Skip to main content
  • Research Article
  • Open access
  • Published:

Antimicrobial activities of saponins from Melanthera elliptica and their synergistic effects with antibiotics against pathogenic phenotypes

Abstract

Background

Resistance of bacteria and fungi to antibiotics is one of the biggest problems that faces public health. The present work was designated to evaluate the antimicrobial activities of saponins from Melanthera elliptica and their synergistic effects with standard antibiotics against pathogenic phenotypes. The plant extract was prepared by maceration in methanol. The methanol extract was partitioned into ethyl acetate and n-butanol extracts. Column chromatography of the n-butanol extract followed by purification of different fractions led to the isolation of four saponins. Their structures were elucidated on the basis of spectra analysis, and by comparison with those from the literature. The antimicrobial activities of the extracts/compounds alone and their combinations with tetracycline and fluconazole were evaluated using the broth microdilution method through the determination of minimum inhibitory concentration (MIC) and minimum microbicidal concentration.

Results

Four compounds: 3-O-β-d-glucuronopyranosyl-oleanolic acid (1), 3-O-β-d-glucuronopyranosyloleanolic acid 28-O-β-d-glucopyranosyl ester (2), 3-O-β-d-glucopyranosyl(1 → 2)-β-d-glucuronopyranosyl oleanolic acid (3) and 3-O-β-d-glucopyranosyl(1 → 2)-β-d-glucuronopyranosyl oleanolic acid 28-O-β-d-glucopyranosyl ester (4) were isolated. Compounds 1, 2 and 3 showed the largest antibacterial activities (MIC = 8–128 μg/mL) whereas compound 4 displayed the highest antifungal activities (MIC = 8–16 μg/mL). The antibacterial activities of compounds 1 and 2 (MIC = 16–32 μg/mL) against multi-drug-resistant Escherichia coli S2 (1) and Shigella flexneri SDINT are equal to those of vancomycin (MIC = 16–32 μg/mL) used as reference antibiotic.

Conclusions

The present study showed significant antimicrobial activity of compounds 1, 2, 3 and 4 against the tested microorganisms. The saponins act in synergy with the tested standard antibiotics. This synergy could lead to new options for the treatment of infectious diseases and emerging drug resistance.

Introduction

The development and spread of resistance to currently available antibiotics is a global concern [1]. Many investigations have reported multidrug-resistant pathogens, including Escherichia coli, Pseudomonas aeruginosa, Shigella flexneri, Staphylococcus aureus, Candida, Cryptococcus, Aspergillus and Fusarium [2, 3]. With the increase in bacterial and fungal resistance to antibiotics, plant-based antimicrobials have attracted attention in the scientific research. The use of natural antimicrobial compounds is important not only in food preservation, but also in the control of human and plant infectious diseases [4]. The use of natural products with therapeutic properties, whether vegetable, animal, and mineral, for a long time were the main sources of important therapeutic agents as well as important raw materials for the manufacture of traditional and modern medicines [5]. Many bioassay reports have indicated the presence of antimicrobial compounds including saponins from several medicinal plants in Cameroon [6,7,8]. The combination of saponins with antibiotics therapeutic approach may lead to new ways to treat infectious diseases. Therefore, many researchers have studied experimentally the synergistic effect resulting from the association of antibiotics with various plant extracts [9,10,11,12].

Saponins constitute a large group of glycosides having in their breasts a hydrophilic part consisting of monosaccharides and a lipophilic part commonly called genin. They are characterized by their surfactant properties because they dissolve in water forming foaming solutions. They are abundant in many plants and divided into two groups namely steroidal saponins and triterpenoid saponins. Many biological activities of saponins have been reported such as antibacterial, antifungal, antiviral, anti-inflammatory, anti-ulcer, haemolytic and hepatoprotective properties [13,14,15,16,17,18]. In addition, the saponins demonstrated the potential to act synergistically with antibiotics, contributing to the recycling of old antibiotics that were once considered ineffective due to resistance problems [19,20,21,22]. Hence, the synergistic effect of combinations of saponins with standard antibiotics will open a complete new field of possible applications in medicine to overcome resistance in multidrug resistant microorganisms.

