Search Results (4)

Valonea, a natural product from Quercus variabilis, is rich in bioactive phenolic compounds; however, its compact physical structure restricts the efficient extraction of these components, limiting its high-value applications. To address this issue, the present study examined the influence of steam explosion (SE) pretreatment on the physical structure, phenolic profile, and bioactivity of valonea and identified optimal processing parameters. Under optimal conditions (1.0 MPa and 10 min), the content of total polyphenols increased by 63.1%, reaching 553.0 mg/g extract, while gallic acid and ellagic acid concentrations increased by 380.6% and 1280.0%, respectively. Electrospray ionization mass spectrometry identified 12 major phenolic constituents, providing a compositional basis for the observed bioactivities. The extract exhibited strong antioxidant and anti-inflammatory properties, confirming that SE not only augments phenolic content but also preserves or enhances the functional quality of the extract. As an efficient and environmentally friendly pretreatment technology, SE substantially improves the bioavailability and activity of phenolics in valonea. Thus, this study offers a reliable strategy for the high-value utilization of valonea in fields such as pharmaceuticals, functional foods, and animal feed. Full article

The genus Quercus is widely distributed globally and serves as a potential source of phenolic compounds, which are renowned for their potent biological activities. The primary objective of this study was to determine the concentrations of metabolite components and evaluate the relative antioxidant activities of valonea (acorn cups) from Quercus variabilis (Q. variabilis) of different geographic origins using a UPLC-ESI-MS/MS-based metabolomics approach. A total of 791 metabolite components were identified, with significant variations in their concentrations observed among samples from different geographic locations. Among these, 1-O-galloyl-β-D-glucose was identified as a key active compound. The biosynthesis of galloyl sugars, galactose metabolism, and pathways for starch and sucrose metabolism represent the three pathways that correspond to the differential metabolites, encompassing 23, 11, and 7 metabolites, respectively. The variations in the antioxidant effectiveness of valonea could mainly be linked to the synthesis of galloyl sugars. These findings improve our knowledge of the composition of valonea and offer valuable resources for its extensive utilization and focused development. Full article

Valonea tannin is a natural product readily extracted from acorn shells that has been suggested to have potential skin whitening properties. This study investigated the tyrosinase inhibition activity of extracted valonea tannin and the associated structure–function activity. Nuclear magnetic resonance spectroscopy and molecular weight analysis with gel permeation chromatography revealed that valonea tannin could be characterized as a hydrolysable tannin with galloyl, hexahydroxydiphenoyl and open formed-glucose moieties and an average molecular weight of 3042 ± 15 Da. Tyrosinase inhibition assays demonstrated that valonea tannin was 334 times more effective than gallic acid and 3.4 times more effective than tannic acid, which may relate to the larger molecular size. Kinetic studies of the inhibition reactions indicated that valonea tannin provided tyrosinase inhibition through mixed competitive–uncompetitive way. Stern–Volmer fitted fluorescence quenching analysis, isothermal titration calorimetry analysis and in silico molecule docking showed valonea tannin non-selectively bound to the surface of tyrosinase via hydrogen bonds and hydrophobic interactions. Inductively coupled plasma-optical emission spectroscopy and free radical scavenging assays indicated the valonea tannin had copper ion chelating and antioxidant ability, which may also contribute to inhibition activity. These results demonstrated the structure–function activity of valonea tannin as a highly effective natural tyrosinase inhibitor that may have commercial application in dermatological medicines or cosmetic products. Full article

Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with sodium oleate as the collector. The single mineral flotation results showed that valonea extract displayed the strongest depression on calcite, while sodium fluosilicate displayed the strongest depression on barite. These two depressants allowed selective separation of the three minerals through sequential flotation. The flotation of mixed minerals showed that 94% of the calcite was successfully depressed by the valonea extract, and 95% recovery of the fluorite was achieved in the subsequent flotation with sodium fluosilicate depressing barite. The different depressant–mineral interactions were investigated via electro-kinetic studies and molecular dynamics (MD) simulations using the Materials Studio 6.0 program. The valonea extract exhibited the strongest adsorption on the calcite surface, and sodium fluosilicate exhibited the strongest adsorption on the barite surface, which prevented oleate species from reacting with Ca²⁺ or Ba²⁺ surface sites. This study provides useful guidance for how to process fluorite, barite and calcite resources. Full article