Novel Antimicrobial 8-Hydroxyquinoline-Based Agents: Current Development, Structure-Activity Relationships, and Perspectives

The search for new antimicrobials is imperative due to the emergent resistance of new microorganism strains. In this context, revisiting known classes like 8-hydroxyquinolines could be an interesting strategy to discover new agents. The 8-hydroxyquinoline derivatives nitroxoline and clioquinol are used to treat microbial infections; however, these drugs are underused, being available in few countries or limited to topical use. After years of few advances, in the last two decades, the potent activity of clioquinol and nitroxoline against several targets and the privileged structure of 8-hydroxyquinoline nucleus have prompted an increased interest in the design of novel antimicrobial, anticancer, and anti-Alzheimer agents based on this class. Herein, we discuss the current development and antimicrobial structure-activity relationships of this class in the perspective of using the 8-hydroxyquinoline nucleus for the search for novel antimicrobial agents. Furthermore, the most investigated molecular targets concerning 8-hydroxyquinoline derivatives are explored in the final section.

Limonene and Perillyl Alcohol Derivatives: Synthesis and Anticancer Activity

Limonene and perillyl alcohol are natural monoterpenes that have attracted the attention of medicinal chemists due to their promising anticancer activities. Considering this, both compounds were explored as scaffolds to obtain various derivatives with anticancer activity. In this review, the data are organized for the first time, with a focus on the synthetic methods and strategies to obtain the derivatives, throughout the period from 2000 to 2020. A brief discussion regarding the structure and activity relationships of the most active derivatives, stereoisomers and their mechanisms of action is presented. Among the active compounds, a series of limonenes with thiosemicarbazone groups and perillyl alcohol hybrids with glycosides or drugs are illustrated. Taking all of this into account, this review may help researchers develop new promising anticancer candidates based on the structures of limonene and perillyl alcohol.

Modeling Diet-Induced Metabolic Syndrome in Rodents

Standardized animal models represent one of the most valuable tools available to understand the mechanism underlying the metabolic syndrome (MetS) and to seek for new therapeutic strategies. However, there is considerable variability in the studies conducted with this essential purpose. This review presents an updated discussion of the most recent studies using diverse experimental conditions to induce MetS in rodents with unbalanced diets, discusses the key findings in metabolic outcomes, and critically evaluates what we have been learned from them and how to advance in the field. The study includes scientific reports sourced from the Web of Science and PubMed databases, published between January 2013 and June 2020, which used hypercaloric diets to induce metabolic disorders, and address the impact of the diet on metabolic parameters. The collected data are used as support to discuss variables such as sex, species, and age of the animals, the most favorable type of diet, and the ideal diet length to generate metabolic changes. The experimental characteristics propose herein improve the performance of a preclinical model that resembles the human MetS and will guide researchers to investigate new therapeutic alternatives with confidence and higher translational validity.

Amyloid-β oligomers in cellular models of Alzheimer's disease

Amyloid-β (Aβ) dysmetabolism is tightly associated with pathological processes in Alzheimer's disease (AD). Currently, it is thought that, in addition to Aβ fibrils that give rise to plaque formation, Aβ aggregates into non-fibrillar soluble oligomers (AβOs). Soluble AβOs have been extensively studied for their synaptotoxic and neurotoxic properties. In this review, we discuss physicochemical properties of AβOs and their impact on different brain cell types in AD. Additionally, we summarize three decades of studies with AβOs, providing a compelling bulk of evidence regarding cell-specific mechanisms of toxicity. Cellular models may lead us to a deeper understanding of the detrimental effects of AβOs in neurons and glial cells, putatively shedding light on the development of innovative therapies for AD.

SERCA plays a crucial role in the toxicity of a betulinic acid derivative with potential antimalarial activity

Malaria is one of the most significant infectious diseases that affect poor populations in tropical areas throughout the world. Plants have been shown to be a good source for the development of new antimalarial chemotherapeutic agents, as shown for the discovery of quinine and artemisinin derivatives. Our research group has been working with semisynthetic triterpene derivatives that show potential antimalarial activity toward different strains of Plasmodium falciparum by specifically modulating calcium pathways in the parasite. Promising results were obtained for nanomolar concentrations of the semisynthetic betulinic acid derivative LAFIS13 against the P. falciparum 3D7 strain in vitro, with a selectivity index of 18 compared to a mammalian cell line. Continuing these studies, we present here in vitro and in vivo toxicological evaluations of this compound, followed by docking studies with PfATP6, a sarco/endoplasmic reticulum Ca⁺²-ATPase (SERCA) protein. LAFIS13 showed an LD₅₀ between 300 and 50 mg/kg, and the acute administration of 50 mg/kg (i.p.) had no negative effects on hematological, biochemical and histopathological parameters. Based on the results of the in vitro assays, LAFIS13 not exerted significant effects on coagulation parameters of human peripheral blood, but a hemolytic activity was verified at higher concentrations. According to the molecular docking study, the PfATP6 protein may be a target for LAFIS13, which corroborates its previously reported modulatory effects on calcium homeostasis in the parasite. Notably, LAFIS13 showed a higher selectivity for the mammalian SERCA protein than for PfATP6, thus impairing the selectivity between parasite and host. In summary, the direct interaction with calcium pumps and the hemolytic potential of the compound proved to be plausible mechanism of LAFIS13 toxicity.

