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Antibacterial activities of Beilschmiedia obscura and six other Cameroonian medicinal plants against multi-drug resistant Gram-negative phenotypes
BMC Complementary and Alternative Medicine volume 14, Article number: 241 (2014)
The rapid spread of bacteria expressing multi-drug resistance propels the search for new antibacterial agents. The present study was designed to evaluate the antibacterial activities of the methanol extracts from Beilschmiedia obscura and six other Cameroonian plants against a panel of twenty nine Gram-negative bacteria including Multi-drug resistant (MDR) phenotypes.
The phytochemical investigations of the extracts were carried out according to the standard methods and the liquid micro-dilution assay was used for all antibacterial assays.
Phytochemical analysis showed the presence of alkaloids in all studied extracts. Other chemical classes of secondary metabolites such as anthocyanines, anthraquinones flavonoids, saponins, tannins, sterols and triterpenes were selectively detected in the extracts. The extract from the fruits of Beilschmiedia obscura, Pachypodanthium staudtii leaves and Peperomia fernandopoiana (whole plant) displayed the best spectrum of activity with MIC values ranging from 16 to 1024 μg/mL against at least 65% and above of the tested bacteria. The extract from Beilschmiedia obscura was the most active with MIC values below 100 μg/mL against ten of the tested bacteria. This extract also showed MBC values below 1024 μg/mL against 55.17% of the studied microorganisms. Phenylalanine arginine β-naphthylamide (PAβN) significantly modulated the activities of extracts from the leaves and fruits of Pachypodanthium staudtii and Beilschmiedia obscura respectively, by increasing their inhibitory activity against Klebsiella pneumoniae KP55 strain at least four fold.
The overall results of the present investigation provide information for the possible use of the methanol extracts of the studied plant species, especially B. obscura to fight infectious diseases caused by Gram-negative bacteria including MDR phenotypes.
Bacterial chemo-resistance is a worrisome health concern worldwide today [1–3]. The development of multi-drug resistant (MDR) bacteria has severely compromised the efficacy of antimicrobial weapons and has dramatically increased the frequency of therapeutic failure . Several reports highlighted the increased hospital dissemination of the bacterial strains expressing drug efflux mechanism [5, 6]. Among the known efflux mechanisms of resistances in Gram-negative bacterial strains, Resistance-Nodulation-cell Division (RND) pump is one of the most occurring systems . A number of chemicals such as phenylalanine arginine β-naphthylamide (PAβN), 1-(1-naphthylmethyl)-piperazine, some quinolone derivatives  as well as some natural products like reserpine  have been found to inhibit bacteria efflux pumps. The problem of bacterial resistance to commonly used antibiotics then shifted attention towards the discovery of new natural antibacterial compounds. Plants commonly used as herbal medicine may be a source of antibacterial, antifungal and antiviral activities [10–12]. In Cameroon, there is a rich tradition of using medicinal plants for the treatment of various infectious diseases, inflammations, injuries, and other diseases [13, 14]. The aim of the investigation was to determine the antibacterial effects of twelve methanol crude extracts belonging to seven Cameroonian medicinal plants namely Peperomia fernandopoiana C.DC. (Piperaceae); Cinchona succirubia Par. Ex Klotzsk. (Rubiaceae), Pachypodanthium staudtii Engl & Diels (Annonaceae), Vepris soyauxii Engl. (Rutaceae), Crassocephalum biafrae (Oliv. & Hiern) S. Moore; Beilschmiedia obscura (Staph). Engl. (Lauraceae) and Entada gigas (Linn) Fawcelt & Rendle (Mimosaceae) against a panel of MDR Gram-negative bacteria expressing active efflux pumps. Most of these plant species or their related genus are known for their antimicrobial properties (Table 1). The role of efflux pumps was also investigated using pump-deleted bacteria and the efflux pump inhibitor (EPI) PAβN.
