Phenolic profile and antioxidant activity from peels and seeds of melon (Cucumis melo L. var. reticulatus) and their antiproliferative effect in cancer cells.

Melon (Cucumis melo L.) has high economic value and in recent years, its production has increased; however, part of the fruit is wasted. Usually, inedible parts such as peel and seeds are discarded during processing and consumption. Extracts of melon residues were prepared and their phenolic compounds, antioxidants and antiproliferative activities were evaluated. Total phenolic compounds were found in hydroethanolic, hydromethanolic, and aqueous extracts, especially for melon peel (1.016 mg gallic acid equivalent/100 g). Flavonoids total content found for melon peel aqueous extract was 262 µg of catechin equivalent (CA)/100 g. In all extracts of melon peel significant amounts of gallic acid, catechin, and eugenol were found. For total antioxidant capacity, reported as ascorbic acid equivalent, the hydroethanolic and hydromethanolic extracts in peels and hydromethanolic in seeds were 89, 74, and 83 mg/g, respectively. Different extracts of melon showed iron and copper ions chelating activity at different concentrations, especially melon peel aqueous extract, reaching values of 61% for iron and 84% for copper. The hydroethanolic extract of melon peel presented a significant ability for hydroxyl radicals scavenging (68%). To assess the antiproliferative potential in human cancer cell lines, such as kidney carcinoma, colorectal carcinoma, cervical adenocarcinoma and cervical carcinoma, MTT assay was performed. The proliferation was inhibited by 20-85% at extracts concentrations of 0.1-1.0 mg/mL in all cancer cell lines. The results suggest that melon residues extracts display a high antioxidant activity in in vitro assays and have effective biological activity against the growth of human tumor cells.

Biological activities of sulfated polysaccharides from tropical seaweeds.

Sulfated polysaccharides from 11 species of tropical marine algae (one edible specie of Rhodophyta, six species of Phaeophyta and four species of Chlorophyta) collected from Natal city coast (Northeast of Brazil) were evaluated for their anticoagulant, antioxidant and antiproliverative in vitro activities. In the activated partial thromboplastin time (APTT) test, which evaluates the intrinsic coagulation pathway, seven seaweeds presented anticoagulant activity. Dictyota cervicornis showed the highest activity, prolonging the coagulation time to double the baseline value in the APTT with only 0.01 mg/100 microl of plasma, 1.4-fold lesser than Clexane, a low molecular weight heparin. In the protrombin time (PT) test, which evaluates the extrinsic coagulation pathway, only Caulerpa cupresoides showed anticoagulant activity. All species collected showed antioxidant activities. This screening emphasized the great antioxidant potential (total capacity antioxidant, power reducing and ferrous chelating) of four species: C. sertularioide; Dictyota cervicornis; Sargassum filipendula and Dictyopteris delicatula. After 72 h incubation, HeLa cell proliferation was inhibited (p<0.05) between 33.0 and 67.5% by S. filipendula; 31.4 and 65.7% by D. delicatula; 36.3 and 58.4% by Caulerpa prolifera and 40.2 and 61.0% by Dictyota menstrualis at 0.01-2mg/mL algal polysaccharides. The antiproliferative efficacy of these algal polysaccharides were positively correlated with the sulfate content (r=0.934). Several polysaccharides demonstrated promising antioxidant, antiproliferative an/or anticoagulant potential and have been selected for further studies on bioguided fractionation, isolation and characterization of pure polysaccharides from these species as well as in vivo experiments are needed and are already in progress.