Enhancement of Stability and Antioxidant Activity of Mulberry Anthocyanins Through Succinic Acid Acylation.

Research background: Anthocyanins possess valuable health-promoting activities with significant health benefits for humans. However, their instability is a limiting factor for their usage in functional foods and beverages. Experimental approach: In this work, a new method to enhance the stability of anthocyanins from mulberry fruit through acylation by using succinic acid as a selected acyl donor was explored. The Box-Behnken design of response surface methodology was applied to determine the optimized conditions for the acylation process. Results and conclusions: The highest acylation conversion rate was 79.04% at anthocyanins to succinic acid mass ratio 1:8.96, acylation duration 3 h and temperature 50 °C. Structural analysis of acylated anthocyanins revealed that succinic acid introduces a C-O-C bond and a hydroxyl group. The thermostability and light stability of mulberry anthocyanins were significantly improved after acylation, and the antioxidant activity expressed as total reducing power and Fe2+-chelating capacity of the acylated anthocyanins was also enhanced. Novelty and scientific contribution: Succinic acid acylation provides a novel method for stabilizing mulberry anthocyanins, as evidenced by the increased stability and antioxidant ability of anthocyanins, and thus facilitates its use in the food and nutraceutical industries.

The differences in cocoon and silk qualities among sex-related mulberry and silkworm feeding groups.

Sexual dimorphism is seen in many dioecious plant and animal species, which may influence their trophic interactions. The differences in trophic interactions derived from sexual dimorphism in plants may influence herbivorous performance and population dynamics. Both silkworm (Bombyx mori L.) and mulberry (Morus alba L.) usually exhibit sexual dimorphism. However, few studies have been conducted on the effect of sex-related silkworm and mulberry pairings on cocoon and silk qualities, which are crucial in sericulture. Here, we compared the differences in cocoon and silk qualities under four feeding combinations (FS-FL: female silkworm fed with leaves from female mulberry trees; MS-FL: male silkworm fed with leaves from female mulberry trees; FS-ML: female silkworm fed with leaves from male mulberry trees; MS-ML: male silkworm fed with leaves from male mulberry trees). The results showed that silkworms exhibited male-biased herbivory with more male mulberry leaves digested. The FS-ML group had higher silk weight and silk ratio of fresh cocoons than the FS-FL group, and the MS-ML group had lower coarse points than the MS-FL group. Compared with groups FS-ML and FS-FL, both MS-FL and MS-ML had smaller cocoons with longer silk lengths and a higher silk ratio of the fresh cocoons. In addition, the Entropy Weight-TOPSIS method showed the cocoon quality rank as FS-ML > FS-FL > MS-FL > MS-ML, whereas silk quality rank was MS-ML > FS-FL > FS-ML > MS-FL. These results indicate that the quality of cocoon and silk is related to the interaction of silkworm and mulberry at the sex level. Furthermore, female silkworms fed with female and male tree leaves have a higher total yield in cocoon production, while male silkworms fed with male tree leaves produced higher silk quality.

Dual-Targeting Antiproliferation Hybrids Derived from 1-Deoxynojirimycin and Kaempferol Induce MCF-7 Cell Apoptosis through the Mitochondria-Mediated Pathway.

1-Deoxynojirimycin, an α-glucosidase inhibitor, possesses various biological activities such as antitumor, antidiabetic, and antiviral effects. However, the application of 1-deoxynojirimycin is restricted by its poor lipophilicity and low bioavailability. In this study, three 1-deoxynojirimycin derivatives (8-10) comprising 1-deoxynojirimycin and kaempferol were designed and synthesized to modify their pharmacokinetics and improve their antitumor efficacy. Among them, compound 10, a conjugate of 1-deoxynojirimycin and kaempferol linked through an undecane chain, exhibited excellent lipophilicity, antiproliferative effects, and α-glucosidase inhibitory activity. Compared with 1-deoxynojirimycin, kaempferol, and their combination, compound 10 downregulated cyclooxygenase-2 (COX-2) expression, arrested the cell cycle at the S phase, induced cellular apoptosis, and inhibited the migration of MCF-7 cells. Moreover, further investigation indicated that compound 10 induced MCF-7 cell apoptosis through a mitochondrial-mediated pathway via the loss of mitochondrial membrane potential. This led to increasing intracellular levels of reactive oxygen species (ROS) and Ca2+, the downregulation of Bcl-2 expression, and the upregulation of Bax levels.

Effect of the silkworm pupa protein-glucose conjugate on the thermal stability and antioxidant activity of anthocyanins.

