In Vitro Antibacterial Activity and Synergistic Antibiotic Effects of Phlorotannins Isolated from Eisenia bicyclis Against Methicillin‐Resistant Staphylococcus aureus

Six phlorotannins, isolated from Eisenia bicyclis, were evaluated for antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MIC) of the compounds were in the range 32 to 64 µg/mL. Phlorofucofuroeckol‐A (PFF) exhibited the highest anti‐MRSA activity, with an MIC of 32 µg/mL. An investigation of the interaction between these compounds and the β‐lactam antibiotics ampicillin, penicillin, and oxacillin revealed synergistic action against MRSA in combination with compound PFF. To our knowledge, this is the first report on the anti‐MRSA activity of phlorotannins from E. bicyclis. The results obtained in this study suggest that the compounds derived from E. bicyclis can be a good source of natural antibacterial agents against MRSA. Copyright © 2012 John Wiley & Sons, Ltd.     

Drug Resistance Reversal Potential of Isoliquiritigenin and Liquiritigenin Isolated from Glycyrrhiza glabra Against Methicillin‐Resistant Staphylococcus aureus (MRSA)

Isoliquiritigenin (ISL) and liquiritigenin (LTG) are structurally related flavonoids found in a variety of plants. Discovery of novel antimicrobial combinations for combating methicillin‐resistant Staphylococcus aureus (MRSA) infections is of vital importance in the post‐antibiotic era. The present study was taken to explore the in vitro and in vivo combination effect of LTG and ISL with β‐lactam antibiotics (penicillin, ampicillin and oxacillin) against mec A‐containing strains of MRSA. Minimum inhibitory concentration (MIC) of both LTG and ISL exhibited significant anti‐MRSA activity (50–100 µg/mL) against clinical isolates of MRSA. The result of in vitro combination study showed that ISL significantly reduced MIC of β‐lactam antibiotics up to 16‐folds [∑ fractional inhibitory concentration (FIC) 0.312–0.5], while LTG reduced up to 8‐folds (∑FIC 0.372–0.5). Time kill kinetics at graded MIC combinations (ISL/LTG + β‐lactam) indicated 3.27–9.79‐fold and 2.59–3.48‐fold reduction in the growth of clinical isolates of S. aureus respectively. In S. aureus‐infected Swiss albino mice model, combination of ISL with oxacillin significantly (p < 0.05, p < 0.01, p < 0.001) lowered the systemic microbial burden in blood, liver, kidney, lung and spleen tissues in comparison with ISL, oxacillin alone as well as untreated control. Considering its synergistic antibacterial effect, we suggest both ISL and LTG as promising compounds for the development of novel antistaphylococcal combinations. Copyright © 2016 John Wiley & Sons, Ltd.     

Bioactive acylphloroglucinols from Hypericum densiflorum

Three acylphloroglucinol derivatives have been isolated from the hexane and acetone extracts of the aerial parts of Hypericum densiflorum Pursch. The compounds were characterized by NMR spectroscopy and mass spectrometry and identified as 4‐geranyloxy‐2,6‐dihydroxybenzophenone (1), 4‐geranyloxy‐1‐(2‐methylpropanoyl)‐ phloroglucinol (2) and 4‐geranyloxy‐1‐(2‐methylbutanoyl)‐phloroglucinol (3). Compounds 1–3 were evaluated for in vitro cell proliferation inhibitory activity against human breast (MCF‐7), lung (NCI H460), CNS (SF‐268), stomach (AGS) and colon (HCT‐116) tumor cell lines; antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA); inhibition of cyclooxygenase (COX‐1 and ‐2) enzymes; and antioxidant activity in the lipid peroxidation (LPO) assay. All three compounds showed moderate to strong antitumor, antibacterial, antioxidant and inhibition of COX‐2 activities. Also, this is the first reported occurrence of compound 3 in the Hypericum genus. Copyright © 2009 John Wiley & Sons, Ltd.     

