Phytolacca tetramera berries extracts and its main constituents as potentiators of antifungal drugs against Candida spp.

BACKGROUND: Extensive antifungal drug use has enhanced fungal resistance, resulting in persistent mycoses. Combining antifungal plant extracts/compounds with these drugs offers good alternatives to increase the activity of both partners, minimize side effects, and overcome drug resistance. In our previous study, Phytolacca tetramera berries extracts demonstrated activity against Candida spp., correlating with the amount of the main constituent phytolaccoside B and its genin, phytolaccagenin. The extracts and phytolaccagenin altered the fungal plasma membrane by binding to ergosterol, whereas phytolaccoside B increased chitin synthase activity. However, the presence of triterpenoid saponins in Phytolacca spp. has been linked to acute toxicity in humans. PURPOSE: This study aimed to evaluate combinations of P. tetramera berries extracts, phytolaccoside B and phytolaccagenin, together with commercial antifungals [amphotericin B, fluconazole, itraconazole, posaconazole, and caspofungin] against Candida albicans and Candida glabrata, to find synergistic effects with multi-target actions, in which the doses of both partners are reduced, and therefore their toxicity. Additionally, we intended to explore their anti-virulence capacity, thereby hindering the development of drug-resistant strains. METHODS: The effects of these combinations were evaluated using both the checkerboard and isobologram methods. Fractional Inhibitory Concentration Index and Dose Reduction Index were calculated to interpret the combination results. To confirm the multi-target effect, studies on mechanisms of action of synergistic mixtures were performed using ergosterol-binding and quantification assays. The ability to inhibit Candida virulence factors, including biofilm formation and eradication from inert surfaces, was also evaluated. Quantification of active markers was performed using a validated UHPLC-ESI-MS method. RESULTS: Eight synergistic combinations of P. tetramera extracts or phytolaccagenin (but not phytolaccoside B) with itraconazole or posaconazole were obtained against C. albicans, including a resistant strain. These mixtures acted by binding to ergosterol, decreasing its whole content, and inhibiting Candida biofilm formation in 96-well microplates and feeding tubes in vitro, but were unable to eradicate preformed biofilms. CONCLUSIONS: This study demonstrated the synergistic and anti-virulence effects of P. tetramera berries extracts and phytolaccagenin with antifungal drugs against Candida spp., providing novel treatment avenues for fungal infections with reduced doses of both natural products and commercial antifungals, thereby mitigating potential human toxicity concerns.

Prunus persica apoplastic proteome analysis reveals candidate proteins involved in the resistance and defense against Taphrina deformans.

Taphrina deformans is the fungus responsible for the peach leaf curl disease. To gain insight into the molecular mechanisms involved in plant resistance and response to the fungus, apoplastic differentially abundant proteins (DAPs) in a resistant (DR) and/or in a susceptible genotype (FL) were identified after 12 and 96 h post inoculation (hpi) and compared to those at 0 hpi. The Prunus persica apoplastic proteome was assessed by LC-MS/MS analysis. Altogether 332 proteins were identified, and their molecular and biological functions were classified. In both genotypes, major changes occurred at 96 hpi when the fungus had achieved the filamentous form. However, at 96 hpi, DR exhibited a greater number of increased proteins than FL. DAPs were enriched in biotic stress response, with most of the proteins belonging to the pathogenesis related (PR)-type. PRs exhibited the greatest fold changes of induction in DR. While PRs acting on pathogen cell wall (PR2, PR3 and PR4) were increased in both susceptible and resistant genotypes, others were exclusively induced in DR, such as some isoforms of PR5, defensin and PR17. Proteins exclusively induced in DR upon T.deformans inoculation such as four berberine bridge enzymes, two snakins and a GDS-lipase were identified. Moreover, upon inoculation cuticle was thickened to a greater extent in DR than in FL. This work reveals the active role of the apoplast against T. deformans and not only contributes to the elucidation of responses involved in resistance to leaf curl disease but also improves the knowledge on peach defenses against pathogens.

Fungal Biofilms as a Valuable Target for the Discovery of Natural Products That Cope with the Resistance of Medically Important Fungi-Latest Findings.

