Resumo

GUERRERO, Ricardo O et al. Specific bioassays with selected plants of Bangladesh. Rev Cubana Plant Med [online]. 2004, vol.9, n.2. ISSN 1028-4796.

Summary Bangladesh is an Asian country where only 20 per cent of the people are provided with modern healthcare services while the rest 80 per cent are dependent on traditional plant-based systems. Moreover, it is estimated that only 500 medicinal plant species had been recorded in Bangladesh out of 1,900 species regarded as having medicinal value. Purpose: Sixteen collections of medicinal plants of different families were extracted with several solvents (Ethanol 95%, water, chloroform, ethyl ether). The resulting extracts were subjected to five different specific bioassays: 1. Brine shrimp lethality test; 2. Antioxidant activity; 3. Inhibition of xanthine oxidase (XO); 4. Inhibition of ß-glucosidase, and 5. Inhibition of acetylcholinesterase. Methods. 1.The brine shrimp lethality test (BSLT) was conducted in 96-well microplates using serial dilutions. This examination uses the crustacean Artemia salina Leach and is predictive for cytotoxicity, as well as insecticidal, antifungal, and pesticidal activities. 2. A spectrometric method where the DPPH reagent (2,2-diphenyl-1-picrylhydrazyl), is mixed with serial dilutions of the extracts, was utilized to determine the antioxidant potential. 3. The xanthine oxidase inhibitory activity was measured using a spectrometric procedure. XO is the enzyme that acts as a catalytic agent in the conversion of xanthine to uric acid. Inhibition of this enzyme will decrease the blood levels of uric acid and result in antihyperuricemic effect. 4. The inhibition of ß-glucosidase was determined measuring spectrometrically the amount of liberated p-nitrophenol from the substrate p-nitrophenyl-ß-D-glucopyranoside. ß-glucosidase inhibitors such as castanospermine and 1-deoxynojirimycin interfere with the infectivity of HIV in vitro, as well as with syncytium formation. 5. The acetylcholinesterase inhibition activity was established with a spectrometric method. Inhibitors of this enzyme are valuable in the treatment of Alzheimer's disease and other disorders. Results: In the BSLT bioassay, Aphanamixis polystachya L. showed best activity with LD50 75.0 ppm, suggesting the presence of bioactive compounds in this extract. In the antioxidant bioassay, the same extract obtained an ED50 54.24 ppm. Other extracts that showed excellent free radical scavenging activity were Emblica officinalis Gaertn. (Syn. Phyllanthus emblica L.), ED50 132.16 ppm and Shorea robusta Gaertn., ED50 151.62 ppm. The XO inhibition produced several interesting results: best activity was shown by Shorea robusta Gaertn.: 60 % of inhibition, whereas Emblica officinalis Gaertn. displayed 48 % inhibition. Inhibition of the ß-glucosidase enzyme generated acceptable results: 63 % and 45 % with the extracts of S. robusta and E. officinalis, respectively. Finally, in the acetylcholinesterase inhibition, none of the plant extracts showed positive results. Conclusions. As demonstrated by the data, there are some extracts that presented several biological activities. It will be necessary to pursue further investigation to bring about the identification of the responsible metabolites for these activities.

Palavras-chave : Bangladesh; plant extracts; brine shrimp lethality test; antioxidant activity; xanthine oxidase inhibition; ß-glucosidase inhibition; acetylcholinesterase inhibition.