Extracts of the unripe fruit of Ilex paraguariensis as a potential chemical control against the golden apple snail Pomacea canaliculata (Gastropoda, Ampullariidae)

Plant extracts can provide a viable alternative to controlling many crop pests. This study sought to assess the efficacy of vegetable extracts of the unripe fruits of Ilex paraguariensis (yerba maté) for chemical control of the channeled apple snail (Pomacea canaliculata) and of non-target species as the South American catfish (Rhamdia quelen) under laboratory conditions. In P. canaliculata, the LC₅₀ of the decoction extract was 31.39 mg.L^-1 and the LT₅₀ was over 26 h. The LC₅₀ of the butanol extract was 24.75 mg.L^-1 and the LT₅₀ was in the range of 28 to 32 h. In juvenile R. quelen, the LC₅₀ of the decoction was 17.98 mg.L^-1 and the LT₅₀ was in the range of 10-12 h. These extracts are particularly attractive considering the source of compounds and their effectiveness as molluscicides.

Semisynthesis, cytotoxicity, antimalarial evaluation and structure-activity relationship of two series of triterpene derivatives

In this report, we describe the semisynthesis of two series of ursolic and betulinic acid derivatives through designed by modifications at the C-3 and C-28 positions and demonstrate their antimalarial activity against chloroquine-resistant P. falciparum (W2 strain). Structural modifications at C-3 were more advantageous to antimalarial activity than simultaneous modifications at C-3 and C-28 positions. The ester derivative, 3β-butanoyl betulinic acid (7b), was the most active compound (IC₅₀ = 3.4 µM) and it did not exhibit cytotoxicity against VERO nor HepG2 cells (CC₅₀ > 400 µM), showing selectivity towards parasites (selectivity index > 117.47). In combination with artemisinin, compound 7b showed an additive effect (CI = 1.14). While docking analysis showed a possible interaction of 7b with the Plasmodium protease PfSUB1, with an optimum binding affinity of -7.02 kcal/mol, the rather low inhibition displayed on a Bacillus licheniformis subtilisin A protease activity assay (IC₅₀ = 93 µM) and the observed accumulation of ring forms together with a delay of appearance of trophozoites in vitro suggests that the main target of 3β-butanoyl betulinic acid on Plasmodium may be related to other molecules and processes pertaining to the ring stage. Therefore, compound 7b is the most promising compound for further studies on antimalarial chemotherapy. The results obtained in this study provide suitable information about scaffolds to develop novel antimalarials from natural sources.

Chemical analysis and antiviral activity evaluation of Baccharis anomala

The chemical composition and antiviral activity of aqueous extract from Baccharis anomala was studied by bioactivity-guided fractionation. Ethanol precipitation and fractionation by molecular permeation allowed the separation of the anti-herpes simplex virus 1 (HSV-1) active fraction from aqueous extract (Fraction B). Natural Product Reagent A, FeCl₃ and thin-layer chromatography indicated the presence of phenolic compounds in the aqueous extract. Fraction B showed pronounced antiviral activity when tested with HSV-1 strains VR733/ATCC and Acyclovir-resistant 29-R, displaying virucidal but not virustatic activity.

Purification of an Immunoadjuvant Saponin Fraction from Quillaja brasiliensis Leaves by Reversed-Phase Silica Gel Chromatography

Saponins include a large variety of molecules that find several applications in pharmacology. The use of Quillaja saponaria saponins as immunological adjuvants in vaccines is of interest due to their capacity to stimulate both humoral and cellular responses. The congener species Q. brasiliensis has saponins with chemical similarities and adjuvant activity comparable to that of Q. saponaria fraction Quil-A^®, with additional advantages of showing lower toxicity and reduced hemolytic activity. Here we describe in detail the methods for preparing the aqueous extract from Q. brasiliensis leaves, as well as the purification of the bioactive saponin fraction QB-90 using silica reversed-phase chromatography.