The development of new antifungal agents that target biofilms is an urgent need. Natural products, mainly from the plant kingdom, represent an invaluable source of these entities. The present review provides an update (2017-May 2021) on the available information on essential oils, propolis, extracts from plants, algae, lichens and microorganisms, compounds from different natural sources and nanosystems containing natural products with the capacity to in vitro or in vivo modulate fungal biofilms. The search yielded 42 articles; seven involved essential oils, two Brazilian propolis, six plant extracts and one of each, extracts from lichens and algae/cyanobacteria. Twenty articles deal with the antibiofilm effect of pure natural compounds, with 10 of them including studies of the mechanism of action and five dealing with natural compounds included in nanosystems. Thirty-seven manuscripts evaluated Candida spp. biofilms and two tested Fusarium and Cryptococcus spp. Only one manuscript involved Aspergillus fumigatus. From the data presented here, it is clear that the search of natural products with activity against fungal biofilms has been a highly active area of research in recent years. However, it also reveals the necessity of deepening the studies by (i) evaluating the effect of natural products on biofilms formed by the newly emerged and worrisome health-care associated fungi, C. auris, as well as on other non-albicans Candida spp., Cryptococcus sp. and filamentous fungi; (ii) elucidating the mechanisms of action of the most active natural products; (iii) increasing the in vivo testing.

Prenylated Flavonoids with Potential Antimicrobial Activity: Synthesis, Biological Activity, and In Silico Study.

Prenylated flavonoids are an important class of naturally occurring flavonoids with important biological activity, but their low abundance in nature limits their application in medicines. Here, we showed the hemisynthesis and the determination of various biological activities of seven prenylated flavonoids, named 7-13, with an emphasis on antimicrobial ones. Compounds 9, 11, and 12 showed inhibitory activity against human pathogenic fungi. Compounds 11, 12 (flavanones) and 13 (isoflavone) were the most active against clinical isolated Staphylococcus aureus MRSA, showing that structural requirements as prenylation at position C-6 or C-8 and OH at positions C-5, 7, and 4' are key to the antibacterial activity. The combination of 11 or 12 with commercial antibiotics synergistically enhanced the antibacterial activity of vancomycin, ciprofloxacin, and methicillin in a factor of 10 to 100 times against drug-resistant bacteria. Compound 11 combined with ciprofloxacin was able to decrease the levels of ROS generated by ciprofloxacin. According to docking results of S enantiomer of 11 with ATP-binding cassette transporter showed the most favorable binding energy; however, more studies are needed to support this result.

Natural products targeting the synthesis of ß(1,3)-D-glucan and chitin of the fungal cell wall. Existing drugs and recent findings.

BACKGROUND: During the last three decades systemic fungal infections associated to immunosuppressive therapies have become a serious healthcare problem. Clinical development of new antifungals is an urgent requirement. Since fungal but not mammalian cells are encased in a carbohydrate-containing cell wall, which is required for the growth and viability of fungi, the inhibition of cell wall synthesizing machinery, such as ß(1,3)-D-glucan synthases (GS) and chitin synthases (CS) that catalyze the synthesis of ß(1-3)-D-glucan and chitin, respectively, represent an ideal mode of action of antifungal agents. Although the echinocandins anidulafungin, caspofungin and micafungin are clinically well-established GS inhibitors for the treatment of invasive fungal infections, much effort must still be made to identify inhibitors of other enzymes and processes involved in the synthesis of the fungal cell wall. PURPOSE: Since natural products (NPs) have been the source of several antifungals in clinical use and also have provided important scaffolds for the development of semisynthetic analogues, this review was devoted to investigate the advances made to date in the discovery of NPs from plants that showed capacity of inhibiting cell wall synthesis targets. The chemical characterization, specific target, discovery process, along with the stage of development are provided here. METHODS: An extensive systematic search for NPs against the cell wall was performed considering all the articles published until the end of 2020 through the following scientific databases: NCBI PubMed, Scopus and Google Scholar and using the combination of the terms "natural antifungals" and "plant extracts" with "fungal cell wall". RESULTS: The first part of this review introduces the state of the art of the structure and biosynthesis of the fungal cell wall and considers exclusively those naturally produced GS antifungals that have given rise to both existing semisynthetic approved drugs and those derivatives currently in clinical trials. According to their chemical structure, natural GS inhibitors can be classified as 1) cyclic lipopeptides, 2) glycolipids and 3) acidic terpenoids. We also included nikkomycins and polyoxins, NPs that inhibit the CS, which have traditionally been considered good candidates for antifungal drug development but have finally been discarded after enduring unsuccessful clinical trials. Finally, the review focuses in the most recent findings about the growing field of plant-derived molecules and extracts that exhibit activity against the fungal cell wall. Thus, this search yielded sixteen articles, nine of which deal with pure compounds and seven with plant extracts or fractions with proven activity against the fungal cell wall. Regarding the mechanism of action, seven (44%) produced GS inhibition while five (31%) inhibited CS. Some of them (56%) interfered with other components of the cell wall. Most of the analyzed articles refer to tests carried out in vitro and therefore are in early stages of development. CONCLUSION: This report delivers an overview about both existing natural antifungals targeting GS and CS activities and their mechanisms of action. It also presents recent discoveries on natural products that may be used as starting points for the development of potential selective and non-toxic antifungal drugs.

