Polysaccharides are natural biopolymers that have been recognized to be the most promising hosts for the synthesis of metallic nanoparticles (MNPs) because of their outstanding biocompatible and biodegradable properties. Polysaccharides are diverse in size and molecular chains, making them suitable for the reduction and stabilization of MNPs. Considerable research has been directed toward investigating polysaccharide-based metallic nanoparticles (PMNPs) through host–guest strategy. In this review, approaches of preparation, including top-down and bottom-up approaches, are presented and compared. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, dynamic light scattering, UV-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and small-angle X-ray scattering are discussed in detail. Besides, the applications of PMNPs in the field of wound healing, targeted delivery, biosensing, catalysis and agents with antimicrobial, antiviral and anticancer capabilities are specifically highlighted. The controversial toxicological effects of PMNPs are also discussed. This review can provide significant insights into the utilization of polysaccharides as the hosts to synthesize MPNs and facilitate their further development in synthesis approaches, characterization techniques as well as potential applications.

Black soybean seed coat extract (BSSCE) is a rich source of anthocyanins with multiple health effects. This study was aimed at investigating the composition and hypoglycemic and hypolipidemic effects of BSSCE in vitro and in a high-fat diet and streptozotocin (STZ)-induced diabetic mice. The anthocyanins of BSSCE were identified as cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, and peonidin-3-O-glucoside by HPLC-MS. Results demonstrated that BSSCE exhibited strong inhibitory activities for α-amylase, potent inhibition activity against lipid accumulation in HepG2 cells and protection effect on H₂O₂-induced oxidative stress-damaged HepG2 cells. The food and water intake, body weight loss, blood glucose and insulin level of BSSCE treatment group were found to be significantly reduced when compared with those of diabetic mice group (p < 0.05). The fasting blood glucose level and insulin level of the BSSCE 400 mg kg⁻¹ group mice significantly decreased by 47.97% and 46.49%, respectively. The oral glucose tolerance and activities of antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) notably improved (p < 0.05). BSSCE could also ameliorate the atherogenic dyslipidaemia of diabetic mice by remarkably decreasing the content of total cholesterol (T-CHO), total triglyceride (TG), and non-esterified fatty acid (NEFA) and increasing the content of high-density lipoprotein cholesterol (HDL-c) (p < 0.05). BSSCE could protect against liver, kidney and pancreas damages in diabetic mice. This study suggested that cyanidin-3-O-glucoside contributed to BSSCE-induced hypoglycemia and hypolipidemia effects in type 2 diabetes mellitus (T2DM), and BSSCE might be a promising functional food or medicine for T2DM treatment.