Larvicidal activity of natural and modified triterpenoids against Aedes aegypti (Diptera: Culicidae)

BACKGROUND

Insecticide resistance to commonly used substances demands new molecules for the chemical control of the dengue vector Aedes aegypti. Because natural product sources have been an alternative to obtain larvicidal compounds, the aim of this study was to evaluate the triterpenoids betulinic (BA) and ursolic (UA) acids and their semi-synthetic derivatives against larval Ae. aegypti. BA, UA, ten derivatives modified at the C-3 position and a positive control (diflubenzuron) were evaluated. Larvicidal assays were carried out with early fourth-instar larvae, and mortality was observed between 48 and 96 h. Doses from 200 to 10 ppm were used to calculate lethal concentrations (LCs).

RESULTS

Natural compounds, i.e. UA and BA, had the lowest LCs (LC50 of 112 and 142 ppm respectively), except for the modified compound 2b (LC50 of 130 ppm). Larvicidal activity increased significantly from 48 to 96 h for all the compounds evaluated, ranging from 20 to 50% after 48 h and from 48 to 76% after 96 h. Some derivatives, e.g. 2a and 2d, had up to a three-fold larvicidal activity increase from 48 to 96 h.

CONCLUSION

BA, UA and their derivatives showed larvicidal activity against Ae. aegypti larvae, increasing significantly from 48 to 96 h. The presence of a hydroxyl group is essential for larvicidal potential in these triterpenoids. © 2016 Society of Chemical Industry.

Natural and Semi synthetic Antimalarial Compounds: Emphasis on the Terpene Class

Malaria is one of the most important tropical diseases since more than 40% of the world population is at risk. This disease is endemic to more than 100 nations and remains one of the main leading causes of death in children less than five years of age worldwide. Natural product-derived compounds have played a major role in drug discovery, often as prototypes to obtain more active semi synthetic derivatives. Antimalarial pharmacotherapy is a significant example of plant-derived medicines, such as quinine and artemisinin. This review highlights studies on terpenes and their semi synthetic derivatives from natural sources with antimalarial activity reported in the literature during eleven years (2002-2013). A total of 114 compounds are found among terpenes and their semi synthetic derivatives. Cytotoxicity of the compounds is also found in this review. Furthermore, the physicochemical properties of the terpenes addressed are discussed based on seven well established descriptors, which provide a useful source for the elaboration of a terpene library of antimalarial compounds.

Investigation of antimalarial activity, cytotoxicity and action mechanism of piperazine derivatives of betulinic acid

OBJECTIVES

To semisynthesise piperazine derivatives of betulinic acid to evaluate antimalarial activity, cytotoxicity and action mechanism.

METHODS

The new derivatives were evaluated against the CQ-sensitive Plasmodium falciparum 3D7 strain by flow cytometry (FC) using YOYO-1 as stain. Cytotoxicity of 4a and 4b was performed with HEK293T cells for 24 and 48 h by MTT assay. The capability of compound 4a to modulate Ca(2+) in the trophozoite stage was investigated. The trophozoites were stained with Fluo4-AM and analysed by spectrofluorimetry. Effect on mitochondrial membrane potential (ΔΨm) was tested for 4a by FC with DiOC6 (3) as stain. For β-haematin assay, 4a was incubated for 24 h with reagents such as haemin, and the fluorescence was measured by FlexStation at an absorbance of 405 nm.

RESULTS

Antimalarial activity of 4a and 4b was IC50 = 1 and 4 μm, respectively. Compound 4a displayed cytotoxicity with IC50 = 69 and 29 μm for 24 and 48 h, respectively, and 4b was not cytotoxic at the tested concentrations. Addition of 4a leads to an increase in cytosolic Ca(2+) . We have measured ΔΨm after treating parasites with the compound. Data on Figure 4a show that mitochondria were not affected. The action mechanism for 4a, inhibition of β-haematin formation (17%), was lower than CQ treatment (83%; IC50 = 3 mm).

CONCLUSION

Compound 4a showed excellent antimalarial activity, and its action mechanism is involved in Ca(2+) pathway(s).

Anti-Trichomonas vaginalis activity from triterpenoid derivatives

Trichomonas vaginalis is a flagellated parasite that causes trichomonosis, the most common non-viral sexually transmitted disease (STD) in the world. Worryingly, trichomonosis is associated to increased transmission of HIV. Due to high frequency of the infection during pregnancy and the development of metronidazole-resistant isolates, therapeutic alternatives to 5-nitroimidazole are being searched. Triterpenes are natural products presenting several biological activities such as anti-protozoal activity. The aim of this study was to evaluate the in vitro anti-T. vaginalis activity from betulinic and ursolic acids, as well as semisynthetic derivatives obtained. Compounds obtained from betulinic acid presented better activity than those from ursolic acid. Piperazine derivatived from betulinic acid presented minimum inhibitory concentration (MIC) value of 91.2 μM, and the kinetic growth curve performed with parasites treated with this most active compound revealed complete inhibition of trophozoite proliferation at 2 h of incubation and total abolition of trophozoite growth in 24 h, revealing that the piperazine derivative is an efficient trichomonacidal molecule. The same compound promoted total erythrocyte lysis and lactate dehydrogenase (LDH) liberation of 83 and 100% (at 45.6 and 91.2 μM, respectively), indicating parasite membrane damage. The piperazine derivative demonstrated cytotoxic effect against the HMVII and HeLa cell lineages at the MIC value. This is the first report of semisynthetic triterpenoid derivatives with anti-T. vaginalis activity, revealing the high potential of these compounds as trichomonacidal agents.

