Bioassay screening of Amazonian plants.
OBJECTIVE
The purpose of this study was to evaluate several biological activities of thirty plant extracts collected in the North West Amazon (Ecuador). Some of these plants are being used for their reputed medicinal properties by the natives of this region.


METHODS
Five in vitro bioassays were used to screen the plant material. 1. The brine shrimp lethality examination (BSLT) in microplate is a general test that seems capable of detecting a broad spectrum of bioactivity present in crude plant extracts. 2. Free radical scavenging properties were studied in a colorimetric assay using 2,2-diphenyl-1-picrylhydrazyl (DPPH). 3. The beta-glucosidase inhibition test is thought to be a method for the evaluation of anti-AIDS, anti-diabetic or anti-obesity compounds. 4. The xanthine oxidase inhibition assay is used to identify potential anti-gout agents. 5. The antibacterial activity that is being used to isolate and identify antibiotic drugs.


RESULTS
In the BSLT, we found that Piscidia carthagenensis demonstrated very good activity with a LC50: 21.81 micrograms/mL. It is considered that plant extracts with low LC50 values may contain metabolites with cytotoxic, antifungal, insecticidal or pesticide activities. In the antioxidant activity bioassay, several plant extracts were confirmed to have excellent free radical scavenging properties. Rhus juglandifolia and Clusia venusta leaves exhibited an ED50: 3.12 micrograms/mL and 3.61 micrograms/mL, respectively. Piper reticulatum (84%), Inga heteroptera (77%), Clusia venusta (70.9%), and Rhus juglandifolia (70.5%) showed fairly good inhibition activity for beta-glucosidase. On the other hand, none of the plant extracts was capable of inhibiting xanthine oxidase. Finally, the Gram-positive microorganisms Staphylococcus aureus and Corynebacterium diphteriae were found to be sensitive to the majority of the plant extracts, whereas the Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, and Salmonella typhi were proved to be resistant toward the plant extracts.


CONCLUSIONS
It is important to continue investigating our plant kingdom, especially the world tropical reserves as an alternative for finding new or better drugs. It should be essential to follow-up this type of investigation to isolate and elucidate the active principles of the bio-positive plants.
Guerrero
Ricardo O
RO
Department of Pharmaceutical Sciences, School of Pharmacy, University of Puerto Rico, P.O. Box 365067, San Juan, PR 00936-5067. rguerrero@rem.upr.edu
Rivera
Sharon M
SM
Rivera
Sulay
S
Sueiro
Lilly Ann
LA
D000818:Animals; D001156:Artemia / Q000187:drug effects; D001681:Biological Assay; D001713:Biphenyl Compounds; D003124:Colorimetry; D004353:Drug Evaluation, Preclinical; D004484:Ecuador; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006834:Hydrazines; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction; D010851:Picrates; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D010946:Plants, Medicinal / Q000737:chemistry* / Q000633:toxicity; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors
D001713:Biphenyl Compounds; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D006834:Hydrazines; D010851:Picrates; D010936:Plant Extracts; C004931:1,1-diphenyl-2-picrylhydrazyl; D014969:Xanthine Oxidase; D001617:beta-Glucosidase