天然间苯三酚类成分抗菌活性研究进展

抗菌药物的广泛使用甚至滥用使得细菌的耐药性日趋严重,耐药菌感染已成为威胁全球公共健康的重大问题。间苯三酚类成分广泛分布于陆地植物及海洋生物中,该类成分结构新颖、生物活性多样,其中不乏抗菌活性显著的新颖化合物,具有良好的开发前景。具有抗菌活性的天然间苯三酚类成分主要分布在桃金娘科及藤黄科植物中,该类成分对金黄色葡萄球菌及其耐药菌株、枯草芽孢杆菌、肠球菌等革兰阳性菌具有良好的抗菌效果。对近30年来报道的230个间苯三酚类成分的抗菌活性研究进行综述,以期为该类成分进一步研究和开发提供参考。     

Flavonoids from Sophora moorcroftiana and their Synergistic Antibacterial Effects on MRSA

Synergy is now a widely recognized approach that has direct applicability for new pharmaceuticals. The ethanolic extract of the aerial parts of the herb Sophora moorcroftiana showed significant antibacterial activity against drug‐resistant Staphylococcus aureus, and its minimum inhibitory concentration (MIC) was 8 µg/mL. In a phytochemical study of the extract, five flavonoids were obtained. However, the isolates exhibited antibacterial activity in the range of 32–128 µg/mL, which was weaker than the extract. In combination with antibiotics, the antibacterially inactive compound genistein (1) and diosmetin (4) showed significant synergistic activity against drug‐resistant S. aureus. In combination with norfloxacin, genistein (1) reduced the MIC to 16 µg/mL and showed synergy against strain SA1199B with a fractional inhibitory concentration index (FICI) of 0.38. With the antibiotics norfloxacin, streptomycin and ciprofloxacin, diosmetin (4) showed synergy against SA1199B, RN4220 and EMRSA‐15, with FICI values of 0.38, 0.38 and 0.09, respectively. In an efflux experiment to elucidate a plausible mechanism for the observed synergy, genistein showed marginal inhibition of the NorA efflux protein. Copyright © 2013 John Wiley & Sons, Ltd.     

白及不同提取部位抗耐甲氧西林金黄色葡萄球菌的体内外活性

目的:研究白及对“超级细菌”——耐甲氧西林金黄色葡萄球菌(MRSA)的抑菌作用及活性部位.方法:规范提取白及乙酸乙酯部位、正丁醇部位、萃取后水部位、醇提后水煎液部位等4个部位,采用琼脂平板二倍稀释法测定以上4个部位对金黄色葡萄球菌(MSSA)及MRSA共6株病原菌的MIC;用白及乙酸乙酯部位以两种给药方式对小鼠进行预防给药,测定白及对MRSA感染SPF小鼠的保护力.结果:乙酸乙酯部位和正丁醇部位对受试病原菌均具明显抑菌活性,4个部位中尤以乙酸乙醇部位的抑菌活性最强,其MIC为0.065 ～0.26 g·L-1;且白及乙酸乙酯部位对MRSA感染小鼠有很强的保护作用,其中尤以ip0.5 g·kg-1的保护达到100％.结论:白及对MSSA和MRSA有明显的抑菌作用,乙酸乙酯部位是其主要的活性部位.     

黄绵马酸BB对皮肤软组织感染致病菌的抗菌活性及机制研究

目的研究黄绵马酸BB对皮肤软组织感染致病菌的抗菌活性,并探讨其对金黄色葡萄球菌的抗菌机制。方法采用微量稀释法测定黄绵马酸BB对皮肤软组织感染相关致病菌的最低抑菌浓度(minimum inhibitory concentration,MIC)和最低杀菌浓度(minimumbactericidalconcentration,MBC);以对黄绵马酸BB敏感的耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus,MRSA)临床分离株和金黄色葡萄球菌标准株ATCC29213为受试菌,考察黄绵马酸BB对其生长活力和菌体形态结构的影响,采用酶标仪考察黄绵马酸BB对其细胞壁通透性的影响,采用荧光分光光度计考察黄绵马酸BB对细胞膜电位的影响,采用qRT-PCR法考察黄绵马酸BB对青霉素结合蛋白1(penicillin-binding protein1,PBP1)m RNA表达的影响。结果黄绵马酸BB对ATCC29213的MIC为10.0~20.0μg/mL,MBC为10.0~40.0μg/mL,且对MRSA临床分离株的MIC小于头孢唑啉;与对照组比较,黄绵马酸BB组ATCC29213和MRSA生长受到抑制,菌体细胞形态结构改变,细胞膜电位显著降低(P<0.05),1/2MIC黄绵马酸BB可显著下调PBP1 mRNA表达水平(P<0.01),2MIC黄绵马酸BB可显著上调PBP1 mRNA表达水平(P<0.01)。结论黄绵马酸BB对MRSA临床分离株表现出良好的抗菌活性,且其抗菌作用与破坏菌体细胞结构、降低细胞膜电位、影响PBP1 mRNA表达有关。     

