Micellar effects and analytical applications of nitro substitution in 4-Nitro-N-alkyl-1,8-naphthalimide by cysteine derivatives.

The aromatic nucleophilic substitution reactions of the nitro group of 4-Nitro-N-alkyl-1,8-naphthalimides by thiolate anions produce fluorescent derivatives and their rates are strongly accelerated by micelles of hexadecyltrimethylammonium chloride even at low pH. Acceleration factors of this reactions can reach million-fold. As the products are oxidant-insensible, this reaction allows the determination of SH- containing compounds such as cysteine, glutathione or proteins even in oxidative conditions. Limits of detection are as low as 5 × 10-7 M, ten times lower than the limit for the classic 5,5'-dithiobis-(2-nitrobenzoic) acid method. Moreover, this reaction can be developed at pHs between 6.5 and 7.5 thereby diminishing the rate of spontaneous oxidation of the thiols. In addition, we demonstrated that 4-Nitro-N-alkyl-1,8-naphthalimides can be used to evidence SH groups in peptides, proteins and living cells.

Central nervous system activity of yangambin from Ocotea duckei Vattimo (Lauraceae) in mice.

This work presents behavioral effects of yangambin isolated from the leaves of Ocotea duckei on open field, rota rod, barbiturate sleeping time, forced swimming and elevated plus maze test in mice. Yangambin was intraperitoneally administered to male mice at single doses of 12.5, 25 and 50 mg/kg. The results showed that yangambin in the doses of 25 and 50 mg/kg decreased the locomotor activity and the number of rearing. However, no change was observed in the rota rod test between the yangambin groups as compared to the control group. Reduction on the sleep latency and a prolongation of the sleeping time induced by pentobarbital was observed only with the yangambin dose of 50 mg/kg. In the forced swimming test, yangambin (25 and 50 mg/kg) increased the immobility time. Yangambin, in the doses of 25 and 50 mg/kg, decreased the number of entries and the time of permanence in the open arms of the elevated plus maze test. However, this effect can not be related to anxiogenic effects, but to a decrease in locomotor activity. The results showed that yangambin presents a depressant activity in the open field, forced swimming and pentobarbital sleeping time tests. These effects probably were not due to peripheral neuromuscular blockade, since there was no alteration on the rota rod test. Also, no anxiolytic effect was observed after the treatment with yangambin.