Antioxidant properties of phenolic compounds from Baccharis articulata and B. usterii

As a continuation of our research on the Baccharis genus, the evaluation of the antioxidant effect by TRAP and TBARS assays of three isolated compounds from n-butanol fractions of B. articulata and B. usterii is reported. The structures of these compounds were established as 4-O-beta-D-glucopyranosyl-3,5-dimethoxybenzyl-methanol (1), 5-O-[E]-dicaffeoylquinic acid (2), and 7-hydroxy-5,4'-dimethoxyflavone (3). In the TRAP assay it was possible to observe an antioxidant effect of both n-butanol fractions at 1.25 microg/mL. Among the isolated compounds, compound 2 displayed a remarkable contribution to the total antioxidant capacity of the n-butanol fraction of B. usterii. Moreover, the n-butanol fractions of both species, compounds 1 and 2 at 40.0 microg/mL were efficient in protection of lipid peroxidation in the TBARS experiment. They are promising lead compounds for use in medicinal chemistry studies.

Antioxidant Properties of Phenolic Compounds from Baccharis articulata and B. usterii

As a continuation of our research on the Baccharis genus, the evaluation of the antioxidant effect by TRAP and TBARS assays of three isolated compounds from n-butanol fractions of B. articulata and B. usterii is reported. The structures of these compounds were established as 4- O-β-D-glucopyranosyl-3,5-dimethoxybenzyl-methanol (1), 5- O-[ E]-dicaffeoylquinic acid (2), and 7-hydroxy-5,4′-dimethoxyflavone (3). In the TRAP assay it was possible to observe an antioxidant effect of both n-butanol fractions at 1.25 μg/mL. Among the isolated compounds, compound 2 displayed a remarkable contribution to the total antioxidant capacity of the n-butanol fraction of B. usterii. Moreover, the n-butanol fractions of both species, compounds 1 and 2 at 40.0 μg/mL were efficient in protection of lipid peroxidation in the TBARS experiment. They are promising lead compounds for use in medicinal chemistry studies.

Phloroglucinol derivatives present an antidepressant-like effect in the mice tail suspension test (TST)

The antidepressant-like effects of phloroglucinol and seven synthetic related derivatives were investigated using the tail suspension test (TST) in mice. Compounds 2-methyl-1-[2,4,6-trihydroxy-3-(2-methylpropanoyl)phenyl] propan-l-one (5), 1-(2,4,6-trihydroxyphenyl)ethan-l-one (6), 1-(3-acetyl-2,4,6-trihydroxyphenyl)ethan-l-one (7), 2-methyl-1 -[2,4,6-trihydroxy-3-(2-methylpropanoyl)-5-{ [2,4,6-trihydroxy-3,5-bis(2-methylpropanoyl)phenyl]methyl phenyl] propan-1-one (9) and 1-{3-acetyl-5-[(3,5-diacetyl-2,4,6-trihydroxyphenyl)methyl]-2,4,6-trihydroxyphenyl}ethan-1-one (10), containing acyl groups, decreased the immobile behavior of mice treated orally with equimolar doses of imipramine 20 mg/kg, with no alterations in locomotor activity as assessed by the open-field test. These results suggest that these phloroglucinol derivatives could represent a new molecular model in the search for antidepressant drugs.

Phloroglucinol Derivatives Present an Antidepressant-like Effect in the Mice Tail Suspension Test (TST)

The antidepressant-like effects of phloroglucinol and seven synthetic related derivatives were investigated using the tail suspension test (TST) in mice. Compounds 2-methyl-1-[2,4,6-trihydroxy-3-(2-methylpropanoyl)phenyl] propan-1-one (5), 1-(2,4,6-trihydroxyphenyl)ethan-1-one (6), 1-(3-acetyl-2,4,6-trihydroxyphenyl)ethan-1-one (7), 2-methyl-1-[2,4,6-trihydroxy-3-(2-methylpropanoyl)-5-{[2,4,6-trihydroxy-3,5-bis(2-methylpropanoyl)phenyl]methyl} phenyl] propan-1-one (9) and 1-{3-acetyl-5-[(3,5-diacetyl-2,4,6-trihydroxyphenyl)methyl]-2,4,6-trihydroxyphenyl}ethan-1-one (10), containing acyl groups, decreased the immobile behavior of mice treated orally with equimolar doses of imipramine 20 mg/kg, with no alterations in locomotor activity as assessed by the open-field test. These results suggest that these phloroglucinol derivatives could represent a new molecular model in the search for antidepressant drugs.