Antioxidant/Antibacterial Activities of a Topical Phytopharmaceutical Formulation Containing a Standardized Extract of Baccharis incarum,an Extremophile Plant Species from Argentine Puna

The antimicrobial and antioxidant activities of standardized extracts of Baccharis incarum in 60° and 80° ethanol and of a phytopharmaceutical formulation obtained from them were measured. Baccharis tinctures showed antimicrobial activity against clinically isolated antibiotic resistant Staphylococcus aureus and Enterococcus faecalis, with MIC values of 40–80 µg GAE/mL. Both tinctures exhibited ABTS^●+ scavenging activity with SC₅₀ values between 1.6 and 4.0 µg GAE/mL. The tinctures were not genotoxic in the Salmonella assay. For this reason, the tincture in 60° ethanol was incorporated into a topical pharmaceutical formulation (Hydrogel/ Carbopol® 934). The phytopharmaceutical formulation also showed antibacterial and antioxidant activities in the in vitro assays. The hydrogel showed microbiological, chemical, physical and functional stability during storage at room temperature. Studies that measure drug release as a determination of bioavailability were also carried out using the Franz diffusion cell (FC). The results demonstrated the release of two bioactive compounds (chlorogenic acid and 4′,5‐dihydroxy‐3′,3,6,7,8‐pentamethoxyflavone) from the phytotherapic preparation in HPLC studies of FC receptor solution. In consequence, the phytopreparation applied topically could be used to treat skin and soft tissue infection produced by methicillin‐resistant Staphylococcus aureus (MRSA) or Enterococcus faecalis and opens new opportunities for the use of active natural ingredients in the cosmeceutical field as antiacne and antioxidant. Copyright © 2012 John Wiley & Sons, Ltd.     

Two New Xanthones from Hypericum sampsonii and biological activity of the isolated compounds

Phytochemical investigation of the CH₂Cl₂ extract of the aerial part of Hypericum sampsonii yielded two new prenylated xanthones, hypericumxanthone A and B, together with three known xanthones. Their structures were elucidated by analysis of physical and spectral (UV, IR, mass and NMR) data and comparison of spectroscopic data with those reported previously. All these compounds were evaluated for in vitro antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA). Two new compounds were also tested for their cytotoxicity against human breast (MCF‐7), hepatoma (HepG2), colon (HT‐29) and lung (A549) tumour cell lines. Two new compounds showed moderate antibacterial activities at minimum inhibitory concentrations (MIC) of 16 and 32 µg/mL, respectively, whereas the positive standard antibacterial drug, vancomycin, showed an MIC of 8 µg/mL. The other compounds were inactive against MRSA. In addition, hypericumxanthone B showed weak inhibitory activities against four human tumour cell lines. Copyright © 2010 John Wiley & Sons, Ltd.     

Synergistic effects of baicalein with ciprofloxacin against NorA over-expressed methicillin-resistant Staphylococcus aureus (MRSA) and inhibition of MRSA pyruvate kinase

Ethnopharmacological relevance

Baicalein, the active constituent derived from Scutellaria baicalensis Georgi., has previously been shown to significantly restore the effectiveness of β-lactam antibiotics and tetracycline against methicillin-resistant Staphylococcus aureus (MRSA). With multiple therapeutic benefits, the antibacterial actions of baicalein may also be involved in overcoming other bacterial resistance mechanisms. The aim of the present study was to further investigate antibacterial activities of baicalein in association with various antibiotics against selected Staphylococcus aureus strains with known specific drug resistance mechanisms.

