Physicochemical properties and antioxidant activities of tree peony (Paeonia suffruticosa Andr.) seed protein hydrolysates obtained with different proteases.

The physicochemical and antioxidant properties of tree peony seed protein (TPSP) hydrolysates by Alcalase, Neutrase, Papain, Protamex, and Flavourzyme were investigated in this study. The physicochemical properties were characterized by SDS-PAGE, particle size distribution, fourier transform infrared and fluorescence spectroscopy etc. The antioxidant activities were determined by DPPH radical, ABTS radical, Fe2+ chelating, and reducing power. The results showed five proteases produced hydrolysates with a significantly reduced average particle size, α-helices, and surface hydrophobicity compared to TPSP. Alcalase and Neutrase hydrolysis enhanced the nutritional value of the hydrolysates. Alcalase hydrolysates possessed the highest degree of hydrolysis (27.97%) and lowest molecular weight (<13 kDa) with average particle size (231.33 nm). Alcalase hydrolysate displayed the highest radical scavenging (DPPH IC50 = 0.18 mg/mL, ABTS IC50 = 1.57 mg/mL), Fe2+ chelating activity (IC50 = 0.99 mg/mL), and reducing power (0.594). These results provide the fundamentals for TPSP hydrolysates as antioxidants to be employed in food industry or pharmaceutical industry.

Profiling of neuraminidase inhibitory polyphenols from the seeds of Paeonia lactiflora.

Bacterial neuraminidase (NA) is a lynch pin enzyme in the formation of biofilms. Thus NA continues to be one of the key enzymes targeted by bacterial infection. The purpose of this manuscript is to communicate four new naturally derived inhibitors of neuraminidase (IC50s 3.7-24.4µM). All these active species (1-4) contained a resveratrol chemotype, however resveratrol itself was inactive (IC50>100µM). 1-4 were isolated from the 60% aqueous ethanol extract of seeds of Paeonia lactiflora, which exhibited potent neuraminidase inhibition. Purification of the extracts yielded four chiral polyphenols, suffruticosol A (1), suffruticosol B (2), trans-ε-viniferin (3), and trans-gnetin H (4). Mechanistic analysis of 1-4's inhibition showed that they were all reversible, noncompetitive inhibitors. Trans-ε-viniferin (3) underwent trans-cis isomerization, which led to a reduction in inhibition potency. This correlates with the fact that the cis-isomer is a weaker inhibitor of neuraminidase than the trans-isomer. Importantly, significantly different optical rotations ([α]D) compared to previous reports were found for suffruticosols A (+95 vs -34) and B (+136 vs +13). These two species are the most important standard metabolites in the whole paeoniaceae family and therefore correction of this error is important.