Chemical Profile and Biological Potential of Scaptotrigona Bee Products (Hymenoptera, Apidae, Meliponini): An Review.

Stingless bees belong to the Meliponini tribe and are widely distributed in the tropics and subtropics, where they perform important ecological services. Among the best distributed groups of stingless bees is the genus Scaptotrigona, which includes 22 species distributed throughout the neotropical region, including the area from Mexico to Argentina. Bees of this genus are responsible for the production of products such as honey, propolis, geopropolis and fermented pollen ("saburá"). This review aimed to provide an overview of the chemical composition and biological activities associated with derived products from stingless bees of the genus Scaptotrigona. The bibliographic review was carried out through searches in the Scopus, Web of Science, ScienceDirect and PubMed databases, including publications from 2003 to January 2023. The study of the chemodiversity of products derived from Scaptotrigona demonstrated the mainly presence of flavonoids, phenolic acids, terpenoids and alkaloids. It was also demonstrated that products derived from bees of the genus Scaptotrigona exhibit a wide range of biological effects, such as antibacterial, antioxidant, anti-inflammatory and antifungal activities, among other bioactivities. This review provides an overview of phytochemical and pharmacological investigations of the genus Scaptotrigona. However, it is essential to clarify the toxicity and food safety of these products.

Molecular Docking and GC/MS-Based Approach for Identification of Anxiolytic Alkaloids from Griffinia (Amaryllidaceae) Species in a Zebrafish Model.

Griffinia gardneriana Ravenna, Griffinia liboniana Morren and Griffinia nocturna Ravenna (Amarillydaceae) are bulbous plants found in tropical regions of Brazil. Our work aimed to determine the alkaloid profiles of Griffinia spp. and evaluate their anxiolytic potential through in vivo and in silico assays. The plants grown in greenhouses were dried and their ground bulbs were subjected to liquid-liquid partitions, resulting in alkaloid fractions that were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). Anxiolytic activity was evaluated in zebrafish (Danio rerio) through intraperitoneal injection at doses of 40, 100 and 200 mg/kg in light-dark box test. GC-MS analyses revealed 23 alkaloids belonging to different skeleton types: lycorine, homolychorine, galanthamine, crinine, haemanthamine, montanine and narcisclasine. The chemical profiles were relatively similar, presenting 8 alkaloids common to the three species. The major component for G. gardneriana and G. liboniana was lycorine, while G. nocturna consisted mainly of anhydrolycorine. All three alkaloid fractions demonstrated anxiolytic effect. Furthermore, pre-treatment with diazepam and pizotifen drugs was able to reverse the anxiolytic action, indicating involving the GABAergic and serotonergic receptors. Molecular docking showed that the compounds vittatine, lycorine and 11,12-dehydro-2-methoxyassoanine had high affinity with both receptors, suggesting them to be responsible for the anxiolytic effect.

Neuromodulation of Acid-Sensitive Ion Channels (ASICs) and Anti-Inflammatory Potential by Lichenxanthone in Adult Zebrafish (Danio rerio): Experimental and Docking Studies.

The xanthone lichenxanthone did not show toxic effects (LC50>1.0 mg/mL). lichenxanthone prevented nociceptive behavior induced by acidic saline, and its analgesic effect was blocked by amiloride, highlighting the involvement of neuromodulation of acid-sensitive ion channels (ASICs). In the analysis of anti-inflammatory activity, concentrations of 0.1 and 0.5 mg/mL of lichenxanthone reduced the edema induced by k-carrageenan 3.5 %, observed from the fourth hour of analysis. This effect was similar to that observed with ibuprofen (positive control). No leukocyte infiltrates were observed in lichenxanthone, suggesting that the compound acts in the acute inflammatory response. The results of the molecular docking study revealed that lichenxanthone exhibited better affinity energy when compared to the ibuprofen control against the two targets evaluated.

Evaluation of the antibacterial and inhibitory activity of the MepA efflux pump of Staphylococcus aureus by riparins I, II, III, and IV.