Melanthera elliptica O. Hoffm., belonging to Asteraceae family, is a perennial bushy herb to 1.3 m high, commonly found in tropical West and Central Africa [23]. The leaves are used in folk medicine to treat cough, malaria and stomach ache [24]. In Cameroon, the herbalists use the leaf decoction to treat gonorrhea, feverish headache and pulmonary haemorrhage. The aqueous and ethanol whole plant extract of Melanthera scandens showed antibacterial activities against a group of microorganisms that are implicated in either typhoid fever and/or other gastrointestinal disorders such as diarrhea and dysentery [25, 26]. The phytochemical screening of the ethanolic extract of the leaves of M. scandens revealed the presence of cardiac glycosides, tannins, saponins, terpenes and flavonoids [27]. To the best of our knowledge no study has been carried on the phytochemical analysis and antimicrobial properties of M. elliptica. This work was carried out in order to evaluate the antimicrobial activities of saponins from M. elliptica and their synergistic effects with standard antibiotics against pathogenic phenotypes namely E. coli, S. flexneri, S. aureus, Candida albicans, Candida parapsilosis and Cryptococcus neoformans.

Methods

General experimental procedures

The isolation of secondary metabolites was done using column chromatography on Merck silica gel 60 (70–230 mesh) and gel permeation on Sephadex LH-20. TLC was carried out on silica gel GF254 pre-coated plates developed with ternary systems consisting of AcOEt–MeOH–H2O in the proportion (8-1-1 or 8-2-1). Detection was accomplished by spraying with 50% H2SO4 followed by heating at 100 °C, or by visual inspection under UV lamp at 254 and 365 nm. In order to determine the structures of the isolated compounds, the 1D and 2D NMR spectra were made. In fact, 1H and 13C NMR spectra were recorded on a Bruker Avance III 600 spectrometer equipped with a cryoprobe (1H at 600 MHz and 13C at 150 MHz). The 2D NMR experiments were recorded using Bruker microgram firmware (Xwin-NMR software version 2.1 TopSpin 3.2). Chemical shifts (δ) were reported in parts per million (ppm) using the residual solvent signals as a secondary reference to the TMS (δ = 0), while the coupling constants (J values) are given in Hertz (Hz).

Plant material

The aerial parts of M. elliptica were collected at FOTO Village (Menoua Division, Western region of Cameroon) in January 2014. Authentication was done by Mr. Fulbert Tadjouteu, a Botanist of the Cameroon National Herbarium, Yaoundé, where a voucher specimen (N°8002/HNC) was deposited.

Extraction and isolation

The air-dried plant material (4 kg) was powdered and extracted at room temperature with methanol (3 × 20 L, 72 h). The solvent was evaporated under reduced pressure, leaving an extract (220 g). Part of this extract (210 g) was suspended in water (300 mL) and successively extracted with equal volumes (500 mL) of ethyl acetate (EtOAc) and n-BuOH (saturated with water) yielding respectively 65 g and 30 g extracts after evaporation to dryness.

A part of the n-BuOH extract (25 g) was subjected to silica gel column chromatography using EtOAc–MeOH (100:0 → 40:60) gradient elution. Forty-seven fractions of 250 mL each were collected and combined on the basis of their TLC profiles to give five fractions: A (1–7), B (8–12), C (13–15), D (16–47) and E (24–47). Fraction B (3 g) was also purified on silica gel column chromatography eluted with EtOAc to give compound 1 (75 mg). Fraction C (5 g) mainly yielded compounds 2 (30 mg) and 3 (30 mg) after multiple chromatographic steps over silica gel using EtOAc–MeOH–H2O (95:5:2) and (90:5:5) as eluents. Fraction D (6 g) eluted by EtOAc–MeOH (80:20) on column chromatography separation over silica gel yielded three sub-fractions (D1–D3). Compounds 4 (35 mg) was obtained from fraction D2 after multiple chromatography separation over silica gel using EtOAc–MeOH–H2O (80:10:10) and (80:20:10) as eluents.

Antimicrobial assay

Microorganisms

The studied microorganisms were three strains of bacteria (S. aureus ATCC 25923, E. coli S2 (1) and S. flexneri SDINT) and three strains of yeasts (C. parapsilosis ATCC 22019, C. albicans ATCC 9002 and C. neoformans IP95026) taken from our laboratory collection. The bacterial and fungal species were grown at 37 °C and maintained on nutrient agar (NA, Conda, Madrid, Spain) and Sabouraud Dextrose Agar (SDA, Conda) slants respectively.

