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Antibacterial activity of six medicinal Cameroonian plants against Gram-positive and Gram-negative multidrug resistant phenotypes



Infectious diseases due to multidrug-resistant bacteria are one of the causes of treatment failures contributing to an increase in mortality and/or morbidity. In this study, we evaluated the antibacterial potential of different parts of six medicinal plants namely Alstonia boonei, Ageratum conyzoides, Croton macrostachys, Cassia obtusifolia, Catharanthus roseus and Paullinia pinnata against a panel of 36 multi-drug resistant (MDR) Gram-negative and Gram-positive bacteria.


Minimum Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) of the methanol extracts from different parts of the plants were determined using broth microdilution method; standard phytochemical methods were used for phytochemical screening.


Several phytochemical classes such as polyphenols, sterols, triterpenes, alkaloids, flavonoids and saponins were identified in the plant extracts. MIC values obtained ranged from 64 to 1024 μg/mL. Leaves extract of Catharanthus roseus (86.11 %), Croton macrostachys (83.33 %) and Paullinia pinnata (80.55 %) displayed the best antibacterial spectra. The lowest MIC value of 64 μg/mL was obtained with the Paullinia pinnata stems extract and Cassia obtusifolia extract against the strain of Staphylococcus aureus MRSA8. Results also showed that the tested samples generally displayed bacteriostatic effects with MBC values obtained in only 3.35 % of the cases where plant extracts were active.


The results obtained at the end of this study demonstrate for the first time the antibacterial activity of the studied medicinal plants against MDR bacteria. The tested plants could be a reservoir of molecules to fight against MDR bacterial infections.

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Infectious diseases caused by multidrug-resistant bacteria are growing steadily and are associated with a significant attributable mortality [1, 2]. The emergence of multi-drug resistant (MDR) phenotypes was first linked to nosocomial infections; but nowadays they are increasingly responsible for community infections and all pathogenic microorganisms are concerned. In Gram-negative bacteria, one of the mechanisms of resistance is the lowering of intracellular amount of antibacterial substances due to the presence of the resistance nodulation cell division (RND)-type efflux pumps. This phenomenon gives possibility to bacteria developing resistance to a wide range of antibiotics, as well as several biocides [3, 4]. Gram-positive bacteria are also a major cause of hospitalization; infections due to Staphylococcus aureus resistant to methicillin (MRSA) are a major health problem both in hospitals and community environments [5]. MRSA is responsible for 80461 severe infections and causing the death of 11,285 patients annually in the United States [6]. One of the possible ways to overcome this phenomenon of multi-resistance is the continual search for new antibacterial molecules active vis-à-vis of MDR bacteria. With regard to the broad diversity of their secondary metabolites, medicinal plants represent undeniable sources of antibacterial agents. According to WHO [7], 80 % of people in Africa have used medicinal plants for their health care; it is also estimated that among medicines sold worldwide, 30 % contain compounds derived from medicinal plants [8]. Several African medicinal plants previously investigated for biological potential showed good antibacterial activities. Some of them include Treculia obovoidea [9], Albizia adianthifolia Laportea ovalifolia [10], Alchornea cordifolia, Pennisetum purpureum [11]. In our continuous search of phytochemicals to combat MDR bacterial infections, we designed the present study to evaluate the antimicrobial potential of six Cameroonian medicinal plants namely Alstonia boonei, Catharanthus roseus, Ageratum conyzoides, Croton macrostachys, Cassia obtusifolia, and Paullinia pinnata vis-à-vis MDR Gram-negative and Gram-positive phenotypes.


Plant materials and extraction

Various parts of plant (Table 1) were collected from different regions in Cameroon during the month of February 2014. These include Alstonia boonei (leaves and bark), Catharanthus roseus (leaves and stem), Ageratum conyzoides (whole plant), Croton macrostachys (leaves), Cassia obtusifolia (whole plant), and Paullinia pinnata (leaves and stem). After drying, each part was powdered and soaked in methanol for 48 h at room temperature, and then filtered using Whatman filter paper N°1. The filtrate obtain were concentrated at 50 °C under reduce pressure in a vacuum to obtain each plant extract.