Anthocyanin (cyanidin-3-O-glucose) is a natural water-soluble pigment with a robust antioxidant capacity. However, its poor stability and bioavailability limits its application as a functional food ingredient. This study explored the ability of the silkworm pupa protein-glucose (Spp-Glu) conjugate, developed under wet-heating conditions, to improve the thermal stability and antioxidant activity of cyanidin-3-O-glucose (C3G) at pH 3.0 and 6.8. The characterization experiments suggested that C3G complexed with the Spp-Glu conjugate could modify the protein's microenvironment and cause unfolding of the protein's secondary structures under varied pH conditions. Spectroscopic techniques further revealed the formation of complexes via hydrophobic interactions and static quenching processes when C3G was bound to Spp or Spp-Glu. The formation of these complexes effectively attenuated C3G degradation, thereby enhancing its stability under heat treatment over a range of pH values, and the experiments measuring antioxidant activity suggested that the Spp-Glu conjugate formed does not affect the efficacy of C3G after complexation. Therefore, our study suggests that Spp-Glu has the potential to effectively protect and deliver anthocyanins during industrial application for functional food formulation.

Chemical synthesis, inhibitory activity and molecular mechanism of 1-deoxynojirimycin-chrysin as a potent α-glucosidase inhibitor.

Hyperglycemia can be efficaciously regulated by inhibiting α-glucosidase activity and this is regarded as an effective strategy to treat type 2 diabetes. 1-Deoxynojimycin, an α-glucosidase inhibitor, can penetrate cells rapidly to potently inhibit α-glucosidase in a competitive manner. However, the application of 1-deoxynojimycin is limited by its poor lipophilicity and low bioavailability. Herein, three 1-deoxynojimycin derivatives 4-6 were designed and synthesized by linking 1-deoxynojimycin and chrysin to ameliorate the limitations of 1-deoxynojimycin. Among them, compound 6, a conjugate of 1-deoxynojimycin and chrysin linked by an undecane chain, could better bind to the α-glucosidase catalytic site, thereby exhibiting excellent α-glucosidase inhibitory activity (IC50 = 0.51 ± 0.02 µM). Kinetics analyses revealed that compound 6 inhibited the activity of α-glucosidase in a reversible and mixed competitive manner. Fluorescence quenching and UV-Vis spectra showed that compound 6 changed the conformation of the α-glucosidase via complex formation, which triggered a static fluorescence quenching of the enzyme protein.

Comparative transcriptome analysis of mulberry reveals anthocyanin biosynthesis mechanisms in black (Morus atropurpurea Roxb.) and white (Morus alba L.) fruit genotypes.

BACKGROUND: To gain a better understanding of anthocyanin biosynthesis in mulberry fruit, we analyzed the transcriptome of the mulberry varieties Da 10 (Morus atropurpurea Roxb., black fruit) and Baisang (Morus alba L., white fruit). RESULTS: We found that whereas Da 10 had high levels of cyanidin 3-O-glucoside (Cy), and pelargonidin 3-O-glucoside (Pg), Baisang contained only Cy, at low levels. Based on a comparative transcriptome analysis, we annotated more than 27,085 genes (including 1735 new genes). Genes that were differentially expressed between Da 10 and Baisang were detected at three stages of fruit development: S1 [4256 genes, 10 days post-anthesis (DPA)], S2 (5612 genes, 19 DPA), and S3 (5226 genes, 28 DPA). Anthocyanin biosynthesis was found to be associated with the expression of 15 core genes and 5 transcription factors. Relative to Baisang, Da 10 showed a significant upregulation of genes involved in the early stages (production of the intermediate compounds chalcone and dihydroflavonol) and late stages (production of Cy and Pg) of anthocyanin biosynthesis. Baisang showed a significant downregulation of the genes involved in the early stages of anthocyanin biosynthesis and overexpression of flavanone 3-hydroxylase (FLS), resulting in the generation of quercetin and/or myricetin but not anthocyanins. CONCLUSIONS: The biosynthesis of anthocyanin in mulberry fruit is initiated from the precursor, phenylalanine, and mediated by the upregulation of dihydroflavonol 4-reductase, anthocyanidin synthase, anthocyanidin 3-O-glucosyltransferase, and cyanidin-3-O-glucoside 2-O-glucuronosyltransferase, and downregulation of FLS to produce Cy and Pg.

Studies on the interactional characterization of preheated silkworm pupae protein (SPP) with anthocyanins (C3G) and their effect on anthocyanin stability.

In this paper, the interaction of silkworm pupae protein (SPP) with cyanidin-3-O-glucoside (C3G) was studied the protective anthocyanins stability. Characterization experiments suggested that C3G-SPP complexes mainly through hydrophobic interactions, with a decrease in the α-helix content and increases in the ß-sheet and ß-turn contents. Fluorescence results revealed that C3G quenched the intrinsic fluorescence of SPP by static quenching. The highest quenching constant, Kq, was recorded to be1.26 × 1012 M-1s-1 for the SPP preheated at 80 °C. Following the C3G-SPP complexes, the degradation rate constant decreased, and the half-life of C3G was prolonged from 64.81 ± 1.07 to 261.99 ± 13.32 min at 80 °C (p < 0.05). The SPP preheated at 80 °C exhibited the highest binding affinity towards C3G and also effectively increased the thermal and oxidative stability of the C3G. The obtained results suggest that the novel protein proposed in this study could expand the application of anthocyanins as stable, functional food ingredients.