-products (AGEs) were also investigated. In the in vitro model system of protein glycation using bovine serum albumin (BSA) and glucose, addition of SbExt or SbEtAc inhibited the formation of fluorescent AGEs, in parallel to minor levels of fructosamine (SbEtAc) and markers of tyrosine and tryptophan oxidation (SbExt and SbEtAc). Protein crosslinking, which represents changes of late stages of protein glycation, was reduced in the presence of SbExt and SbEtAc. Siolmatra brasiliensis stems seem to be a promising source of compounds having ability to prevent glycoxidation changes, arising as an interesting option to be studied as a complementary therapy for complications of diabetes.

Combretum lanceolatum flowers ethanol extract inhibits hepatic gluconeogenesis: an in vivo mechanism study.

Context Ethnopharmacological studies have demonstrated that plants of the Combretum genus presented antidiabetic activity, including Combretum lanceolatum Pohl ex Eichler (Combretaceae). Objective This study investigated the hepatic mechanisms of action of C. lanceolatum flowers ethanol extract (ClEtOH) related to its antihyperglycaemic effect in streptozotocin-diabetic rats. Materials and methods Male Wistar rats were divided into normal (N) and diabetic control (DC) rats treated with vehicle (water); diabetic rats treated with 500 mg/kg metformin (DMet) or 500 mg/kg ClEtOH (DT500). After 21 d of treatment, hepatic glucose and urea production were investigated through in situ perfused liver with l-glutamine. Changes in the phosphoenolpyruvate carboxykinase (PEPCK) levels and in the activation of adenosine monophosphate-activated protein kinase (AMPK) and insulin-signalling intermediates were also investigated. Results Similar to DMet, DT500 rats showed a reduction in the rates of hepatic production of glucose (46%) and urea (22%) in comparison with DC. This reduction was accompanied by a reduction in the PEPCK levels in liver of DT500 (28%) and DMet (43%) when compared with DC. AMPK phosphorylation levels were higher in the liver of DT500 (17%) and DMet (16%) rats. The basal AKT phosphorylation levels were increased in liver of DT500 rats, without differences in the insulin-stimulated AKT phosphorylation and in the insulin receptor levels between DC and DT500 rats. Discussion and conclusion The antidiabetic activity of ClEtOH can be attributed, at least in part, to inhibition of hepatic gluconeogenesis, probably due to the activation of both AMPK and AKT effectors and reduction in the PEPCK levels.

Evaluation of toxicity of Calophyllum brasiliense stem bark extract by in vivo and in vitro assays.

ETHNOPHARMACOLOGICAL RELEVANCE: Calophyllum brasiliense Camb., Clusiaceae, is commonly known as "guanandi" and its stem bark is used in Brazilian traditional medicine to treat rheumatism, vein problems, hemorrhoids and gastric ulcers. The aim of this study was to evaluate the toxicity of hexane extract of Calophyllum brasiliense stem bark (HECb) using in vitro and in vivo experimental models. MATERIALS AND METHODS: In vitro toxicity was evaluated by Alamar Blue cytotoxicity assay and micronucleus test, using Chinese hamster ovary (CHO-k1) epithelial cells. in vivo toxicity was evaluated by oral acute and subchronic toxicity assays. In the oral acute toxicity screening, a single dose of HECb was administered to mice at doses ranging from 250 to 1000 mg/kg. In the subchronic study, HECb was administered orally for 30 days to Wistar rats at doses of 100 mg/kg and 500 mg/kg. Phytochemical analyses were performed by HPLC/UV-vis, secondary metabolites were quantified by spectrophotometric methods. RESULTS: HECb presented IC50=119.94±4.31 µg/mL after a 24 h cytotoxicity test using CHO-k1 cells, showing low cytotoxicity. However, when the cells were exposed to HECb for 72 h, the IC50 value was 8.39±2.00 µg/mL, showing in this case, a pronounced cytotoxic effect. In the oral acute toxicity studies, doses up to 500 mg/kg of HECb did not cause any changes in both male and female mice. At 1000 mg/kg, male mice showed signs typical of depression and stimulation that were reversed at 72 h. Besides, female mice were more sensitive to the toxic effect of HECb at 1000 mg/kg, which initially presented typical agitation signals, followed by depression signals, leading to death of all the animals at 24h. In subchronic assay with rats, HECb administered orally at doses of 100 and 500 mg/kg did not cause significant changes in all clinical parameters evaluated. Histopathological analyses showed no deleterious effect in the vital organs of rats. Preliminary phytochemical analysis revealed the presence of phenolic compounds, steroids, and volatile coumarins. Analysis by HPLC showed two major peaks characteristic of chromanones. CONCLUSIONS: In vitro toxicological tests showed that HECb exhibited cytotoxicity especially after 72 h of exposition, and mutagenicity on the highest tested dose. The in vivo studies demonstrated that HECb produced some toxicity signs at the highest dose tested, particularly, in the acute toxicity test but showed no significant signs of toxicity in the subchronic assay. Based on these and previous pharmacological studies, it is possible to say that HECb did not exhibit significant toxicity at its effective dose. This suggests that HECb is relatively safe in humans at its effective dose.

Evaluation of antiulcer activity of chromanone fraction from Calophyllum brasiliesnse Camb.

ETHNOPHARMACOLOGICAL RELEVANCE: Calophyllum brasiliense Camb. (Clusiaceae), popularly known as 'guanandi', is found in the tropical areas and swampy lands. The latex exuding from its bark is used in the treatment of gastric ulcer in folk medicine. Several active compounds have been isolated from its stem bark among them, are the chromanone acids. Therefore, this study aimed to evaluate antiulcer activity and probable mechanism(s) of action of a fraction containing a mixture of chromanone acids (BI), derived by column chromatography fractionation of the hexane extract of the stem bark of Calophyllum brasiliense (HECb), using experimental in vitro and in vivo models. MATERIALS AND METHODS: Ulcer was induced by oral administration of ethanol (75%, v/v) and indomethacin (50mg/kg). Malondialdehyde, reduced glutathione and catalase activity was measured in stomach tissue after ethanol induced ulcer. In order to evaluate the effect of BI on nitric oxide, ulcer was induced by ethanol in l-NAME pretreated animals. Anti-Helicobacter pylori activity was verified in disk diffusion and broth microdilution in vitro assays, using cagA+ and vacA+ Helicobacter pylori strains. RESULTS: BI prevented the gastric ulceration caused by ethanol and indomethacin treatments. Its gastroprotective mechanism in ethanol-induced ulcer was partly due to reduction of MDA and CAT levels in the gastric tissue. BI did not affect the GSH levels and its gastroprotective effect was not reversed by pretreatment with l-NAME. BI showed anti-Helicobacter pylori in the both assays. CONCLUSION: The results indicate that BI is partly responsible for the HECb antiulcer and anti-Helicobacter pylori effects.