Table 1 Information on plant used in the present study

Preliminary phytochemical screenings

The presence of alkaloids, triterpenes, sterols, flavonoids, polyphenols and saponins were screened according to the common phytochemical methods described by Harborne [12].


Chloramphenicol and ciprofloxacin (Sigma–Aldrich, St. Quentin Fallavier, France) were used as reference antibiotics meanwhile p-Iodonitrotetrazolium chloride (INT) was used as microbial growth indicator.

Bacterial strains and culture media

The studied microorganisms included ATCC (American Type Culture Collection) and MDR clinical strains of Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, Providencia stuartii, Klebsiella pneumoniae and Enterobacter cloacae) and Gram-positive bacteria (Staphyloccocus aureus). Their bacterial features are summarized in Table 2; they were maintained at 4 °C on McConkey agar and Mannitol Salt Agar (MSA) for Gram negative and Gram positive bacteria respectively, and sub-cultured on Mueller Hinton Agar (MHA) for 24 h before any test. Mueller Hinton Broth (MHB) was used for MIC and MBC determinations.

Table 2 Bacterial strains used in this study and their features

INT colorimetric assay for MIC and MBC determinations

Minimal inhibitory concentrations (MIC) of different plant extracts were determined using broth microdilution method described by Kuete et al. [13] with some modifications [9]. Briefly, plant extracts, chloramphenicol and ciprofloxacin were dissolved in dimethylsufoxide (DMSO)-MHB (10:90) and 100 μL each solution was added to a 96 wells microplate containing MHB, then serially diluted two-fold, followed by adding of 100 μL of inoculum prepared in MHB. The microplate was sealed and incubated for 18 h at 37 °C. The final concentration of inoculum was 1.5 ×106 CFU/mL and less than 2.5 % for DMSO in each well; Wells containing DMSO 2.5 % and inoculums were used as negative control whereas chloramphenicol and ciprofloxacin consist of positive control. After 18 h incubation, 40 μL of INT (0.2 mg/mL) was added to each well and re-incubated for 30 min. MIC was defined as the lowest concentration of plant extract that inhibited bacterial growth.

The determination of MBC was made by introducing 150 μL of MHB in each well of 96 well plate. Then 50 μL of the well contents which did not show any growth after incubation during MIC assays was introduced in the aforesaid plate accordingly, and incubated at 37 °C for 48 h. The MBC was defined as the lowest concentration of plant extract, which did not produce a color change after addition of INT as described previously.


Phytochemical composition

The results of qualitative analysis (Table 3) showed that plant extracts contain various phytochemical classes of secondary metabolites. Polyphenols, triterpenes and saponins were present in all plant extracts except those from Cassia obtusifolia, Catharanthus roseus leaves and stem respectively.

Table 3 Extraction yields and phytochemical composition of the plant extracts

In vitro antibacterial effect of plant extract

The methanol extracts from different parts of plants were tested on 36 bacterial strains including 7 Gram-positive and 29 Gram-negative bacterial strains. As shown in Table 4, extracts from leaves of Alstonia bonnei, Paullinia pinnata and Catharanthus roseus displayed wide spectra of activity in comparison to those from bark and stems of the same plants. The various plant extracts (when they were active) had MIC between 64 and 1024 μg/mL. Leaves of Catharanthus roseus showed the best spectrum of activity, inhibiting the growth of 86.11 % (31/36) of the bacteria (24/29 Gram-negative bacteria and 7/7 Gram-positive bacteria). The leaves extract of Croton macrostachys also had an interesting activity (30/36; 83.33 %), followed by extract of the leaves of P. pinnata (29/36; 80.55 %) and the whole plant extract of A. conyzoides (25/36; 69.44 %). The lowest MIC value of 64 μg/mL was obtained with the Paullinia pinnata stems extract and Cassia obtusifolia extract against the strain of Staphylococcus aureus MRSA8. In general, analysis of results shows that MBCs were obtained in 3.35 % (7/209) of cases where plant extracts were active.

