The effect of ultrasound on the activity of α-amylase, papain and pepsin was investigated and the mechanism of the effect was explored by determining their conformational changes. With the irradiation of power ultrasound, the activity of α-amylase and papain was inhibited, while the activity of pepsin was activated. According to the analysis of circular dichroism, Fourier transform infrared and fluorescence spectroscopy, the πo → π(∗) amide transitions and secondary structural components, especially β-sheet, of these three enzymes were significantly influenced by ultrasound. The tryptophan fluorescence intensity of the three enzymes was also observed to be affected by sonication. Furthermore, it was found that the pepsin molecule might gradually be resistant to prolonged ultrasonic treatment and recover from the ultrasound-induced damage to its original structure. The results suggested that the activity of α-amylase, papain and pepsin could be modified by ultrasonic treatment mainly due to the variation of their secondary and tertiary structures.
The aim of this study was to determine the main constituents of the essential oil isolated from
Fortunella crassifolia
Swingle peel by hydro-distillation, and to test the efficacy of the essential oil on antimicrobial activity. Twenty-five components, representing 92.36% of the total oil, were identified by GC-MS analysis. The essential oil showed potent antimicrobial activity against both Gram-negative (
E. coli
and
S. typhimurium
) and Gram-positive (
S. aureus
,
B. cereus
,
B. subtilis
,
L. bulgaricus
, and
B. laterosporus
) bacteria, together with a remarkable antifungal activity against
C. albicans
. In a food model of beef extract, the essential oil was observed to possess an effective capacity to control the total counts of viable bacteria. Furthermore, the essential oil showed strongly detrimental effects on the growth and morphological structure of the tested bacteria. It was suggested that the essential oil from
Fortunella crassifolia
Swingle peel might be used as a natural food preservative against bacteria or fungus in the food industry.
The antioxidant, antibrowning, and cytoprotective activities of Ligustrum robustum (Rxob.) Blume extract (LRE) were investigated and the main antioxidant component was isolated and identified. With its high content of phenols and flavonoids, the LRE showed remarkable antioxidant capacity to scavenge free radicals in vitro and to inhibit oil oxidation in a peanut oil system. Moreover, LRE was observed to inhibit tyrosinase action and browning of fresh-cut apple slices effectively. Furthermore, the cytoprotective activity of LRE was evaluated in a human intestine model using Caco-2 cell lines. According to the activity-guided isolation and identification, by using column chromatography, high-performance liquid chromatography, time-of-flight mass spectrometry, and nuclear magnetic resonance analyses, ursolic acid was characterized as the main antioxidant component of LRE; it showed the strongest free radical-scavenging activity. The results suggested that L. robustum (Rxob.) Blume could be a new resource for preparing functional food and nutraceutical products for use in food and pharmacology industries.
The influence of ultrasound to the activity of tyrosinase was investigated. According to the analyses of ultraviolet-visible spectrometry and Fourier transform infrared spectroscopy, both monophenolase and diphenolase activities of tyrosinase treated by ultrasound were higher than that of control, with the decrease of lag time and the increase of activity. No oxytyrosinase was observed and β-sheet conformation was predominant in the tyrosinase under ultrasound treatment. Moreover, with the observation of atomic force microscopy, the large molecular groups of tyrosinase were broken into small ones under the treatment of ultrasound. The present result suggested the activity of tyrosinase could be activated under the tested ultrasound treatment, mainly due to the increased likelihood of the combination of substrate and enzyme, or the possible change and exposure of the active site in tyrosinase.
The first organic-inorganic hybrid guanidine molybdenyl iodate [C(NH2)3]2Mo2O5(IO3)4•2H2O was successfully synthesized via an improved moderate hydrothermal method. It features an unprecedented boat-shaped zero-dimensional [Mo2O5(IO3)4]2- polyanion cluster, which induces a wide...
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