Acetylcholinesterase and insect growth inhibitory activities of Gutierrezia microcephala on fall armyworm Spodoptera frugiperda J.E. Smith.

From the aerial parts of Gutierrezia microcephala (Asteraceae), four oxyflavones were isolated, namely 5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone (1); 5,7,4'-trihydroxy-3,6,8-trimethoxyflavone (2); 5,7,2',4'-tetrahydroxy-3,6,8,5'-tetramethoxyflavone (3); 5,2'-dihydroxy-3,6,7,8,4',5'-hexamethoxyflavone (4), and an ent-clerodane, bacchabolivic acid (5). Compounds 1-5, the synthetic methyl ester (6), n-hexane and MeOH extracts were evaluated against the fall armyworm (Spodoptera frugiperda). Gedunin, a known insect growth regulator isolated from Cedrela spp. was used as a positive control. When tested for activity on neonate larvae into the no-choice artificial diet bioassay, flavone (1), clerodane (5), its methyl ester (6), MeOH and n-hexane extracts caused significant larval mortality with MC50 of 3.9, 10.7, 3.46, 7.95 and 7.5 ppm at 7 days, respectively, as well as growth reduction. They also increased the development time of surviving larvae and a significant delay in time to pupation and adult emergence. Acute toxicity against adults of S. frugiperda was also found, 5, 6, gedunin and n-hexane extract had the most potent activity with LD50 value of 6.59, 15.05, 10.78, and 12.79 ppm, respectively. In addition, MeOH, n-hexane extracts, 5, 6 and gedunin caused acetylcholinesterase inhibition with 93.7, 100, 90.2, 62.0 and 100% at 50.0 ppm, respectively; whereas 1-4 exhibited only moderate inhibitory activity. Compounds 1, 5 and 6 showed inhibitory activities comparable with gedunin. These compounds could be responsible of the insect growth inhibitory activity of this plant.

Chromene chalcones from Tephrosia carrollii and the revised structure of Oaracacin.

The aerial parts of Tephrosia carrollii afforded two chromene chalcones. Their structures and stereochemistry were established by spectroscopic methods. The structure of oaxacacin was revised and confirmed by X-ray diffraction. In this paper, we describe the isolation of the chalcone known as "oaxacacin" and the new chalcone named epoxyobovatachalcone. The compound der. oaxacacin was found to be identical with obovatachalcone based on spectroscopic evidence and X-ray diffraction.

Antiviral effect of flavonoids on the dengue virus.

In the present study we analysed the possible antiviral effect on dengue viruses of different flavonoids extracted and identified at the Chemistry Institute, UNAM, from the Mexican plants Tephrosia madrensis, Tephrosia viridiflora and Tephrosia crassifolia. The flavonoids glabranine and 7-O-methyl-glabranine presented 70% inhibition on the dengue virus at a concentration of 25 microM, while methyl-hildgardtol A, hildgardtol A and elongatine had no effect on viral growth. Our results show that glabranine and 7-O-methyl-glabranine isolated from Tephrosia s.p. exert a dose-dependent inhibitory effect in vitro on the dengue virus.

Flavanones and 3-hydroxyflavanones from Lonchocarpus oaxacensis.

The roots of the tropical tree Lonchocarpus oaxacensis afforded the 3-hydroxyflavanones jayacanol and mundulinol, as well as two flavanones, mundulin and minimiflorin. Flavonoids bearing 6,7-(dimethylpyran) and 8-(gammagamma-dimethyl allyl) substituents are characteristic for species grouped in the Minimiflori subsection. Therefore this subsection seems to be chemically and morphologically homogeneous. The antifungal activity of the four isolated compounds was tested against the wood rotting fungus Postia placenta, but only jayacanol was active.

Antitermitic activity ofLonchocarpus castilloi flavonoids and heartwood extracts.

The heartwood of the tropical treeLonchocarpus castilloi Standley (Leguminosae) is highly resistant to attack by the drywood termitesCryptotermes brevis (Walker); nevertheless successive extraction with hexane, diethyl ether, acetone, methanol, and water reduced its resistance to these organisms. Antitermitic properties of the extracts were bioassayed using impregnated filter paper disks. Although the five extracts reduced both feeding and survival ofC. brevis, no significant differences among them were detected. Choice feeding tests showed that termites avoided eating the paper treated with the extracts. Two flavonoid compounds isolated from the heartwood, castillen D and castillen E, impregnated into filter paper showed concentration-dependent feeding deterrent activity, but were not toxic toC. brevis.

Preliminary results on the protective effect of (-)-edunol, a pterocarpan from Brongniartia podalyrioides (Leguminosae), against Bothrops atrox venom in mice.

(-)-Edunol a prenylated pterocarpan was isolated from the roots of two Mexican 'snakeweeds', Brongniartia podalyrioides and B. intermedia (Leguminosae). Edunol (3.1 mg/kg, i.p.) reduced the expected mortality of mice previously treated by the same route with the LD50 of the venom of the serpent Bothrops atrox. The molecular structure and properties of edunol are similar to those previously reported for cabenegrins A-I and A-II.