The antifungal activity and mechanisms of action of quantified extracts from berries, leaves and roots of Phytolacca tetramera.

BACKGROUND: Phytolacca tetramera is an endemic plant from Argentina that is currently at serious risk because its environment is subjected to a high anthropic impact. A previous study has shown that berry extracts obtained from this plant display antifungal activity against multiple human-pathogenic fungi when tested with a non-standardized method. Further evidences of the antifungal properties of other parts of the plant and studies of mechanism of antifungal action of the antifungal chemically characterized extracts are required. PURPOSE: This study aimed to gain further evidence of the antifungal activity of P. tetramera berry, leaf and root extracts in order to find the most active extract to be developed as an Herbal Medicinal Antifungal Product. The medicinal usefulness of P. tetramera extracts as antifungal agents will serve as an important support to create concience and carry out actions tending to the preservation of this threatened species and its environment. MATERIALS AND METHODS: Chemical analysis of all P. tetramera extracts, including quantitation of selected markers, was performed through UHPLC-ESI-MS/MS and UPLC-ESI-MS techniques according to the European Medicines Agency (EMA). The antifungal activity of the quantified extracts was tested with the standardized CLSI microbroth dilution method against Candida spp. Antifungal mechanisms of the most active extract were studied by examination of morphological changes by phase-contrast and fluorescence microscopies and both, cellular and enzymatic assays targeting either the fungal membrane or the cell wall. RESULTS: The antifungal activity of twelve P. tetramera extracts was tested against Candida albicans and Candida glabrata. The dichloromethane extract from berries (PtDEb) showed the best activity. Phytolaccagenin (PhytG) and phytolaccoside B (PhytB) were selected as the main active markers for the antifungal P. tetramera extracts. The quantitation of these active markers in all extracts showed that PtDEb possessed the highest amount of PhytG and PhytB. Finally, studies on the mechanism of antifungal action showed that the most active PtDEb extract produces morphological changes compatible with a damage of the cell wall and/or the plasma membrane. Cellular and enzymatic assays showed that PtDEb would not damage the fungal cell wall by itself, but would alter the plasma membrane. In agreement, PtDEb was found to bind to ergosterol, the main sterol of the fungal plasma membrane. CONCLUSION: Studies of the anti-Candida activity of P. tetramera extracts led to the selection of PtDEb as the most suitable extract, confirming the antifungal properties of the threatened species P. tetramera. The new data give a valuable reason for the definitive protection of this sp. and its natural environment thus allowing further studies for the future development of an Herbal Medicinal Antifungal Product.

Approaches to the mechanism of antifungal activity of Zuccagnia punctata-Larrea nitida bi-herbal combination.

