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.

Efceto Hipoglicemiante de Costus Speciosus (Zingiberaceae), en ratas / Hipoglycemic effect of Costus Specius (Zingiberaceae), on rats

Durante muchos siglos la gente ha usado plantas con propiedades medicinales para el tratamiento de diversas enfermedades. Una de estas enfermedades es diabetes mellitus. Una de las plantas usadas ampliamente por la población en Puerto Rico es Costus speciosus conocida vulgarmente como insulina. El objetivo principal de este estudio fue analizar las propiedades hipoglicemiantes que se le atribuyen al extracto de esta planta. Con estos fines se llevaron a cabo experimentos con ratas Sprague Dawley, a las cuales se les había inducido diabetes por medio de la inyección de estreptozotocina i.p. A un grupo de diez de estas ratas en ayunas (Grupo A) se le dio a tomar el extracto por 24 horas, mientras que a otro grupo testigo de diez ratas (grupo B) se le administró agua. El grupo A tuvo niveles de glucosa sanguínea significativamente inferiores a las ratas del grupo testigo. En otro experimento se incubaron células endoteliales con o sin el extracto de la planta en presencia de 2-desoxi-3H-glucosa (DG). Hubo una mayor captación de DG en las células que contenían el extracto de la planta. Esto indica que el extracto contiene algún o algunos compuestos que facilitan la entrada de glucosa a las células cuya acción es similar a la de insulina. En los ensayos de toxicidad general usando Artemia salina L., el valor CL50 18.45 :g/mL demuestra la presencia de uno o varios agentes farmacológicamente activos en el extracto. En conclusión, el extracto de Costus speciosus muestra un efecto hipoglicemiante en ratas diabéticas inducidas con estreptozotocina. Además, el extracto de esta planta estimula la captación de DG en las células endoteliales

Inhibition of xanthine oxidase by Puerto Rican plant extracts

OBJECTIVES: This study was conducted to search for xanthine oxidase inhibitors in natural products obtained from plants collected in Puerto Rico and to assess the influence of these extracts in the prevention of cataractogenesis. BACKGROUND: Allopurinol is currently a xanthine oxidase inhibitor used in the treatment of gout. New alternatives with increased therapeutic activity and less side effects should be investigated. Preclusion of cataractogenesis in diabetic rats is also the focus of this investigation. Natural products in the form of plant extracts from Puerto Rico offer a rich and relatively untapped source for the discovery of new drugs that may address these kind of problems. METHODS: Nineteen collections of Myrtaceae plant extracts were screened for xanthine oxidase inhibition. A spectrophotometrical method was used employing allopurinol as positive control and a blank as negative control. A protocol of the assay with slight modifications was followed from the literature. Two extracts with the highest percentages of xanthine oxidase inhibition were evaluated for possible prevention of cataractogenesis in streptozotocin diabetic rats. The animals were given to drink these plant extracts ad libitum for three months while controls received water. The appearance of cataracts was assessed physically. RESULTS: Two of the nineteen plant extracts showed high inhibition percentages of xanthine oxidase. Eucalyptus deglupta and Syzygium malaccense displayed 51 per cent and 64 per cent inhibitions (IC50 44.5 micrograms/ml and IC50 51 micrograms/ml), respectively. As for the cataractogenesis inhibition, laboratory animals that drank E. deglupta for three months did not develop cataracts. CONCLUSIONS: Two plant extracts provided positive results with varying degrees of inhibition of xanthine oxidase. S. malaccense demonstrated the greatest xanthine oxidase inhibitory activity whereas E. deglupta presented the best finding for cataractogenesis prevention. The procedures used in this investigation are useful for the in vitro screening of xanthine oxidase inhibition and the in vivo evaluation of cataractogenesis prevention.

Endemic plants of Puerto Rico: brine shrimp lethality and antibacterial activity

A total of 49 endemic plants of Puerto Rico were evaluated for their toxicological and antibacterial activities. The toxicological analysis was conducted with brine shrimp (Artemia salina Leach) lethality bioassay and the antibacterial screening was carried out by means of the agar diffusion test. In the toxicological bioassay, six plant extracts showed LC-50 values below 200 g/ml., indicating the potential presence of bioactive compounds. In the antibacterial screening, over 80 per cent of the plant extracts displayed activity against gram positive bacteria, whereas only 6 per cent of the extracts inhibited the growth of the gram negative bacteria