Determination of minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC)

Minimum inhibitory concentration values were determined by a broth micro-dilution method as described earlier [28] with slight modifications. Each test sample was dissolved in dimethylsulfoxide (DMSO) and the solution was then added to Mueller Hinton Broth (MHB) for bacteria or Sabouraud Dextrose Broth (SDB) for yeasts to give a final concentration of 8192 μg/mL. This was serially diluted twofold to obtain a concentration range of 0.125–4096 μg/mL. Then, 100 μL of each concentration were added in each well (96-well microplate) containing 95 μL of MHB or SDB and 5 μL of inoculum for final concentrations varying from 0.0625 to 2048 μg/mL. The inoculum was standardized at 2.5 × 105 cells/mL for yeasts and 106 CFU/mL for bacteria using a JENWAY 6105 UV/Vis spectrophotometer. The final concentration of DMSO in each well was <  1% [preliminary analyses with 1% (v/v) DMSO did not inhibit the growth of the test organisms]. The negative control well consisted of 195 μL of MHB or SDB and 5 μL of the standard inoculum. The cultured micro plates were covered; then, the contents of each well were mixed thoroughly using a plate shaker (Flow Laboratory, Germany) and incubated at 35 °C for 24 h (bacteria) and 48 h (yeasts) under shaking. The assay was repeated three times. The MIC values of samples were determined by adding 50 μL of a 0.2 mg/mL p-iodonitrotetrazolium violet solution followed by incubation at 35 °C for 30 min. Viable microorganisms reduced the yellow dye to a pink color. MIC values were defined as the lowest sample concentrations that prevented this change in color indicating a complete inhibition of microbial growth. For the determination of MMC values, a portion of liquid (5 μL) from each well that showed no growth of microorganism was plated on Mueller Hinton Agar or SDA and incubated at 35 °C for 24 h (for bacteria) or 35 °C for 48 h (for yeasts). The lowest concentrations that yielded no growth after this subculturing were taken as the MMC values [29]. Vancomycin (Sigma-Aldrich, Steinheim, Germany) and fluconazole (Merck, Darmstadt, Germany) were used as positive controls for bacteria and yeasts, respectively.

Combined effect of antibiotics and isolated compounds

The interaction between combination of reference antibiotics and isolated compounds (1, 3 and 4) was performed by using the broth microdilution method. The antimicrobial activity of the isolated compounds in the presence of reference antibiotics (1/4 × MIC) and that of reference antibiotics in the presence of the isolated compounds (1/4 × MIC) were evaluated as described above. The preliminary tests allowed the selection of MIC/4 as the sub-inhibitory concentrations of the samples. The fractional inhibitory concentration (FIC) index for combinations of two antibacterial agents was calculated according to the following equation: FIC index = FIC A + FIC C; where FIC A = MIC of antibiotic in combination/MIC of antibiotic alone; FIC C = MIC of the isolated compound in combination/MIC of the isolated compound alone. The FIC indices were interpreted as follows: ≤ 0.5, synergy; > 0.5–1, addition; > 1 and ≤ 4, indifference and > 4, antagonism [30]. All the experiments were performed in triplicate.

Results

Chemical analysis

The purification of n-BuOH extract of aerial parts of M. elliptica led to the isolation of four saponins (Fig. 1). Structures of these compounds were assigned on the basis of spectroscopic data (1H and 13C NMR, 1H-1H COSY, HSQC, HMBC, and ROESY) and by the comparison of their spectroscopic data with those reported in the literature. These compounds are: 3-O-β-d-glucuronopyranosyl-oleanolic acid (1) [31], 3-O-β-d-glucuronopyranosyloleanolic acid 28-O-β-d-glucopyranosyl ester (2) [31], 3-O-β-d-glucopyranosyl(1 → 2)-β-d-glucuronopyranosyl oleanolic acid (3) [32] and 3-O-β-d-glucopyranosyl(1 → 2)-β-d-glucuronopyranosyl oleanolic acid 28-O-β-d-glucopyranosyl ester (4) [33].

Fig. 1
figure 1

Chemical structures of saponins (1–4) isolated from n-BuOH extract of areal parts of M. elliptica. 1: 3-O-β-d-glucuronopyranosyl-oleanolic acid; 2: 3-O-β-d-glucuronopyranosyloleanolic acid 28-O-β-d-glucopyranosyl ester; 3: 3-O-β-d-glucopyranosyl(1 → 2)-β-d-glucuronopyranosyl oleanolic acid; 4: 3-O-β-d-glucopyranosyl(1 → 2)-β-d-glucuronopyranosyloleanolic acid 28-O-β-d-glucopyranosyl ester

Antimicrobial activity of the isolated saponins

The antimicrobial activities of MeOH, n-BuOH and EtOAc extracts as well as their isolated compounds were examined by microdilution susceptibility assay against three bacterial and three fungal strains selected on the basis of their relevance as human pathogens. The results showed that the extracts and isolated compounds exhibited variable MICs, depending on the microbial strains (Table 1). The MeOH and n-BuOH extracts were active only against bacterial species whereas the EtOAc extract displayed antimicrobial activity against both bacterial and fungal species. The EtOAc extract was the most active extract followed in decreasing order by n-BuOH and MeOH extracts.