BACKGROUND: In our previous study the synergism of four combinations of Zuccagnia punctata (ZpE) and Larrea nitida (LnE) exudates with the reliable statistical-based MixLow method was assessed, and the markers of the most anti-C. albicans synergistic ZpE-LnE bi-herbal combination were quantified according to European Medicines Agency (EMA). PURPOSE: To study the mechanisms of action as well as the cytotoxic properties of the ZpE-LnE most synergistic combination found in the previous work. MATERIALS AND METHODS: Minimum Fungicidal Concentration (MFC) and rate of killing of ZpE-LnE were assessed with the microbroth dilution and the time-kill assays respectively. Morphological alterations were observed with both confocal and fluorescence microscopy on the yeast Schizosaccharomyces pombe. The ergosterol exogenous assay, the quantification of ergosterol, the sorbitol as well as glucan synthase (GS) and chitin synthase (ChS) assays were used to detect the effects on the fungal membrane and cell wall respectively. The capacity of ZpE-LnE of inhibiting Candida virulence factors was assessed with previously reported methods. The effect of ZpE-LnE and of ZpE or LnE alone on cell viability was determined on human hepatoma cells line Huh7. RESULTS: ZpE-Ln E was fungicidal killing C. albicans in a shorter time than amphotericin B and produced malformations in S. pombe cells. ZpE-LnE showed to bind to ergosterol but not to inhibit any step of the ergosterol biosynthesis. ZpE-LnE showed a low or moderate capacity of inhibiting GS and ChS. Regarding inhibition of virulence factors, ZpE-LnE significantly decreased the capacity of adhesion to eukaryotic buccal epithelial cells (BECs), did not inhibit the germ tube formation and inhibited the secretion of phospholipases and proteinases but not of haemolysins. ZpE-LnE demonstrated very low toxicity on Huh7 cells, much lower than that each extract alone. CONCLUSION: The fungicidal properties of ZpE-LnE against C. albicans, its dual mechanism of action targeting the fungal membrane's ergosterol as well as the cell wall, its capacity of inhibiting several important virulence factors added to its low toxicity, make ZpE-LnE a good candidate for the development of a new antifungal bi-Herbal Medicinal Product.

Intermolecular interaction energies and molecular conformations in N-substituted 4-aryl-2-methylimidazoles with promising in vitro antifungal activity.

A convenient one-pot synthesis of 4-aryl-2-methyl-N-phenacylimidazoles (4) through a microwave-assisted pseudo-tricomponent reaction of α-bromoacetophenones (1) with acetamidine hydrochloride (2) is reported. Ketones (4) were successfully used as substrates for the preparation of the respective N-(2-hydroxyethyl)imidazoles (5) with yields up to 87%. The synthesized compounds were characterized by NMR and high-resolution mass spectrometry analyses, and several structures were confirmed and studied by single-crystal X-ray diffraction. The analysis of the whole-of-molecule interactions shows that, despite the difference in the atom-atom contacts forming the crystals, dispersion energies make the largest contribution to the formation of the solids, giving an isotropic tendency in the topology of the energy framework diagrams for pairs of molecules. In addition, the in vitro antifungal activity of both families of compounds [ketones (4) and alcohols (5)] against Candida albicans and Cryptococcus neoformans was evaluated, where the 2,4-dichlorophenyl-substituted alcohol (5f), an isomer of the drug miconazole, showed the highest activity (IC50 = 7.8 µg ml-1 against C. neoformans).

Studies via X-ray analysis on intermolecular interactions and energy frameworks based on the effects of substituents of three 4-aryl-2-methyl-1H-imidazoles of different electronic nature and their in vitro antifungal evaluation.

The crystal structures of 2-methyl-4-phenyl-1H-imidazole, C10H10N2, (3a), 4-(4-chlorophenyl)-2-methyl-1H-imidazole hemihydrate, C10H9ClN2·0.5H2O, (3b), and 4-(4-methoxyphenyl)-2-methyl-1H-imidazole, C11H12N2O, (3c), have been analyzed. It was found that the electron-donating/withdrawing tendency of the substituent groups in the aryl ring influence the acid-base properties of the 2-methylimidazole nucleus, changing the strength of the intermolecular N-H...N interactions. This behaviour not only influences the crystal structure but also seems to have an important effect on the antifungal activity. Considering the substituent groups, that is, H in (3a), Cl in (3b) and OMe in (3c), the formation of strong N-H...N connections has the probability (3a) > (3b) > (3c), while compound (3c) proves to be more active than (3a) and (3b) at all concentrations against C. neoformans.

