Subchronic toxicity and anti-HSV-1 activity in experimental animal of dolabelladienetriol from the seaweed, Dictyota pfaffii.

This study examined in rats the subchronic toxicity and anti- HSV-1activity after oral administration of dolabelladienetriol (D1), a diterpene isolated from the seaweed Dictyota pfaffii. In subchronic toxicity (SCT) tests, female rats received D1 by gavage 15 mg/kg/day (n = 5) for 50 days, and general behavior, death, hematological, biochemical and histological changes in the liver, kidney, stomach, and duodenum were determined. For the anti-HSV-1 activity, female mice were infected and treated orally with a dose of 20 mg/kg (n = 5) twice a day with D1 and any lesions in the skin were then recorded for 18 days. Dolabelladienetriol in SCT did not significantly change behavior, body weight, hematological or biochemical profiles. The liver and kidneys, however, showed some alterations in rats treated with D1, similar to those in rats treated with ACV, while the other tissues had no significant changes. The anti-HSV-1 activity of D1 had a similar efficacy to the ACV drug control in mice. Our results showed that D1 has potential commercial development as a new HSV-1drug.

Inhibitory effect of a Brazilian marine brown alga Spatoglossum schröederi on biological activities of Lachesis muta snake venom

The ability of crude extracts of the brown seaweed Spatoglossum schröederi to counteract some of the biological activities of Lachesis muta snake venom was evaluated. In vitro assays showed that only the extract of S. schröederi prepared in ethyl acetate was able to inhibit the clotting of fibrinogen induced by L. muta venom. On the other hand, all extracts were able to inhibit partially the hemolysis caused by venom and those prepared in dichloromethane or ethyl acetate fully neutralized the proteolysis and hemorrhage produced by the venom. Moreover, the dichloromethane or ethyl acetate extracts inhibited the hemolysis induced by an isolated phospholipase A2 from L. muta venom, called LM-PLA2-I. In contrast, the hexane extract failed to protect mice from hemorrhage or to inhibit proteolysis and clotting. These results show that the polarity of the solvent used to prepare the extracts of S. schröederi algae influenced the potency of the inhibitory effect of the biological activities induced by L. muta venom. Thus, the seaweed S. schröederi may be a promising source of natural inhibitors of the enzymes involved in biological activities of L. muta venom.

Marine natural seaweed products as potential antiviral drugs against Bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is an etiologic agent that causes important economic losses in the world. It is endemic in cattle herds in most parts of the world. The purpose of this study was to evaluate the in vitro cytotoxic effect and antiviral properties of several marine natural products obtained from seaweeds: the indole alkaloid caulerpin (CAV, 1) and three diterpenes: 6-hydroxydichotoma-3,14-diene-1,17-dial (DA, 2), 10,18-diacetoxy-8-hydroxy-2,6-dolabelladiene (DB1, 3) and 8,10,18-trihydroxy-2,6-dolabelladiene (DB3, 4). The screening to evaluate the cytotoxicity of compounds did not show toxic effects to MDBK cells. The antiviral activity of the compounds was measured by the inhibition of the cytopathic effect on infected cells by plaque assay (PA) and EC50 values were calculated for CAV (EC=2,0± 5.8), DA (EC 2,8± 7.7), DB1 (EC 2,0±9.7), and DB3 (EC 2,3±7.4). Acyclovir (EC50 322± 5.9) was used in all experiments as the control standard. Although the results of the antiviral activity suggest that all compounds are promising as antiviral agents against BVDV, the Selectivity Index suggests that DB1 is the safest of the compounds tested.

Allelopathic potential of extracts the from marine macroalga Plocamium brasiliense and their effects on pasture weed

Four extracts from the marine red alga Plocamium brasiliense (Greville) M.A.Howe & W.R.Taylor were prepared to identify and characterize their potential allelopathic effects on seed germination, radicle elongation and hypocotyl development of the weeds Mimosa pudica L. and Senna obtusifolia (L.) Irwin & Barneby. The four extracts were prepared in a sequence of solvents of increasing polarity: n-hexane, dichloromethane, ethyl acetate and ethanol/water (7:3). The germination bioassay was carried out at 25 °C with a 12 h photoperiod and the radicle elongation and hypocotyl development at 25 °C with a 24 h photoperiod. The dichloromethane extract showed inhibitory effects on seed germination of both plants (35 and 14%, respectively, in M. pudica and S. obtusifolia), radical germination (52 and 41.7%, respectively) and hypocotyl development (17.1 and 25.5%, respectively). Given the high sensitivity of this parameter to the potential allelopathic effects and the insufficient number of references found in the literature, these results are expected to stimulate new tests with other species of marine algae. Given the high sensitivity of the method for the detection of allelopathic potential, the species P. brasiliense emerges as a possible source of allelopathic substances against weed species. The results are attributed to the chemical composition, especially in relation to the presence of halogenated monoterpenes.

Evaluation of the acute toxicity of dolabelladienotriol, a potential antiviral from the brown alga Dictyota pfaffii, in BALB/c mice

Dolabelladienotriol is a product extracted from the brown marine alga Dictyota pfaffii from Brazil that has been shown to have antiviral activity and low cytotoxicity. Our studies have evaluated the acute toxicity of dolabelladienotriol in BALB/c mice for ten days after administration of a single dose. Among the parameters considered were behavior, weight, biochemical and histological analyses of blood samples taken at three different times (Bs.0, Bs.1 and Bs.2) and optical microscopic examination of organs like liver, kidney, stomach and small intestine. Mice deaths were not observed at any dose during the ten day period. There were some changes in the biochemical analysis results for urea nitrogen (BUN) and alanine aminotransferase (ALT), but the changes were not significantly different from the reference levels of the animals before administration of the substance. Histological analyses of tissues were very similar for all animals. The alterations in liver and kidney tissues did not affect the animals´ behavior at any concentration, not even at 50 mg/kg, where the most significant changes in tissues were seen. This study indicates that dolabelladienotriol has low toxicity in administered dose range.