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

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.

Antiproliferative Cancer Cell and Fungicidal Effects of Yellow and Red Araçá (Psidium cattleianum Sabine) Fruit Extract

Araçá is a native Brazil fruit, and has two morphological types, yellow and red; however, it is still little consumed by the population. Although there are few studies on the araçá fruit, some phytochemical propriety benefits have been described for this plant, such as antioxidant effects. To explore the benefits of araçá fruit, the physicochemical characteristics and in vitro toxicological effects of red and yellow araçá fruit were evaluated. In this work, the toxicity of araçá extracts in NIH/3T3 cell lines, the antiproliferative effects in cancer cell lines (C6, HT-29, and DU149), and the overall antifungal effects were evaluated. The irritant potential of araçá extracts was assessed by the HET-CAM test. The results demonstrated that the fruits are rich in fiber content and showed high phenols content. In addition, the araçá extracts had no present toxicity effects in cell lines; however, the red araçá extracts showed antiproliferative effects in HT-29 cancer cells at 50 mg/mL. The antifungal effects of araçá extract were promising in 23 isolates of Candida spp., and both araçá extracts showed no irritant effects. Therefore, this study demonstrated that red and yellow araçá fruit extract has promising biological and pharmacological effects that should be further explored.

Senna singueana (Delile) lock: Ethnomedicinal uses and medicinal properties

Senna singueana (Delile) Lock is a potential medicinal plant commonly used to mitigate various infectious and non-infectious diseases including malaria, typhoid, gonorrhoea, bilharzia, cancer, epilepsy and ulcer. The phytochemical profile of S. singueana indicates the presence of different phytoconstituents corresponding to the pharmacological properties. The pharmacological potentials such as antibacterial, antifungal, antioxidant, antimalarial and antidiabetics are possessed by S. singueana. This review comprehensively discusses the potential of S. singueana for the mitigation of medical conditions. The information is collected from various online databases such as Google scholar, ScienceDirect, Springer, Web of Science and PubMed. Among other information, ethnomedicinal uses, phytochemistry, pharmacology and mechanisms of action are extensively presented. A review concluded by highlighting the challenges and potential future outlooks.

Major Phytochemical Compounds, In Vitro Antioxidant, Antibacterial, and Antifungal Activities of Six Aqueous and Organic Extracts of Crocus sativus L. Flower Waste

PURPOSE

After being considered as a neglected product, agricultural waste is nowadays considered of paramount importance. It has become a source of many chemical compounds with industrial, pharmaceutical, and food applications. This study aims to evaluate the primary phytochemical content, the antioxidant properties, and the antimicrobial activities of different extracts of saffron flower waste (SFE) against bacterial and fungal strains involved in diverse pathologies in southern Morocco.

METHODS

Total phenolic and flavonoid contents were determined. The antioxidant potentials were assessed by DPPH, FRAP, and β-carotene assays. The antimicrobial activity against four bacteria and four fungi was also evaluated. The findings in terms of the relationships between phytochemical content and all activities were depicted by PCA analyses.

RESULTS

SFEs contained large amounts of phenolic and flavonoid compounds that contribute to the significant antioxidant activities. Diethyl ether (DE), n-Butanol (n-B), and Ethyl acetate (EA) fractions respectively exhibited more DPPH scavenging capacity, FRAP reducing power, and β-carotene bleaching inhibition. DE and EA have a remarkable effect mainly against Staphylococcus aureus strain, compared to Listeria monocytogenes, Escherichia coli and Klebsiella pneumoniae. Both SFEs showed antifungal antagonism towards key fungi species involved in post-harvest mold and crop yield losses. Botrytis cinerea was more susceptible than Fusarium solani, Penicillium expansum, and Penicillium digitatum.

CONCLUSION

These results reveal new data about extracts obtained from SFE that could be a potential source of natural antioxidant and antimicrobial agents opening new possibilities for their applications in the food system as a natural preservative and a sustainable alternative to conventional ingredients.

Present scenarios and future prospects of herbal nanomedicine for antifungal therapy

The current COVID-19 epidemic is a sobering reminder that human susceptibility to infectious diseases remains even in our modern civilization. After all, infectious diseases are still the major reason of death globally. Healthcare authorities have often underestimated and ignored the threat posed by "microbial dangers," although they put millions of lives at risk every year. Overlooked developing diseases including fungal infections (FIs) contribute to roughly 1.7 million fatalities per year. As many as 150 million cases of severe and potentially life-threatening FIs are reported each year. In the last few years, the number of instances has steadily increased. Most of them are invasive fungal infections that require specialized treatment and hospital care. In recent years herbal antifungal compounds have been explored to acquire effective and safe therapy against fungal infections. However, potential therapeutic effects are hampered by the poor solubility, stability, and bioavailability of these important chemicals as well as the gastric degradation that occurs in the gastrointestinal tract. To get around this issue, researchers have turned to novel drug delivery systems such as nanoemulsions, ethosomes, metallic nanoparticles, liposomes, lipid nanoparticles, transferosomes, etc by improving their limits, nanocarriers can enhance the medicinal effects of herbal oils and extracts. The present review article focuses on the available antifungal agents and their characteristics, mechanism of antifungal drugs resistance, herbal oils and extract as antifungal agents, challenges in the delivery of herbal drugs, and application of nano-drug delivery systems for effective delivery of antifungal herbal compounds.