Design of Two Alternative Routes for the Synthesis of Naftifine and Analogues as Potential Antifungal Agents.

Two practical and efficient approaches have been implemented as alternative procedures for the synthesis of naftifine and novel diversely substituted analogues 16 and 20 in good to excellent yields, mediated by Mannich-type reactions as the key step of the processes. In these approaches, the γ-aminoalcohols 15 and 19 were obtained as the key intermediates and their subsequent dehydration catalyzed either by Brønsted acids like H2SO4 and HCl or Lewis acid like AlCl3, respectively, led to naftifine, along with the target allylamines 16 and 20. The antifungal assay results showed that intermediates 18 (bearing both a ß-aminoketo- and N-methyl functionalities in their structures) and products 20 were the most active. Particularly, structures 18b, 18c, and the allylamine 20c showed the lowest MIC values, in the 0.5-7.8 µg/mL range, against the dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes. Interesting enough, compound 18b bearing a 4-Br as the substituent of the phenyl ring, also displayed high activity against Candida albicans and Cryptococcus neoformans with MIC80 = 7.8 µg/mL, being fungicide rather than fungistatic with a relevant MFC value = 15.6 µg/mL against C. neoformans.

Plant phenolics and terpenoids as adjuvants of antibacterial and antifungal drugs.

BACKGROUND: The intensive use of antibacterial and antifungal drugs has dramatically increased the microbial resistance and has led to a higher number of difficult-to-eradicate infections. Combination therapy with two or more antimicrobial drugs has emerged some years ago to overcome the issue, but it has proven to be not completely effective. Natural secondary metabolites of MW ≤ 500 represent promising adjuvants for antimicrobials and have been the object of several researches that have increased in the last two decades. PURPOSE: The purpose of this Review is to do a literature search of the natural compounds that showed high enhancing capacity of antibacterials' and antifungals' effects against planktonic bacteria and fungi and to analyze which are the natural products most used in combination with a focus on polyphenols and terpenoids. RESULTS: One hundred of papers were collected for reviewing. Fifty six (56) of them deal with combinations of low MW natural products with antibacterial drugs against planktonic bacteria and forty four (44) on natural products with antifungal drugs against planktonic fungi. Of the antibacterial adjuvants, 41 (73%) were either polyphenols (27; 48%) or terpenes (14; 25%). The remaining 15 papers (27%), deal with different class of natural products. Since most natural potentiators belong to the terpene or phenolic structural types, a more detailed description of the works dealing with these type of compounds is provided here. Bacterial and fungal resistance mechanisms, the modes of action of the main classes of antibacterial and antifungal drugs and the methodologies most used to assess the type of interactions in the combinations were included in the Review too. CONCLUSIONS AND PERSPECTIVES: Several promising results on the potentiation effects of antifungals' and antibacterials' activities by low MW natural products mainly on polyphenols and terpenes were reported in the literature and, in spite of that most works included only in vitro assays, this knowledge opens a wide range of possibilities for the combination antimicrobial therapy. Further research including in vivo assays and clinical trials are required to determine the relevance of these antimicrobial enhancers in the clinical area and should be the focus of future studies in order to develop new antimicrobial combination agents that overpass the drawbacks of the existing antibiotics and antifungals in clinical use.

Hybrid combinations containing natural products and antimicrobial drugs that interfere with bacterial and fungal biofilms.

