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BACKGROUND: Gallocatechin gallate (GCG), a catechin of tea polyphenols, possesses inhibitory ability against tyrosinase, but few studies have reported how common processing methods affect it. In this research, the influence of heating and ultrasound treatments on the inhibition of GCG against tyrosinase was explored by ultraviolet-visible absorption, fluorescence spectroscopy, high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry.RESULTS: Both heating and ultrasound treatments of GCG alone improved GCG's inhibitory ability against tyrosinase compared with the untreated, and a combination of heating and ultrasound treatment (100 °C, 20 min + 630 W, 20 min) further decreased the relative tyrosinase activity to 26.8%. The treated GCG exhibited a stronger fluorescence quenching effect on tyrosinase, but did not have any influence on the static quenching mechanism. Compared to the untreated GCG, the binding constants of treated GCG by heating, ultrasound and their combination with tyrosinase significantly increased, but the number of binding sites was still approximately one and the main driving force of the treated GCG was still hydrophobic interaction. After treatments of heating, ultrasound and their combination, the composition of GCG solutions was changed.CONCLUSION: The enhanced inhibition of treated GCG on tyrosinase may be due to partial conversion of GCG into epigallocatechin-3-gallate (EGCG) and gallic acid (GA), which may cooperate with GCG to better inhibit the enzyme activity. This study has provided some valuable information for the application of catechins against tyrosinase in food processing and cosmetic industry.

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Increasing evidence suggests that fungal communities are key components of biogeochemical cycles in coastal ecosystems. However, at a regional scale, the major drivers of the seasonal and spatial distribution of fungi in areas impacted by mariculture remain largely unknown. Intensive aquaculture takes place in Dongshan Bay of Fujian, China, a typical subtropical marine ecosystem with multiple environmental gradients extensively perturbed by anthropogenic activities. To better understand the consequences of mariculture on fungal community composition and activities, we simultaneously evaluated the temporal (four different seasons) and spatial dynamics in total (DNA) and active (RNA) fungal communities of Dongshan Bay in relation to several major physicochemical properties. Our results revealed that fungal communities in the Bay were highly diverse, but showed the ubiquitous dominance of Dikarya and the occasional predominance of Glomeromycota, Mucoromycota, Mortierellomycota, Chytridiomycota, Olpidiomycota, and Rozellomycota. Fungal diversity varied much more with season than with the degree of aquaculture activity, for both total and active communities. This notion is supported by co-occurrence networks exhibiting a clear seasonal pattern. Furthermore, fungal community structure in coastal waters showed distinct relationships with environmental factors varying both with season and in space. For both total and active fungal communities, a combination of environmental variables including temperature, dissolved oxygen, and nitrite exhibited the greatest impact on community structure. Our study demonstrates a distinct spatiotemporal dynamics of both total and active fungi and provides a foundation to better understand the ecological roles of marine fungi in coastal ecosystems in relation to mariculture activities.