Antifungal activity of modified hederagenin glycosides from the leaves of Kalopanax pictum var. chinense

The intramolecular self-assembly of bidesmosidic kalopanaxsaponins

The phenomena of intramolecular self-assembly of bidesmosidic kalopanaxsaponins was identified for the first time in this paper. NMR (1H-NMR, NOESY), transmission electron microscopy (TEM), and molecular dynamics (MD) simulation techniques were used to compare the spatial structures of bidesmosidic kalopanaxsaponins and monodesmosidic kalopanaxsaponins. The results showed that the bidesmosidic kalopanaxsaponins formed a clustered and twisted structure in space, whereas the monodesmosidic kalopanaxsaponins were in an extended state. This discovery confirmed the presence of intramolecular self-assembly in bidesmosidic kalopanaxsaponins.

Anticandidal Activity of Kalopanaxsaponin A: Effect on Proliferation, Cell Morphology, and Key Virulence Attributes of Candida albicans

Background

The pathogenicity of Candida albicans is attributed to various virulence factors including adhesion to the surface of epithelial cells or mucosa, germ tube formation, hyphal morphogenesis, development of drug resistant biofilms, and so on. The objective of this study was to investigate the effects of Kalopanaxsaponin A (KPA) on the virulence of C. albicans.

Methods

The effect of KPA on the virulence of C. albicans was characterized by an XTT reduction assay and fluorescent microscopic observation. The action mechanism was further explored using GC/MS system and BioTek Synergy2 spectrofluorophotometry. The cytotoxicity and therapeutic effect of KPA were evaluated by the Caenorhabditis elegans-C. albicans infection model in vivo.

Results

The minimum inhibitory concentration (MIC) of KPA was 8∼16 μg/mL for various genotypes of C. albicans. The compound was identified as having remarkable effect on the adhesion, morphological transition and biofilm formation of C. albicans. The results of fluorescent microscopy and GC/MS system suggested that KPA could promote the secretion of farnesol by regulating the expression of Dpp3 and decrease the intracellular cAMP level, which together inhibited morphological transition and biofilm formation. Notably, KPA showed low toxicity in vivo and a low possibility of developing resistance.

Conclusion

Our results demonstrated that KPA had remarkable efficacy against C. albicans pathogenicity, suggesting that it could be a potential option for the clinical treatment of candidiasis.

Recent Status and Advancements in the Development of Antifungal Agents: Highlights on Plant and Marine Based Antifungals

The developing resistance in fungi has become a key challenge, which is being faced nowadays with the available antifungal agents in the market. Further search for novel compounds from different sources has been explored to meet this problem. The current review describes and highlights recent advancement in the antifungal drug aspects from plant and marine based sources. The current available antifungal agents act on specific targets on the fungal cell wall, like ergosterol synthesis, chitin biosynthesis, sphingolipid synthesis, glucan synthesis etc. We discuss some of the important anti-fungal agents like azole, polyene and allylamine classes that inhibit the ergosterol biosynthesis. Echinocandins inhibit β-1, 3 glucan synthesis in the fungal cell wall. The antifungals poloxins and nikkomycins inhibit fungal cell wall component chitin. Apart from these classes of drugs, several combinatorial therapies have been carried out to treat diseases due to fungal resistance. Recently, many antifungal agents derived from plant and marine sources showed potent activity. The renewed interest in plant and marine derived compounds for the fungal diseases created a new way to treat these resistant strains which are evident from the numerous literature publications in the recent years. Moreover, the compounds derived from both plant and marine sources showed promising results against fungal diseases. Altogether, this review article discusses the current antifungal agents and highlights the plant and marine based compounds as a potential promising antifungal agents.

Plant bioactive molecules bearing glycosides as lead compounds for the treatment of fungal infection: A review

Despite therapeutic advancement in the treatment of fungal infections, morbidity and mortality caused by these infections are still very high. There are approximately 300 fungal species that are infectious and can cause a variety of diseases. At present, several synthetic antifungal drugs are in clinical practice, many of them, however, are vulnerable to multidrug-resistant strains of microbes, and thus compromising the overall treatment outcomes. Glycosides are naturally occurring plant secondary metabolites with important therapeutic potential and clinical utility. The aim of this review was to focus on the antifungal effects of glycosides in preclinical studies with possible mechanism(s) wherein described. Published research show significant susceptibility of different fungi towards phytoglycosides, mediated through multiple mechanisms. Further detailed studies are needed to explain the clinical applications and limitations of these glycosides.