Table 4 MIC and MBC (in bracket) of plant extracts and reference drugs


Several classes of secondary metabolites such as alkaloids, triterpenes, sterols, flavonoids, polyphenols and saponins have been reported to have antibacterial properties [1315]. Their presence in the studied plant extracts could explain the antibacterial effects of the tested samples. The need to find new molecules from medicinal plants with effective mechanisms of action against the multidrug-resistant phenotype is a necessity nowadays. All plants used in traditional medicine which have MIC values less than 8 mg/mL are considered active [16]. A plant extract has significant antibacterial activity if MIC is ˂100 μg/mL, moderate if its MIC is between 100 and 625 μg/mL and low when MIC is above 625 μg/mL [17]. Based on the above criteria, it can be deduced that all tested plants had antibacterial activity as MIC values below 8 mg/mL were obtained with each extract on at least one bacterial strain. MIC values above 625 μg/mL were obtained with extract from A. boonei bark against 2/36 (5.5 %) tested bacteria as well as with C. roseus stem extract against 6/36 (16.7 %) microorganisms tested, indicating that they rather displayed low antibacterial effects. Nonetheless, the activity obtained with the Paullinia pinnata stems extract and Cassia obtusifolia extract against the strain of Staphylococcus aureus MRSA8 (MIC value of 64 μg/mL) could be considered important. Moderate activity was obtained in many cases. In fact, MIC values ranged from 128 to 512 μg/mL were obtained with extract from A. conyzoides (whole plant) against 12/36 (33.3 %) tested bacteria, A. boonei leaves against 19/36 (52.8 %), C. obtusifolia (whole plant) against 17/36 (47.2 %), C. roseus leaves against 18/36 (50 %), C. macrostachys (leaves) against 25/36 (69.4 %), and P. pinnata stem and leaves against 13/36 (36.1 %) and 19/36 (52.8 %) respectively.

Though the antibacterial activities of some of the tested plants have already been reported, their effects against MDR phenotypes are being documented for the first time. The extract from the leaves of C. roseus had a broad antibacterial activity (31/36; 86.11 %); Nayak and Pereira [18] and Kamaraj et al. [19] reported the antibacterial activity of this plant extract on some sensitive bacteria. Several alkaloids were isolated from this plant [20, 21] and these compounds could also be responsible for the antibacterial activity of this plant [22]. MIC values obtained with extract of leaves of C. macrostachys are between 128 and 1024 μg/mL; Antibacterial compounds previously isolated from this plant include the triterpenoid, lupeol [23]. The extract of P. pinnata possessed a good activity (MIC of 64 μg/mL) against S. aureus MRSA8 while the extract from the leaves was active against 80.55 % (29/36) of the studied microorganisms. Lunga et al. [24] demonstrated the activity of this plant on strains of Salmonella sp. with a bacteriostatic effect, corroborating our findings. The extract of C. obtusifolia significantly inhibited the growth of S. aureus MRSA8 with MIC of 64 μg/mL, and was active on 22 of the 36 tested microorganisms. The activity obtained in this study is much better than that mentioned by Doughari et al. [25]. In fact, they obtained MIC of 2000 μg/mL and 1000 μg/mL on clinical isolate of S. aureus and P. aeruginosa respectively. This could be due to the difference of phytochemical composition as the environmental conditions influence the availability as well as the amounts of some secondary metabolites in the plant. One of the best suited secondary metabolite from this plant is emodin (anthraquinone) which possesses a good antibacterial activity against S. aureus [26]; this could explain the interesting activity observed vis-à-vis of MRSA in this study. The extract of A. conyzoides had a relatively low activity on all studied microorganisms. Nevertheless, MIC of 256 μg/mL vis-a-vis E. aerogenes EA-CM64 and EA27, P. stuartii PS2636, S. aureus MRSA 4 which are multi-drug resistant clinical strains were obtained; this could explain the use of this plant in traditional medicine. Leaves and bark extracts of A. bonnei had a moderate activity against Gram-negative bacteria whilst bark extract was not active against Gram-positive species; this is explained by the fact that some antimicrobial compounds have specific activity spectrum (narrow) and therefore will not be active on certain categories or certain species of microorganisms [27]. Though the overall activity of the tested plants can be considered moderate, the results of this study are interesting taking in account the fact that most of the tested bacterial strains were MDR phenotypes.