Table 1 Antimicrobial activity (MIC and MMC in µg/mL) of extracts, isolated compounds and reference antimicrobial drugs

The lowest MIC value was recorded on S. aureus with compound 1 and on C. neoformans with compound 4, whereas the lowest MBC value was obtained on S. aureus with compounds 1 and 2 and on C. neoformans with compounds 1 and 4. However, the highest MIC value was recorded on C. parapsilosis and C. albicans with compound 1 and the highest MBC value was obtained on C. parapsilosis, C. albicans and C. neoformans with compound 1. The antibacterial activities of compounds 1 and 2 against E. coli S2 (1) and S. flexneri SDINT are equal to those of vancomycin used as reference antibiotic.

Antimicrobial activity of the combination between antibiotics and saponins

The effect of the interaction between the isolated saponins (1, 3 and 4) and antibiotics (vancomycin and fluconazole) was studied and the results are depicted in Tables 2, 3 and 4. The MIC values of the isolated saponins in combination with antibiotics at the concentration of MIC/4 are smaller than that of the isolated saponins used alone, suggesting an increase in the activity of saponins in combination with antibiotics (Table 2). The MIC values of antibiotics (vancomycin and fluconazole) in combination with the isolated saponins at the concentration of MIC/4 are also smaller than those of vancomycin or fluconazole alone, indicating an increase in the activity of vancomycin or fluconazole in combination with the isolated saponins at the concentration of MIC/4 (Table 3).

Table 2 Antimicrobial activities of the isolated compounds in the presence of reference antibioticsa at 1/4 of MIC as a function of microorganisms
Table 3 Antimicrobial activities of the reference antibiotics in the presence of compounds 1, 3 and 4 at 1/4 of MIC as a function of microorganisms
Table 4 Fractional inhibitory concentrations (FIC) calculated for the combination of reference antibiotics and compounds 1, 3 and 4 as a function of microorganisms

According to the obtained results, the combination of compound 1 with tetracycline showed a synergistic effect against E. coli and S. aureus while an additive effect was observed in S. flexneri (Table 4). The application of fluconazole with compound 1 led to a synergistic effect on C. albicans and C. neoformans and to an additive effect on C. parapsilosis. Combination of compound 3 with tetracycline had a synergistic effect against E. coli and S. shigella, and an additive effect against S. aureus. A synergistic effect was recorded on C. parapsilosis, C. albicans and C. neoformans with the combination of compound 3 and fluconazole. The interaction between compound 4 and tetracycline/fluconazole led to a synergistic effect against the tested bacterial and fungal strains. The combinatory effect of saponins and antibiotics was tested against six pathogenic microorganisms including two multi-drug-resistant (MDR) pathogenic bacteria [E. coli S2 (1) and S. flexneri SDINT]. The MIC of tetracycline changed to the susceptible range (MIC: ≤ 1 mg/mL) when saponins at the concentration of MIC/4 was added. This result provides strong evidence for the therapeutic potential of saponins in combination with defined antibiotic drugs to fight MDR pathogenic bacteria.

Discussion

The findings of the present study indicated that the MeOH, n-BuOH and EtOAc extracts as well as their isolated saponins showed antimicrobial activity against different bacterial and fungal strains, but at different levels. According to the literature, saponins and extracts of Melanthera scandens are known for their antibacterial activities [15, 18, 25, 26]. The results of this study also revealed that all the tested microorganisms were sensitive to EtOAc extract, suggesting that the fractionation enhanced the antimicrobial activity of this extract and diluted that of n-BuOH extract. According to Tamokou et al. [34], a plant extract is considered to be highly active if the MIC < 100 μg/mL; significantly active when 100 ≤ MIC ≤ 512 μg/mL; moderately active when 512 < MIC ≤ 2048 μg/mL; weakly active if MIC > 2048 μg/mL and not active when MIC > 10 mg/mL. Hence, the n-BuOH and MeOH extracts were significantly active (100 ≤ MIC ≤ 512 μg/mL) against the bacterial strains and weakly active (MIC > 2048 μg/mL) against the tested yeasts whereas the EtOAc extract was highly active (MIC < 100 μg/mL) against S. aureus, significantly active on E. coli, S. flexneri and C. neoformans and moderately active (512 < MIC ≤ 2048 μg/mL) vis-à-vis C. parapsilosis and C. albicans. These findings highlight the traditional use of the M. elliptica in the treatment of infectious diseases, especially those caused by the tested microorganisms.

