Extraction optimization and identification of four advanced glycation-end products inhibitors from lotus leaves and interaction mechanism analysis.

Previous research indicated lotus leaves extract could effectively inhibit advanced glycation end-products (AGEs) formation, but the optimal extraction condition, bio-active compounds and interaction mechanism remain unclear. The current study was designed to optimize the extraction parameters of AGEs inhibitors from lotus leaves by bio-activity-guided approach. The bio-active compounds were enriched and identified, the interaction mechanisms of inhibitors with ovalbumin (OVA) were investigated by fluorescence spectroscopy and molecular docking. The optimum extraction parameters were solid-liquid ratio of 1:30, ethanol concentration of 70 %, ultrasonic time of 40 min, temperature of 50 °C, and power of 400 W. Isoquercitrin, hyperoside, astragalin, and trifolin were identified from the 80 % ethanol fraction of lotus leaves (80HY). Hyperoside and isoquercitrin were dominant AGEs inhibitors and accounted for 55.97 % of 80HY. Isoquercitrin, hyperoside, trifolin interacted with OVA via the same mechanism, hyperoside exhibited the strongest affinity, trifolin caused the most conformational changes.

Traceability and identification of fish gelatin from seven cyprinid fishes by high performance liquid chromatography and high-resolution mass spectrometry.

The broad application prospect of fish gelatin makes the traceability and identification of fish gelatin imminent. High performance liquid chromatography and high-resolution mass spectrometry (HPLC-MS/MS) was used to identify fish gelatins in seven commercial cyprinid fishes, namely, black carp, grass carp, silver carp, bighead carp, common carp, crucian carp, and Wuchang bream. By comparison with theoretical mammalian collagen (bovine and porcine collagen), the common and unique theoretical peptides were found in the collagen of grass carp, silver carp, and crucian carp, respectively. HPLC-MS/MS results showed that 7 common characteristic peptides were obtained from seven cyprinid fish gelatins. Moreover, 44, 36, and 42 unique characteristic peptides were detected in the gelatins of grass carp, silver carp, and crucian carp, respectively. The combined use of common and unique characteristic peptides could improve the accuracy and authenticity of traceability and identification of fish gelatin in comparison with mammalian gelatin.

Inhibitory activity and mechanism of guavinoside B from guava fruits against α-glucosidase: Insights by spectroscopy and molecular docking analyses.

Guavinoside B (GUB) is the main active substance in guava fruit and shows promising biological activities. In this study, the inhibitory activity and mechanism of GUB on α-glucosidase were studied by using spectroscopic techniques, kinetic analysis, and molecular docking. Results indicated that GUB possessed significant inhibition ability on α-glucosidase, which was about 10 times that of acarbose. The GUB was a mixed-type inhibitor, which suppressed the activity of α-glucosidase through a reversible process. Fluorescence analysis revealed that GUB quenched the fluorescence of α-glucosidase statically, the formation of GUB-α-glucosidase complex was a spontaneous and exothermic process, van der Waals forces, hydrogen bonding, and hydrophobic interaction were the predominant driving forces, only one single-binding site on α-glucosidase was involved in the binding process. GUB inserted into the hydrophobic pocket of α-glucosidase with 11 hydrogen bonds and two π-π stacking formed. The presence of GUB changed the microenvironment near the fluorescent amino acids of α-glucosidase, and the structure of α-glucosidase was slightly changed, eventually leading to the decrease of α-glucosidase activity. PRACTICAL APPLICATIONS: Diabetes mellitus (DM) is a worldwide chronic metabolic disease threatening human health seriously. Guava fruit is a popular fruit, and its extracts were reported to show many biological activities. GUB is the main benzophenone glycoside in guava fruits. However, the inhibitory activity and mechanism of its specific active compound GUB are still unclear. Studies have shown that GUB could reversibly inhibit the activity of α-glucosidase, and its inhibitory ability was about 10 times that of acarbose. The kinetics and mechanism of inhibition were revealed. These will facilitate the further research and application of guava fruit and GUB in functional and healthy foods against hyperglycinaemia or even DM.