Candida albicans PROTEIN PROFILE CHANGES IN RESPONSE TO THE BUTANOLIC EXTRACT OF Sapindus saponariaL

Candida albicans is an opportunistic human pathogen that is capable of causing superficial and systemic infections in immunocompromised patients. Extracts of Sapindus saponaria have been used as antimicrobial agents against various organisms. In the present study, we used a combination of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) to identify the changes in protein abundance of C. albicans after exposure to the minimal inhibitory concentration (MIC) and sub-minimal inhibitory concentration (sub-MIC) of the butanolic extract (BUTE) of S. saponaria and also to fluconazole. A total of six different proteins with greater than 1.5 fold induction or repression relative to the untreated control cells were identified among the three treatments. In general, proteins/enzymes involved with the glycolysis (GPM1, ENO1, FBA1), amino acid metabolism (ILV5, PDC11) and protein synthesis (ASC1) pathways were detected. In conclusion, our findings reveal antifungal-induced changes in protein abundance of C. albicans. By using the previously identified components of the BUTE of S. saponaria(e.g., saponins and sesquiterpene oligoglycosides), it will be possible to compare the behavior of compounds with unknown mechanisms of action, and this knowledge will help to focus the subsequent biochemical work aimed at defining the effects of these compounds.

Experimental Study of Antiatherosclerosis Effects with Hederagenin in Rats

The research tries to establish Wistar rat's model of atherosclerosis for evaluating the antiatherosclerotic effect of hederagenin and exploring its antiatherosclerosis-related mechanisms. The statistical data have shown that hederagenin exhibits multiple pharmacological activities in the treatment of hyperlipidemia, antiplatelet aggregation, liver protection, and anti-inflammation, indicating that hederagenin may exert a protective effect on vascular walls by improving lipid metabolism disorders and lipid deposition. The results show that hederagenin can correct the imbalance of endothelial function by inhibiting the release of large amounts of iNOS and increasing eNOS contents and inhibits the IKKβ/NF-κB signaling pathway to reduce the release of IL-6, IFN-γ, TNF-α, and other inflammatory factors. The experimental results indicated that hederagenin can inhibit or ameliorate the pathological changes associated with AS, displaying an excellent preventive function against AS.

β-Aescin at subinhibitory concentration (sub-MIC) enhances susceptibility of Candida glabrata clinical isolates to nystatin

Aescin (escin) derived from the seeds of horse chestnut (Aesculus hippocastanum L.) is a natural mixture of triterpene saponins exhibiting a wide variety of pharmacological properties, including antiinflammatory, analgesic, and antipyretic activities. However, data concerning antifungal activities of these compounds are limited. This study aims to evaluate the in vitro antifungal susceptibility of Candida glabrata clinical isolates to α-aescin sodium, β-aescin crystalline and β-aescin sodium using the disk diffusion (DD) and broth microdilution (BMD) methods. Moreover, the influence of subinhibitory concentration (0.5×MIC) of β-aescins on the nystatin MIC was also studied. In general, the results obtained by the DD assay correlated well with those obtained by the BMD method. Both β-aescins effectively inhibited the growth of all 24 strains tested. The minimum inhibitory concentration (MIC) values ranging from 8 to 32 μg/ml for β-aescin crystalline, whereas those of β-aescin sodium were slightly lower and ranged from 4 to 16 μg/ml. In contrast, α-aescin sodium was found to be completely ineffective against the strains studied. MIC values of nystatin were reduced 2-16-fold and 2-4-fold in the presence of subinhibitory concentration of β-aescin crystalline and β-aescin sodium, respectively. Results of the present study may suggest the additive interaction between β-aescin and nystatin.

Antimicrobial activity, growth inhibition of human tumour cell lines, and phytochemical characterization of the hydromethanolic extract obtained from Sapindus saponaria L. aerial parts

The hydromethanolic extract of Sapindus saponaria L. aerial parts was investigated for antimicrobial activity (against several Gram-positive and Gram-negative bacteria and fungi) and capacity to inhibit the growth of different human tumor cell lines as also nontumor liver cells. The evaluated extract was further characterized in terms of phytochemicals using UV, (1)H-NMR, (13)C-NMR, and MS spectroscopic tools. The extract has shown a significant antimicrobial activity on all tested bacterial and fungal species. The best activity was achieved against Bacillus cereus and Staphylococcus aureus among bacteria and against all three Penicillium species tested. It also revealed cytotoxicity against human colon (HCT-15), cervical (HeLa), breast (MCF-7), and lung (NCI-H460) carcinoma cell lines, with HeLa being the most susceptible tumor cell line. The extract was not toxic for nontumor liver cells. Chromatographic separation of the extract resulted in the isolation and identification of stigmasterol, oleanolic acid, luteolin, luteolin 8-C-β-glucoside (orientin), luteolin 6-C-β-glucoside (isoorientin), luteolin 7-O-β-glucuronide, and rutin. The results of the present findings may be useful for the discovery of novel antitumor and antimicrobial agents from plant origin.

