Toxicity Of Leaf Extract Research Articles

Toxicity of aquaeous leaf extracts of Gongronema latifolium on behaviourial and haematological characteristics of Clarias gariepinus (Burchell, 1822) juveniles

A static bioassay experiment was set up to investigate effects of acute (96-hrLC50) concentrations of aqueous leaf extracts of Gongronema latifolium on behaviourial and haematological characteristics of Clarias gariepinus (Burchell, 1822) juveniles. Evaluation of toxicity of leaf extracts at concentrations of: 0, 10, 25, 50, 75, and 100mg/l was done at various time intervals on the fish. A total of 180 catfish juveniles with average initial weight of 8.37±1.36g and total length of 12.10±2.45cm were used. The fish were distributed among the treatments on complete randomized design. Each treatment had three replicates. The results showed that aqueous leaf extracts were toxic to experimental fish. There was an observed erratic movement, colour change from black to ash-brown and dark coloured belly of treated fish. There were slight changes in water quality parameters, with no significant effect (p>0.05) on the tolerance level of fish on G. latifolium leaf extracts. Mean values of 96-hrLC50 were 90.14mg/l and 2.78mg/l for the upper and lower limits while the threshold value was 0.26mg/l. Phyto-chemical analysis of the leaves showed constituents of flavonoids, saponins, tannins, anthrocyanide, alkaloids and glycosides. Effects of aqueous extracts on haematological indices revealed increasing values of pack cell volume, haemoglobin, white blood cell, red blood cell, mean corpuscular volume, mean corpuscular heamoglobin and mean corpuscular heamoglobin concentration counts with extract concentration. Thus, G. latifolium could be used as feed additive for improved fish production at concentration below 70%.
 Keywords: Gongronema latifolium, leaf extracts, behaviour, haematology, Clarias gariepinus

Antifeedant activity and toxicity of leaf extracts from Porteresia coarctata Takeoka and their effects on the physiology of Spodoptera litura (F.)

Antifeeding and toxic effects of chemical extracts from Porteresia coarctata Takeoka on the insect pest Spodoptera litura (F.) were investigated in the laboratory. Hexane extracts of P. coarctata leaves were re-dissolved in dimethyl sulfoxide and applied in water to leaves of Ricinus communis L. (castor). A concentration of 1,000 and 2,000 ppm extract exhibited significant antifeeding and toxic effects to third instar larvae when compared to the same concentration of dimethyl sulfoxide in water as control. One day after feeding on extract-treated castor leaves, the mortality of S. litura larvae was 50%. Mortality increased to 95% after 11 days at a dosage of 2,000 ppm. Compared to the control, third instar larvae fed on castor leaves treated with P. coarctata leaf extract at different concentrations showed significant reduction in protein and DNA content in the fat body and midgut tissues. Results demonstrate the insecticidal and antifeedant properties of P. coarctata leaf extract against the generalist pest S. litura leading to biochemical changes in the insect body. Thus, P. coarctata contains phytochemicals, and the extract, in crude and pure form, has potential as a botanical insecticide in alternative control strategies against Lepidoptera pests.

Extracts from virus infected hypersensitive tobacco leaves are detrimental to protoplast survival

Tobacco mesophyll protoplasts cultured in vitro were killed when extracts, prepared from the leaves of Nicotiana tabacum L. cv. Xanthi nc (hypersensitive host) infected with tobacco mosaic virus (TMV), were included in the medium. Protoplast survival was not significantly diminished by similar extracts from plants of N. tabacum L. cv. Xanthi (systemic host) infected with TMV or from tobacco plants sham inoculated with water only. Protoplasts from the hypersensitive host were more susceptible to being killed by toxic leaf extracts than protoplasts from systemic hosts. Protoplasts were not killed immediately upon resuspension in toxic leaf extracts when the criterion for viability was their ability to reduce the vital stain methylene blue. Instead, there was a lag phase of 8 to 10 h; the killing reaction was virtually complete by 1 day. Toxicity of leaf extracts was detected 24 h before lesions appeared, and was related to both lesion number and lesion development. Toxicity of leaf extracts was apparently due to a non-dialysable, thermolabile substance or group of substances. The toxicity was reduced by Ca ++ ions, and increased by pre-treating extracts with ethylenediaminetetra-acetic acid (EDTA) or incubating protoplasts in the dark, in culture medium containing toxic leaf extract. The significance of these results is discussed in relation to necrogenesis in virus infected plants responding hypersensitively.