The present study demonstrates that plants studied and mostly C. macrostachys, C. roseus and P. pinnata contain phytochemicals with valuable antibacterial activities vis-à-vis multi-drug resistant phenotypes. They could be used in the management of bacterial infections including MDR phenotypes.


A. conyzoides :

Ageratum conyzoides

Alstonia boonei :

Alstonia boonei


American type culture collection

C. macrostachys :

Croton macrostachys

C. roseus :

Catharanthus roseus

Cassia obtusifolia :

Cassia obtusifolia


Colony forming unit



E. aerogenes :

Enterobacter aerogenes

E. cloacae :

Enterobacter cloacae

E. coli :

Escherichia coli


p-Iodonitrotetrazolium chloride

K. pneumoniae :

Klebsiella pneumoniae


Minimal bactericidal concentration


Multi-drug resistant


Mueller Hinton Agar


Mueller Hinton Broth


Minimum inhibitory concentration


Methicillin resistant Staphylococcus aureus


Mannitol Salt Agar

P. aeruginosa :

Pseudomonas aeruginosa

P. pinnata :

Paullinia pinnata

P. stuartii :

Providencia stuartii


Resistance nodulation cell division

S. aureus :

Staphyloccocus aureus


  1. Pop-Vicas A, Tacconelli E, Gravenstein S, Lu B, D’Agata EM. Influx of multidrug-resistant, gram-negative bacteria in the hospital setting and the role of elderly patients with bacterial bloodstream infection. Infect Control Hosp Epidemiol. 2009;30(4):325–31.

    Article  PubMed  Google Scholar 

  2. Garnacho-Montero J, Corcia-Palomo Y, Amaya-Villar R, Martin-Villen L. How to treat VAP due to MDR pathogens in ICU patients. BMC Infect Dis. 2014;14:135.

    Article  PubMed  PubMed Central  Google Scholar 

  3. Vargiu VA, Ruggerone P, Opperman JT, Nguyen TS, Nikaido H. Molecular Mechanism of MBX2319 inhibition of Escherichia coli AcrB multidrug efflux pump and comparison with other inhibitors. Antimicrob Agents Chemother. 2014;58(10):6224–34.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Linhares I, Raposo T, Rodrigues A, Almeida A. Incidence and Diversity of Antimicrobial Multidrug Resistance Profiles of Uropathogenic Bacteria. Biomed Res Int. 2015;2015:354084.

  5. Rice BL. Antimicrobial Resistance in Gram-Positive Bacteria. Am J Med. 2006;119:11–9.

    Article  Google Scholar 

  6. CDC. Antibiotic resistance threats in the United States. Atlanta: U.S. Department of Health and Human Services, CDC; 2013.

    Google Scholar 

  7. WHO. Traditional medicine. 2003. Accessed 20 June 2016.

  8. FAO. Trade in medicinal plants. 2004. Accessed 20 June 2016.

  9. Kuete V, Metuno R, Ngameni B, Tsafack AM, Ngandeu F, Fotso GW, et al. Antimicrobial activity of the methanolic extracts and compounds from Treculia obovoidea (Moraceae). J Ethnopharmacol. 2007;112:531–6.

    Article  CAS  PubMed  Google Scholar 

  10. Tchinda FC, Voukeng KI, Penlap BV, Kuete V. Antibacterial activities of the methanol extracts of Albizia adianthifolia, Alchornea laxiflora, Laportea ovalifolia and three other Cameroonian plants against multi-drug resistant Gram-negative bacteria. Saudi J Biol Sci. 2016. doi:10.1016/j.sjbs.2016.01.033.

    Google Scholar 

  11. Mambe TF, Voukeng KI, Penlap BV, Kuete V. Antibacterial activities of methanol extracts from Alchornea cordifolia and four other Cameroonian plants against MDR phenotypes. J Taibah Univ Med Sci. 2016;11(2):121–7.