Saponins from Glycine max Merrill (soybean)

Saponins are a diverse group of plant secondary metabolites with a wide array of activities, as well as a significant role in nutrition and health. Saponins occur as multi-component mixtures of compounds with very similar polarities. Soysaponins are a special group of saponins. These represent the main source of saponins in Glycine max (soybeans, Fabaceae). In a study of the chemical profiling of plants, to investigate the possible misidentification and authentication of dietary supplements, the hydro-alcoholic extract of G. max was investigated. Three new saponins, designated as soysaponins M1 (1), M2 (2) and M3 (3) along with seven known soysaponins (4-10) were isolated by normal and reverse phase liquid chromatography. All compounds were characterized by spectroscopic techniques including 2D NMR spectroscopy.

In vivo activity of Sapindus saponaria against azole-susceptible and -resistant human vaginal Candida species

Background

Study of in vivo antifungal activity of the hydroalcoholic extract (HE) and n-BuOH extract (BUTE) of Sapindus saponaria against azole-susceptible and -resistant human vaginal Candida spp.

Methods

The in vitro antifungal activity of HE, BUTE, fluconazole (FLU), and itraconazole (ITRA) was determined by the broth microdilution method. We obtained values of minimal inhibitory concentration (MIC) and minimum fungicide concentration (MFC) for 46 strains of C. albicans and 10 of C. glabrata isolated from patients with vulvovaginal candidiasis (VVC). VVC was induced in hyperestrogenic Wistar rats with azole-susceptible C. albicans (SCA), azole-resistant C. albicans (RCA), and azole-resistant C. glabrata (RCG). The rats were treated intravaginally with 0.1 mL of HE or BUTE at concentrations of 1%, 2.5% and 5%; 100 μg/mL of FLU (treatment positive control); or distilled water (negative control) at 1, 24, and 48 h after induction of the infection, and the progress of VVC was monitored by culturing and scanning electron microscopy (SEM). The toxicity was evaluated in cervical cells of the HeLa cell line.

Results

The extracts showed in vitro inhibitory and fungicidal activity against all the isolates, and the MIC and MFC values for the C. glabrata isolates were slightly higher. In vivo, the SCA, RCA, and RCG infections were eliminated by 21 days post-infection, with up to 5% HE and BUTE, comparable to the activity of FLU. No cytotoxic action was observed for either extract.

Conclusions

Our results demonstrated that HE and BUTE from S. saponaria show inhibitory and fungicidal activity in vitro, in addition to in vivo activity against azole-resistant vaginal isolates of C. glabrata and azole-susceptible and resistant isolates of C. albicans. Also considering the lack of cytotoxicity and the low concentrations of the extracts necessary to eliminate the infection in vivo, HE and BUTE show promise for continued studies with purified antifungal substances in VVC yeast isolates.

Molecular activities, biosynthesis and evolution of triterpenoid saponins

Saponins are bioactive compounds generally considered to be produced by plants to counteract pathogens and herbivores. Besides their role in plant defense, saponins are of growing interest for drug research as they are active constituents of several folk medicines and provide valuable pharmacological properties. Accordingly, much effort has been put into unraveling the modes of action of saponins, as well as in exploration of their potential for industrial processes and pharmacology. However, the exploitation of saponins for bioengineering crop plants with improved resistances against pests as well as circumvention of laborious and uneconomical extraction procedures for industrial production from plants is hampered by the lack of knowledge and availability of genes in saponin biosynthesis. Although the ability to produce saponins is rather widespread among plants, a complete synthetic pathway has not been elucidated in any single species. Current conceptions consider saponins to be derived from intermediates of the phytosterol pathway, and predominantly enzymes belonging to the multigene families of oxidosqualene cyclases (OSCs), cytochromes P450 (P450s) and family 1 UDP-glycosyltransferases (UGTs) are thought to be involved in their biosynthesis. Formation of unique structural features involves additional biosynthetical enzymes of diverse phylogenetic background. As an example of this, a serine carboxypeptidase-like acyltransferase (SCPL) was recently found to be involved in synthesis of triterpenoid saponins in oats. However, the total number of identified genes in saponin biosynthesis remains low as the complexity and diversity of these multigene families impede gene discovery based on sequence analysis and phylogeny. This review summarizes current knowledge of triterpenoid saponin biosynthesis in plants, molecular activities, evolutionary aspects and perspectives for further gene discovery.

