Garcinia kola (Heckel) and Alchornea cordifolia (Schumach. & Thonn.) Müll. Arg. from Cameroon possess potential antisalmonellal and antioxidant properties.

Drug resistant Salmonella species and shortcomings related to current drugs stress the urgent need to search for new antimicrobial agents to control salmonellosis. This study investigated the antisalmonellal and antioxidant potentials of methanolic and hydro-ethanolic extracts of Garcinia kola and Alchornea cordifolia as potential sources of drugs to control Salmonella species and to reduce related oxidative stress. The antisalmonellal activity was assessed using the broth microdilution, membrane destabilization and time-kill kinetic assays. While, the DPPH, ABTS and FRAP assays were used for the determination of the antioxidant activities. The minimum inhibitory concentrations ranged from 125 to 1000 μg/mL, with the methanolic root extract of G. kola being the most active. The time kill kinetic assay revealed a concentration-dependent bacteriostatic activity for promising extracts. Potent extracts from G. kola showed the ability to destabilize S. typhi outer membrane, with the methanolic root extract presenting the highest activity; two-fold higher than those of polymyxin B tested as reference. In addition, this methanolic root extract of G. kola also provoked nucleotide leakage in a concentration-dependent manner. From the antioxidant assays, the hydro-ethanolic extract from the stem bark of A. cordifolia presented significant activities comparable to that of Vitamin C. The methanolic root extract of G. kola also presented appreciable antioxidant activities, though less than that of A. cordifolia. Overall, the phytochemical screening of active extracts revealed the presence of anthocyanins, flavonoids, glycosides, phenols, tannins, triterpenoids and steroids. These results provide evidence of the antibacterial potential of G. kola and offer great perspectives in a possible standardisation of an antisalmonellal phytomedicine

Antibacterial Activity of Eight Medicinal Plants from the Traditional Pharmacopoeia of Niger

The emergence of multidrug bacterial resistance poses a great public health problem and requires a constant search for new antibacterial agents. However, Niger’s flora possesses several medicinal plants used in traditional medicine to cure infectious diseases and can be used as sources of bioactive ingredients. This current study was designed to evaluate the antibacterial activity of eight plants used in the traditional pharmacopeia of Niger. The extracts were prepared by maceration using ethanol, methanol, and distilled water. The obtained extracts were screened against Salmonella spp., Shigella spp., and Escherichia coli using the microdilution method coupled with a resazurin-based assay. Phytochemical screening was performed using colorimetry, while the quantification of total polyphenols, total flavonoids, and total tannins was determined by spectrophotometry. Out of the eight plants obtained, five named Cassia italica, Limeum pterocarpum, Phyllanthus pentandrus, Strychnos innocua, and Ximenia americanum exhibited antibacterial activity with MICs ranging from 500 μg/mL to 2000 μg/mL. Phytochemical screening showed the presence of alkaloids, saponosides, tannins, flavonoids, terpenes/sterols, quinones, and polyphenols. The ethanolic and methanolic extracts of X. americana contained important quantities of total polyphenols, with 43.59 ± 0.15 and 41.97 ± 0.02 mg EAG/100 mg of extract, respectively. These extracts showed the highest contents of total tannins at 46.49 g/L and 45.52 g/L, respectively. For total flavonoids, the highest content was obtained with the methanolic extract of P. pentandrus, with 3.12 ± 0.01 mg QE/100 mg of extract. These findings justify the uses of these plants in traditional medicine for the treatment of infectious diseases such as diarrhea and can be used as starting points for the development of phytodrugs against infectious diarrhea

Potentiation effect of mallotojaponin B on chloramphenicol and mode of action of combinations against Methicillin-resistant Staphylococcus aureus.

Staphylococcus aureus, the causative agent of many infectious diseases has developed resistance to many antibiotics, even chloramphenicol which was the essential antibiotic recommended for the treatment of bacterial infection. Thus, other alternatives to fight against S. aureus infections are necessary; and combinatory therapy of antibiotics with natural compounds is one of the approaches. This study evaluated the activity of the combination of mallotojaponin B and chloramphenicol against Methicillin-resistant Staphylococcus aureus (MRSA). Antibacterial activities were evaluated by broth microdilution and the checkerboard methods. Modes of action as time-kill kinetic, Nucleotide leakage, inhibition and eradication of biofilm, and loss of salt tolerance were evaluated. Cytotoxicity was evaluated on Vero and Raw cell lines. Mallotojaponin B showed good activity against MRSA with a MIC value of 12.5 μg/mL. MRSA showed high resistance to chloramphenicol (MIC = 250 μg/mL). The combination produced a synergistic effect with a mean FICI of 0.393. This combination was bactericidal, inducing nucleotide leakage, inhibiting biofilm formation, and eradicating biofilm formed by MRSA. The synergic combination was non-cytotoxic to Vero and Raw cell lines. Thus, the combination of mallotojaponin B and chloramphenicol could be a potential alternative to design a new drug against MRSA infections

New lignan glycosides from Justicia secunda Vahl (Acanthaceae) with antimicrobial and antiparasitic properties