Material and methods

A panel of clinical MRSA strains was used for further confirmation of the antibacterial activities of baicalein. The effect of baicalein on inhibiting the enzymatic activity of a newly discovered MRSA-specific pyruvate kinase (PK), which is essential for Staphylococcus aureus growth and survival was also examined.

Results

In the checkerboard dilution test and time-kill assay, baicalein at 16 μg/ml could synergistically restore the antibacterial actions of ciprofloxacin against the NorA efflux pump overexpressed SA-1199B, but not with the poor NorA substrate, pefloxacin. Moreover, synergistic effects were observed when baicalein was combined with ciprofloxacin against 12 out of 20 clinical ciprofloxacin resistant strains. For MRSA PK studies, baicalein alone could inhibit the enzymatic activity of MRSA PK in a dose-dependent manner.

Conclusion

Our results demonstrated that baicalein could significantly reverse the ciprofloxacin resistance of MRSA possibly by inhibiting the NorA efflux pump in vitro. The inhibition of MRSA PK by baicalein could lead to a deficiency of ATP which might further contribute to the antibacterial actions of baicalein against MRSA.     

Antimicrobial,anti-inflammatory activities and toxicology of phenylethanoid glycosides from Monochasma savatieri Franch. ex Maxim

Ethnopharmacological relevance

Monochasma savatieri Franch. ex Maxim is used for treating many diseases in Traditional Chinese Medicine.

Aim of the study

The present study was designed to evaluate antibacterial, anti-inflammatory activities and toxicity of the total phenylethanoid glycosides from Monochasma savatieri Franch. ex Maxim (TPG).

Materials and methods

The antibacterial activity of TPG was checked by MIC and MBC in vitro; survival of mice with Pseudomonas aeruginosa or Staphylococcus aureus infection-induced sepsis was investigated to evaluate antibacterial activity of TPG in vivo. Additionally, antibacterial activities of TPG were also investigated in a Pseudomonas aeruginosa infection-induced pneumonia in the mice model. Cotton pellet induced granuloma and xylene induced ear swelling in mice models were used to quantify the anti-inflammatory activity.

Results

TPG showed a significant possess bacteriostatic properties against five bacteria strains at a concentration between 0.0625 and 16 mg/ml. Moreover, TPG has bactericidal activity against Pseudomonas aeruginosa, Streptococcus pneumoniae or Escherichia coli. TPG (60, 120, and 180 mg/kg) prolonged survival rate of mice with Pseudomonas aeruginosa or Staphylococcus aureus infection-induced sepsis. In addition, TPG (180 mg/kg) could reduce the bacterial colony-forming units in lung tissue. Furthermore, TPG (60–180 mg/kg) had significantly reduced xylene-induced ear edema and granulomat formation induced by cotton pellet at a dose-dependent manner. In addition, administration of TPG (1.5 g/kg) for 15 days did not result in toxicities in liver, kidney, spleen and thymus tissue in rats.

Conclusion

These results indicated that TPG might be useful for the development of a novel treatment for respiratory infections or pneumonia caused by Pseudomonas aeruginosa or Staphylococcus aureus.     

大黄等5味中药及单体成分对临床多重耐药菌的抑制作用

目的:研究大黄、丁香、蒲公英、姜黄、金银花5味中药及大黄素、芦荟大黄素、丁香酚、咖啡酸、绿原酸和姜黄素对临床多重耐药菌的抑制作用。方法:用微量稀释法测定各药物的最小抑菌浓度(MIC)。记录细菌连续24 h的吸光度A595,绘制生长曲线,用聚丙烯酰胺凝胶电泳(SDS-PAGE)分析细菌可溶性蛋白质。结果:大黄的抑菌效果显著,MIC在6.25~12.50g·L-1;丁香的抑菌谱最广,对所有实验菌株均有抑菌作用,MIC在3.13~25.00 g·L-1,蒲公英、金银花和姜黄在本实验中未见抑菌活性;6种单体药物在实验中对铜绿假单胞菌均没有抑菌效果;大黄素、芦荟大黄素和丁香酚对金黄色葡萄球菌的抑菌效果优于其他临床耐药菌株;大黄素的抑菌效果显著,MIC在1.95~15.63 mg·L-1;芦荟大黄素的抑菌效果稍弱,MIC在2.34~75.00 mg·L-1;丁香酚是唯一对鲍曼不动杆菌有抑菌活性的单体化合物,MIC在5.32~10.64 mg·L-1;姜黄素、咖啡酸、绿原酸在实验中未显示抑菌活性。大黄素作用下,金黄色葡萄球菌的生长及可溶性蛋白表达发生明显改变。结论:大黄和丁香以及大黄素和芦荟大黄素、丁香酚对金黄色葡萄球菌等多种临床多重耐药菌具有显著的抑制效果。大黄素、芦荟大黄素和丁香酚分别是大黄和丁香发挥抑菌作用的主要成分,其具体作用机制有待于深入研究。     