Plants of the Phytolaccaceae family with antimicrobial activity: A systematic review

Phytolaccaceae is a plant family of the order Caryophyllales, which includes species used in traditional medicine to treat diseases. The purpose of this study was to investigate Phytolaccaceae family plants with potential antimicrobial action, through a systematic review. The study was conducted following the criteria of PRISMA protocol. The search was performed in the electronic databases PubMed, Web of Science, Scopus, and LILACS, in March 2021. The search strategy used free descriptors and terms, limiting articles to the English language, regardless of publication year. The risk of bias and the quality of publications were based on the CONSORT checklist, modified for in vitro studies and SYRCLE's RoB tool for in vivo study. Five independent judges performed quality assessments of publications and risk of bias analysis. Ninety-five publications were retrieved from the databases and, after screening and eligibility criteria, 22 articles remained, from 1998 to 2019. In the selected studies, the plants were obtained from eight countries. In vivo and in vitro studies of extracts from the Phytolaccaceae family plants, evaluating antibacterial (8 publications), antifungal (8), anti-Trypanosoma (2), anti-Leishmania (2), antiviral (1), and antiamoebic (1) activities, are included. The plant species identified belong to genera Petiveria, Phytolacca, Gallesia, Trichostigma, and Seguieria. The risk of bias in the 22 publications both in vitro and in vitro was suboptimal. The evidence obtained showed that the Phytolaccaceae family, a source of plants with antimicrobial action, can serve as a basis for the creation of new herbal medicines, expanding the possibility of treatment for infectious diseases and stimulating their preservation and biodiversity. However, more high-quality studies are needed to establish the clinical efficacy of the plant.

The effects of Ziziphus Spina leaves’ Hydro-Alcoholic Extract Vaginal Cream and Clotrimazole on Candida albicans in Wistar Rats

Background:

In vitro, Ziziphus Spina-Christi (ZSC) leaves have been shown to have antimicrobial and antifungal effects. This study aimed to examine the effects of Ziziphus Spina leaves hydro-alcoholic extracts with Clotrimazole against Candida albicans in female rats.

Methods:

Four groups of rats were infected vaginally with C. Albicans, and 1 group not infected was considered negative control. The infected groups received the following treatments: 2 groups were treated with vaginal 5%, or 10%, of Ziziphus Spina extract creams. One group received 1% clotrimazole, and 1 group did not receive any treatment considered a positive control.

Results:

The mean number of colony-forming units (CFUs) before the intervention was 195.83 ± 395.126 in the 5% ZSC group, 346.33 ± 396.719 in the 10% ZSC group, 345.17 ± 507.431 in the clotrimazole group, 212.20 ± 148.304 in the positive control group (P = .604), and 0 in the negative control group (P = .003). After 1 week, the average number of CFUs considerably dropped to 65.14 ± 36.03 in the 5% ZSC group, 1.43 ± 3.60 in the 10% ZSC group, and 0.43 ± 1.13 in the clotrimazole group. The number in the positive control group remained unchanged (212.20 ± 148.304) (P = .005). After 2 weeks, the average number of CFUs was 0 in the 10% ZSC group, Clotrimazole and negative control groups and was 4.57 ± 23.99 in the 5% ZSC group (P < .001).

Conclusions:

Our findings indicated that the effectiveness of Vaginal creams containing 10% Ziziphus Spina is similar to Clotrimazole in eliminating C. Albicans.

The role of antifungal activity of ethyl acetate extract from Artemisia argyi on Verticillium dahliae

AIMS

This study investigated the antifungal activity and mechanisms of ethyl acetate extract of Artemisia argyi (EAAA) against Verticillium dahliae.

METHODS AND RESULTS

Optical and scanning electron microscopy observation showed that 2.0 mg ml^-1 EAAA treatment reduced spore germination rate to 4.56%. Histochemical staining showed that 2.0 mg ml^-1 EAAA treatment increased reactive oxygen species (ROS) by more than two times. Physiological test showed that EAAA treatment decreased the contents of soluble proteins and sugars, and reduced the activities of malate dehydrogenase and succinate dehydrogenase by nearly half. Transcriptome analysis showed that EAAA treatment down-regulated the expression of genes involved in primary metabolic pathways of V. dahliae.