Antimicrobial cut-off points of pure compounds have been defined as follows: highly active: MIC below 1 µg/mL (or 2.5 µM), significantly active: 1 ≤ MIC ≤ 10 µg/mL (or 2.5 ≤ MIC < 25 µM), moderately active: 10 < MIC ≤ 100 µg/mL (or 25 < MIC ≤ 250 µM), weakly active: 100 < MIC ≤ 1000 µg/mL (or 250 < MIC ≤ 2500 µM and not active: MIC > 1000 µg/mL (or > 2500 µM) [34]. Based on this, the antimicrobial activity of compound 1 on S. aureus as well as that of compound 4 on C. neoformans can be considered significant. The strain of E. coli S2 (1) and S. flexneri [12, 35, 36] included in the present study were MDR clinical isolates and these were resistant to commonly used drugs such as tetracycline, streptomycin, ampicillin, nalidixic acid, co-trimoxazole, furazolidone, etc. However, most of the tested saponins displayed moderated antibacterial activities against these bacterial strains, suggesting that their administration may represent an alternative treatment against multidrug resistant E. coli and S. flexneri.

With regard to the structure–activity relationship analysis, the four saponins with the same basic skeleton, showed different degrees of antimicrobial activity. Compounds 1, 2 and 3 with less than 3 sugar moieties showed the largest antibacterial activities with the best MIC value recorded with compound 1 on S. aureus whereas compound 4 with 3 sugar moieties displayed the highest antifungal activities with the best MIC value recorded with this compound on C. neoformans. In general, compound 1 was the most active followed in decreasing order by compound 4, compound 3 and compound 2. These observations show that the sugar moieties should be responsible for the difference in the observed activity.

The Gram-positive bacterium, S. aureus was found to be more sensitive compared to Gram-negative bacteria, E. coli and S. flexneri. The findings of the present study showed that the antimicrobial activities varied with the bacterial and fungal strains. These variations may be due to genetic differences between the microorganisms.

With regard to the MIC and MMC values, a lower MMC/MIC (≤ 4) value signifies that a minimum amount of plant extracts/pure compounds is used to kill the microbial species, whereas, a higher value signifies the use of comparatively more amount of sample for the control of any microorganism [37].

Combined antibiotic therapy has been shown to delay the emergency of microbial resistance and may also produce favorable synergistic effects in the treatment of infectious diseases. Drug synergism between known antibiotics and bioactive plant extracts is one of the novel ways to overcome the resistance mechanisms of microorganisms. Since lipophilic saponins targeting the biomembrane usually accompany polar polyphenols in phytomedical preparations, we decided to investigate their effect as single substances and in combination with standard antibiotics to gain further insight into potential synergistic effects of herbal medicine. In this study, the application of saponins with tetracycline or fluconazole showed synergistic effect on most of the tested microbial strains. This is very promising since the observed synergistic effect could lead to new options for the treatment of infectious diseases and emerging drug resistance. This result corroborates that of Brahim et al. [38] who showed that the combination of saponins extracts and fluconazole exhibited a total synergism against C. albicans, C. parapsilosis, Candida krusei and Candida glabrata. Synergistic activities were also verified when combining saponins with tetracycline, erythromycine and ciprofloxacine against S. aureus XU212, S. aureus RN4220 and S. aureus SA1199B [39]. The saponin of Quillaja saponaria enhanced the sensitivity of the Gram-negative bacteria Proteus mirabilis towards colistin [21]. In a murine wound model induced by S. aureus or E. faecalis infected BALB/c mice, the coapplication of local saponin (HSM-1) and intraperitoneal treatment with vancomycin or daptomycin resulted in a higher reduction of bacteria in infected BALB/c mice as compared to the respective antibiotic treatment alone [22]. These observations reinforce the advantageous antimicrobial effect of phytochemical-antibiotic combinations.

Conclusions

The overall results of the present work provide baseline information for the possible use of M. elliptica extracts and mostly the isolated saponins in the treatment of infectious diseases caused by the tested microorganisms. In addition, the isolated saponins of this plant could be used in association with tetracycline and fluconazole to combat multidrug resistant pathogens subject to further toxicological and pre-clinical studies.