    Google Scholar 

  12. Harborne JB. Phytochemical Methods. New York: Chapman and Hall; 1973.

    Google Scholar 

  13. Kuete V, Ngameni B, Simo CC, Tankeu RK, Ngadjui BT, Meyer JJ, Lall N, Kuiate JR. Antimicrobial activity of the crude extracts and compounds from Ficus chlamydocarpa and Ficus cordata (Moraceae). J Ethnopharmacol. 2008;120(1):17–24.

    Article  CAS  PubMed  Google Scholar 

  14. Cowan MM. Plant products as antimicrobial agents. Clin Microbiol Rev. 1999;12(4):564–82.

    CAS  PubMed  PubMed Central  Google Scholar 

  15. Mbaveng TA, Sandjo LP, Tankeo SB, Ndifor AR, Pantaleon A, Nagdjui TB, Kuete V. Antibacterial activity of nineteen selected natural products against multi-drug resistant Gram-negative phenotypes. SpringerPlus. 2015;4:823.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Fabry W, Okemo PO, Ansorg R. Antibacterial activity of East African medicinal plants. J Ethnopharmacol. 1998;60:79–84.

    Article  CAS  PubMed  Google Scholar 

  17. Kuete V. Potential of Cameroonian plants and derived-products against microbial infections: A review. Planta Med. 2010;76:1479–91.

    Article  CAS  PubMed  Google Scholar 

  18. Nayak BS, Pereira PLM. Catharanthus roseus flower extract has wound-healing activity in Sprague Dawley rats. BMC Complement Altern Med. 2006;6:41.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Kamaraj C, Rahuman AA, Siva C, Iyappan M, Kirthi VA. Evaluation of antibacterial activity of selected medicinal plant extracts from south India against human pathogens. Asian Pac J Trop Biomed. 2012;2(1):296–301.

    Article  Google Scholar 

  20. Goyal P, Khanna A, Chauhan A, Chauhan G, Kaushik P. In vitro evaluation of crude extracts of Catharanthus roseus for potential antibacterial activity. Int J Green Pharm. 2008;2(3):176–81.

    Article  Google Scholar 

  21. Almagro L, Fernandez-Perez F, Pedreno MA. Indole alkaloids from Catharanthus roseus: bioproduction and their effect on human health. Molecules. 2015;20:2973–3000.

    Article  PubMed  Google Scholar 

  22. Ali AMA, Lafta HA, Jabar HKS. Antibacterial activity of alkaloidal compound isolated from leaves of Catharanthus roseaus (L.) against multi-drug resistant strains. Res Pharm Biotech. 2014;5(2):13–21.

    Google Scholar 

  23. Obey KJ, von Wright A, Orjala J, Kauhanen J, Tikkanen-Kaukanen C. Antimicrobial activity of Croton macrostachyus stem bark extracts against several human pathogenic bacteria. J Pathog. 2016;2016:1453428.

  24. Lunga KP, Tamokou JDD, Fodouop CSP, Kuiate JR, Tchoumboue J, Gatsing D. Antityphoid and radical scavenging properties of the methanol extracts and compounds from the aerial part of Paullinia pinnata. Springerplus. 2014;3:302.

    Article  PubMed  PubMed Central  Google Scholar 

  25. Doughari JH, El-mahmood AM, Tyoyina I. Antimicrobial activity of leaf extracts of Senna obtusifolia (L). Afr J Pharm Pharmacol. 2008;2(1):7–13.

    Google Scholar 

  26. Zhou L, Yun BY, Wang YJ, Xie MJ. Antibacterial mechanism of emodin on Staphylococcus aureus. Chin J Biochem Mol Biol. 2011;27(12):1156–60.

    CAS  Google Scholar 

  27. Yamamoto T, Matsui H, Yamaji K, Takahashi T, Overby A, Nakamura M, Matsumoto A, Nonaka K, Sunazuka T, Omura S, Nakano H. Narrow-spectrum inhibitors targeting an alternative menaquinone biosynthetic pathway of Helicobacter pylori. J Infect Chemother. 2016. doi:10.1016/j.jiac.2016.05.012.