The efflux pump mechanism contributes to the antibiotic resistance of widely distributed strains of Staphylococcus aureus. Therefore, in the present work, the ability of the riparins N-(4-methoxyphenethyl)benzamide (I), 2-hydroxy-N-[2-(4-methoxyphenyl)ethyl]benzamide (II), 2, 6-dihydroxy-N-[ 2-(4-methoxyphenyl)ethyl]benzamide (III), and 3,4,5-trimethoxy-N-[2-(4-methoxyphenethyl)benzamide (IV) as potential inhibitors of the MepA efflux pump in S. aureus K2068 (fluoroquinolone-resistant). In addition, we performed checkerboard assays to obtain more information about the activity of riparins as potential inhibitors of MepA efflux and also analyzed the ability of riparins to act on the permeability of the bacterial membrane of S. aureus by the fluorescence method with SYTOX Green. A molecular coupling assay was performed to characterize the interaction between riparins and MepA, and ADMET (absorption, distribution, metabolism, and excretion) properties were analyzed. We observed that I-IV riparins did not show direct antibacterial activity against S. aureus. However, combination assays with substrates of MepA, ciprofloxacin, and ethidium bromide (EtBr) revealed a potentiation of the efficacy of these substrates by reducing the minimum inhibitory concentration (MIC). Furthermore, increased EtBr fluorescence emission was observed for all riparins. The checkerboard assay showed synergism between riparins I, II, and III, ciprofloxacin, and EtBr. Furthermore, riparins III and IV exhibited permeability in the S. aureus membrane at a concentration of 200 µg/mL. Molecular docking showed that riparins I, II, and III bound in a different region from the binding site of chlorpromazine (standard pump inhibitor), indicating a possible synergistic effect with the reference inhibitor. In contrast, riparin IV binds in the same region as the chlorpromazine binding site. From the in silico ADMET prediction based on MPO, it could be concluded that the molecules of riparin I-IV present their physicochemical properties within the ideal pharmacological spectrum allowing their preparation as an oral drug. Furthermore, the prediction of cytotoxicity in liver cell lines showed a low cytotoxic effect for riparins I-IV.

Trypanocidal potential of synthetic p-aminochalcones: In silico and in vitro evaluation.

Chagas disease (CD) is a neglected tropical disease of worldwide health concern, caused by the flagellate protozoan Trypanosoma cruzi (T. cruzi), endemic in Latin America and present in North America and Europe. The WHO recommended drug for CD, benznidazole has low safety profile and several limitations. Therefore, an entity with better therapeutic potential to treat CD is required. Chalcones are an important class of compounds, which have shown antichagasic potential. Thus, the objective of this study was to evaluate the activity of synthetic p-aminochalcones against T. cruzi. Chalcones 1 and 2 were synthesized by Claisen-Schmidt condensation and characterized by both spectroscopic and theoretical methods. Initially, they were submitted to molecular docking simulations using cruzain and trypanothione reductase (TR) enzymes. It was expected to observe the possible interactions of chalcones with the catalytic site and other important regions of these main pharmacological targets of T. cruzi. Their cytotoxicity within host cells were assessed by MTT reduction assay using LLC-MK2 cells, with CC50 = 85.6 ± 9.2 µM and 1115 ± 381.7 µM for chalcones 1 and 2, respectively. These molecules were also tested against epimastigote and trypomastigote life forms of T. cruzi, causing reduction in the number of viable parasites. For the evaluation of the effect on intracellular amastigotes, infected LLC-MK2 cells were incubated with the chalcones for 24 h, causing reduction in the percentage of infected cells and the number of amastigotes/100 cells. Finally, flow cytometry assays were performed for analyzing cell death mechanisms (7-AAD/AxPE labelling), cytoplasmic ROS accumulation (DCFH-DA assay) and mitochondrial transmembrane potential disruption (Rho123 assay). Both chalcones (1 and 2) caused membrane damage, ROS accumulation and mitochondrial depolarization. In conclusion, the synthetic p-aminochalcones presented trypanocidal effect, causing membrane damage and oxidative stress. Their mechanism of action may be related to cruzain and TR inhibition.

Floral Visitation, Phytochemical and Biological Activities of Bioproducts from Tetragonisca angustula (Hymenoptera, Apidae, Meliponini): A Review.

