Preparation of chitosan/peony (Paeonia suffruticosa Andr.) leaf extract composite film and its application in sustainable active food packaging.

Considering the problem of food perishability and the environmental pollution of plastic packaging, the natural active packaging prepared by incorporating plant leaf (e.g. peony leaf) extract into biodegradable food packaging materials may be a key to addressing these issues. In the study, a novel green bioactive composite film (CS-PLE) with antioxidant and antibacterial propertiese was developed by blending peony leaf extract (PLE) into chitosan (CS) film through the solution casting method. The physical properties and biological activities of a series of films, including CS film and CS-PLEs incorporated with different concentrations of PLE, were studied by appropriate experimental protocols. The results demonstrated that addition of PLE improved thermal stability, the barrier performance of UV-A and total phenolic content of CS film, and the antioxidant activities of CS-PLEs increased by 60.6 % ~ 73.2 % with the appending proportion of PLE from 0.1 wt% ~ 0.7 wt% compared to CS film. Furthermore, CS-PLEs had better inhibiting effect on bacteria. Notably, CS-PLE (0.7 wt%) wrapping apples showed the least degree of browning among all the groups. Hence, the study of CS-PLEs can provide a new strategy for the preparation of food packaging materials that are green alternatives and reduce environmental pollution.

Zinc supplementation alleviates diabetic peripheral neuropathy by inhibiting oxidative stress and upregulating metallothionein in peripheral nerves of diabetic rats.

We investigated the effect of zinc supplementation on the expression of metallothionein, lipid peroxidation (malondialdehyde, MDA), and poly(ADP-ribose) polymerase-1 (PARP-1) in the sciatic nerve, motor nerve conduction velocity of the left sciatic posterior tibial nerve in streptozotocin (STZ)-induced diabetic rats. Twenty-four male rats were equally divided into four groups. The first group served as untreated controls although the second group received 5 mg/kg/day zinc chloride. The third group was treated with STZ to induce diabetes, and the fourth group was treated with STZ and supplemented with zinc. A gradual but insignificant decline in motor nerve conduction velocity was observed at 2 weeks of induction of diabetes. Zinc supplementation markedly attenuated the decrease in motor nerve conduction velocity at week 8 post-induction of diabetes. Furthermore, the tactile response threshold of diabetic rats receiving normal saline was lower than that of diabetic rats receiving zinc supplementation. Additionally, zinc supplementation accentuated the increase in the mRNA transcript levels of metallothionein but attenuated the increase in the mRNA transcript levels of PARP-1. At week 8 post-induction of diabetes, diabetic rats receiving normal saline had markedly higher MDA contents than diabetic rats receiving zinc supplementation. In conclusion, the present study shows that zinc has a protective effect against diabetes-induced peripheral nerve damage by stimulating metallothionein synthesis and downregulating oxidative stress.