Investigating on the Correlation Between Some Biological Activities of Marine Sponge-Associated Bacteria Extracts and Isolated Diketopiperazines.

Marine organisms have been considered as the richest sources of novel bioactive metabolites, which can be used for pharmaceutical purposes. In the last years, the interest for marine microorganisms has grown for their enormous biodiversity and for the evidence that many novel compounds isolated from marine invertebrates are really synthesized by their associated bacteria. Nevertheless, the discovery of a chemical communication Quorum sensing (QS) between bacterial cells and between bacteria and host has gained the researchers to expand the aim of their study toward the role of bacteria associated with marine invertebrates, such as marine sponge. In the present paper, we report the evaluation of biological activities of different extracts of bacteria Vibrio sp. and Bacillus sp. associated with marine sponges Dysidea avara and Ircinia variabilis, respectively. Moreover, we evaluated the biological activities of some diketopiperazines (DKPs), previously isolated, and able to activate QS mechanism. The results showed that all extracts, fractions, and DKPs showed low scavenging activity against DPPH and superoxide anion, low cytotoxic and anti-tyrosinase activities, but no antimicrobial and acetylcholinesterase inhibitory activities. One DKP [cyclo-(trans-4-hydroxy-L-prolyl-L-leucine)] has the highest α-glucosidase inhibitory activity even than the standard acarbose.

Antioxidant activity and bioactive compound contents before and after in vitro digestion of new tomato hybrids.

BACKGROUND: The antioxidant properties and bioactive compound contents of fresh new tomato hybrids before and after in vitro digestion were investigated. To this aim, the antioxidant activities of lipophilic, hydrophilic and polyphenolic extracts of tomato hybrids were determined by ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), DMPD (N,N-dimethyl-p-phenylenediamine dihydrochloride) and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods respectively, while the bioactive compound contents were estimated via Folin-Ciocalteu (polyphenols), pH differential (anthocyanins) and high-performance liquid chromatography (lycopene and ß-carotene) methods. RESULTS: After the digestion process, a marked loss (ranging from 37 to 77%) of antioxidant capacity linked to the hydrophilic fraction was observed. In contrast, the lipophilic and methanolic fractions showed an increase in antioxidant activity (ranging from 9 to 40%) after gastric digestion, and a rapid decrease was observed after total digestion. Moreover, the presence of anthocyanins and carotenoids after simulated digestion was a notable result. CONCLUSION: The bioavailability of bioactive metabolites from nutraceutical food and their healthful properties in humans are strictly dependent on the digestion process. © 2017 Society of Chemical Industry.