BACKGROUND: Biofilms contribute to the pathogenesis of many chronic and difficult-to eradicate infections whose treatment is complicated due to the intrinsic resistance to conventional antibiotics. As a consequence, there is an urgent need for strategies that can be used for the prevention and treatment of biofilm-associated infections. The combination therapy comprising an antimicrobial drug with a low molecular weight (MW) natural product and an antimicrobial drug (antifungal or antibacterial) appeared as a good alternative to eradicate biofilms. PURPOSE: The aims of this review were to perform a literature search on the different natural products that have showed the ability of potentiating the antibiofilm capacity of antimicrobial drugs, to analyze which are the antimicrobial drugs most used in combination, and to have a look on the microbial species most used to prepare biofilms. RESULTS: Seventeen papers, nine on combinations against antifungal biofilms and eight against antibacterial biofilms were collected. Within the text, the following topics have been developed: breaf history of the discovery of biofilms; stages in the development of a biofilm; the most used methodologies to assess antibiofilm-activity; the natural products with capacity of eradicating biofilms when acting alone; the combinations of low MW natural products with antibiotics or antifungal drugs as a strategy for eradicating microbial biofilms and a list of the low MW natural products that potentiate the inhibition capacity of antifungal and antibacterial drugs against biofilms. CONCLUSIONS AND PERSPECTIVES: Regarding combinations against antifungal biofilms, eight over the nine collected works were carried out with in vitro studies while only one was performed with in vivo assays by using Caenorhabditis elegans nematode. All studies use biofilms of the Candida genus. A 67% of the potentiators were monoterpenes and sesquiterpenes and six over the nine works used FCZ as the antifungal drug. The activity of AmpB and Caspo was enhanced in one and two works respectively. Regarding combinations against bacterial biofilms, in vitro studies were performed in all works by using several different methods of higher variety than the used against fungal biofilms. Biofilms of both the gram (+) and gram (-) bacteria were prepared, although biofilm of Staphylococcus spp. were the most used in the collected works. Among the discovered potentiators of antibacterial drugs, 75% were terpenes, including mono, di- and triterpenes, and, among the atibacterial drugs, several structurally diverse types were used in the combinations: aminoglycosides, ß-lactams, glucopeptides and fluoroquinolones. The potentiating capacity of natural products, mainly terpenes, on the antibiofilm effect of antimicrobial drugs opens a wide range of possibilities for the combination antimicrobial therapy. More in vivo studies on combinations of natural products with antimicrobial drugs acting against biofilms are highly required to cope the difficult to treat biofilm-associated infections.

Antifungal toxicity of linear geranylphenol. Influence of oxigenate substituents.

Twenty four linear geranylphenols were evaluated for their antifungal properties against ATCC and clinical isolates of Candida albicans and Cryptococcus neoformans. For the analysis of their antifungal behavior the compounds were grouped into two series: (i) compounds with only one geranyl substituent on the benzene ring and (ii) compounds with two geranyl moieties on the benzene ring. Results showed that compounds of series (i) present better antifungal activities than those of series (ii). In addition, within group (i) all compounds showed better activities against C. neoformans than against C. albicans which can be easily verified by comparing MIC100 or MIC50 of each compound against both fungi. Di- (10 and 11) and tri-hydroxy (3 and 4) compounds showed significant anti-cryptoccocal activity, being 3, 10 and 11 highly active with MIC100 or MIC50 = 3.9 µg/mL similar to the standard drug amphotericin B. Moreover, when evaluating the toxicity of compounds 6, 10 and 11 on the HDF cell line (human dermal fibroblasts), results were obtained with IC50 values > 100 µM, considered as non-toxic for the cell. This indicates that the toxicity of the analyzed compounds is selective towards fungi, which makes them a very attractive family for the development of future drugs.

Synthesis and antifungal activity of bile acid-derived oxazoles.

Peracetylated bile acids (1a-g) were used as starting materials for the preparation of fourteen new derivatives bearing an oxazole moiety in their side chain (6a-g, 8a-g). The key step for the synthetic path was a Dakin-West reaction followed by a Robinson-Gabriel cyclodehydration. A simpler model oxazole (12) was also synthesized. The antifungal activity of the new compounds (6a-g) as well as their starting bile acids (1a-g) was tested against Candida albicans. Compounds 6e and 6g showed the highest percentages of inhibition (63.84% and 61.40% at 250 µg/mL respectively). Deacetylation of compounds 6a-g, led to compounds 8a-g which showed lower activities than the acetylated derivatives.