Plant materials and extraction
All medicinal plants used in the work were collected in different areas of Cameroon between January and April 2012. The plants were identified at the National Herbarium (Yaounde, Cameroon), where voucher specimens were deposited under the reference numbers (Table 1). The air-dried and powdered plant material was weighed (300 g) and soaked in 1 L of methanol (MeOH) for 48 h at room temperature. The filtrate obtained through Whatman filter paper No1was concentrated under reduced pressure in a vacuum to obtain the crude extracts. All crude extracts were kept at 4°C until further uses.
Preliminary phytochemical investigations
The plant extracts were screened for the presence of major secondary metabolite classes such as alkaloids, anthocyanins, anthraquinones, flavonoids, phenols, saponins, sterols and triterpenes according to common phytochemical methods previously described by Harbone .
Chloramphenicol (CHL) (Sigma-Aldrich, St Quentin Fallavier, France) was used as reference antibiotic (RA). p-Iodonitrotetrazolium chloride (INT) and phenylalanine arginine β-naphthylamide (PAβN) (Sigma-Aldrich) were used as bacteria growth indicator and efflux pumps inhibitor (EPI) respectively.
Bacterial strains and culture media
MDR isolates (Laboratory collection) and reference strains (from the American Type Culture Collection: Escherichia coli ATCC8739 and ATCC10536; Enterobacter aerogenes ATCC13048; Klebsiella pneumoniae ATCC11296; and Providencia stuartii ATCC29916) of Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, and Providencia stuartii were used. Their features were previously reported [39, 40]. They were maintained at 4°C and sub-cultured on a fresh appropriate Mueller Hinton Agar (MHA) for 24 h before any antibacterial test.
Microdilution assay for MIC and MBC determinations
The microdilution inhibitory concentration (MIC) of the seven plant extracts and chloramphenicol were determined using a rapid microdilution assay [41, 42]. Briefly, the samples were first dissolved in 10% dimethyl sulfoxide (DMSO)/Mueller Hinton Broth (MHB). The solution obtained was then added to MHB and serially diluted two fold (in a 96-well microplate). One hundred microliters of inoculum (1.5 × 106 CFU/mL) prepared in MHB were then added. The plates were covered with a sterile plate sealer and then agitated with a shaker to mix the contents of the wells and incubated at 37°C for 18 h. The final concentration of DMSO was less than 2.5%, and did not affect the microbial growth. Wells containing MHB, 100 μl of inoculum, and DMSO at a final concentration of 2.5% served as the negative control. The MIC of each sample was detected after 18 h of incubation at 37°C following addition of 40 μl INT (0.2 mg/mL) and incubation at 37°C for 30 min. The MIC was defined as the lowest sample concentration that prevented color change of the medium and that resulted in the complete inhibition of bacterial growth . Viable bacteria reduced the yellow dye to a pink. The minimum bactericidal concentration (MBC) of the sample was determined by sub-culturing 50 μl of the suspensions from the wells which did not show any growth after incubation during MIC assays to 150 μl of fresh broth, and re-incubated at 37°C for 48 hours before re-evaluation. The MBC was defined as the lowest concentration of sample which completely inhibited the growth of bacteria [44, 45]. Each assay was performed in three independent tests in triplicate.
The tested samples, the samples were also tested in the presence of PAβN at a final concentration of 20 μg/mL as previously described  against nine of the most resistant bacteria strains. The MIC was determined as described above.
Phytochemical composition of the plant extracts
The results of the qualitative phytochemical analysis indicated that alkaloids were present in all plant extracts. Each of the studied plant extract contained at least two classes of secondary metabolites (Table 2).
Antibacterial activity of the plant extracts
The data depicted in Table 3 show that all extracts were active on at least two bacterial strains with MIC values varying from 16 to 1024 μg/mL. Extracts from P. staudtii leaves and P. fernandopoina (whole plant) displayed the highest spectrum of activity, their inhibitory effects being observed against 72.41% (21/29) of the bacterial strains, followed by those from the fruits of B. obscura (65.52%), stem barks of V. soyauxii, P. staudtii (55.17%), P. staudtii stem bark and V. soyauxii leaves (51.72%). The extract from B. obscura showed the best activity with MIC values below 100 μg/mL recorded against ten of the tested bacteria. The MIC values of this extract were lower than those of choramphenicol against K. pneumoniae Kp55 and E. aerogenes EA27 strains. Other extracts exhibited weak activities against a limited number of strains studied. The Bactericidal activity of the extracts was mostly noted with the extract from B. obscura.
