Pseudostellarin A

Antamanide Analogs as Potential Inhibitors of Tyrosinase.[Pubmed:35682928]

Int J Mol Sci. 2022 Jun 2;23(11):6240.

The tyrosinase enzyme, which catalyzes the hydroxylation of monophenols and the oxidation of o-diphenols, is typically involved in the synthesis of the dark product melanin starting from the amino acid tyrosine. Contributing to the browning of plant and fruit tissues and to the hyperpigmentation of the skin, leading to melasma or age spots, the research of possible tyrosinase inhibitors has attracted much interest in agri-food, cosmetic, and medicinal industries. In this study, we analyzed the capability of antamanide, a mushroom bioactive cyclic decapeptide, and some of its glycine derivatives, compared to that of Pseudostellarin A, a known tyrosinase inhibitor, to hinder tyrosinase activity by using a spectrophotometric method. Additionally, computational docking studies were performed in order to elucidate the interactions occurring with the tyrosinase catalytic site. Our results show that antamanide did not exert any inhibitory activity. On the contrary, the three glycine derivatives AG9, AG6, and AOG9, which differ from each other by the position of a glycine that substitutes phenylalanine in the parent molecule, improving water solubility and flexibility, showed tyrosinase inhibition by spectrophotometric assays. Analytical data were confirmed by computational studies.

Synthesis of Natural Cyclopentapeptides Isolated from Dianthus chinensis.[Pubmed:27326468]

J Nat Prod. 2016 Jul 22;79(7):1769-74.

The first syntheses of the naturally occurring cyclic peptides dianthin I (1), Pseudostellarin A (2), and heterophyllin J (3) are described. The linear protected peptide precursors were prepared efficiently via Fmoc-solid-phase synthesis and subsequently cyclized in solution under dilute conditions. The structures of the synthetic cyclopentapeptides were confirmed by NMR spectroscopy and mass spectrometry and were in agreement with the literature data reported for the natural products.

HPLC-ESI-MS(n) Analysis, Fed-Batch Cultivation Enhances Bioactive Compound Biosynthesis and Immune-Regulative Effect of Adventitious Roots in Pseudostellaria heterophylla.[Pubmed:26137876]

Appl Biochem Biotechnol. 2015 Sep;177(1):63-75.

A electrospray ionization tandem mass spectrometry (ESI-MS(n)) analysis was performed in order to identify the active composition in Pseudostellaria heterophylla adventitious roots. Pseudostellarin A, C, D, and G were identified from P. heterophylla adventitious roots on the basis of LC-MS(n) analysis. The culture conditions of adventitious roots were optimized, and datasets were subjected to a partial least squares discriminant analysis (PLS-DA), in which the growth ratio and some compounds showed a positive correlation with an aeration volume of 0.3 vvm and inoculum density of 0.15 %. Fed-batch cultivation enhanced the contents of total saponin, polysaccharides, and specific oxygen uptaker rate (SOUR). The maximum dry root weight (4.728 g l(-1)) was achieved in the 3/4 Murashige and Skoog (MS) medium group. PLS-DA showed that polysaccharides contributed significantly to the clustering of different groups and showed a positive correlation in the MS medium group. The delayed-type hypersensitivity (DTH) reaction on the mice induced by 2,4-dinitrofluorobenzene (DNFB) was applied to compare the immunocompetence effects of adventitious roots (AR) with field native roots (NR) of P. heterophylla. As a result, AR possessed a similar immunoregulation function as NR.

Cyclopentapeptides from Dianthus chinensis.[Pubmed:25869116]

J Pept Sci. 2015 Jul;21(7):550-3.

A new cyclopentapeptide dianthin I (1), together with two known ones Pseudostellarin A (2) and heterophyllin J (3), was isolated from the aerial parts of Dianthus chinensis. The structure of 1 was elucidated as cyclo-(Gly(1)-L-Phe(2)-L-Pro(3)-L-Ser(4)-L-Phe(5)) on the basis of extensive spectroscopic analyses and chemical methods.