Abbreviations

13C-NMR:

carbon thirteen nuclear magnetic resonance

1H NMR:

proton nuclear magnetic resonance

2D NMR:

two-dimension nuclear magnetic resonance

ATCC:

American Type Culture Collection

CC:

column chromatography

COSY:

correlation spectroscopy

DMSO:

dimethylsulfoxide

EtOAc:

ethyl acetate

HMBC:

heteronuclear multiple bond connectivities

HNC:

Herbier National du Cameroun

HR-EI-MS:

high resolution electron impact mass spectrometry

HR-TOFESIMS:

high-resolution time of flight electrospray ionization mass spectrometry

HSQC:

the heteronuclear single quantum coherence

IR :

infra-red

MBC:

minimum bactericidal concentration

MDR:

multi-drug-resistant

MeOH:

methanol

MHA:

Mueller–Hinton agar

MHB:

Mueller–Hinton broth

MIC:

minimum inhibitory concentration

MMC:

minimum microbicidal concentration

NA:

nutrient agar

n-BuOH:

n-butanol

NMR:

nuclear magnetic resonance

Rf:

retention factor

TLC:

thin layer chromatography

TMS:

tetramethylsilane

TOF-ESIMS:

time of flight electrospray ionization mass spectrometry

UV:

ultra-violet

References

  1. Chanda SK, Rakholiya K (2011) Combination therapy: synergism between natural plant extracts and antibiotics against infectious diseases. In: Mendez-Vilas A (ed) Science against microbial pathogens: communicating current research and technological advances. Formatex Research Center, Badajoz, pp 520–529

    Google Scholar 

  2. Grundmann H, de Kraker M, Davey P (2011) Clinical impact of antimicrobial resistance: design matters. Lancet Infect Dis 11(5):344–345

    Article  Google Scholar 

  3. Lai CC, Wang CY, Chu CC, Tan CK, Lu CL, Lee YC, Huang YT, Lee PI, Hsueh PR (2011) Correlation between antibiotic consumption and resistance of Gram-negative bacteria causing healthcare-associated infections at a University Hospital in Taiwan from 2000 to 2009. J Antimicrob Chemother 66:1374–1382

    Article  CAS  Google Scholar 

  4. Choi HS (2010) Antioxidative activity. In: Sawamura M (ed) Citrus essential oils: flavor and fragrance. Wiley, New Jersey, pp 231–243

    Google Scholar 

  5. Ishrat JB, Laizuman N, Farhana AR, Obaydul H (2011) Antibacterial, cytotoxic an antioxidant activity of chloroform, n-hexane and ethyl acetate extract of plant Amaranthus spinosus. Int J PharmTech Res 3(3):1675–1680

    Google Scholar 

  6. Lunga PK, Tamokou JD, Fodouop SPC, Kuiate JR, Tchoumboue J, Gatsing D (2014) Antityphoid and radical scavenging properties of the methanol extracts and compounds from the aerial part of Paullinia pinnata. Springerplus 3:302

    Article  Google Scholar 

  7. Lunga PK, Qin X-J, Yang XW, Kuiate JR, Du ZZ, Gatsing D (2014) Antimicrobial steroidal saponin and oleanane-type triterpenoid saponins from Paullinia pinnata. BMC Complement Altern Med 14:369

    Article  Google Scholar 

  8. Fankam AG, Kuete V, Voukeng IK, Kuiate JR, Pages JM (2011) Antibacterial activities of selected Cameroonian spices and their synergistic effects with antibiotics against multidrug-resistant phenotypes. BMC Complement Altern Med 11:104

    Article  CAS  Google Scholar 

  9. Fouedjou TR, Teponno RB, Quassinti L, Bramucci M, Petrelli D, Vitali LA, Fiorini D, Tapondjou AL, Barboni L (2014) Steroidal saponins from the leaves of Cordyline fruticosa (L.) A. Chev. and their cytotoxic and antimicrobial activity. Phytochem Lett 7:62–68

    Article  CAS  Google Scholar 

  10. Olajuyigbe OO, Afolayan AJ (2012) Synergistic interactions of methanolic extract of Acacia mearnsii De Wild. with antibiotics against bacteria of clinical relevance. Int J Mol Sci 13:8915–8932

    Article  CAS  Google Scholar 

  11. Stefanovic O, Comic L (2012) Synergistic antibacterial interaction between Melissa officinalis extracts and antibiotics. J Appl Pharm Sci 2:1–5

    Google Scholar 

  12. Tamokou JD, Fosso MJA, Njouendou AJ, Ekom SE, Kengne IC (2017) Antibacterial activity of three Cameroonian medicinal plants traditionally used for the treatment of urinary tract infections and their synergistic effects with amoxicillin and serum. J Adv Med Pharm Sci 15(2):1–14