Role of efflux pumps in susceptibility of Gram-negative bacteria to the tested plant extracts
When combined, PAβN modulated significantly the activities (by decreasing the MIC values at least four times) of the extract from P. staudtii leaves and B. obscura on K. pneumoniae Kp55 strain. Therefore, PAβN in general had little or no effects on the increase of the activities of the tested plant extracts. It improved the activity of chloramphenicol on MDR bacteria used (Table 4).
Phytochemical composition of the plant extracts
The selective distribution of the secondary metabolites in the plant extracts may be due to the difference in the plant genus and family or the plant parts used. In fact, the presence of a particular metabolite can be influenced by the metabolisms which take place in the different plant parts. Compounds belonging to alkaloids as well as phenolics and terpenoids are well documented for their antibacterial activities . Their presence in the studied extracts could therefore explain the observed activities.
Antibacterial activity of the plant extracts
Phytochemicals are routinely classified as antimicrobials on the basis of susceptibility tests that produce MIC in the range of 100 to 1000 μg/mL . Moreover, for crude extract, antimicrobial activity is considered to be significant if MIC values are below 100 μg/mL and moderate when 100 < MIC < 625 μg/mL . Therefore, the activity recorded with B. obscura against ten of tested bacteria strains namely E. coli (ATCC10536, AG8739, AG100, W3110), K. pneumoniae ATCC11296, KP63), E. aerogenes ( ATCC13048, EA27 and EA294) and P. stuarti ATCC29916 can be considered important. If we considered the alternative criteria described by Fabry et al. , where extracts having MIC values below 8000 μg/mL have noteworthy antimicrobial activity, the overall activity recorded with most of the studied extracts can be considered important, notably the extracts from P. fernandopoina, B. obscura, V. soyauxii and P. staudtii leaves. When analysing the MIC and MBC results for the crude extract, MBC/MIC ratios lower than 4 were noted with most of the studied samples, suggesting that their killing effects could be expected. Therefore, the extract from B. obscura displayed in many cases, a bacteriostatic effect (MBC/MIC > 4) . To the best of our knowledge, the antibacterial activity of the plant extracts used is being reported herein for the first time, particularly towards MDR bacteria. Nevertheless, the antimicrobial potentials of the related genus for the most active plants have been demonstrated, particularly those of genus Beilschmiedia. Chouna et al.  demonstrated that compounds like beilschmiedic acid C from B. anacardioides were significantly active against Bacillus subtilis, Micrococcus luteus and Streptococcus faecalis. Beilschmiedia cinnamomea was previously demonstrated to have significant to moderate activities (64–1024 μg/mL) against the tested MDR bacteria . Some compounds previously isolated from the genus Beilschmiedia and belonging to alkaloids, phenols, saponines, sterols and triterpenoids [50–52] were reported to possess antimicrobial activities . The genus Beilschmiedia is also known traditionally to possess antimicrobial activities . The fruits of B. obscura used herein are also used as soup ingredient in Cameroun . This highlights its importance in the control of microbial infections and mostly those involving MDR phenotypes. Compounds belonging to alkaloids, flavonoids, sterols and triterpenoids classes previously isolated from P. staudtii [21–25] may be responsible for their observed activities. Bioactive alkaloids like araliopsin were previously isolated from V. soyauxii .
