Several methods for treatment of data from toxicity tests to determine the median lethal concentration (LC50) are discussed. The probit and logit models widely used for these calculations have deficiencies; therefore, a calculational method, named the 'trimmed Spearman-Karber method', is developed. Examples of actual and hypothetical bioassay test data are given, and comparisons are made of the abilities of these three methods to treat these data. The trimmed Spearman-Karber method is not subject to the problems of the probit and logit models, has good statistical properties, is easy to use, and is recommended for accurate and precise calculation of LC50 values and their 95% confidence interval end points.
Trimmed Spearman-Karber Program
A number of tropical plant species have been recognised as molluscicidal plants, and Barringtonia racemosa (L.) is one of these. The toxicity effects of B. racemosa seed kernel extracts on Pomacea canaliculata were evaluated. The lethal concentration at 50% [LC50 (lower-upper limits)] values, in ppm/48 hours, were 70.71 (41.33-120.97), 94.39 (62.48-142.59), 186.84 (129.21-270.17), and 672.72 (366.57-1234.53) for the extracts withdrawn using dichloromethane (DCM), methanol (MeOH), ethyl acetate (EtOAc), heptane (hp) solvents, respectively at 95% confidence interval (C. I.). All analyses were conducted using Trimmed Spearman-Karber (TSK) program version 1.5. It is assumed that the observed biological effects of the extracts may be due to the saponins and flavonoids present in the seed. The dichloromethanic and methanolic extracts contain saponin and flavonoid substances. Therefore these extracts have shown more potent molluscicidal activity towards the tested organism compared to the remaining extracts. This observed biological activity suggests a promising role for B. racemosa in the control of P. canaliculata. 2ff7e9595c
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