Cinnamaldehyde inhibit Escherichia coli associated with membrane disruption and oxidative damage.

In this study, the antimicrobial mechanism of cinnamaldehyde (CIN) against Gram-negative Escherichia coli ATCC 25922 (E. coli) based on membrane and gene regulation was investigated. Treatment with low concentration (0, 1/8, 1/4, 3/8 MIC) of CIN can effectively suppress the growth of E. coli by prolonging its lag phase and Raman spectroscopy showed obvious distinction of the E. coli after being treated with these concentration of CIN. The determination of relative conductivity indicated that CIN at relatively high concentration (0, 1, 2, 4 MIC) can increase the cell membrane permeability, causing the leakage of cellular content. Besides, the content of malondialdehyde (MDA) and the activity of total superoxide dismutase (SOD) of E. coli increased with increasing treatment concentration of CIN, implying that CIN can cause oxidative damage on E. coli cell membrane and induce the increase of total SOD activity to resist this oxidative harm. Moreover, quantitative real-time RT-PCR (qRT-PCR) analysis revealed the relationship between expression of antioxidant genes (SODa, SODb, SODc) and treatment CIN concentration, suggesting that SOD, especially SODc, played a significant role in resistance of E. coli to CIN. The underlying inactivation processing of CIN on E. coli was explored to support CIN as a potential and natural antimicrobial agent in food industry.

Protective effect of baicalein on DNA oxidative damage and its binding mechanism with DNA: An in vitro and molecular docking study.

In this work, the protective effect of baicalein on DNA oxidative damage and its possible protection mechanisms were investigated. 2-thiobarbituric acid (TBA) colorimetry and agarose gel electrophoresis study found that baicalein protected the deoxyribose residue and double-stranded backbone of DNA from the damage of hydroxyl radicals. Antioxidant analysis results showed that baicalein has excellent radicals scavenging effects and Fe2+ chelating ability, which might be the mechanism of baicalein protecting DNA. DNA binding studies indicated that baicalein bound to the minor groove of DNA with moderate binding affinity (K = (7.35 ±â€¯0.91) × 103 M-1). Hydrogen bonding and van der Waals forces played a major role in driving the binding process. Molecular docking further confirmed the experimental results. This binding could stabilize DNA double helix structure, thereby protecting DNA from oxidative damage. This study may provide theoretical basis for designing new functional foods of baicalein for DNA damage protection.

Hydroxyl-related differences for three dietary flavonoids as inhibitors of human purine nucleoside phosphorylase.

In this work, the hydroxyl-related differences of binding properties and inhibitory activities of dietary flavonoids, namely chrysin, baicalein and apigenin against purine nucleoside phosphorylase (PNP) were investigated. It was found that the hydroxylation on position C4' of chrysin (→apigenin) mildly decreased the binding affinities for PNP, whereas on the position C6 of chrysin (→baicalein) significantly increased binding affinities. Comparatively, the hydroxylation on position C4' and C6 greatly improved their PNP inhibitory effects. The IC50 values of apigenin and baicalein were 6.09 × 10-5 M and 8.94 × 10-5 M, respectively, which is significantly lower than that of chrysin (2.13 × 10-4 M). Results from molecular modeling revealed that there are two binding sites, i.e. active site (major) and tryptophan site (minor) on PNP, and the binding of these flavonoids might induce a serious conformational destabilization of PNP as a result of altering the micro-environment and morphology by flavonoids.