To assess the implication of efflux pumps in the susceptibility of Gram-negative bacteria to the tested plant extracts, PAβN a potent inhibitor of RND efflux systems and particularly active on AcrAB–TolC (of Enterobaceriaceae) and MexAB–OprM (of Pseudomonas species) [8, 55] has been used at a concentration of 20 μg/mL. This concentration had no intrinsic effect on the bacteria as previously determined [46, 56]. A significant increase of the antibacterial activities of the extract from P. staudtii and B. obscura was observed against resistant bacteria K. pneumoniae Kp55 strain, showing that one or more active compounds present in these plant extracts could be substrate(s) of efflux pumps of this bacteria. However, little or no increase of activities observed with the remaining extracts in the presence of EPI may be an indication that either secondary metabolites of these extracts are not active against the studied bacteria or that RND efflux pumps are not the main resistance mechanisms involved. The tested bacteria are good models in investigating MDR as they expressed active efflux pumps as observed when choramphenicol was tested in the presence of PAβN.
The investigation provided informative data for the use of the crude medicinal plant extracts tested, especially those from Beilschmiedia obscura, Peperomia fernandopoiana and Pachypodanthium staudtii in the fight against MDR bacteria. The isolation of active constituents from these plants will further be performed in order to identify their active antibacterial ingredients.
Blot S, Depuydt P, Vandewoude K, De Bacquer D: Measuring the impact of multidrug resistance in nosocomial infection. Curr Opin Infect Dis. 2007, 20: 391-396. 10.1097/QCO.0b013e32818be6f7.
Rice LB: The clinical consequences of antimicrobial resistance. Curr Opin Microbiol. 2006, 12: 476-481.
Gandhi TN, DePestel DD, Collins CD, Nagel J, Washer LL: Managing antimicrobial resistance inintensive care units. Crit Care Med. 2010, 38 (8 Suppl): S315-S323.
Falagas ME, Bliziotis IA: Pan drug-resistant Gram-negative bacteria: the dawn of the post-antibiotic era?. Int J Antimicrob Agents. 2007, 29: 630-636. 10.1016/j.ijantimicag.2006.12.012.
Li XZ, Nikaido H: Efflux-mediated drug resistance in bacteria: an update. Drugs. 2009, 69: 1555-1623. 10.2165/11317030-000000000-00000.
Pagès JM, Alibert-Franco S, Mahamoud A, Bolla JM, Davin-Regli A, Chevalier J, Garnotel E: Efflux pumps of gram-negative bacteria, a new target for new molecules. Curr Top Med Chem. 2010, 8: 1848-1857.
Lomovskaya O, Watkins W: “Inhibition of efflux pumps as a novel approach to combat drug resistance in bacteria”. J Mol Microbiol Biotechnol. 2001, 3 (2): 225-236.
Pagès J-M, Amaral L: Mechanisms of drug efflux and strategies to combat them: challenging the efflux pump of Gram-negative bacteria. Biochim Biophys Acta. 2008, 1794: 826-833.
Stavri M, Piddock L, Gibbons S: Bacterial efflux pump inhibitors from natural sources. J Antimicrob Chemother. 2007, 59: 1247-1260. 10.1093/jac/dkl460.
Cowan MM: Plant products as antimicrobial agents. Clin Microbiol Rev. 1999, 12: 564-582.
Kuete V: Potential of Cameroonian plants and derived-products against microbial infections: A review. Planta Med. 2010, 76: 1479-1491. 10.1055/s-0030-1250027.
Maiyo ZC, Ngure RM, Matasyoh JC, Chepkorir R: Phytochemical constituents and antimicrobial activity of leaf extracts of three Amaranthus plant species. Afr J Biotechnol. 2010, 9: 3178-3182.
Adjanohoun EJ, Aboubakar N, Dramane K, Ebot ME, Ekpere JA, Enow-Orock EG, Focho D, Gbilé ZO, Kamanyi A, Kamsu Kom J, Keita A, Mbenkum T, Mbi CN, Mbiele AL, Mbome IL, Mubiru NK, Nancy WL, Nkongmeneck B, Satabie B, Sofowora A, Tamze V, Wirmum CK: Contribution to ethnobotanical and floristic studies in Cameroon. Scientific Technical and Research Commission/Organization of African Unity, Cameroon. 1996
Noumi E: Treating fibromyoma with herbal medicines in South Cameroon. Indian J Tradit Know. 2010, 9 (4): 736-741.