Tetragonisca angustula (Latreille, 1811) is an indigenous neotropical stingless bee, popularly known as "Jataí", with a wide distribution in the Brazilian territory. T. angustula produces other derivatives such as propolis, geopropolis, fermented (saburá pollen), cerumen and resins, which are important in folk medicine. In this review, the objective was to gather research on the main plant species visited by T. angustula, as well as studies that verified the chemical composition and biological properties of T. angustula bioproducts. The bibliographic review was performed by searching the Scopus, Web of Science, ScienceDirect, and PubMed databases for publications from 2003 to February 2023. We found 78 studies that analyzed the interactions between T. angustula and floral species, with species from the botanical families Fabaceae, Asteraceae, Malvaceae, Bignoniaceae, Solanaceae, Myrtaceae and Lamiaceae being the most reported as the main food sources for this species. The presence of compounds belonging to the class of flavonoids, phenolic acids, terpenoids and alkaloids has been identified by studying the chemical composition of honey, propolis, geopropolis and fermented pollen (saburá) in 21 studies. The data collected in the literature emphasize that these T. angustula products have remarkable biological properties, especially their antibacterial and antioxidant activities.

Chemical Composition Determination and Evaluation of the Antimicrobial Activity of Essential Oil from Croton blanchetianus (Euphorbiaceae) against Clinically Relevant Bacteria.

In this study, the chemical composition of the essential oil (EO) extracted from Croton blanchetianus Baill leaves was identified, and antimicrobial and antibiofilm activities against Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli strains were determined. Moreover, the effects of EO in combination with ampicillin and tetracycline were investigated. Thirty-four components, mainly mono-and sesquiterpenes that represented 94.05 % of the chemical composition, were identified in the EO. The EO showed bacteriostatic and bactericidal activities against all strains tested. Furthermore, the EO showed a synergistic effect with ampicillin and tetracycline. EO significantly inhibited biofilm formation and reduced the number of viable cells in biofilms. The EO may be a promising natural product for preventing bacterial biofilm infections.

Antibacterial and antibiotic modifying activity of chalcone (2E)-1-(4'-aminophenyl)-3-(4-methoxyphenyl)-prop-2-en-1-one in strains of Staphylococcus aureus carrying NorA and MepA efflux pumps: In vitro and in silico approaches.

A large number of infections are caused by multi-resistant bacteria worldwide, increasing to around 700,000 deaths per year. Because of that, many strategies are being developed to combat the resistance of microorganisms to drugs, and recently, chalcones have been studied for this purpose. Chalcones are known as α, ß-unsaturated ketones, characterized by having the presence of two aromatic rings that are joined by a three-carbon chain. They are a class of compounds considered an exceptional model due to chemical simplicity and a wide variety of biological activities, including anticancer, anti-inflammatory, antioxidants, antimicrobials, anti-tuberculosis, anti-HIV, antimalarial, anti-allergic, antifungal, antibacterial, and antileishmaniasis. The objective of this work was to evaluate the antibacterial and antibiotic modifying activity of chalcone (2E)-1-(4'-aminophenyl)-3-(4-methoxyphenyl)-prop-2-en-1-one against the bacteria Staphylococcus aureus carrying a NorA and MepA efflux pump. The results showed that chalcone showed no toxicity on macrophage cells and was able to synergistically modulate the action of Norfloxacin and Ethidium Bromide against the bacteria Staphylococcus aureus 1199B and K2068, respectively. Furthermore, the theoretical physicochemical and pharmacokinetic properties of chalcone showed that it did not present a severe risk of toxicity such as genetic mutation or cardiotoxicity, constituting an excellent pharmacological active ingredient.

In silico study of the potential interactions of 4'-acetamidechalcones with protein targets in SARS-CoV-2.