Antibacterial activity of flavonoids and their structure–activity relationship: An update review

Based on World Health Organization reports, resistance of bacteria to well‐known antibiotics is a major global health challenge now and in the future. Different strategies have been proposed to tackle this problem including inhibition of multidrug resistance pumps and biofilm formation in bacteria and development of new antibiotics with novel mechanism of action. Flavonoids are a large class of natural compounds, have been extensively studied for their antibacterial activity, and more than 150 articles have been published on this topic since 2005. Over the past decade, some promising results were obtained with the antibacterial activity of flavonoids. In some cases, flavonoids (especially chalcones) showed up to sixfold stronger antibacterial activities than standard drugs in the market. Some synthetic derivatives of flavonoids also exhibited remarkable antibacterial activities with 20‐ to 80‐fold more potent activity than the standard drug against multidrug‐resistant Gram‐negative and Gram‐positive bacteria (including Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus). This review summarizes the ever changing information on antibacterial activity of flavonoids since 2005, with a special focus on the structure–activity relationship and mechanisms of actions of this broad class of natural compounds.     

Synergistic activity of lawsone methyl ether in combination with some antibiotics and artocarpin against methicillin-resistant Staphylococcus aureus, Candida albicans, and Trychophyton rubrum

Objective: One appealing strategy to overcome and prevent resistant problem is the use of combined two or more antibacterial substances. Lawsone methyl ether(LME) is the naphthoquinone found in the leaves of Impatiens balsamina. The objective of this study is to determine the interaction of LME with some antibiotics(ampicillin, tetracycline, norfloxacin, and clotrimazole) and a natural compound, artocarpin against methicillin-resistant Staphylococcus aureus(MRSA), Candida albicans, and Trychophyton rubrum.Methods: A broth microdilution method was used to determine the minimum inhibition concentration(MIC). Synergistic effects were evaluated at their own MIC using the checkerboard method and time-kill assay.Results: LME showed moderate antibacterial activity against MRSA with MIC value of 15.6 μg/mL, and exhibited strong antifungal activities against T. rubrum and C. albicans with MIC values of 7.8 and 3.9 μg/m L,respectively. The interaction of LME with the natural compound artocarpin against MRSA produced a synergy with fractional inhibitory concentration index(FICI) value of 0.31, while the combination of LME and clotrimazole exhibited synergy against C. albicans and T. rubrum with FICI values of 0.38 and 0.24, respectively. The time-kill assays confirmed that the compounds in combination enhanced their antimicrobial activities against the resistant microorganisms with different degrees.Conclusion: LME in combination with clotrimazole exhibited synergy effect against C. albicans and T.rubrum. In combination with artocarpin, it showed synergy effect against MRSA.     

1‐methyl malate from Berberis integerrima fruits enhances the antibacterial activity of ampicillin against Staphylococcus aureus

The enhancement of the antibacterial activity of ampicillin by different extracts of Berberis integerrima fruits was evaluated against Staphylococcus aureus. Disk diffusion and agar dilution methods were used to determine the antibacterial activity of ampicillin in the absence and presence of different plant extracts or various fractions eluted by column chromatography. A clinical isolate of S. aureus was used as a test strain. The active component of B. integerrima fruits involved in the enhancement of ampicillin activity was purified and identified as 1‐methyl malate using different spectroscopic methods. Both the ethanol extract of B. integerrima fruits and 1‐methyl malate enhanced the antibacterial activity of ampicillin. The total extract as well as 1‐methyl malate increased the antibacterial activity of ampicillin against the test strain. The potency of ampicillin against the test strain was increased 64‐fold when tested with a sub‐toxic concentration of total extract of B. integerrima fruits. Also, 1‐methyl malate increased the bactericidal activity of ampicillin. In the presence of 2 mg/mL of 1‐methyl malate the MIC of ampicillin for S. aureus decreased from 128 to 1 µg/mL (128‐fold). Copyright © 2009 John Wiley & Sons, Ltd.     

