ABSTRACT
A pair of epimers of flavonoid alkaloids, with a pyrrolidone moiety, 2S,5''R-eupodoratin A (1), 2S,5''S-eupodoratin A (2), together with two known analogues, drahebephin A (3), drahebephin B (4), were isolated from the flowers of Chromolaena odorata (L.) R.M.King & H.Rob. Their structures were elucidated on the basis of HR-ESI-MS, 1D/2D NMR spectral analyses. The absolute configuration of compounds (1) and (2) was determined by its experimental and calculated electronic circular dichroism (ECD) spectra. All compounds were isolated from the Asteraceae family for the first time. The ABTS·+ scavenging activity of compound (4) reached 93.56% at a concentration of 0.5 mM, while the scavenging capacity of positive control Trolox was 55.94%. In addition, all compounds show moderate antimicrobial activity against Escherichia coli (ATCC, 337304), Staphylococcus aureus (ATCC, 337371) and Candida albicans (ATCC, 186382) with a MIC value of more than 50 µg/mL.
ABSTRACT
A new bicyclic lactam derivatives penicilactam B (1) and a new monocyclic amide penicillamide D (2), along with four known compounds (3-6), were isolated from the fermentation broth of the derived fungus Penicillium rubens PQJ-2. Their structures and stereochemistry were elucidated by comprehensive spectroscopic analyses and quantum ECD calculations. All the compounds were evaluated for their antibacterial activities against Staphylococcus aureus subsp, Candida albicans, Escherichia coli and insecticidal activity against Helicoverpa armigera Hubner. Compounds 1-3 exhibited modest insecticidal activity against H. armigera Hubner.
ABSTRACT
In this paper, the fluorogenic property of vindoline was exploited and, as a probe, used to analyze the interaction of vindoline with HSA by fluorescence and absorption spectra in combination with molecular modeling under a simulated physiological conditions. The evidences from synchronous fluorescence and absorption spectroscopes showed the effect of vindoline on the microenvironment around HSA in aqueous solution. Data obtained by the fluorescence spectroscopy indicated that binding of vindoline with HSA leads to dramatic enhancement of the fluorescence emission intensity. The binding constants and the number of binding sites between vindoline and HSA at different temperatures (303, 310 and 317 K) were calculated according to the data obtained from fluorescence titration. Molecular docking was performed to reveal the possible binding mode or mechanism and suggested that vindoline can bind strongly to HSA. It is considered that vindoline binds to HSA mainly by a hydrophobic interaction and there are four hydrogen bonds interactions between the drug and the residues Ala291, Arg222, Arg218 and Lys195, separately. Fluorescent displacement measurements confirmed that vindoline bind HSA on site II. The thermodynamic parameters obtained (the enthalpy change deltaH0 and the entropy change deltaS0 were calculated to be -10.30 kJ x mol(-1) and 79.98 J x mol(-1) x K(-1), respectively, according to the Van't Hoff equation) suggested that hydrophobic and electrostatic interaction is the predominant intermolecular forces stabilizing the complex.