    Article  Google Scholar 

  13. Zhang S, Hu Z (1985) Anti-ulcerogenic effects of Ginseng flower saponins in the rat Zhongyao Tongbao 10: 331. Chem Abstr 104:512

    Google Scholar 

  14. Okubo K, Kudou S, Uchida T, Yoshiki Y, Yoshikoshi M, Tonomura M (1994) Soyabean saponin and isoflavonoids: structure and antiviral activity against Human Immunodeficiency virus in vitro. In: ACS Symp Ser, pp 546

  15. Sen S, Makkar HPS, Muetzel S, Becker K (1998) Effect of Quillaja saponaria saponins and Yucca schidigera plant extract on growth of Escherichia coli. Lett Appl Microbiol 27:35–38

    Article  CAS  Google Scholar 

  16. Chao AC, Nguyen JV, Broughall M, Recchia J, Kensil CR, Daddona PE, Fix JA (1998) Enhancement of intestinal model compound transport by DS-1, a modified Quillaia saponin. J Pharm Sci 87(11):1395–1399

    Article  CAS  Google Scholar 

  17. Just MJ, Recsio MG, Gner RM, Cuellar MJ, Marez S, Bilia AR, Rios J (1998) Anti-inflammatory activity of unusual lupane saponins from Buleurum fruiticescens. Planta Med 64(5):404–407

    Article  CAS  Google Scholar 

  18. Woldemichael GM, Wink M (2001) Identification and biological activities of triterpenoid saponins from Chenopodium quinoa. J Agric Food Chem 49(5):2327–2332

    Article  CAS  Google Scholar 

  19. Kim HS, Han SS, Oh KW, Jeong TS, Nam KY (1987) Effect of ginseng saponin on the antimicrobial activities of some antibiotics. Korean J Mycol 15(2):87–91

    CAS  Google Scholar 

  20. Sung WS, Lee DG (2008) The combination effect of Korean red ginseng saponins with kanamycin and cefotaxime against methicillin-resistant Staphylococcus aureus. Biol Pharm Bull 31(8):1614–1617

    Article  CAS  Google Scholar 

  21. Arabski M, Wasik S, Dworecki K, Kaca W (2009) Laser interferometric and cultivation methods for measurement of colistin/ampicilin and saponin interactions with smooth and rough of Proteus mirabilis lipopolysaccharides and cells. J Microbiol Methods 77(2):178–183

    Article  CAS  Google Scholar 

  22. Cirioni O, Myszka H, Dawgul M, Ghiselli R, Orlando F, Silvestri C, Brescini L, Kamysz W, Guerrieri M, Giacometti A (2011) In vitro activity and in vivo efficacy of the saponin diosgenyl 2-amino-2-deoxy-β-d-glucopyranoside hydrochloride (HSM1) alone and in combination with daptomycin and vancomycin against Gram-positive cocci. J Med Microbiol 60(9):1337–1343

    Article  CAS  Google Scholar 

  23. Burkill HM (1985) The useful plants of west tropical Africa. vol 1, 2nd ed. Royal Botanic Gardens, Kew, UK, p 960

    Google Scholar 

  24. Yapi AB, Kassi NJ, Fofie NBY, Zirihi GN (2015) Etude ethnobotanique des Asteraceae médicinales vendues sur les marches du district autonome d’Abidjan (Côte d’Ivoire). Int J Biol Chem Sci 9(6):2633–2647

    Article  Google Scholar 

  25. Bolou GEK, Bagré I, Ouattara K, Djaman AJ (2011) Evaluation of the antibacterial activity of 14 medicinal plants in Côte d’Ivoire. Trop J Pharm Res 10(3):335–340

    Article  Google Scholar 

  26. Kokora PA, Ackah JAAB, Nanga ZY, Kra MAK, Loukou GY, Coulibaly A, Djaman J (2013) Antibacterial activity of ethanolic and aqueous extracts of four medicinal plants on the in vitro growth of Escherichia coli and Staphylococcus aureus. J Drug Deliv Ther 3(3):113–116

    Google Scholar 

  27. Okokon JE, Udoh AE, Frank SG, Amazu LU (2012) Anti-inflammatory and analgesic activities of Melanthera scandens. Asian Pac J Trop Biomed 2(2):144–148

    Article  Google Scholar 

  28. Nyaa TBL, Tapondjou AL, Barboni L, Tamokou JD, Kuiate JR, Tane P, Park H (2009) NMR assignment and antimicrobial/antioxidant activities of 1-hydroxyeuscaphic acid from the seeds of Butyrospermum parkii. Nat Prod Sci 15:76–82

