Quimica

The ethyl acetate extract of the roots of Moutabea guianensis gave 1,6dihydroxy-4,7,8-trimethoxy-9H-xanthen-9-one (1), a new xanthone. The isolation was accomplished by column chromatography on silica gel and the structural elucidation of this compound was established by spectroscopic analyses including 1D and 2D NMR and HRESIMS.

The aim of this study was to evaluate the phytotoxic effects of dihydrochalcones obtained by biotransformation reactions of the corresponding chalcones, promoted by the endophytic fungus Aspergillus flavus. The compounds 3,4,5-trimethoxydihydrochalcone (1a) and 2,3,4,4'-tetramethoxydihydrochalcone (2a) obtained from their corresponding chalcones (1 and 2) were submitted to the bioassays monitored under controlled temperature of 25 o C and photoperiod of 12 hours. For bioassays were used as test plants two invasive species, Mimosa pudica L. (malícia) e Senna obtusifolia (L.) Irwin & Barneby (matapasto), belonging to the Fabaceae family. The phytotoxic effects of dihydrochalcones were analyzed at concentrations of 80 and 160 mg L-1. Substances 1a and 2a, at a concentration of 160 mg L-1 , showed significant inhibitions, respectively, 54% and 65% , against the germination of the species M. pudica. Inhibitions of 61% and 49% of M. pudica radicle growth were observed, respectively, to compounds 1a and 2a at concentration 160 mg L-1. In the bioassays performed, no significant phytotoxic activity of the tested substances was observed, at concentrations of 80 and 160 mg L-1 on the weed S. obtusifolia.

Endopleura uchi (Huber) Cuatrec. (Humiriaceae), a Brazilian Amazon plant, is used in folk medicine for the treatment of arthritis. Bergenin, one of the chemical constituents of E. uchi, has several biological activities, including anti-inflammatory properties. Acetylbergenin was obtained from acetylation of bergenin to investigate the antinociceptive effect assessed in models of nociception in mice. This compound dosed at 1, 5, 10, 15 and 25 mg/kg in the writhing test reduced the abdominal constrictions in a significant manner, in 28.2 %, 52.7 %, 61.1 %, 68.3 % and 95.0 %, respectively with ED50 of 6.8 mg/kg. Acetylbergenin in the hot plate test was assayed at 6.8 mg/kg producing no alterations in the latency time when compared to the control. It was tested at 6.8 mg/kg in the formalin test inhibiting significantly the second phase of the algic stimulous, in 88.3 %. These results suggest that acetylbergenin has analgesic activity, probably of peripheral origin. The mechanism involved is not completely understood, however, the results suggest that the opioid system must be involved in the antinociceptive action.

This study aimed establish the variations in the phytotoxic activity of hexane, ethyl acetate and methanol extracts of Moutabea guianensis, and methyl caffeate and scopoletin isolated from the ethyl acetate extract, variyng the concentration and the receptor species. Phytotoxic activity bioassays of germination (at 25 °C and 12 hours of photoperiod) and development of radicle and hypocotyl (25 °C and 24 hours of photoperiod) were developed. The seed germination of Mimosa pudica was sensitive to the roots hexane, ethyl acetate and methanol extracts at 1% (w/v), with inhibition potentials in 92%, 100% and 100%, respectively. Comparative analysis on the phytotoxic activity of the tested compounds revealed that scopoletin showed a higher inhibition potential on the seed germination bioassay against Mimosa pudica. Senna obtusifolia was not sensitive to the tested compounds. Methyl caffeate showed the highest potential to inhibit the development of radicle and hypocotyls, and the intensit...