Structure-biological activity relationships in triterpenic saponins: the relative activity of protobassic acid and its derivatives against plant pathogenic fungi

BACKGROUND

Triterpenic saponins from Sapindus mukorossi Gaertn. and Diploknema butyracea JF Gmelin were evaluated for in vitro antifungal activity against four phytopathogenic fungi. The study of the structure-antifungal activity relationships of protobassic acid saponins was widened by including semi-synthetic derivatives.

RESULTS

Diploknema butyracea saponins exhibited significant antifungal activity against three fungi (ED(50) 230-455 microg mL(-1)), whereas S. mukorossi saponin was effective against two fungi (ED(50) 181-407 microg mL(-1)). The n-butanol extract after preparative HPLC separation provided two saponins from D. butyracea saponin mixture: 3-O-[beta-D-glucopyarnosyl-beta-D-glucopyranosyl]-16-alpha-hydroxyprotobassic acid-28-O-[arabinopyranosyl-glucopyranosyl-xylopyranosyl]-arabinopyranoside (MI-I), and 3-O-beta-D-glucopyranosyl-glucopyranosyl-glucopyranosyl-16-alpha-hydroxyprotobassic acid-28-O-[arabinopyranosyl-xylopyranosyl-arabinopyranosyl]-apiofuranoside (MI-III). The single saponin extracted from S. mukorossi saponin mixture was identified as 3-O-[O-acetyl-beta-D-xylopyranosyl-beta-D-arabinopyranosyl-beta-D-rhamnopyranosyl] hederagenin-28-O[beta-D-glucopyranosyl-beta-D-glucopyranosyl-beta-D-rhamnopyranosyl] ester (SM-I). Monodesmosides resulting from the partial degradation of hederagenin and hydroxyprotobassic acid bisdesmosides exhibited significant reduction in antifungal effect. Further removal of sugar moiety yielded complete loss in activity. The antifungal activity of the triterpenic saponins was associated with their aglycone moieties, and esterification of the hydroxyl group led to change in antifungal activity.

CONCLUSION

Sapindus mukorossi saponin, which is effective against Rhizoctonia bataticola (Taub.) Briton Jones and Sclerotium rolfsii Sacc., can be exploited for the development of a natural fungicide. A sugar moiety is a prerequisite for the antifungal activity of triterpenic saponin.

Identification of defense compounds in Barbarea vulgaris against the herbivore Phyllotreta nemorum by an ecometabolomic approach

Winter cress (Barbarea vulgaris) is resistant to a range of insect species. Some B. vulgaris genotypes are resistant, whereas others are susceptible, to herbivory by flea beetle larvae (Phyllotreta nemorum). Metabolites involved in resistance to herbivory by flea beetles were identified using an ecometabolomic approach. An F2 population representing the whole range from full susceptibility to full resistance to flea beetle larvae was generated by a cross between a susceptible and a resistant B. vulgaris plant. This F2 offspring was evaluated with a bioassay measuring the ability of susceptible flea beetle larvae to survive on each plant. Metabolites that correlated negatively with larvae survival were identified through correlation, cluster, and principal component analyses. Two main clusters of metabolites that correlate negatively with larvae survival were identified. Principal component analysis grouped resistant and susceptible plants as well as correlated metabolites. Known saponins, such as hederagenin cellobioside and oleanolic acid cellobioside, as well as two other saponins correlated significantly with plant resistance. This study shows the potential of metabolomics to identify bioactive compounds involved in plant defense.

