Saponins increase susceptibility of vancomycin-resistant enterococci to antibiotic compounds

Herbal Products and Their Active Constituents Used Alone and in Combination with Antibiotics against Multidrug-Resistant Bacteria

The purpose of this review is to summarize the current knowledge acquired on herbal products and their active constituents with antimicrobial activity used alone and in combination with antibiotics against multidrug-resistant bacteria. The most promising herbal products and active constituents used alone against multidrug-resistant bacteria are Piper betle (methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase, Acinetobacter baumannii, Pseudomonas aeruginosa), Glycyrrhiza glabra (methicillin-resistant S. aureus, vancomycin-resistant Enterococcus, P. aeruginosa), and berberine (methicillin-resistant S. aureus, A. baumannii, P. aeruginosa), respectively. The synergistic effect of the combination of herbal products and their active constituents with antibiotics against multidrug-resistant bacteria are also described. These natural antibacterial agents can be promising sources of inhibitors, which can modulate antibiotic activity against multidrug-resistant bacteria, especially as efflux pump inhibitors. Other possible mechanisms of action of herbal therapy against multidrug-resistant bacteria including modification of the bacterial cell wall and/or membrane, inhibition of the cell division protein filamenting temperature sensitive Z-ring, and inhibition of protein synthesis and gene expression, all of which will also be discussed. Our review suggests that combination herbal therapy and antibiotics can be effectively used to expand the spectrum of their antimicrobial action. Therefore, combination therapy against multidrug-resistant bacteria may enable new choices for the treatment of infectious diseases and represents a potential area for future research.

Optimization of Subcritical Fluid Extraction for Total Saponins from Hedera nepalensis Leaves Using Response Surface Methodology and Evaluation of Its Potential Antimicrobial Activity

(1) Background: Hedera nepalensis (Araliaceae) is a recognized medicinal plant founded in Asia that has been reported to work in antioxidant, antifungal, antimicrobial, and antitumor capacities. (2) Methods: The subcritical fluid extraction of saponin from Hedera nepalensis leaves and the optimum of the extraction process based on yield of saponin contents (by calculating the hederacoside C contents in dried Hedera nepalensis leaves) are examined by response surface methodology (RSM). Furthermore, the antimicrobial activity of the extract is tested for potential drug applications in the future. (3) Results: Based upon RSM data, the following parameters are optimal: extraction time of 3 min, extraction temperature of 150 °C, and a sample/solvent ratio of 1:55 g/mL. Under such circumstances, the achieved yield of saponin is 1.879%. Moreover, the extracts inhibit the growth of some bacterial strains (Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenza) at a moderate to strong level with inhibition zone diameter values ranging from 12.63 to 19.50 mm. (4) Conclusions: The development of such a model provides a robust experimental process for optimizing the extraction factors of saponin contents from Hedera nepalensis extract using subcritical fluid extraction and RSM. Moreover, the current work reveals that saponin extracts of Hedera nepalensis leaves exhibit a potential antimicrobial activity, which can be used as scientific evidence for further study.

Antibacterial Activity of Medicinal Plants and Their Constituents in the Context of Skin and Wound Infections, Considering European Legislation and Folk Medicine-A Review

Bacterial infections of skin and wounds may seriously decrease the quality of life and even cause death in some patients. One of the largest concerns in their treatment is the growing antimicrobial resistance of bacterial infectious agents and the spread of resistant strains not only in the hospitals but also in the community. This trend encourages researchers to seek for new effective and safe therapeutical agents. The pharmaceutical industry, focusing mainly on libraries of synthetic compounds as a drug discovery source, is often failing in the battle with bacteria. In contrast, many of the natural compounds, and/or the whole and complex plants extracts, are effective in this field, inactivating the resistant bacterial strains or decreasing their virulence. Natural products act comprehensively; many of them have not only antibacterial, but also anti-inflammatory effects and may support tissue regeneration and wound healing. The European legislative is in the field of natural products medicinal use formed by European Medicines Agency (EMA), based on the scientific work of its Committee on Herbal Medicinal Products (HMPC). HMPC establishes EU monographs covering the therapeutic uses and safe conditions for herbal substances and preparations, mostly based on folk medicine, but including data from scientific research. In this review, the medicinal plants and their active constituents recommended by EMA for skin disorders are discussed in terms of their antibacterial effect. The source of information about these plant products in the review is represented by research articles listed in scientific databases (Science Direct, PubMed, Scopus, Web of Science, etc.) published in recent years.

Aesculus hippocastanum-Derived Extract β-Aescin and In vitro Antibacterial Activity

Objectives:

The objective of this study was to investigate the antibacterial activity of β-aescin against common Gram-negative and Gram-positive bacteria.

Materials and Methods:

Agar well diffusion assay was used to determine the antibacterial activity of β-aescin against common Gram-negative and Gram-positive bacteria including Klebsiella pneumoniae, Escherichia coli, Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of β-aescin were evaluated by serial dilution method.

Results:

β-aescin led to significant antibacterial effects on the tested Gram-negative and Gram-positive bacteria compared to the negative control, P < 0.05 for K. pneumoniae and P. aeruginosa and P < 0.01 for E. coli, S. epidermidis, and S. aureus. On the other hand, β-aescin produced a comparable less antibacterial effect on K. pneumoniae, E. coli, and P. aeruginosa compared to the positive control, P < 0.01, whereas β-aescin illustrated a comparable effect with that of the positive control on Gram-positive S. epidermidis,P = 0.05. Furthermore, β-aescin illustrated a concentration-dependent antibacterial effect against Gram-positive S. epidermidis and S. aureus compared to the different concentrations, P < 0.01. MIC and MBC of β-aescin were high for Gram-negative bacteria and low for Gram-positive bacteria compared to MIC of the positive control.