Antifungal drugs combinations: a patent review 2000-2015.

INTRODUCTION: Combination therapy has emerged as an approach to improve the efficacy of antifungal drugs. Its main objective is to achieve synergistic interaction with higher antifungal properties and lower toxic effects than each substance alone. AREAS COVERED: Twenty-four patents disclosed in the period of 2000-2015 were covered in this review. Twenty of them were devoted to pharmacodynamic potentiation, while four were dedicated to pharmacokinetic actions. EXPERT OPINION: The common characteristic of most patents published in this area is that the main partner is a commercial antifungal drug. In the most innovative combinations the second component was either a modifier of proton homeostasis, an antibody, an inhibitor of the adhesion of epithelial or endothelial cells or a keratinolytic agent that improves the skin penetration. The evaluation of synergism is always made with simple in vitro methods, which constitutes a weakness of the disclosed patents, due to the lack of in vivo studies, since the in vitro tests cannot predict the in vivo behavior. Also, it is surprising that none of the patents analyze the toxicity of the new combinations, taking into account that one of the main objectives of the combinations is to reduce the toxicity of the existing antifungal drugs.

Antifungal Activity of Pyranonaphthoquinones Obtained from Cipura paludosa Bulbs.

Previous studies with the bulbs of Cipura paludosa (Iridaceae) showed the presence of pyranonaphthoquinones, including eleutherine, isoeleutherine and eleutherol. The aim of this study was to evaluate the antifungal properties of these compounds. The activity was tested against the clinically relevant yeasts Candida albicans, C. tropicalis, Saccharomyces cerevisiae and Cryptococcus neoformans with the microbroth dilution method, following the guidelines of CLSI. Eleutherine, isoeleutherine and eleutherol all presented significant antifungal activity, especially the first two, the major components, with MIC values between 7.8 and 250 µg/mL. In conclusion, these results demonstrate that C. paludosa bulbs produce active principles with relevant antifungal potential, contributing, at least in part, to the antimicrobial effect evidenced for this plant and justifying its popular use against infections.

Synergistic mutual potentiation of antifungal activity of Zuccagnia punctata Cav. and Larrea nitida Cav. extracts in clinical isolates of Candida albicans and Candida glabrata.

BACKGROUND: Zuccagnia punctata Cav. (Fabaceae) and Larrea nitida Cav. (Zygophyllaceae) are indistinctly or jointly used in traditional medicine for the treatment of fungal-related infections. Although their dichloromethane (DCM) extract have demonstrated moderate antifungal activities when tested on their own, antifungal properties of combinations of both plants have not been assessed previously. PURPOSE: The aim of this study was to establish with statistical rigor whether Z. punctata (ZpE) and L. nitida DCM extract (LnE) interact synergistically against the clinically important fungi Candida albicans and Candida glabrata and to characterize the most synergistic combinations. STUDY DESIGN: For synergism assessment, the statistical-based Boik's design was applied. Eight ZpE-LnE fixed-ratio mixtures were prepared from four different months of 1 year and tested against Candida strains. Lϕ (Loewe index) of each mixture at different fractions affected (ϕ) allowed for the finding of the most synergistic combinations, which were characterized by HPLC fingerprint and by the quantitation of the selected marker compounds. METHODS: Lϕ and confidence intervals were determined in vitro with the MixLow method, once the estimated parameters from the dose-response curves of independent extracts and mixtures, were obtained. Markers (four flavonoids for ZpE and three lignans for LnE) were quantified in each extract and their combinations, with a valid HPLC-UV method. The 3D-HPLC profiles of the most synergistic mixtures were obtained by HPLC-DAD. RESULTS: Three over four IC50ZpE/IC50LnE fixed-ratio mixtures displayed synergistic interactions at effect levels ϕ > 0.5 against C. albicans. The dosis of the most synergistic (Lϕ = 0.62) mixture was 65.96 µg/ml (ZpE = 28%; LnE = 72%) containing 8 and 36% of flavonoids and lignans respectively. On the other hand, one over four IC50ZpE/IC50LnE mixtures displays synergistic interactions at ϕ > 0.5 against C. glabrata. The dosis of the most synergistic (Lϕ = 0.67) mixture was 168.23 µg/ml (ZpE = 27%; LnE = 73%) with 9.7 and 31.6% of flavonoids and lignans respectively. CONCLUSIONS: Studies with the statistical-based MixLow method, allowed for the finding of the most ZpE-LnE synergistic mixtures, giving support to a proper joint use of both antifungal herbs in traditional medicine.