Synthesis of isosteric triterpenoid derivatives and antifungal activity

Dermatomycoses are among the most widespread and common superficial and cutaneous fungal infections in humans. There is an urgent need to develop efficient and non-toxic antimycotic agents with a specific spectrum of activity. Triterpenes have been demonstrated to exhibit a wide range of biological activities, including antifungal activities. In this study, through hemisynthesis, we aimed to obtain triterpene-isosteric molecules from betulinic and ursolic acids to improve the antifungal activity and spectrum of action of these compounds. Six compounds were resynthesized and tested against eleven mucocutaneous and cutaneous mycotic agents. The results of the susceptibility assays were expressed as the minimal inhibitory concentration (MIC). The MIC values of the piperazinyl derivatives of ursolic and betulinic acids that were active against pathogenic yeasts were in the range of 16-32 μg/mL and 4-16 μg/mL, respectively, whereas fungicidal effects were observed at concentrations ranging from 16 to 128 μg/mL and 8 to 128 μg/mL, respectively. The piperazinyl derivative of betulinic acid exhibited an antifungal profile similar to that of terbinafine and was the most effective derivative against dermatophytes. This strategy led to a promising candidate for the development of a new antifungal agent.

The inhibitory effects of phenolic and terpenoid compounds from Baccharis trimera in Siha cells: differences in their activity and mechanism of action

Baccharis trimera is used in folk medicine as a tea for digestive and liver diseases. It possesses anti-inflammatory and antioxidant properties that are related to the presence of phenolic compounds. The aim of this work was to investigate the anti-proliferative properties of phenolic (PHE) and terpenoid (SAP) compounds from B. trimera on human cervical cancer. The treatment of SiHa cells with PHE for 24 h suppressed colony formation in a dose-dependent manner, inhibited proliferation and inhibited cell motility. Although SAP inhibited the proliferation of SiHa cells in a dose-dependent manner, it increased colony formation and did not inhibit cell motility. PHE and SAP also promoted a significant increase in lactate dehydrogenase levels in the culture medium in a dose-dependent manner, indicating a loss of cell membrane integrity. Moreover, PHE promoted necrotic cell death, whereas SAP induced apoptosis. These compounds are new anticancer prototypes due their significant anticancer activity demonstrated herein.

Accumulation of a bioactive triterpene saponin fraction of Quillaja brasiliensis leaves is associated with abiotic and biotic stresses

The saponins from leaves of Quillaja brasiliensis, a native species from Southern Brazil, show structural and functional similarities to those of Quillaja saponaria barks, which are currently used as adjuvants in vaccine formulations. The accumulation patterns of an immunoadjuvant fraction of leaf triterpene saponins (QB-90) in response to stress factors were examined, aiming at understanding the regulation of accumulation of these metabolites. The content of QB-90 in leaf disks was significantly increased by application of different osmotic stress agents, such as sorbitol, sodium chloride and polyethylene glycol in isosmotic concentrations. Higher yields of bioactive saponins were also observed upon exposure to salicylic acid, jasmonic acid, ultrasound and UV-C light. Experiments with shoots indicated a significant increase in QB-90 yields with moderate increases in white light irradiance and by mechanical damage applied to leaves. The increased accumulation of these terpenes may be part of a defense response. The results herein described may contribute to further advance knowledge on the regulation of accumulation of bioactive saponins, and at defining strategies to improve yields of these useful metabolites.

Two series of new semisynthetic triterpene derivatives: differences in anti-malarial activity, cytotoxicity and mechanism of action

BACKGROUND

The discovery and development of anti-malarial compounds of plant origin and semisynthetic derivatives thereof, such as quinine (QN) and chloroquine (CQ), has highlighted the importance of these compounds in the treatment of malaria. Ursolic acid analogues bearing an acetyl group at C-3 have demonstrated significant anti-malarial activity. With this in mind, two new series of betulinic acid (BA) and ursolic acid (UA) derivatives with ester groups at C-3 were synthesized in an attempt to improve anti-malarial activity, reduce cytotoxicity, and search for new targets. In vitro activity against CQ-sensitive Plasmodium falciparum 3D7 and an evaluation of cytotoxicity in a mammalian cell line (HEK293T) are reported. Furthermore, two possible mechanisms of action of anti-malarial compounds have been evaluated: effects on mitochondrial membrane potential (ΔΨm) and inhibition of β-haematin formation.

RESULTS

Among the 18 derivatives synthesized, those having shorter side chains were most effective against CQ-sensitive P. falciparum 3D7, and were non-cytotoxic. These derivatives were three to five times more active than BA and UA. A DiOC(6)(3) ΔΨm assay showed that mitochondria are not involved in their mechanism of action. Inhibition of β-haematin formation by the active derivatives was weaker than with CQ. Compounds of the BA series were generally more active against P. falciparum 3D7 than those of the UA series.