Momeni J, Ntchatchoua WPDD, Fadimatou F, Akam MT, Ngassoum MB: Antioxidant activities of some cameroonian plants extracts used in the treatment of intestinal and infectious diseases. Indian J Pharm Sci. 2010, 72 (1): 140-144. 10.4103/0250-474X.62236.
Ikpeme EV, Ekaluo UB, Udensi OU, Ekerette EE: Potential effect of some local antimalarial herbs on reproductive functions of male albino rat. Indian J Pharm Sci. 2013, 3 (4): 742-751.
Vaquette J, Hifnawy MS, Pousset JL, Fournet A, Bouquet A, Cavé A: Alcaloides d'Araliopsis soyauxii. Isolement d'un nouvel alcaloide, l'araliopsine. Phytochemistry. 1976, 15: 743-145. 10.1016/S0031-9422(00)94434-0.
Irvine FR: Woody plants of Ghana. 1961, London: Oxford University Press, 6-
Kerharo J, Bouquet A: Plantes médicinales et toxiques de la Côte d’Ivoire Haute Volta. Mission d’étude de la pharmacopée indigène en A.O.F. 1950, Paris: Vogot Frères, 250-
Bouquet A, Debray M: Plantes médicinales de Côte d’Ivoire. Mission d’étude de la pharmacopée indigène en A.O.F. Edited by: Mission O.R.S.T.O.M 32 ème. 1974, Paris: Vogot Frères, 232-
Ngadjui BT, Lontsi D, Ayafor JF, Sondengam BL: Pachypophyllin and pachypostaudins A and B: three bisnorlignans from Pachypodanthium staudtii. Phytochemistry. 1989, 28: 231-234. 10.1016/0031-9422(89)85044-7.
Bévalot F, Leboeuf M, Cavé A: La pachypodanthine, nouvel alcaloide aporphinique du Pachypodanthium staudtii Engl. et Diels, Annonacées. CR Acad Sci Paris. 1976, 282: 865-866.
Bévalot F, Leboeuf M, Cavé A: Le pachysontol, composé aromatique nouveau extrait du Pachypodanthium staudtii Engl. et Diels, Annonacées. CR Acad Sci Paris. 1978, 286: 405-408.
Cavé A, Kunesh N, Leboeuf M, Bévalot F, Chiaroni A, Riche C: Alcaloides des annonacees XXV: la staudine, nouvel alcaloide isoquinoleique du Pachypodanthium staudtii Engl. et Diels. J Nat Prod. 1980, 43: 203-211.
Yapi TA, Boti JB, Félix TZ, Ahibo AC, Tomi F, Bighelli A: Pachypodanthium Staudtii Engl & Diels from Côte d’Ivoire: composition of leaf, stem bark and roots oils. Eur J Sci Res. 2012, 69 (1): 137-142.
Koona P, Koona OES: Testing fractionated extracts gained from the ethnobotanical Pachypodanthium Staudtii (Annonaceae) for bruchid insect control (Coleoptera: Bruchidae). Res J Agric & Biol Sci. 2006, 2 (6): 410-414.
Ngadjui BT, Ayafor JF, Lontsi D: Unusual norlignans and antiviral agents from Pachypodanthium staudtii. Fitoterapia. 1987, 56: 340-341.
Iwu MM: Handbook of Africa medicinal plants. 1993, Ann Arbor Florida USA: C.R.C. Press Boca Raton
Adebayo AG: Inventory of antidiabetic plants in selected districts of Lagos State, Nigeria. J Ethnopharmacol. 2009, 121: 135-139. 10.1016/j.jep.2008.10.013.