    CAS  Google Scholar 

  29. Tamokou JD, Kuiate JR, Tene M, Kenla Nwemeguela TJ, Tane P (2011) The antimicrobial activities of extract and compounds isolated from Brillantaisia lamium. Iran J Med Sci 36:24–31

    PubMed Central  Google Scholar 

  30. Bone RC (1994) Gram-positive organisms and sepsis. Arch Intern Med 154(1):26–34

    Article  CAS  Google Scholar 

  31. Vidal-Ollivier E, Balansard G, Faure R, Babadjamian A (1989) Revised structures of triterpenoid saponins from the flowers of Calendula officinalis. J Nat Prod 52:1156–1159

    Article  CAS  Google Scholar 

  32. Paphassarang S, Raynaud J, Lussignol M (1989) Triterpenoid saponins from Polysczas scutellarza. J Nat Prod 52:239–242

    Article  CAS  Google Scholar 

  33. Tan N, Zhou J, Zhao S (1999) Advances in structural elucidation of glucuronide oleanane-type triterpene carboxylic acid 3, 28-O-bisdesmosides (1962–1997). Phytochemistry 52(2):153–192

    Article  CAS  Google Scholar 

  34. Tamokou JD, Mbaveng TA, Kuete V (2017) Antimicrobial activities of African medicinal spices and vegetables. In: Kuete V (ed) Medicinal spices and vegetables from Africa: therapeutic potential against metabolic, inflammatory, infectious and systemic diseases. 1st edn, Chap 8. Academic Press, Cambridge, Elsevier, pp 207–237

    Chapter  Google Scholar 

  35. Acharyya S, Sarkar P, Saha DR, Patra A, Ramamurthy T, Bag PK (2015) Intracellular and membrane damaging activities of methyl gallate isolated from Terminalia chebula against multi-drug resistant Shigella species. J Med Microbiol 64(8):901–909

    Article  CAS  Google Scholar 

  36. Jouda JB, Tamokou JD, Djama Mbazoa C, Douala-Meli C, Sarkar P, Bag PK, Wandji J (2016) Antibacterial and cytotoxic cytochalasins from the endophytic fungus Phomopsis sp. harbored in Garcinia kola (Heckel) nut. BMC Complement Altern Med 16:462

    Article  Google Scholar 

  37. Djouossi MG, Tamokou JD, Ngnokam D, Kuiate JR, Tapondjou AL, Harakat D, Nazabadioko LV (2015) Antimicrobial and antioxidant flavonoids from the leaves of Oncoba spinosa Forssk. (Salicaceae). BMC Complement Altern Med 15:134

    Article  Google Scholar 

  38. Brahim MAS, Fadli M, Markouk M, Hassani L, Larhsini M (2015) Synergistic antimicrobial and antioxidant activity of saponins-rich extracts from Paronychia argentea. Eur J Med Plants 7(4):193–204

    Article  Google Scholar 

  39. Monte J, Abreu AC, Borges A, Simões LC, Simões M (2014) Antimicrobial activity of selected phytochemicals against Escherichia coli and Staphylococcus aureus and their biofilms. Pathogens 3:473–498

    Article  CAS  Google Scholar 

Download references

Authors’ contributions

CNT and ICK contributed to the data collection and analysis. JDT designated the study, did the biological assays and helped in manuscript writing and editing. JDT, DN and LVN supervised and revised the manuscript critically for important intellectual content. All authors read and approved the final manuscript.

Acknowledgements

The study was supported in part by the University of Dschang and the Cameroonian Ministry of Higher Education.

Competing interests

The authors declare that they have no competing interests.

Availability of data and materials

The datasets supporting the conclusions of this article are presented in this paper. Plant materials used in this study have been identified at the Cameroon National Herbarium where voucher specimens are deposited.

Consent to participate

Not applicable.

Ethics approval and consent to participate

Not applicable.

Funding

No funding.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Author information

Authors and Affiliations

Authors

Corresponding authors

Correspondence to Jean-de-Dieu Tamokou or David Ngnokam.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Tagousop, C.N., Tamokou, JdD., Kengne, I.C. et al. Antimicrobial activities of saponins from Melanthera elliptica and their synergistic effects with antibiotics against pathogenic phenotypes. Chemistry Central Journal 12, 97 (2018). https://doi.org/10.1186/s13065-018-0466-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s13065-018-0466-6

Keywords