Pumpkin Skin Polysaccharide–Zn(II) Complex: Preparation, Characterization, and Suppression of Inflammation in Zebrafish

In this study, pumpkin (Cucurbita moschata) skin polysaccharide-zinc(II) (PSP-Zn) complex was successfully prepared. The structure and physicochemical properties of PSP and PSP-Zn were analyzed. The anti-inflammatory activity of PSP and PSP-Zn was investigated in zebrafish larvae induced by copper sulphate. PSP and PSP-Zn consisted of rhamnose, arabinose, galactose, glucose, and galacturonic acid. The molecular weight (Mw) of PSP and PSP-Zn were 3.034 × 106 and 3.222 × 106 Da, respectively. Fourier transform infrared spectrum (FT-IR) and circular dichroism (CD) analysis results suggested that the chemical modification of zinc might occur through hydroxyl groups of PSP. The PSP-Zn complex had lamellar texture, smooth surface morphology, and larger particle size. X-ray Diffraction (XRD) analysis revealed that both PSP and PSP-Zn were semi-crystalline substances. PSP-Zn solution showed superior stability in a weak acid and alkaline environment, especially at pH = 6.0. Moreover, PSP and PSP-Zn showed a good inhibitory effect on inflammation cells in zebrafish. Real-time quantitative polymerase chain reaction (RT-PCR) result suggested that the anti-inflammatory mechanism of PSP and PSP-Zn were through downregulation of the expression of nitric oxide synthase 2b (nos2b), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and nuclear factor-kappa B2 (NF-κB2). The present study indicated that PSP-Zn is expected to be a safe and efficient novel zinc supplement with anti-inflammatory activity.