CONCLUSIONS

Our results revealed that EAAA inhibited the growth and development of V. dahliae from multiple levels and multiple targets, including inhibiting the germination and development of V. dahliae spores, destroying the structure of cell membranes, inducing ROS burst, reducing the activities of respiratory-related enzymes and down-regulating the expression of genes in primary metabolic pathways.

SIGNIFICANCE AND IMPACT OF THE STUDY

The mechanism of the multitarget effects of EAAA against V. dahliae may limit the potential of fungus developing resistance and provide the efficient methods to control verticillium wilt disease in the future.

Preliminary Study on Antifungal Mechanism of Aqueous Extract of Cnidium monnieri Against Trichophyton rubrum

Trichoderma rubrum (T. rubrum) is one of the important pathogens because it is the cause of most dermatomycosis. The treatment of Trichophyton rubrum infection is time-consuming and very expensive; it is easy for the infections to reoccur, leading to therapeutic failures, persistence, and chronic infection. These issues have inspired researchers to study natural alternative therapies instead. Cnidium monnieri (L.), as a kind of traditional Chinese medicine, has a variety of pharmacological activities and a wide range of applications, so it has a high potential for researching and economic value. We detected the effect of aqueous extract of C. monnieri (L.) on the activity of T. rubrum by Cell Count Kit-8 assay (CCK-8), and we found that 128 and 256 μg/ml of aqueous extracts of C. monnieri (L.) co-cultured with T. rubrum for 24 h showed the inhibitory effect on T. rubrum. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that aqueous extract of C. monnieri (L.) damaged the T. rubrum. At the same time, mass spectrometry screening with T. rubrum before and after the treatment of 256 μg/ml of aqueous extracts of C. monnieri (L.) showed that 966 differentially expressed proteins were detected, including 524 upregulated differentially expressed genes (DEGs) and 442 downregulated DEGs. The most significantly downregulated protein was chitin synthase (CHS); and the results of qRT-PCR and Western blotting demonstrated that the expression level of CHS was downregulated in the 256 μg/ml group compared with the control group. The study showed that the aqueous extract of C. monnieri (L.) could destroy the morphology of mycelia and the internal structure of T. rubrum, and it could inhibit the growth of T. rubrum. The antifungal effect of aqueous extract of C. monnieri (L.) may be related to the downregulation of the expression of CHS in T. rubrum, and CHS may be one of the potential targets of its antifungal mechanism. We concluded that aqueous extract from C. monnieri (L.) may be a potential candidate for antifungal agents.

Natural products targeting the synthesis of β(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 β(1,3)-D-glucan synthases (GS) and chitin synthases (CS) that catalyze the synthesis of β(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.

Esculentosides: Insights into the potential health benefits, mechanisms of action and molecular targets

BACKGROUND

Esculentosides and related phytolaccosides form a group of oleanene-type saponins isolated from plants of the Phytolaccaceae family, essentially Phytolacca esculenta, P. americana and P. acinosa. This chemical family offers a diversity of glycosylated compounds, including molecules with a mono-, di- or tri-saccharide unit at position C-3, and with or without a glucose residue at position C-28. The esculentosides, which derive essentially from the sapogenin jaligonic acid or its 30-methyl ester phytolaccagenin, exhibit anti-inflammatory, antifungal and anticancer activities.

PURPOSE

The objective of the review was to identify the 26 esculentosides (ES) and phytolaccosides known to date, including 16 monodesmosidic and 10 bidesmosidic saponins, and to review their pharmacological properties and molecular targets.

METHODOLOGY

The retrieval of potentially relevant studies was done by systematically searching of scientific databases like Google Scholar and PubMed in January-May 2020. The main keywords used as search terms were related to esculentosides, phytolaccosides and Phytolaccaceae. The systematic search retrieved about 110 papers that were potentially relevant and after an abstract-based selection, 68 studies were analyzed in details and discussed.

RESULTS

The structural relationship between the compounds and their sapogenin precursors has been studied. In addition, the pharmacological properties of the main ES, such as ES-A, -B and -H, have been analyzed to highlight their mode of action and potential targets. ES-A is a potent inhibitor of the release of cytokines and this anti-inflammatory activity contributes to the anticancer effects observed in vitro and in vivo. Potential molecular targets of ES-A/B include the enzymes cyclooxygenase 2 (COX-2) and casein kinase 2 (CK2). In addition, the targeting of the protein high-mobility group box 1 (HGMB1) by ES-A/B is proposed, based on molecular modeling and the structural analogy with the related saponin glycyrrhizin, a potent HGMB1 alarmin inhibitor.

CONCLUSION

More work is needed to properly characterize the molecular targets but otherwise compounds like ES-A and ES-H emerge as potent anti-inflammatory and anticancer agents and ES-B as an antifungal agent. A preclinical development of these three compounds should be considered.