CONCLUSIONS

Three new anti-malarial prototypes were obtained from natural sources through an easy and relatively inexpensive synthesis. They represent an alternative for new lead compounds for anti-malarial chemotherapy.

Repeated administration of an aqueous spray-dried extract of the leaves of Passiflora alata Curtis (Passifloraceae) inhibits body weight gain without altering mice behavior

ETHNOPHARMACOLOGICAL RELEVANCE

Passiflora alata is a Southern American species that constitutes many traditional remedies as well as phytomedicines used for sedative and anxiolytic purposes in Brazil. However studies on repeated treatment effects are scarce.

AIM OF THE STUDY

To evaluate behavioral, physiological and biochemical effects of the repeated treatment with an aqueous spray-dried extract of Passiflora alata leaves containing 2.5% (w/v) of flavonoids (PA) in mice.

MATERIAL AND METHODS

Male adult CF1 mice were treated (p.o.) for 14 days with PA (2.5; 25 or 250 mg/kg). The feeding behavior was evaluated at the beginning (1h after the first administration) and at the end of the treatment (15th day). The body weight gain and food consumption were monitored along the days. On day 15 mice were evaluated on plus maze, spontaneous locomotor activity, catalepsy and barbiturate sleeping time tests. Serum glucose, lipids, ALT and AST enzymes were determined. Liver, kidney, perirenal fat, epididymal and peritoneal fat were analyzed.

RESULTS

The repeated treatment with the highest dose tested (250 mg/kg) did not alter the mice behavior on open field, elevated plus maze, catalepsy and barbiturate sleeping time tests. Repeated administration of PA 250 decreased mice feeding behavior and weight gain. PA 25 and PA 250 reduced mice relative liver weight and caused mild hepatic hydropic degeneration as well as a decrease in alanine aminotransferase (ALT) serum level.

CONCLUSIONS

These results indicate that Passiflora alata does not present central cumulative effects and point to the needs of further studies searching for its hepatotoxicity as well as potential anorexigenic.

Antithrombotic effect of chikusetsusaponin IVa isolated from Ilex paraguariensis (Maté)

The triterpene chikusetsusaponin IVa was isolated from the fruit of Ilex paraguariensis. Using biochemical and pharmacological methods, we demonstrated that chikusetsusaponin IVa (1) prolongs the recalcification time, prothrombin time, activated partial thromboplastin time, and thrombin time of normal human plasma in a dose-dependent manner, (2) inhibits the amidolytic activity of thrombin and factor Xa upon synthetic substrates S2238 and S2222, (3) inhibits thrombin-induced fibrinogen clotting (50% inhibition concentration, 199.4 ± 9.1 μM), and (4) inhibits thrombin- and collagen-induced platelet aggregation. The results also indicate that chikusetsusaponin IVa preferentially inhibits thrombin in a competitive manner (K(i)=219.6 μM). Furthermore, when administered intravenously to rats, chikusetsusaponin IVa inhibited thrombus formation in a stasis model of venous thrombosis, although it did not induce a significant bleeding effect. Chikusetsusaponin IVa also prolonged the ex vivo activated partial thromboplastin time. Altogether, these data suggest that chikusetsusaponin IVa exerts antithrombotic effects, including minor hemorrhagic events. This appears to be important for the development of new therapeutic agents.

Synthesis and antiplasmodial activity of betulinic acid and ursolic acid analogues

More than 40% of the World population is at risk of contracting malaria, which affects primarily poor populations in tropical and subtropical areas. Antimalarial pharmacotherapy has utilised plant-derived products such as quinine and artemisinin as well as their derivatives. However, worldwide use of these antimalarials has caused the spread of resistant parasites, resulting in increased malaria morbidity and mortality. Considering that the literature has demonstrated the antimalarial potential of triterpenes, specially betulinic acid (1) and ursolic acid (2), this study investigated the antimalarial activity against P. falciparum chloroquine-sensitive 3D7 strain of some new derivatives of 1 and 2 with modifications at C-3 and C-28. The antiplasmodial study employed flow cytometry and spectrofluorimetric analyses using YOYO-1, dihydroethidium and Fluo4/AM for staining. Among the six analogues obtained, compounds 1c and 2c showed excellent activity (IC₅₀ = 220 and 175 nM, respectively) while 1a and b demonstrated good activity (IC₅₀ = 4 and 5 μM, respectively). After cytotoxicity evaluation against HEK293T cells, 1a was not toxic, while 1c and 2c showed IC₅₀ of 4 μM and a selectivity index (SI) value of 18 and 23, respectively. Moreover, compound 2c, which presents the best antiplasmodial activity, is involved in the calcium-regulated pathway(s).

