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An unprecedented saponin is being reported herein together with five known compounds from the methanol extract of the roots of Albizia adianthifolia . The metabolites were obtained over repeated open column chromatography methods and spectroscopic followed by spectrometric techniques. The isolated compounds were tested against eleven Gram-negative bacteria including multidrug resistant strains. The results revealed considerable inhibition of the new saponin against the studied bacteria with MIC values ranging from 16 to 128 μg/mL.

Background: Albizia adianthifolia (Schum.) is medicinally used in Cameroon to manage bronchitis and skin diseases. Our previous study documented the antibacterial potential of its roots' methanol extract. In this study, methanol roots extract was subjected to chromatography techniques and fractions (AARa and AARb), sub-fractions (AARa1-4, AARb1-2 and AARb11-14) together with isolated phytochemicals were assessed for their antimicrobial as well as their antibiotic-potentiating effects towards Gram-negative multidrug resistant (MDR) bacteria., Methods: The antibacterial activities of the samples (determination of Minimal Inhibitory « MIC » and Minimal Bactericidal Concentration « MBC ») were determined by the modified rapid p-iodonitrotetrazolium chloride (INT) colorimetric assay, as well as those of antibiotics in association with the compounds. Column chromatography was applied to isolate phytochemicals from roots extract and their chemical structures were determined using spectroscopic techniques., Results: The phytochemicals isolated were stearic acid (1), a mixture (1:1) of stigmasterol and β-sitosterol (2 +  3), β-sitosterol 3-O-β- D -glucopyranoside (4), palmatin (5), homomangiferin (6) and mangiferin (7). Fraction AARa exhibited selective inhibitory effects whilst all tested bacteria were inhibited by AARb in MIC ranges of 8 to 1024 μg/mL. Sub-fractions AARb1-2 had MIC values between 8 μg/mL and 1024 μg/mL on all tested bacteria. Phytochemicals 4, 2 +  3 and 7 inhibited the growth of 54.54% (6/11), 45.45% (5/11) and 27.27% (3/11) tested bacterial strains, respectively. When tested with an efflux pumps inhibitor (Phenylalanine-Arginine-β-Naphthylamide or PAβN), the inhibitory effects of compounds 2 + 3 and 4 increased towards all the tested bacteria. In association with erythromycin (ERY), streptomycin (STR) and tetracycline (TET), compounds 2 + 3 and 4 had the most significant synergistic activity on the seven selected bacteria., Conclusion: The present study provides information on the possible use of Albizia adianthifolia and its constituents in the control of Gram-negative infections including MDR phenotypes.

Background: Nutmeg is the seed kernel inside the fruit of Myristica fragrans Houtt. (Myristicaceae). It possesses various pharmacological activities but is used in Cameroon only for its flavor in making cakes. The present study thus aimed to investigate the in vitro antibacterial activity and antibiotic modifying activities of crude seed kernel methanol extract (MFS), fractions (MFSa-e) as well as 3',4',7-trihydroxyflavone from Myristica fragrans against a panel of multi-drug resistant (MDR) Gram-negative bacteria., Methods: The modified rapid p-iodonitrotetrazolium chloride (INT) colorimetric assay was used to determine the Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) on the tested bacteria, as well as those of antibiotics in association with the extract and/or isolated compound. Column chromatography was used for the fractionation and purification of the seed kernel extract whilst the chemical structures of compounds were determined using spectroscopic techniques., Results: Phytochemical investigations lead to the isolation of 3',4',7-trihydroxyflavone from the fraction MFSb. The crude extract showed antibacterial activity with MICs ranging from 32 to 1024 μg/mL on the majority of the 29 tested Gram-negative bacterial strains. Fraction MFSb inhibited the growth of 100% (29/29) of the tested bacterial strains, as well as the compound 3',4',7-trihydroxyflavone (12/12) with a MIC values ranging from 32 to 1024 μg/mL, and 4 to 128 μg/mL respectively. The lowest MIC value (4 μg/mL) was recorded with 3',4',7-trihydroxyflavone against Providencia stuartii ATCC299645 as well as the best MBC value (16 μg/mL) against the same strain. In the presence of Phenylalanine-Arginine-β-Naphthylamide (PAßN), an efflux pumps inhibitor, the activity of the extract increased on 73.33% (11/15) meanwhile that of 3',4',7-trihydroxyflavone increased on 100% tested bacteria. The compound 3',4',7-trihydroxyflavone potentiated the activity of antibiotics in the majority of the tested bacterial strains., Conclusion: The results of the present work provide additional information on the use of nutmeg and it major antibacterial component, 3',4',7-trihydroxyflavone, as a potential drug in the treatment of bacterial infections including multidrug resistant phenotypes.