Natural products as a basis for new drugs

Isolation and Synthesis of Novel Meroterpenoids from Rhodomyrtus tomentosa: Investigation of a Reactive Enetrione Intermediate

Rhodomyrtusials A-C, the first examples of triketone-sesquiterpene meroterpenoids featuring a unique 6/5/5/9/4 fused pentacyclic ring system were isolated from Rhodomyrtus tomentosa, along with several biogenetically-related dihydropyran isomers. Two bis-furans and one dihydropyran isomer showed acetylcholinesterase (AChE) inhibitory activity. Structures of the isolates were unambiguously established by a combination of spectroscopic data, ECD analysis, and total synthesis. Bioinspired total syntheses of six isolates were achieved in six steps utilizing a reactive enetrione intermediate generated in situ from a readily available hydroxy-endoperoxide precursor.

Nantenine alkaloid presents anticonvulsant effect on two classical animal models

The present study investigated the anticonvulsant and convulsant profiles of nantenine, an aporphine alkaloid found in several vegetal species. At lower doses (20-50 mg/kg, i.p.) the alkaloid proved to be effective in inhibiting pentylenotetrazol- (PTZ 100 mg/kg, s.c.) and maximal electroshock-induced seizures (80 mA, 50 pulses/s, 0.2 s), suggesting its potential as an anticonvulsant drug. However, at higher doses (> or = 75 mg/kg, i.p.) a convulsant activity was observed. Comparing the present in vivo nantenine effects on seizures with previous in vitro biphasic action on Na+, K+-ATPase activity, the convulsant effect appears to be related to inhibition of these phosphatase at high doses whereas anticonvulsant effect, observed at low doses, seems attributable to its stimulation and the resultant decrease of Ca2+-influx into the cell.

The zoapatle III--biological and uterotonic properties of aqueous plant extract

Differences in uterotonic activity were observed between zoapatle Montanoa (Cerv.), plants growing in their natural habitat and plants growing in an experimental agricultural plot. Details of an in vitro analogic model for assaying uterotonic potency in guinea pig strips is described. Important species differences on the uterine response to zoapatle aqueous crude extract were noticed in rats, hamsters, guinea pigs, cats and Rhesus monkeys. The need for proper biological evaluation of chemical substances already isolated from zoapatle specimens, is mentioned, and the advantages of working with zoapatle specimens grown under controlled ecological conditions are pointed out.