Phenolic compounds from maté (Ilex paraguariensis) inhibit adipogenesis in 3T3-L1 preadipocytes

Leaves of Ilex paraguariensis are used to prepare a tea known as maté which is a common beverage in several South American countries. The ethanol extract was fractionated to identify the compounds responsible for the anti-adipogenic activity in 3T3-L1 cells. Extracts of both fresh and dried maté leaves were subjected to column chromatography using molecular permeation to obtain the saponin (20 % yields) and the polyphenol extracts (40 % yields) from the fresh and dried leaves. The phenolic content was determined using high-performance liquid chromatography analysis and the Folin-Ciocalteau method. Also, maté extracts (50 μg/ml to 1,000 μg/ml) did not display citotoxicity using MTT. The polyphenol extract from the dried leaves was the most effective (50 μg/ml) in the inhibition of triglyceride accumulation in 3T3-L1 adipocytes, and rutin (100 μg/ml) likely accounted for a large portion of this activity. Additionally, maté extracts had a modulatory effect on the expression of genes related to the adipogenesis as PPARγ2, leptin, TNF-α and C/EBPα.

Micellar aggregates of saponins from Chenopodium quinoa: characterization by dynamic light scattering and transmission electron microscopy

Entire seeds of Chenopodium quinoa Willd are a rich protein source and are also well-known for their high saponin content. Due to their amphiphily quinoa saponins are able to form intricate micellar aggregates in aqueous media. In this paper we study the aggregates formed by self-association of these compounds from two quinoa saponin fractions (FQ70 and FQ90) as well as several distinctive nanostructures obtained after their complexation with different ratios of cholesterol (CHOL) and phosphatidylcholine (PC). The FQ70 and FQ90 fractions were obtained by reversed-phase preparative chromatography. The structural features of their resulting aggregates were determined by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Novel nanosized spherical vesicles formed by self-association with mean diameter about 100-200 nm were observed in FQ70 aqueous solutions whereas worm-like micelles an approximate width of 20 nm were detected in FQ90 aqueous solutions. Under experimental conditions similar to those reported for the preparation of Quillaja saponaria ISCOM matrices, tubular and ring-like micelles arose from FQ70:CHOL:PC and FQ90:CHOL:PC formulations, respectively. However, under these conditions no cage-like ISCOM matrices were observed. The saponin composition of FQ70 and FQ90 seems to determine the nanosized structures viewed by TEM. Phytolaccagenic acid, predominant in FQ70 and FQ90 fractions, is accountable for the formation of the nanosized vesicles and tubular structures observed by TEM in the aqueous solutions of both samples. Conversely, ring-like micelles observed in FQ90:CHOL:PC complexes can be attributed to the presence of less polar saponins present in FQ90, in particular those derived from oleanolic acid.

Immunoadjuvant activity, toxicity assays, and determination by UPLC/Q-TOF-MS of triterpenic saponins from Chenopodium quinoa seeds

The adjuvant activity of Chenopodium quinoa (quinoa) saponins on the humoral and cellular immune responses of mice subcutaneously immunized with ovalbumin (OVA) was evaluated. Two quinoa saponin fractions were obtained, FQ70 and FQ90, and 10 saponins were determined by UPLC/Q-TOF-MS. Mice were immunized subcutaneously with OVA alone or adjuvanted with Quil A (adjuvant control), FQ70, or FQ90. FQ70 and FQ90 significantly enhanced the amount of anti-OVA-specific antibodies in serum (IgG, IgG1, and IgG2b) in immunized mice. The adjuvant effect of FQ70 was significantly greater than that of FQ90. However, delayed type hypersensitivity responses were higher in mice immunized with OVA adjuvanted with FQ90 than mice treated with FQ70. Concanavalin A (Con A)-, lipopolysaccharide-, and OVA-stimulated splenocyte proliferation were measured, and FQ90 significantly enhanced the Con A-induced splenocyte proliferation. The results suggested that the two quinoa saponin fractions enhanced significantly the production of humoral and cellular immune responses to OVA in mice.

Phenolic enriched extract of Baccharis trimera presents anti-inflammatory and antioxidant activities

Baccharis trimera is a plant popularly used as a tea and to treat gastrointestinal diseases and inflammatory processes as well. The total phenolic content was determined and the antioxidant and anti-inflammatory activities of six extracts (dichloromethane, ethyl acetate, butanol, aqueous, saponin and phenolic) from B. trimera were evaluated. Using carrageenan-induced pleurisy as a model of acute inflammation, the phenolic extract at 15 mg/kg decreased significantly the analyzed parameters when compared to the carrageenan group (p < 0.05), thus showing potential anti-inflammatory activity. The total phenolic content and antioxidant activity were evaluated by the Folin-Ciocalteau and DPPH methods, respectively. Phenolic and ethyl acetate extracts presented higher antioxidant activity (p < 0.05) than ascorbic acid. The phenolic extract also showed the highest antioxidant potential in relation to the other extracts, thus suggesting that the antioxidant and anti-inflammatory activities were due to the presence of phenolic compounds.

