Insights into the Unusual Activity of a Novel Homospermidine Synthase with a Promising Application to Produce Spermidine.

Spermidine is a naturally occurring polyamine with multiple biological activities and potential food and agricultural applications. However, sustainable and scalable spermidine production has not yet been attained. In this study, a homospermidine synthase (HSS) from Pseudomonas frederiksbergensis (PfHSS) capable of catalyzing the synthesis of spermidine from 1,3-diaminopropane and putrescine was identified based on multiple sequence alignment using Blastochloris viridis HSS (BvHSS) as a template. The optimal reaction pH and temperature for purified PfHSS were determined to be 8.5 and 45 °C, respectively, and K+ was able to promote the enzyme activity. Further analysis of the structural and functional relationships through molecular docking and molecular dynamics simulation indicates that glutamic acid at position 359 is the essential residue for the enzyme-catalyzed synthesis of spermidine. The whole-cell catalytic reaction yielded 1321.4 mg/L spermidine and 678.2 mg/L of homospermidine. This study presents a novel, promising, and sustainable biological method for producing spermidine.

Quantitative analysis of resveratrol derivatives in the seed coats of tree peonies and their hypoglycemic activities in vitro/vivo.

Tree peonies are well-known horticultural and medicinal plants. The tree peony seeds, as emerging woody oil crops, recently have attracted great attention for their metabolites and bioactivities. In this study, the phytochemicals isolated from tree peony seed coats were systematically investigated. Seven polyphenolics were separated and prepared, mainly belonging to resveratrol derivatives. There was a great variation in the seed coat polyphenolic content among eight Paeonia species, and the contents of the resveratrol trimers and dimers were significantly higher in the seed coats of Paeonia ostii than other species. Based on the HPLC fingerprint characteristics and chemometric analysis, a clear discrimination among Paeonia plants was found, including the composition patterns and contents of the constituents. Moreover, the characteristic phytochemicals (vateriferol and trans-ε-viniferin) could significantly reduce the starch-mediated levels of postprandial blood glucose in diabetic/normal mice. In addition, in vitro enzyme tests showed that the two compounds could effectively and competitively inhibit α-glucosidase, with the IC50 values of 3.01 and 7.75 µM, respectively, indicating that vateriferol and trans-ε-viniferin could be therapeutic potential agents for hyperglycemia and diabetes mellitus.