Three new lignan glucosides, namely, justisecundosides A (1), B (2a), and C (2b), were isolated from the whole plant of Justicia secunda together with seven known compounds (3−9). Their structures were established based on a comprehensive analysis of HR-ESI-MS, IR, UV, and CD, in conjunction with their 1D and 2D-NMR data. A putative biogenetic pathway of compounds 1−2a,b from coniferyl alcohol was proposed. In addition, the antimicrobialactivities of the extract, fractions, and some isolated compounds were assessed against multiresistant bacterial and fungal strains. Furthermore, the antiplasmodial, antileishmanial, and antitrypanosomal activities were assessed against the sensitive (3D7) and multidrug-resistant (Dd2) strains of P. falciparum, promastigote and bloodstream forms of L. donovani, and Trypanosoma brucei, respectively. Compound 4 exhibited moderate antibacterial activity against Staphylococcus aureus SA RN 46003 with a MIC value of 62.5 μg/mL. Besides, compound 6 demonstrated a very good activity against sensitive (IC50 Pf3D7: 0.81 μg/mL) and multidrug-resistant (IC50 PfDd2: 14.61 μg/mL) strains of P. falciparum while compound 4 displayed good antitrypanosomal activity (IC50: 1.19 μg/mL). Also, compound 1 was the most active on the promastigote form of L. donovani with an IC50 of 13.02 μg/mL

Effect of the mallotojaponin B and the different combinations on nucleotide leakage MRSA ATCC 33591.

MIC: Minimum Inhibitory Concentration; PC: positive control (TritonX); NC: negative control; Comb: combination; Comb 1: 0.781 μg/mL of mallotojaponin B and 1.95 μg/mL of chloramphenicol; Comb 2: 0.781 μg/mL of mallotojaponin B and 7.812 μg/mL of chloramphenicol; Comb 3: 1.562 μg/mL of mallotojaponin B and 3.9 μg/mL of chloramphenicol.</p

Variation in the number of <i>S</i>. <i>aureus</i> colonies as a function of extract and NaCl concentration.

MIC: Minimum Inhibitory Concentration; PC: positive control; NC: negative control; Comb: Combination; Comb 1: 0.781 μg/ml of mallotojaponin B and 1.95 μg/mL of chloramphenicol; Comb 2: 0.781 μg/mL of mallotojaponin B and 7.812 μg/mL of chloramphenicol; Comb 3: 1.562 μg/mL of mallotojaponin B and 3.9 μg/mL of chloramphenicol; For each salt concentration, histograms carrying the same letters are not significantly different (p˃0.05); while for each test sample, histograms with same Greek alphabets are not significantly different, Waller Duncan test.</p

Growth curves of MRSA following exposure to various concentrations of mallotojaponin B and synergistic combinations.

MIC: Minimum Inhibitory Concentration; PC: positive control (Ciprofloxacin); NC: negative control; Comb: combination; Comb 1: 0.781 μg/mL of mallotojaponin B and 1.95 μg/mL of chloramphenicol; Comb 2: 0.781 μg/mL of mallotojaponin B and 7.812 μg/mL of chloramphenicol; Comb 3: 1.562 μg/mL of mallotojaponin B and 3.9 μg/mL of chloramphenicol.</p

Biofilms eradication percentage of mallotojaponin B at different concentrations and combinations.

PC: Ciprofloxacin; Comb: Combination; Comb 1: 0.781 μg/mL of mallotojaponin B and 1.95 μg/mL of chloramphenicol; Comb 2: 0.781 μg/mL of mallotojaponin B and 7.812 μg/mL of chloramphenicol; Comb 3: 1.562 μg/mL of mallotojaponin B and 3.9 μg/mL of chloramphenicol; MIC: Minimum Inhibitory Concentration; NC: Negative Control. Histograms with the same letters are not significantly different at p ≤0.05.</p

Percentage of inhibition of synergistic combinations and chloramphenicol on Vero and Raw cells.

CPL: chloramphenicol; Comb: combination; Comb 1: 0.781 μg/mL of mallotojaponin B and 1.95 μg/mL of chloramphenicol; Comb 2: 0.781 μg/mL of mallotojaponin B and 7.812 μg/mL of chloramphenicol; Comb 3: 1.562 μg/mL of mallotojaponin B and 3.9 μg/mL of chloramphenicol; Comb 4: 0.781 μg/mL of mallotojaponin B and 15.625 μg/mL of chloramphenicol; Comb 5: 0.781 μg/mL of mallotojaponin B and 31.25 μg/mL of chloramphenicol; Comb 6: 3.125 μg/mL of mallotojaponin B and 3.9 μg/mL of chloramphenicol; PODO: Podophyllotoxin; For the same cell lines, bars with the same letter show that there is no significant difference between the different treatments at p ≤0.05.</p

Fig 7 -

(A and B). Biomass of biofilms produced by MRSA ATCC 33591 in different cultures medium after 24 and 48hrs of incubation. MHB: Muller Hinton Broth; MHB 1%: Muller Hinton Broth with Glucose 1%; MHB 2%: Muller Hinton Broth with Glucose 2%; TSG 1%: Tryptic Soy with Glucose 1%; TSG2%: Tryptic Soy with Glucose 2%; BHI: Brain Heart Infusion; BHI 1%: Brain Heart Infusion with Glucose 1%; BHI 2%: Brain Heart Infusion with Glucose 2%. Histograms with the same letters are not significantly different (p ˃0.05), while those carrying the same Greek alphabet are not significantly different for the same medium.</p