The sanitary emergency generated by the pandemic COVID-19, instigates the search for scientific strategies to mitigate the damage caused by the disease to different sectors of society. The disease caused by the coronavirus, SARS-CoV-2, reached 216 countries/territories, where about 20 million people were reported with the infection. Of these, more than 740,000 died. In view of the situation, strategies involving the development of new antiviral molecules are extremely important. The present work evaluated, through molecular docking assays, the interactions of 4'-acetamidechalcones with enzymatic and structural targets of SARS-CoV-2 and with the host's ACE2, which is recognized by the virus, facilitating its entry into cells. Therefore, it was observed that, regarding the interactions of chalcones with Main protease (Mpro), the chalcone N-(4'[(2E)-3-(4-flurophenyl)-1-(phenyl)prop-2-en-1-one]) acetamide (PAAPF) has the potential for coupling in the same region as the natural inhibitor FJC through strong hydrogen bonding. The formation of two strong hydrogen bonds between N-(4[(2E)-3-(phenyl)-1-(phenyl)-prop-2-en-1-one]) acetamide (PAAB) and the NSP16-NSP10 heterodimer methyltransferase was also noted. N-(4[(2E)-3-(4-methoxyphenyl)-1-(phenyl)prop-2-en-1-one]) acetamide (PAAPM) and N-(4-[(2E)-3-(4-ethoxyphenyl)-1-(phenyl)prop-2-en-1-one]) acetamide (PAAPE) chalcones showed at least one strong intensity interaction of the SPIKE protein. N-(4[(2E)-3-(4-dimetilaminophenyl)-1-(phenyl)-prop-2-en-1-one]) acetamide (PAAPA) chalcone had a better affinity with ACE2, with strong hydrogen interactions. Together, our results suggest that 4'-acetamidechalcones inhibit the interaction of the virus with host cells through binding to ACE2 or SPIKE protein, probably generating a steric impediment. In addition, chalcones have an affinity for important enzymes in post-translational processes, interfering with viral replication.

Potentiating activity of Norfloxacin by synthetic chalcones against NorA overproducing Staphylococcus aureus.

Staphylococcus aureus is responsible for a series of infections occurring in both human and animal hosts. S. aureus SA1199B is a strain resistant to hydrophilic fluoroquinolone due to overproduction of the NorA efflux pump that has been used as a microbial model to evaluate if a compound act as efflux pump inhibitor. Finding substances from natural or synthetic origin able to reverse resistance mechanisms like those of efflux pumps is a challenge. The use of Chalcones and their derivatives is of great chemical and pharmacological interest, as they present a simple structure and several pharmacological activities. This study aims to evaluate the antibacterial potential of 4 synthetic chalcones, as well as to evaluate their action in the modulation of Norfloxacin resistance against the strain SA1199B strain. Microdilution assays were performed for evaluation of the antimicrobial activity. For evaluation of the modulating effect on resistance to Norfloxacin or EtBr, MIC values of these compounds were determined in the absence or presence of subinhibitory concentrations used of each chalcone. MICs values of both Norfloxacin and EtBr were significantly reduced in the presence of all tested chalcones, indicating that inhibition of the active efflux of these compounds by NorA could be a possible mechanism of action of the chalcones. These results show that the compounds studied have a high potential as a NorA inhibitor, with the best modulating effect verified for the compound 3. Pharmacokinetic and toxicity predictive studies indicated a high intestinal absorption and good volume of distribution for chalcones by oral administration, activity in the central nervous system and ease to be transported between biological membranes. Emphasizing that analogs 1 and 4 were easily metabolized by CYP3A4 enzyme, constituting a pharmacological active ingredient without toxic risk due to metabolic activation. These chalcones combined with Norfloxacin could be a promise technological strategy to be applied in the treatment of infections caused by S. aureus overproducing NorA.

Leishmanicidal and healing effects of 3ß,6ß,16ß-trihydroxy lup-20 (29)-ene isolated from Combretum leprosum on Leishmania braziliensis infection in vitro and in vivo.

Treatment of cutaneous leishmaniasis depends on drugs that potentially cause serious side effects and resistance. Thus, topical therapies are attractive alternatives to the drugs currently used. 3ß, 6ß, 16ß-trihydroxylup-20 (29)-ene is a lupane triterpene isolated from Combretum leprosum Mart. leaves (CLF-1), with reports of in vitro antileishmanial effect against L. amazonensis and to promote lesion healing in animal model. Herein, we evaluated the in vitro and in vivo antileishmanial and healing effects of CLF-1 against L. braziliensis. CLF-1 treatment showed low toxicity in macrophages and significantly reduced parasite load in vitro. CLF-1 induced higher IL-12 and TNF-α production and more discrete IL-4 and IL-10 production. For in vivo evaluation, a CLF-1 cream formulation was prepared to treat hamsters infected with L. braziliensis. CLF-1 treatment was able to reduce parasite load of the infected skin and lymph node more efficiently than the conventional treatment. Histopathological analysis indicated a strong inflammatory response accompanied by an important healing response. Data from this study indicate that topical CLF-1 treatment was effective and non-toxic in L. braziliensis infected hamsters suggesting its potential for further development as a future therapeutic intervention.

