Halophytes as a potential source of melanosis-inhibiting compounds. Mechanism of inhibition of a characterized polyphenol extract of purslane (Portulaca oleracea)

Abstract

The market value of crustaceans depreciates during storage due to the appearance of melanosis caused by polyphenol oxidases. Sulfite derivatives are used as melanosis-inhibiting agents, but their unhealthy effects make it preferable to replace them with natural preservatives. In this work, a crude enzymatic extract from whiteleg shrimp (Penaeus vannamei) was characterized and used to test the diphenol oxidase-inhibiting activity of polyphenol extracts of five underutilized halophyte plants, namely crystalline ice plant, seaside arrowgrass, purslane, sea fennel, and seashore aster. The extracts inhibited diphenol oxidase activity more efficiently than sodium sulfite. The purslane extract was rich in isoorientins, isovitexin, and apigenin, and showed the highest inhibiting effect, being this classified as mixed or non-competitive. Hydroxyl groups in the phenyl B ring could be responsible for the inhibitory activity of the extract. The polyphenol extracts tested in this work could be promising melanosis-inhibiting agents of interest for seafood industries. ; This work was supported by the Spanish Ministry of Economy and Competitiveness project (grant number AGL2014-52825-R) and cofounded with European Union ERDF funds (European Regional Development Fund). Author A. Tzamourani was funded by the Erasmus Program. ; Peer reviewed