Microwave-Assisted Synthesis of Novel Pyrazolo[3,4-g][1,8]naphthyridin-5-amine with Potential Antifungal and Antitumor Activity.

The microwave assisted reaction between heterocyclic o-aminonitriles 1 and cyclic ketones 2 catalyzed by zinc chloride led to new series of pyrazolo[3,4-b] [1,8]naphthyridin-5-amines 3 in good yields. This procedure provides several advantages such as being environmentally friendly, high yields, simple work-up procedure, broad scope of applicability and the protocol provides an alternative for the synthesis of pyrazolonaphthyridines. The whole series showed antifungal activities against Candida albicans and Cryptococcus neoformans standardized strains, being compounds with a 4-p-tolyl substituent of the naphthyridin scheleton (3a, 3d and 3g), the most active ones mainly against C. albicans, which appear to be related to their comparative hydrophobicity. Among them, 3d, containing a cyclohexyl fused ring, showed the best activity. The anti-Candida activity was corroborated by testing the three most active compounds against clinical isolates of albicans and non-albicans Candida strains. These compounds were also screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Compounds 3a and 3e showed remarkable antitumor activity against cancer cell lines, with the most important GI50 values ranging from 0.62 to 2.18 µM.

Synthesis, antiproliferative and antifungal activities of 1,2,3-triazole-substituted carnosic Acid and carnosol derivatives.

Abietane diterpenes exhibit an array of interesting biological activities, which have generated significant interest among the pharmacological community. Starting from the abietane diterpenes carnosic acid and carnosol, twenty four new triazole derivatives were synthesized using click chemistry. The compounds differ in the length of the linker and the substituent on the triazole moiety. The compounds were assessed as antiproliferative and antifungal agents. The antiproliferative activity was determined on normal lung fibroblasts (MRC-5), gastric epithelial adenocarcinoma (AGS), lung cancer (SK-MES-1) and bladder carcinoma (J82) cells while the antifungal activity was assessed against Candida albicans ATCC 10231 and Cryptococcus neoformans ATCC 32264. The carnosic acid γ-lactone derivatives 1-3 were the most active antiproliferative compounds of the series, with IC50 values in the range of 43.4-46.9 µM and 39.2-48.9 µM for MRC-5 and AGS cells, respectively. Regarding antifungal activity, C. neoformans was the most sensitive fungus, with nine compounds inhibiting more than 50% of its fungal growth at concentrations ≤250 µg∙mL-1. Compound 22, possessing a p-Br-benzyl substituent on the triazole ring, showed the best activity (91% growth inhibition) at 250 µg∙mL-1 In turn, six compounds inhibited 50% C. albicans growth at concentrations lower than 250 µg∙mL-1.

Antifungal terpenoids from Hyalis argentea var. latisquama.

A detailed chemical study of the aerial parts and rhizomes of Hyalis argentea var. latisquama yielded a variety of sesqui- and diterpenes. In total, 26 compounds were isolated and identified, of which four are new, namely, two ent-kaurenes (1 and 2), a diterpene lactone (3), and a lindenanolide (4). The previously reported compounds included a series of lindenanolides, guaianolides, elemanolides, and additional diterpenes. The antifungal activity of the isolated compounds was tested against Cryptococcus neoformans and Candida albicans. Among the isolated compounds, the lindenanolides were the only structural class that showed strong antifungal activity, and onoseriolide acetate (5) was the most active. On the other hand, the isolated guaianolides were only moderately active, while the diterpenes did not show significant antifungal activity.