Conclusions:

β-aescin is an effective antibacterial herb mainly against Gram-positive S. epidermidis and S. aureus in a concentration-dependent manner.

Combined Effect of Nitrofurantoin and Plant Surfactant on Bacteria Phospholipid Membrane

Due to the increasing use of antibiotics, measures are being taken to improve their removal from the natural environment. The support of biodegradation with natural surfactants that increase the bioavailability of impurities for microorganisms that degrade them, raises questions about their effect on bacterial cells. In this paper we present analysis of the interaction of nitrofurantoin (NFT) and saponins from the Saponaria officinalis on the environmental bacteria membrane and the model phospholipid membrane mimicking it. A wide perspective of the process is provided with the Langmuir monolayer technique and membrane permeability test with bacteria. The obtained results showed that above critical micelle concentration (CMC), saponin molecules are incorporated into the POPE monolayer, but the NFT impact was ambiguous. What is more, differences in membrane permeability between the cells exposed to NFT in comparison to that of the non-exposed cells were observed above 1.0 CMC for Achromobacter sp. KW1 or above 0.5 CMC for Pseudomonas sp. MChB. In both cases, NFT presence lowered the membrane permeability. Moreover, the Congo red adhesion to the cell membrane also decreased in the presence of a high concentration of surfactants and NFT. The results suggest that saponins are incorporated into the bacteria membrane, but their sugar hydrophilic part remains outside, which modifies the adsorption properties of the cell surface as well as the membrane permeability.

New perspectives for natural triterpene glycosides as potential adjuvants

BACKGROUND

Triterpene glycosides are a vast group of secondary metabolites widely distributed in plants including a high number of biologically active compounds. The pharmacological potential is evaluated by using many bioassays particularly in the field of cancerology, immunology, and microbiology. The adjuvant concept is well known for these molecules in vaccines, but there is little preclinical evidence to support this concept in the management of cancer, infections and inflammation.

PURPOSE

We aim to review some examples of triterpene glycosides from natural sources which exhibit adjuvant activity when they are co-adminitered with anticancer drugs, targeted toxins, antimicrobial, anti-inflammatory drugs and with antigens in vaccines.

METHODS

The scientific literature on the adjuvant potential of triterpene glycosides covering mainly the last two decades has been identified by using relevant key words in the databases, using the online service such as Medline/PubMed, Scopus, Web of Science, Google Scholar.

RESULTS

We divided these findings in four kind of examples, the combination of triterpene glycosides (1) with chemotherapeutic agents in conventional tumor therapies and with targeted toxins, (2) with antimicrobial drugs, (3) with antiinflammatory drugs, and (4) with an antigen in prophylactic and therapeutic vaccines. Pharmacological studies have revealed that some triterpene glycosides co-administered with anticancer drugs such as cisplatin, paclitaxel, cyclophosphamide, etoposide, 5-fluorouracyl, mitoxantrone exhibited increased cytotoxicity in tumor cells better than when the drugs were administered alone. However in vivo toxicological and pharmacokinetic studies are required before the combination strategy can be applied into clinical practice. Other studies showed that combined application of triterpene glycosides with targeted toxins resulted in the increased efficacy of the toxin, simultaneously reducing the dosage, and side effects. It was also shown that the co-administration of the triterpenoids with corticosteroids synergistically inhibited the inflammatory response induced by carrageenan in rats. The search for new alternative adjuvants in vaccines in comparison with the aluminium salts inducing only a Th2-type immune response resulted in the discovery of the promising purified fraction QS-21 from Quillaja saponaria, which has been used in the development of a variety of prophylactic and therapeutic vaccines. Over 120 clinical trials for around 20 vaccine indications in infectious diseases, cancer, degenerative disorders have been reported involving more than 50,000 patients.

CONCLUSION

This review summarized the successfull in vitro and in vivo studies showing that this combination approach of triterpene glycosides co-adminitered with anticancer, antimicrobial and anti-inflammatory drug may provide an exciting road for further developments in the treatment of some cancers, parasitic and inflammatory diseases and in the rational design of vaccines against infectious diseases and cancer. From a clinical point of view, the potential benefit of QS-21, a promising triterpene glycoside from Quillaja saponaria has been highlighted in several vaccine clinical trials with a favorable ratio efficacy/toxicity.

Shin'iseihaito (Xinyiqingfeitang) Suppresses the Biofilm Formation of Streptococcus pneumoniae In Vitro

Streptococcus pneumoniae (S. pneumoniae) is the important pathogen that causes otolaryngeal diseases such as sinusitis. S. pneumoniae frequently forms the biofilm to prevent severe circumstances such as antimicrobial agents. Shin'iseihaito (xinyiqingfeitang) is a formula of Japanese traditional Kampo medicine that has 9 crude drugs and provides the medicinal usage for sinusitis. The objective of the present study is to reveal the mechanism of antibiofilm activity by Shin'iseihaito extract (SSHT). SSHT significantly inhibited the formation of biofilm from S. pneumoniae ATCC 49619 in dose- and time-dependent manners. SSHT also significantly suppressed the biofilm formation by other five different cps types of S. pneumoniae clinical isolates. We found that the extracts of 8 out of 9 components in Shin'iseihaito had the inhibitory effects of biofilm formation, and the extract of the root of Scutellaria baicalensis had the strongest effect among the ingredients of Shin'iseihaito. We found that the capsule of SSHT-treated S. pneumoniae was significantly thinner than that of the untreated group and that SSHT reduced the hydrophobicity of bacterial cell surface. Our results suggest that Shin'iseihaito may be a useful agent for the treatment of S. pneumoniae-induced sinusitis because of the inhibition of biofilm formation of S. pneumoniae.