Preparative isolation and purification of isobenzofuranone derivatives and saponins from seeds of Nigella glandulifera Freyn by high-speed counter-current chromatography combined with gel filtration

Although the medicinal plant and food Nigella glandulifera Freyn has been researched for decades, isobenzofuranones have never been isolated before. Two isobenzofuranone derivatives and two saponins were successfully separated and purified from seeds of N. glandulifera Freyn by high-speed counter-current chromatography (HSCCC) with the optimized two-phase solvent system, n-hexane-ethyl acetate-methanol-water (7:3:5:5, v/v). Salfredin B(11) (22.1mg, HPLC purity 95.3%), 5, 7-dihydroxy-6-(3-methybut-2-enyl) isobenzofuran-1(3H)-one (18.9mg, HPLC purity 97.3%) and crude sample 2 (555mg) were separated from 600mg of ethyl acetate extract of N. glandulifera Freyn. Following a cleaning-up step by chromatography on Sephadex LH-20, hederagenin (12mg) and 3-O-[beta-d-xylopyranosyl-(1-->3)-alpha-l-rhamnopyranosyl-(1-->2)-alpha-l-arabinopyranosyl]-hederagenin (45mg) were separated from sample 2. All of the fractions before peak II were collected and subjected to a Sephadex LH-20 column and eluted by methanol, two of triterpene saponins (12mg of hederagenin and 45mg of 3-O-[beta-d-xylopyranosyl-(1-->3)-alpha-l-rhamnopyranosyl-(1-->2)-alpha-l-arabinopyranosyl]-hederagenin) were isolated. The structures of peak fractions were identified by IR, electron ionization MS, (1)H NMR and (13)C NMR. 5, 7-Dihydroxy-6-(3-methybut-2-enyl) isobenzofuran-1(3H)-one was isolated for the first time from higher plant and salfredin B11 was isolated for the first time in this plant.

Antifungal activity of the extracts and saponins from Sapindus saponaria L

Extracts from the dried pericarp of Sapindus saponaria L. (Sapindaceae) fruits were investigated for their antifungal activity against clinical isolates of yeasts Candida albicans and C. non-albicans from vaginal secretions of women with Vulvovaginal Candidiasis. Four clinical isolates of C. albicans, a single clinical isolated of each of the species C. parapsilosis, C. glabrata, C. tropicalis, and the strain of C. albicans ATCC 90028 were used. The hydroalcoholic extract was bioactivity-directed against a clinical isolate of C. parapsilosis, and showed strong activity. The n-BuOH extract and one fraction showed strong activity against all isolates tested. Further column-chromatography on silica gel separation of this fraction afforded two pure triterpene acetylated saponins: 3-O-(4-acetyl-beta-D-xylopyranosyl)-(1->3)-alpha-Lrhamnopyranosyl-(1->2)-alpha-L-arabinopyranosyl-hederagenin (1) and 3-O-(3,4-di-acetyl-beta-D-xylopyranosyl)-(1->3)-alpha-L-rhamnopyranosyl-(1->2)-alpha-L-arabynopyranosyl-hederagenin (2). The structures of the compounds were based on spectral data (¹H and 13C NMR, HSQC, HMBC and MS), and on with literature. The saponins isolated showed strong activity against C. parapsilosis.

In Vitro and in Vivo Antifungal Activities of the Eight Steroid Saponins from Tribulus terrestris L. with Potent Activity against Fluconazole-Resistant Fungal

Antifungal activity of natural products is being studied widely. Saponins are known to be antifungal and antibacterial. We have isolated eight steroid saponins from Tribulus terrestris L., namely TTS-8, TTS-9, TTS-10, TTS-11, TTS-12, TTS-13, TTS-14 and TTS-15. TTS-12 and TTS-15 were identified as tigogenin-3-O-beta-D-xylopyranosyl(1-->2)-[beta-D-xylopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-[alpha-L-rhamnopyranosyl(1-->2)]-beta-D-galactopyranoside and tigogenin-3-O-beta-D-glucopyranosyl(1-->2)-[beta-D-xylopyranosyl(1-->3)]-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside, respectively. The in vitro antifungal activities of the eight saponins against six fluconazole-resistant yeasts, Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei, and Cryptococcus neoformans were studied using microbroth dilution assay. The results showed that TTS-12 and TTS-15 were very effective against several pathogenic candidal species and C. neoformans in vitro. It is noteworthy that TTS-12 and TTS-15 were very active against fluconazole-resistant C. albicans (MIC(80)=4.4, 9.4 microg/ml), C. neoformans (MIC(80)=10.7, 18.7 microg/ml) and inherently resistant C. krusei (MIC(80)=8.8, 18.4 microg/ml). So in vivo activity of TTS-12 in a vaginal infection model with fluconazole-resistant C. albicans was studied in particular. Our studies revealed TTS-12 also showed in vivo activities against fluconazole-resistant yeasts. In conclusion, steroid saponins TTS-12 and TTS-15 from Tribulus terrestris L. have significant in vitro antifungal activity against fluconazole-resistant fungi, especially TTS-12 also showed in vivo activity against fluconazole-resistant C. albicans.