Antioxidant and anti-inflammatory properties of Capsicum baccatum: from traditional use to scientific approach

ETHNOPHARMACOLOGICAL RELEVANCE

Peppers from Capsicum species (Solanaceae) are native to Central and South America, and are commonly used as food and also for a broad variety of medicinal applications.

AIM OF THE STUDY

The red pepper Capsicum baccatum var. pendulum is widely consumed in Brazil, but there are few reports in the literature of studies on its chemical composition and biological properties. In this study the antioxidant and anti-inflammatory activities of Capsicum baccatum were evaluated and the total phenolic compounds and flavonoid contents were determined.

MATERIALS AND METHODS

The antioxidant property was assayed by scavenging abilities using DPPH and the anti-inflammatory activity was tested through the carrageenan-induced pleurisy model in mice. The total phenolic compounds and flavonoid contents were determined spectrophotometrically.

RESULTS

The ethanolic and butanol extracts (200mg/kg, p.o.) presented a significant anti-inflammatory activity toward carrageenan-induced pleurisy model in mice in comparison to dexamethasone (0.5mg/kg, s.c.). Among the parameters evaluated, the treatment with these samples inhibited leukocyte migration and reduced the formation of exudate. The contents of flavonoids and total phenolic compounds could be correlated with the antioxidant and anti-inflammatory activities observed for Capsicum baccatum.

CONCLUSIONS

Our findings suggest that Capsicum baccatum contains potential antioxidant and anti-inflammatory compounds which could be tested as drug candidates against oxidative and inflammation-related pathological processes in medicinal chemistry studies.

New ferrocenic pyrrolo[1,2-a]quinoxaline derivatives: synthesis, and in vitro antimalarial activity--Part II

Following our search for antimalarial compounds, novel series of ferrocenyl-substituted pyrrolo[1,2-a]quinoxalines 1-2 were synthesized from ferrocene-carboxaldehyde and tested for their in vitro activity upon the erythrocytic development of Plasmodium falciparum strains with different chloroquine-resistance status. The ferrocenic pyrrolo[1,2-a]quinoxalines 1-2 were prepared in 6 or 9 steps through a Barton-Zard reaction. Promising pharmacological results against FcB1, K1 and F32 strains were obtained with ferrocenyl pyrrolo[1,2-a]quinoxalines 1j-l linked by a bis-(3-aminopropyl)piperazine linker substituted by a nitrobenzyl moiety.

Production of plant bioactive triterpenoid saponins: elicitation strategies and target genes to improve yields

Triterpenoid saponins are a class of plant secondary metabolites with structure derived from the precursor oxidosqualene in which one or more sugar residues are added. They have a wide range of pharmacological applications, such as antiplatelet, hypocholesterolemic, antitumoral, anti-HIV, immunoadjuvant, anti-inflammatory, antibacterial, insecticide, fungicide and anti-leishmanial agents. Their accumulation in plant cells is stimulated in response to changes mediated by biotic and abiotic elicitors. The enhancement of saponin yields by methyl jasmonate in plants and cell cultures in several species indicates the involvement of these metabolites in plant defence mechanisms. The elucidation of their biosynthesis at the molecular level has advanced recently. Most studies to date have focused on the participation of early enzymes in the pathway, including oxidosqualene cyclase, squalene synthase and dammarenediol synthase, as well as in isolating and characterizing genes that encode beta-amyrin synthase. Yields of bioactive saponins in various plant species and experimental systems have been successfully increased by treating cells and tissues with jasmonate or by exposing these to oxidative stress. These elicitation and molecular studies are consolidating a robust knowledge platform from which to launch the development of improved sources for commercial supply of bioactive saponins.

Green tea extract-patents and diversity of uses

Green tea is one of the most consumed beverages in the world. Presently, Camellia sinensis has become a source not only for the development of several food extracts but also nutraceutical, cosmetic and medicinal purposes. The technology developed to produce these extracts aims to improve the organoleptic characteristics of the products as taste and smell, and their shelf life. But it also searches to demonstrate some medicinal attributes like antioxidant, anti-aging, anti-tumor and anti-viral activities in relation to the chemical composition of the green tea catechins, especially (-)-epigallocatechin gallate (EGCG). The target of this review is to present the various patents related to the extraction methods and their claims, and to discuss the evidence found in the literature about the pharmacological activities of green tea. It summarizes the recent progress in technology to obtain the green tea extract and in clinical studies on its applications. Health-promoting products and disease-preventing applications of green tea extract or compounds isolated from it also take part of this text.