    Google Scholar 

  28. Majekodunmi SO, Adegoke OA, Odeku OA. Formulation of the extract of the stem bark of Alstonia boonei as tablet dosage form. Trop J Pharm Res. 2008;7(2):987–94.

    Article  Google Scholar 

  29. Adotey JPK, Adukpo GE, Boahen YO, Armah FA. A review of the ethnobotany and pharmacological importance of Alstonia boonei De wild (Apocynaceae). ISRN Pharmacol. 2012. doi:10.5402/2012/587160.

    PubMed  PubMed Central  Google Scholar 

  30. Bello IS, Oduola T, Adeosun OG, Omisore NOA, Raheem GO, Ademosun AA. Evaluation of Antimalarial Activity of Various Fractions of Morinda lucida Leaf Extract and Alstonia boonei stem Bark. Global J Pharmacol. 2009;3(3):163–65.

    Google Scholar 

  31. Akinmoladun CA, Ibukun EO, Afor E, Akinrinlola BL, Onibon TR, Akinboboye AO, Obuotor EM, Farombi EO. Chemical constituents and antioxidant activity of Alstonia boonei. Afr J Biotechnol. 2007;6(10):1197–201.

    CAS  Google Scholar 

  32. Olajide OA, Awe OS, Makinde MJ, Ekhelar IA, Olusola A, Morebise O, Okpako TD. Studies on the anti-inflammatory, antipyretic and analgesic properties of Alstonia boonei stem bark. J Ethnopharmacol. 2000;71:179–86.

    Article  CAS  PubMed  Google Scholar 

  33. Ferreres F, Pereira DM, Valentao P, Andrade PB, Seabra RM, Sottomayor M. New phenolic compounds and antioxidant potential of Catharanthus roseus. J Agric Food Chem. 2008;56(21):9967–74.

    Article  PubMed  Google Scholar 

  34. Mustafa RN, Verpoorte R. Phenolic compounds in Catharanthus roseus. Phytochem Rev. 2007;6:243–58.

    Article  CAS  Google Scholar 

  35. Okunade AL. Ageratum conyzoides L. (Asteraceae). Fitoterapia. 2002;73(1):1–16.

    Article  CAS  PubMed  Google Scholar 

  36. Lavergne R. Tisaneurs et Plantes Médicinales Indigènes de La Réunion. Saint Denis de La Réunion: Orphie; 2001.

    Google Scholar 

  37. Jonville MC, Kodja H, Strasberg D, Pichette A, Ollivier E, Frederich M, Angenot L, Legault J. Antiplasmodial, anti-inflammatory and cytotoxic activities of various plant extracts from the Mascarene Archipelago. J Ethnopharmacol. 2011;136:525–31.

    Article  CAS  PubMed  Google Scholar 

  38. Kuete V, Voukeng KI, Tsobou R, Mbaveng TA, Wiench B, Penlap BV, Efferth T. Cytotoxicity of Elaoephorbia drupifera and other Cameroonian medicinal plants against drug sensitive and multidrug resistant cancer cells. BMC Complement Altern Med. 2013;13:250.

    Article  PubMed  PubMed Central  Google Scholar 

  39. Bantie L, Assefa S, Teklehaimanot T, Engidawork E. In vivo antimalarial activity of the crude leaf extract and solvent fractions of Croton Macrostachyus Hocsht. (Euphorbiaceae) against Plasmodium berghei in mice. BMC Complement Altern Med. 2014;14:79.

    Article  PubMed  PubMed Central  Google Scholar 

  40. Salatino A, Salatino FML, Negri G. Traditional uses, Chemistry and Pharmacology of Croton species (Euphorbiaceae). J Braz Chem Soc. 2007;18(1):11–33.

    Article  CAS  Google Scholar 

  41. Kalayou S, Haileselassie M, Gebre-Egziabher G, Tikue T, Sahle S, Taddele H, Ghezu M. In-vitro antimicrobial activity screening of some ethnoveterinary medicinal plants traditionally used against mastitis, wound and gastrointestinal tract complication in Tigray Region, Ethiopia. Asian Pac J Trop Biomed. 2012;2(7):516–22.

