Polysaccharides from Polygonatum kingianum Collett & Hemsl ameliorated fatigue by regulating NRF2/HO-1/NQO1 and AMPK/PGC-1α/TFAM signaling pathways, and gut microbiota.

Polygonatum kingianum Coll & Hemsl is an important Chinese medicine used for enhancing physical function and anti-fatigue, and polysaccharides (PKPs) are considered as the main bioactive components. However, the mechanisms through which PKPs exert their anti-fatigue effects are not fully understood. This study aimed more comprehensively to explore the anti-fatigue mechanisms of PKPs, focusing on metabolism, protein expression, and gut flora, by using exhaustive swimming experiments in mice. Results showed a significant increase in the exhaustive swimming time of the mice treated with PKPs, especially in the high-dose group (200 mg/kg/day). Further studies showed that PKPs remarkably improves several fatigue-related physiological indices. Additionally, 16S rRNA sequence analysis showed that PKPs increased antioxidant bacteria (e.g., g_norank_f_Muribaculaceae) and the production of short-chain fatty acids (SCFAs), while reducing the abundance of harmful bacteria (e.g., g_Escherichia-Shigella and g_Helicobacter). PKPs also mitigated oxidative stress through activating the NRF2/HO-1 signaling pathway, and promoted energy metabolism by upregulating the expression of AMPK/PGC-1α/TFAM signaling pathway proteins. This research may offer theoretical support for incorporating PKPs as a novel dietary supplement in functional foods targeting anti-fatigue properties.

The profiles of free, esterified and insoluble-bound phenolics in peach juice after high pressure homogenization and evaluation of their antioxidant capacities, cytoprotective effect, and inhibitory effects on α-glucosidase and dipeptidyl peptidase-â £.

The phenolic profiles, antioxidant capacities, cytoprotective effect, and α-glucosidase and DPP-IV inhibitory capacity of free (FP), esterified (EP) and insoluble-bound (IBP) phenolic fractions in 'Lijiang snow' peach juice after high pressure homogenization (HPH) were investigated, and the molecular docking was used to explore the enzyme inhibition mechanism. HPH increased total phenolic and total flavonoid contents in three fractions without changing compositions. The IC50 of radicals scavenged by three fractions were all reduced by HPH. The best inhibition on intracellular ROS production were found for phenolic fractions after HPH at 300 MPa, with ROS levels ranged within 95.26-119.16 %. HPH at 300 MPa reduced the apoptosis rates of FP and EP by 16.52 % and 9.33 %, respectively. All phenolic fractions showed effective inhibition on α-glucosidase and DPP-IV by formation of hydrogen bonding and van der Waals forces. This study explored the feasibility of HPH to enhance the phenolics and bioactivity of peach juice.

Comparing the Effect of HPP on the Structure and Stability of Soluble and Membrane-Bound Polyphenol Oxidase from 'Lijiang Snow' Peach: Multispectroscopic and Molecular Dynamics Simulation.

Polyphenol oxidase (PPO) easily causes fruits and vegetables to lose their color and nutritional value. As a non-thermal process, high-pressure processing (HPP) showed different inactivation effects on endogenous enzymes. In this work, soluble PPO (sPPO) and membrane-bound PPO (mPPO) from 'Lijiang snow' peaches were purified, and then the effect of high pressure on the conformation of sPPO and mPPO was investigated and compared at the molecular level. The maximum activation of sPPO and mPPO by 11.2% and 4.8% was observed after HPP at 200 MPa, while their activities both gradually decreased at 400 MPa and 600 MPa; in particular, the residual activities of sPPO and mPPO at 600 MPa for 50 min were 41.42% and 72.95%, respectively. The spectroscopic results indicated that the secondary structure of PPOs was little affected by HPP, but HPP led to obvious changes in their tertiary structure. The simulations showed that the decreasing distance between the copper ion and His residue in the copper-binding region of two PPOs at 200 MPa was favorable to catalytic activity, while the increasing distance between copper ions and His residues and the disordered movement of the loop region above 400 MPa were unfavorable. In addition, the structure of sPPO was relatively looser than that of mPPO, and high pressure showed a more significant effect on the conformation of sPPO than that of mPPO. This study clarified the effect of HPP on PPO's structure and the relationship between its structure and activity and provided a basis for the prevention of enzymatic browning.

Comparison on inhibitory effect and mechanism of inhibitors on sPPO and mPPO purified from 'Lijiang snow' peach by combining multispectroscopic analysis, molecular docking and molecular dynamics simulation.

The inhibition mechanisms of soluble PPO (sPPO) by l-cysteine, reduced glutathione and thiourea, and membrane-bound (mPPO) by l-cysteine, reduced glutathione, thiourea, anisaldehyde and cinnamaldehyde were investigated by combining multispectroscopic analysis and computational simulations. Reduced glutathione showed the strongest inhibitory effect, with IC50 of 0.46 and 0.94 mM, respectively. The multispectral results showed that all inhibitors inhibited activity by destroying the secondary and tertiary structure, and the structure of sPPO were more easily affected. Docking showed that hydrogen bond and metal contact were the main driving force for inhibitors binding to sPPO and mPPO, respectively. Simulation showed that sPPO-inhibitor system had more fluctuation than mPPO-inhibitor system, indicating easier inhibition of sPPO activity. This work revealed that the structural differences between sPPO and mPPO led to different inhibition mechanisms of PPOs by inhibitors at the molecular level, which could provide the guidance for the selection of inhibitors in fruit and vegetable processing.