Potential of synthetic chalcone derivatives to prevent marine biofouling.

Biofouling represents a major economic, environmental and health concern for which new eco-friendly solutions are needed. International legislation has restricted the use of biocidal-based antifouling coatings, and increasing efforts have been applied in the search for environmentally friendly antifouling agents. This research work deals with the assessment of the interest of a series of synthetic chalcone derivatives for antifouling applications. Sixteen chalcone derivatives were synthesized with moderate yields (38-85%). Antifouling bioactivity of these compounds was assessed at different levels of biological organization using both anti-macrofouling and anti-microfouling bioassays, namely an anti-settlement assay using mussel (Mytilus galloprovincialis) larvae, as well as marine bacteria and microalgal biofilms growth inhibition bioassays. Results showed that three compounds (11, 12, and 16) were particularly active against the settlement of mussel larvae (EC50 7.24-34.63 µM), being compounds 12 and 16 also able to inhibit the growth of microfouling species (EC50 4.09-20.31 µM). Moreover, the most potent compounds 12 and 16 were found to be non-toxic to the non-target species Artemia salina (<10% mortality at 25 µM). A quantitative structure-activity relationship model predicted that descriptors describing the ability of molecules to form hydrogen bonds and encoding the shape, branching ratio and constitutional diversity of the molecule were implied in the antifouling activity against the settlement of mussel larvae. This work elucidates for the first time the relevance of synthesizing chalcone derivatives to generate new non-toxic products to prevent marine biofouling.

The natural prenylated flavone artelastin is an inhibitor of ROS and NO production.

Artelastin, a prenylated flavone previously isolated from Artocarpus elasticus, was evaluated for its effect on the production of reactive oxygen species (ROS) by human polymorphonuclear neutrophils (PMNs) and nitric oxide (NO) by J774 murine macrophage cell line. Artelastin showed to be an inhibitor of ROS production due to a strong O2- scavenging activity. No effect was observed on the activity of myeloperoxidase (MPO). Artelastin showed also to be an inhibitor of NO production without NO scavenging activity. This flavone seems to interfere with the expression of the inducible nitric oxide synthase (iNOS) immediately after LPS-IFNgamma-macrophage stimulation.

Inhibition of lymphocyte proliferation by prenylated flavones: artelastin as a potent inhibitor.

Eight natural prenylated flavones, previously isolated from Artocarpus elasticus, were evaluated for their effect on the mitogenic response of human lymphocytes to PHA. They all exhibited a dose-dependent suppression effect. An interesting relationship was observed between their antiproliferative activity and their chemical structure. Indeed, the most potent flavones possessed a 3,3-dymethylallyl group (prenyl) at C-8, such as artelastin, which exhibited the highest antiproliferative activity. Studies of the mechanism underlying its effect revealed that artelastin had an irreversible inhibitory effect on the PHA-induced lymphocyte proliferation and could affect the course of the ongoing mitogenic response either at the initial induction phase or at the late phase of proliferation. This prenylated flavone was also shown to be a potent inhibitor of both T- and B-lymphocyte mitogen induced proliferation although B-mitogenic response was the more sensitive one. Artelastin did not affect either the basal levels of the early marker of activation CD69 on non-stimulated splenocytes or its expression on ConA- or LPS-stimulated splenocytes. However, it decreased the production of IFN-gamma, IL-2, IL-4 and IL-10 in ConA-stimulated splenocytes. Furthermore, artelastin had no effect on apoptosis of splenocytes.

Artelastocarpin and carpelastofuran, two new flavones, and cytotoxicities of prenyl flavonoids from Artocarpus elasticus against three cancer cell lines.

Further study of one of the fractions from the wood of Artocarpus elasticus furnished two new prenylated flavonoids artelastocarpin and carpelastofuran as well as ethyl 2,4-dihydroxybenzoate. The two flavonoids and the prenylated flavonoids artelastin, artelastochromene, artelasticin, artocarpesin, and cyclocommunin isolated earlier from this species were tested for cytotoxicity in vitro against three human cell lines. All seven flavonoids were active, the cytotoxic effect varying from strong to moderate and with artelastin showing the most potent activity.

Immunomodulatory Activity of Xanthones from Calophyllum teysmannii var. inuphylloide.

Nine xanthones, including 3-(4-hydroxy-3-metnylbutyl)-4,8-dihydroxyxanthone, were isolated from the wood of a Thai collection of CALOPHYLLUM TEYSMANNII Miq. var. INUPHYLLOIDE (King) P. Stephen. Immunomodulatory activities of eight of these have been investigated.