GABAA receptor participation in anxiolytic and anticonvulsant effects of (E)-3-(furan-2-yl)-1-(2hydroxy-3,4,6-trimethoxyphenyl)prop-2-en-1-one in adult zebrafish.

Anxiety is a mental disorder that affects 25% of patients with epilepsy, and treatments for anxiety and seizures involve the use of benzodiazepines, a class of drugs that have many adverse effects such as decreased motor coordination, drowsiness, and sedation. Thus, new types of drugs with minimal side effects are of immediate requirement. Chalcones comprise a class of compounds with important therapeutic potential and have recently been investigated for their potential as anxiolytic and anticonvulsant agents. Therefore, this study aimed to evaluate the anxiolytic and anticonvulsant effects of the synthetic chalcone (E)-3-(furan-2-yl)-1-(2hydroxy-3,4,6-trimethoxyphenyl)prop-2-en-1-one (FURCHAL) using adult zebrafish as an animal model. Anxiolytic potential was assessed using the light/dark test and the anticonvulsant effect in 3-stage pentylenetetrazol (PTZ)-induced seizure tests. The mechanisms of the anxiolytic effect were analyzed using γ-aminobutyric acid (GABA) and the serotoninergic system. The anxiolytic effect of FURCHAL was verified by a reduction in fish locomotion, similar to diazepam (DZP), which may involve the GABAA receptor, as there was no reversal in the anxiolytic behavior of animals treated with FURCHAL by serotonergic antagonists. In addition, pretreatment with flumazenil blocked the anticonvulsant effect of FURCHAL and DZP at all three stages, indicating that FURCHAL also has anticonvulsant effects and that the presence of the α,ß unsaturated aromatic system and heterocyclic moiety in FURCHAL provided greater affinity for the GABAA receptors. Molecular docking revealed that the interactions involved in the formation of the protein-binding complex FURCHAL-GABAA are formed by three H-bonds involving the oxygen atoms of FURCHAL, and notably, complexes operated in the same region of the DZP site. Thus, this study adds new evidence and highlights that FURCHAL can potentially be used to develop compounds with anxiolytic and anticonvulsant properties.

Aminophenyl chalcones potentiating antibiotic activity and inhibiting bacterial efflux pump.

Chalcones and their derivatives are substances of great interest for medicinal chemistry due to their antibacterial activities. As the bacterial resistance to clinically available antibiotics has become a worldwide public health problem, it is essential to search for compounds capable of reverting the bacterial resistance. As a possibility, the chalcone class could be an interesting answer to this problem. The chalcones (2E)-1-(4'-aminophenyl)-3-(phenyl)­prop-2-en-1-one (APCHAL), and (2E)-1-(4'-aminophenyl)-3-(4-chlorophenyl)­prop-2-en-1-one (ACLOPHENYL) were synthesized by the Claisen-Schmidt condensation and characterized by 1H and 13C nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR), and mass spectrometry (MS), In addition, microbiological tests were performed to investigate the antibacterial activity, modulatory potential, and efflux pump inhibition against Staphylococcus aureus (S. aureus) multi-resistant strains. Regarding the S. aureus Gram-positive model, the APCHAL presented synergism with gentamicin and antagonism with penicillin. APCHAL reduced the Minimum inhibitory concentration (MIC) of gentamicin by almost 70%. When comparing the effects of the antibiotic modifying activity of ACLOPHENYL and APCHAL, a loss of synergism is noted with gentamicin due to the addition of a chlorine to the substance structure. For Escherichia coli (E. coli) a total lack of effect, synergistic or antagonistic, was observed between ACLOPHENYL and the antibiotics. In the evaluation of inhibition of the efflux pump, both chalcones presented a synergistic effect with norfloxacin and ciprofloxacin against S. aureus, although the effect is much less pronounced with ACLOPHENYL. The effect of APCHAL is particularly notable against the K2068 (MepA overexpresser) strain, with synergistic effects with both ciprofloxacin and ethidium bromide. The docking results also show that both compounds bind to roughly the same region of the binding site of 1199B (NorA overexpresser), and that this region overlaps with the preferred binding region of norfloxacin. The APCHAL chalcone may contribute to the prevention or treatment of infectious diseases caused by multidrug-resistant S. aureus.