Yuning Wang

Separation and Identification of Anthocyanin Extracted from Mulberry Fruit and the Pigment Binding Properties toward Human Serum Albumin

Purple pigments were isolated from mulberry extracts using preparative high-speed countercurrent chromatography (HSCCC) and identified by ESI-MS/MS and high performance liquid chromatography (HPLC) techniques. The solvent system containing methyl tert-butyl ether, 1-butanol, acetonitrile, water, and trifluoroacetic acid (10:30:10:50:0.05; %, v/v) was developed in order to separate anthocyanins with different polarities. Cyanidin 3-O-(6″-O-α-rhamnopyranosyl-β-galactopyranoside) (also known as keracyanin) is the major component present in mulberry (41.3%). Other isolated pigments are cyanidin 3-O-(6″-O-α-rhamnopyranosyl-β-glucopyranoside) and petunidin 3-O-β-glucopyranoside. The binding characteristics of keracyanin with human serum albumin (HSA) were investigated by fluorescence and circular dichroism (CD) spectroscopy. Spectroscopic analysis reveals that HSA fluorescence quenched by keracyanin follows a static mode. Binding of keracyanin to HSA mainly depends on van der Waals force or H-bonds with average binding distance of 2.82 nm. The results from synchronous fluorescence, three-dimensional fluorescence, and CD spectra show that adaptive structure rearrangement and decrease of α-helical structure occur in the presence of keracyanin.

Hydrogen-rich water delays postharvest ripening and senescence of kiwifruit.

The effect of hydrogen-rich water (HRW) on prolonging the shelf life of kiwifruit and possible underlying mechanisms were assessed. Our results revealed that HRW (30%, 80%, and 100%) displayed different effects in inhibiting the rot of kiwifruit. Among these treatments, 80% HRW had the most significant effect by decreasing the rot incidence and preserving the firmness of kiwifruit. This conclusion was supported by the fact that 80% HRW treatment could effectively alleviate pectin solubilization and reduce the activities of cell wall-degrading enzymes. On the other hand, HRW treatment was able to reduce the respiration intensity, increase the activity of superoxide dismutase, decrease lipid peroxidation level, and maintain the radical (DPPH,O2(-),andOH)-scavenging activity of kiwifruit. Moreover, the inner membrane of mitochondria exhibited higher integrity. Thus, our results demonstrate that HRW treatment could delay fruit ripening and senescence during storage by regulating the antioxidant defence.