    Article  PubMed  PubMed Central  Google Scholar 

  42. Kapingu MC, Guillaume D, Mbwambo HZ, Moshi JM, Uliso CF, Mahunnah RLA. Diterpenoids from the roots of Croton macrostachys. Phytochemistry. 2000;54(8):767–70.

    Article  CAS  PubMed  Google Scholar 

  43. Tala FM, Tan NH, Ndontsa BL, Tane P. Triterpenoids and phenolic compounds from Croton macrostachyus. Biochem Syst Ecol. 2013;51:138–41.

    Article  CAS  Google Scholar 

  44. Dave H, Ledwani L. A review on anthraquinones isolated from Cassia species and their applications. Indian J Nat Prod Resour. 2012;3(3):291–319.

    CAS  Google Scholar 

  45. Yang YC, Lim MY, Lee HS. Emodin isolated from Cassia obtusifolia (Leguminosae) seed shows larvicidal activity against three mosquito species. J Agric Food Chem. 2003;51(26):7629–31.

    Article  CAS  PubMed  Google Scholar 

  46. Yun-Choi HS, Kim JH, Takido M. Potential inhibitors of platelet aggregation from plant sources, v. anthraquinones from seeds of Cassia obtusifolia and related compounds. J Nat Prod. 1990;53(3):630–33.

    Article  CAS  PubMed  Google Scholar 

  47. Ju MS, Kim HG, Choi JG, Ryu JH, Hur J, Kim YJ, Oh MS. Cassiae semen, a seed of Cassia obtusifolia, has neuroprotective effects in Parkinson’s disease models. Food Chem Toxicol. 2010;48(8–9):2037–44.

    Article  CAS  PubMed  Google Scholar 

  48. Miemanang R, Krohn K, Hussain H, Dongo E. Paullinoside A and paullinomide A: a new cerebroside and a new ceramide from leaves of Paullinia pinnata. Z Naturforsch. 2006;61:1123–27.

    Article  CAS  Google Scholar 

  49. Okpekon T, Yolou S, Gleye C, Roblot F, Loiseau P, Bories C, Grellier P, Frappier F, Laurens A, Hocquemiller R. Antiparasitic activities of medicinal plants used in Ivory Coast. J Ethnopharmacol. 2004;90(1):91–7.

    Article  CAS  PubMed  Google Scholar 

  50. Viveiros M, Jesus A, Brito M, Leandro C, Martins M, Ordway D, Molnar AM, Molnar J, Amaral L. Inducement and reversal of tetracycline resistance in Escherichia coli K-12 and expression of proton gradient-dependent multidrug efflux pump genes. Antimicrob Agents Chemother. 2005;49:3578–82.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  51. Kuete V, Ngameni B, Tangmouo JG, Bolla JM, Alibert-Franco S, Ngadjui BT, Pages JM. Efflux pumps are involved in the defense of Gram-negative bacteria against the natural products isobavachalcone and diospyrone. Antimicrob Agents Chemother. 2010;54:1749–52.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  52. Okusu H, Ma D, Nikaido H. AcrAB efflux pump plays a major role in the antibiotic resistance phenotype of Escherichia coli multiple-antibiotic-resistance (Mar) mutants. J Bacteriol. 1996;178:306–8.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  53. Elkins CA, Mullis LB. Substrate competition studies using whole-cell accumulation assays with the major tripartite multidrug efflux pumps of Escherichia coli. Antimicrob Agents Chemother. 2007;51:923–9.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  54. Kuete V, Alibert-Franco S, Eyong KO, Ngameni B, Folefoc GN, Nguemeving JR, Tangmouo JG, Fotso GW, Komguem J, Ouahouo BM, Bolla JM, Chevalier J, Ngadjui BT, Nkengfack AE, Pages JM. Antibacterial activity of some natural products against bacteria expressing a multidrug-resistant phenotype. Int J Antimicrob Agents. 2011;37:156–61.