Adebooye OC: Solanecio biafrae (Oliv. & Hiern). Edited by: Jeffrey C, Grubben GJH, Denton OA. 2004, Wageningen, Netherlands: PROTA 2: Vegetables/Legumes
Lienou LL, Telefo PB, Bayala BR, Yemele MD, Lemfack MC, Mouokeu C, Goka CS, Tagne SR, Moundipa FP: Ethnopharmacological survey of plants used for the treatment of female infertility in Baham, Cameroon. J Ethnopharmacol. 2010, 136: 178-187.
Focho DA, Nkeng EAP, Lucha CF, Ndam WT, Afegenui A: Ethnobotanical survey of plants used to treat diseases of the reproductive system and preliminary phytochemical screening of some species of malvaceae in Ndop Central Sub-division, Cameroon. J Medic Plant Res. 2009, 3: 301-314.
Tabopda TK, Fotso GW, Ngoupayo J, Mitaine-Offer AC, Ngadjui BT, Lacaille-Dubois MA: Antimicrobial dihydroisocoumarins from Crassocephalum biafrae. Planta Med. 2009, 75 (11): 1258-1261. 10.1055/s-0029-1185545.
Lienou LL, Telefo PB, Bayala BR, Yemele D, Tagne SR, Goka CS, Lemfack MC, Mouokeu C, Moundipa FP: Effect of the aqueous extract of Senecio biafrae (Oliv. & Hiern) J. Moore on sexual maturation of immature female rat. BMC Complement Altern Med. 2012, 12: 36-10.1186/1472-6882-12-36.
Do Céude Madureira M, Martins AP, Gomes M, Paiva J, Proenc A, Cunha D, Do Rosario V: Antimalarial activity of medicinal plants used in traditional medicine in Sao Tome and Principe islands. J Ethnopharmacol. 2002, 81: 23-29. 10.1016/S0378-8741(02)00005-3.
Je H: Drug-resistant malaria. Trends Parasitol. 2005, 21 (11): 494-498. 10.1016/j.pt.2005.08.020.
Lenta BN, Chouna JR, Nkeng-Efouet PA, Fon KS, Tsamo E, Sewald N: Obscurine, a new cyclostachine acid derivative from Beilschmiedia obscura. Nat Prod Commun. 2011, 6 (11): 1591-1592.
Harbone JB: Phytochemical methods: a guide to modern techniques of plant analysis. 1973, London: Chapman & Hall
Fankam A, Kuete V, Voukeng KI, Kuiate J-R, Pages J-M: Antibacterial activities of selected Cameroonian spices and their synergistic effects with antibiotics against multidrug-resistant phenotypes. BMC Complement Altern Med. 2011, 11: 104-10.1186/1472-6882-11-104.
Seukep AJ, Fankam AG, Djeussi DE, Voukeng KI, Tankeo SB, Noumdem KAJ, Nkuete HLA, Kuete V: Antibacterial activities of the methanol extracts of seven Cameroonian dietary plants against bacteria expressing MDR phenotypes. Springer Plus. 2013, 2: 363-10.1186/2193-1801-2-363.
Eloff JN: A sensitive and quick microplate method to determine the minimal inhibitory concentration of plant extracts for bacteria. Planta Med. 1998, 64: 711-713. 10.1055/s-2006-957563.
Mativandlela SPN, Lall N, Meyer JJM: Antibacterial, antifungal and antitubercular activity of Pelargonium reniforme (CURT) and Pelargonium sidoides (DC) (Geraniaceae) root extracts. S Afr J Bot. 2006, 72: 232-237. 10.1016/j.sajb.2005.08.002.
Kuete V, Ngameni B, Simo CCF, Tankeu RK, Ngadjui BT, Meyer JJM, Lall N, Kuiate JR: Antimicrobial activity of the crude extracts and compounds from Ficus chlamydocarpa and Ficus cordata (Moraceae). J Ethnopharmacol. 2008, 120: 17-24. 10.1016/j.jep.2008.07.026.
Cohen MA, Huband MD, Yoder SL, Gage JW, Roland GE: Bacterial eradication by clinafloxacin, CI-990, and ciprofloxacin employing MBC test, in-vitro time-kill and in-vivo time-kill studies. J Antimicrob Chemother. 1998, 41: 605-614. 10.1093/jac/41.6.605.