Antibacterial activity of flavanone isolated from Sophora exigua against methicillin-resistant Staphylococcus aureus and its combination with antibiotics

5,7,2′,4′-Tetrahydroxy-8-lavandulyl-flavanone, isolated from Sophora exigua, completely inhibited the growth of 21 strains of methicillin-resistant Staphylococcus aureus (MRSA) at concentrations of 3.13–6.25 μg/mL. The anti-MRSA effect was based on bactericidal action. In combinations of the flavanone with vancomycin, minocycline and rifampicin, the fractional inhibitory concentration indices were 0.90, 0.88 and 0.85, respectively, indicating partial synergistic effects with anti-MRSA antibiotics. The proposed flavanone would be a potent phytotherapeutic agent against MRSA infections.     

Quinolone Alkaloids from Fructus Euodiae Show Activity Against Methicillin‐Resistant Staphylococcus aureus

Fructus Euodiae is used in Traditional Chinese Medicine to treat infection. In this study, four of the quinolone alkaloids isolated from Fructus Euodiae showed activity against methicillin‐resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentrations (MIC) were 8–128 µg/mL, which were equivalent to or lower than the control antibiotics, oxacillin, erythromycin and tetracycline (MIC ≥128 µg/mL). Among these isolated quinolone alkaloids, evocarpine with a 13 carbon alkenyl chain substituent at position‐2 showed the best activity against MRSA. This study has demonstrated the potential of quinolone alkaloids from Fructus Euodiae as anti‐MRSA compounds and supports the traditional use of the fruit as a treatment for bacterial infections. Copyright © 2013 John Wiley & Sons, Ltd.     

Antibacterial activity of sophoraflavanone G Isolated from the roots of Sophora flavescens against methicillin‐resistant Staphylococcus aureus

In this study, sophoraflavanone G obtained from Sophora flavescens was evaluated against 10 clinical isolates of methicillin‐resistant Staphylococcus aureus (MRSA), either alone or in combination with ampicillin or oxacillin, via checkerboard assay. At the end point of an optically clear well, the minimum inhibitory concentrations (MICs) ranged from 0.5 to 8 µg/ml for sophoraflavanone G, from 64 to 1024 µg/ml for ampicillin, and from 256 to 1024 µg/ml for oxacillin. The combination of sophoraflavanone G and ampicillin or oxacillin yielded a fractional inhibitory concentration index ranging from 0.188 to 0.375, thereby indicating a principally synergistic effect. The synergistic interaction was verified by time‐kill studies using sophoraflavanone G and/or antibiotics. Thirty minutes of treatment with sophoraflavanone G with ampicillin or oxacillin resulted in an increase in the rate of killing in units of CFU/ml to a greater degree than was observed with Sophoraflavanone G alone. These findings indicated that the application of the tested sophoraflavanone G alone or in combination with antibiotics might prove useful in the control and treatment of MRSA infections. Copyright © 2009 John Wiley & Sons, Ltd.     

黑曲霉菌丝体抗菌活性及石油醚部分化学成分

目的:对黑曲霉Aspergillus niger xj抗菌活性及化学成分进行研究以筛选天然抗菌药物。方法:采用滤纸片扩散法对黑曲霉菌丝体石油醚、醋酸乙酯和水提取物进行抗菌活性测定,并对石油醚部位活性部位进行硅胶柱色谱,甲酯化,通过气相色谱-质谱联用技术(GC-MS)对其化学成分进行分析。结果:菌丝体石油醚部分具有一定抗菌活性,从中鉴定出10个化合物。结论:黑曲霉菌丝体的石油醚部分存在抗菌活性物质,其化学成分以脂肪酸占较大比例。