    Article  CAS  PubMed  Google Scholar 

  55. Baglioni P, Bini L, Liberatori S, Pallini V, Marri L. Proteome analysis of Escherichia coli W3110 expressing an heterologous sigma factor. Proteomics. 2003;3:1060–65.

    Article  CAS  PubMed  Google Scholar 

  56. Sar C, Mwenya B, Santoso B, Takaura K, Morikawa R, Isogai N, Asakura Y, Toride Y, Takahashi J. Effect of Escherichia coli wild type or its derivative with high nitrite reductase activity on in vitro ruminal methanogenesis and nitrate/nitrite reduction. J Anim Sci. 2005;83:644–52.

    Article  CAS  PubMed  Google Scholar 

  57. Ghisalberti D, Masi M, Pages JM, Chevalier J. Chloramphenicol and expression of multidrug efflux pump in Enterobacter aerogenes. Biochem Biophys Res Commun. 2005;328:1113–8.

    Article  CAS  PubMed  Google Scholar 

  58. Mallea M, Chevalier J, Bornet C, Eyraud A, Davin-Regli A, Bollet C, Pages JM. Porin alteration and active efflux: two in vivo drug resistance strategies used by Enterobacter aerogenes. Microbiology. 1998;144:3003–9.

    Article  CAS  PubMed  Google Scholar 

  59. Mallea M, Mahamoud A, Chevalier J, Alibert-Franco S, Brouant P, Barbe J, Pages JM. Alkylaminoquinolines inhibit the bacterial antibiotic efflux pump in multidrug-resistant clinical isolates. Biochem J. 2003;376:801–5.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  60. Pradel E, Pages JM. The AcrAB-TolC efflux pump contributes to multidrug resistance in the nosocomial pathogen Enterobacter aerogenes. Antimicrob Agents Chemother. 2002;46:2640–43.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  61. Voukeng IK, Kuete V. Epices Camerounaises et Bactéries multi-résistantes, Volume 1, Activités Biologiques et Synergie avec les Antibiotiques. Éditions universitaires européennes. 2013.

    Google Scholar 

  62. Chevalier J, Pages JM, Eyraud A, Mallea M. Membrane permeability modifications are involved in antibiotic resistance in Klebsiella pneumoniae. Biochem Biophys Res Commun. 2000;274:496–9.

    Article  CAS  PubMed  Google Scholar 

  63. Tran QT, Mahendran KR, Hajjar E, Ceccarelli M, Davin-Regli A, Winterhalter M, Weingart H, Pages JM. Implication of porins in beta-lactam resistance of Providencia stuartii. J Biol Chem. 2010;285:32273–81.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  64. Lorenzi V, Muselli A, Bernardini AF, Berti L, Pages JM, Amaral L, Bolla JM. Geraniol restores antibiotic activities against multidrug-resistant isolates from gram-negative species. Antimicrob Agents Chemother. 2009;53:2209–11.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  65. Paudel A, Hamamoto H, Kobayashi Y, Yokoshima S, Fukuyama T, Sekimizu K. Identification of novel deoxyribofuranosyl indole antimicrobial agents. J Antibiot. 2012;65:53–7.

    Article  CAS  PubMed  Google Scholar 

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Authors are thankful to the Cameroon National Herbarium (Yaounde) for the plant identification. Authors are also thankful to UMR-MD1 (Mediterranean University, Marseille, France) and Dr Jean P. Dzoyem (University of Dschang) for providing some clinical bacteria.


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Availability of data and materials

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

Authors’ contributions

IKV carried out the study; IKV and VK designed the experiments and wrote the manuscript; VK and VPB supervised the work; VK provided the bacterial strains; all authors read and approved the final manuscript.

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The authors declare that they have no competing interests.

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Correspondence to Victor Kuete.

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Voukeng, I.K., Beng, V.P. & Kuete, V. Antibacterial activity of six medicinal Cameroonian plants against Gram-positive and Gram-negative multidrug resistant phenotypes. BMC Complement Altern Med 16, 388 (2016).

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  • Cameroon
  • Gram-negative bacteria
  • Gram-positive bacteria
  • Medicinal plant
  • Multi-drug resistance
  • Antibacterial activity