Neo-clerodane diterpenoids from Conyza pyrrhopappa Sch.Bip. ex A.Rich.

Two hitherto unknown neo-clerodane-type diterpenoids along with twelve known compounds have been isolated from Conyza pyrrhopappa Sch.Bip. ex A.Rich, a medicinal plant traditionally used across tropical Africa to relieve fever. The structures of isolates have been elucidated by a combination of spectroscopic techniques. The crude extract and the isolated compounds were evaluated in the Hela-S3 cell line and in a panel of microorganisms (bacteria and fungi) at concentrations up to 50 µg/mL. The new compounds were inactive while the pentamethylated flavonoids showed low to significant activity against the cancer cell line used. However, none of the samples showed any activity against the tested microorganisms at this concentration. The present manuscript is the first investigation of the cytotoxicity of phytochemicals and extract from C. pyrrhopappa.

Antibacterial and antibiotic-modifying activities of fractions and compounds from Albizia adianthifolia against MDR Gram-negative enteric bacteria.

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 ¼ and Minimal Bactericidal Concentration « MBC ¼) 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 ß-sitosterol (2 +  3), ß-sitosterol 3-O-ß-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-ß-Naphthylamide or PAßN), 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.

A new flavone from the roots of Milicia excelsa (Moraceae).

A new flavonoid identified as 2-(2,4-dihydroxyphenyl)-5-hydroxy-8,8-dimethyl-4H,8H-pyrano[2,3-f]chromen-4-one (2'-hydroxyatalantoflavone) (1) was obtained from the roots of Milicia excelsa along with five known compounds including atalantoflavone (2), neocyclomorusin (3), 6-geranylnorartocarpetin (4), cudraxanthone I (5), and betulinic acid (6). The structures of the isolates were established on the basis of their spectral data and by comparison with those reported in the literature.