Zgoda JR, Porter JR: A convenient microdilution method screening natural products against bacteria and fungi. Pharmaceut Biol. 2001, 39: 221-225. 10.1076/phbi.188.8.131.5234.
Ghisalberti D, Masi M, Pagès J-M, Chevalier J: Chloramphenicol and expression of multidrug efflux pump in Enterobacter aerogenes. Biochem Biophys Res Commun. 2005, 328: 1113-1118. 10.1016/j.bbrc.2005.01.069.
Simões M, Bennett RN, Rosa EA: Understanding antimicrobial activities of phytochemicals against multidrug resistant bacteria and biofilms. Nat Prod Rep. 2009, 26: 746-757. 10.1039/b821648g.
Fabry W, Okemo PO, Ansorg R: Antibacterial activity of East African medicinal plants. J Ethnopharmacol. 1998, 60: 79-84. 10.1016/S0378-8741(97)00128-1.
Carbonnelle B, Denis F, Marmonier A, Pinon G, Vague R: Bactériologie médicale: Techniques usuelles. 1987, Paris: SIMEP
Chouna JR, Nkeng-Efouet PA, Lenta BN, Devkota PK, Neumann B, Stammler HG, Kimbu SF, Sewald N: Antibacterial endiandric acid derivatives from Beilschmiedia anacardioides. Phytochemistry. 2009, 70: 684-688. 10.1016/j.phytochem.2009.02.012.
Chen JJ, Chou ET, Duh CY, Yang SZ, Chen IS: New cytotoxic tatrahydrofuran and dihydrofuran-type lignans from the stem of Beilschmiedia tsangii. Planta Med. 2006, 72: 351-357. 10.1055/s-2005-916220.
Chen JJ, Chou ET, Peng CF, Chen IS, Yang SZ, Huang HY: Novel epoxyfuranoid lignans and antitubercular constituents from the leaves of Beilschmiedia tsangii. Planta Med. 2007, 73: 567-571. 10.1055/s-2007-967195.
Nkeng-Efouet PA: Phytochemicals from Beilschmiedia anacardioides and Their Biological Significance, Phytochemicals - A Global Perspective of Their Role in Nutrition and Health. Tech. Edited by: Venketeshwer R. 2012
Dibong SD, Mpondo ME, Ngoye A: Vulnérabilité des espèces à fruits sauvages vendus dans les marchés de Douala (Cameroun). J Anim Plant Sci. 2011, 11 (3): 1435-1441.
Lomovskaya O, Bostian KA: Practical applications and feasibility of efflux pump inhibitors in the clinic–a vision for applied use. Biochem Pharmacol. 2006, 71: 910-918. 10.1016/j.bcp.2005.12.008.
Lorenzi V, Muselli A, Bernardini AF, Berti L, Pagès JM, Amaral L, Bolla JM: Geraniol restores antibiotic activities against multidrug-resistant isolate from Gram-negative species. Antimicrob Agents Chemother. 2009, 53: 2209-2211. 10.1128/AAC.00919-08.
The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1472-6882/14/241/prepub
Authors are thankful to the Cameroon National Herbarium (Yaounde) for plants identification.
The authors declare that they have no competing interests.
AGF carried out the study; VK designed the experiments. AGF and VK wrote the manuscript; VK and JRK supervised the work; VK provided the bacterial strains; all authors read and approved the final manuscript.
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Fankam, A.G., Kuiate, J.R. & Kuete, V. Antibacterial activities of Beilschmiedia obscura and six other Cameroonian medicinal plants against multi-drug resistant Gram-negative phenotypes. BMC Complement Altern Med 14, 241 (2014) doi:10.1186/1472-6882-14-241
- Antibacterial activity
- Beilschmiedia obscura
- Gram-negative bacteria
- Multi-drug resistance
- Efflux pumps
- Medicinal plants