ABSTRACT
Brine shrimp lethality test is a simple, inexpensive method of screening general bioactivity including cytotoxicity, various pharmacological actions and pesticidal effects of various plants. The objective of the study was to determine the lethality of 10 different plants using the brine shrimp lethality test.The plants are: Calodendrum capense, Clausena anisata, Markhamia lutea, Olinea rochetiana, Rawsonia lucida, Teclea trichorcapa,Turraea mombassana, Vernonia holstii, Warbugia ugadensis, Zantoxylum usambarense.
The plant materials were collected from Ngong’ forest Kajiado county in April 2013. These included leaves, stem barks and aerial parts of the plants. The plants were shade dried, ground and the active ingridients extracted using a solvent mixture of methanol and dichloromethyl in the ratio 1:1. The extracts were then serially diluted into three concentrations: 1000mg/ml, 100mg/ml and 10mg/ml. From each dilution, 5ml was taken and added to a test tube containing ten shrimps whose eggs had earlier been hatched by incubation in salty water for 48 hours. The numbers of shrimps dead after 24 hours were counted for each extract and using software, the LC50 of each plant extract determined.
The LC50 results of the plants using Graphed Prism version 4 Programme were as follows: Teclea trichorcapa (leaves)-141.5, (stem bark)-547.3, Rawsonia lucida ( leaves)-14644, (stem bark)-4077, Markhamia lutea ( leaves)-17626, stem bark-537.1, Zanthoxylum usambarense stem bark-1.074, Clausena anisata ( leaves)-163.7, (stem bark)-5881, Vernonia holstii leaves-31.62, Warbugia ugadensis (stem bark)-47.57, (leaves)-106.6, Turraea mombassana aerial part-176.7, Olinia rochetiana (aerial part)-30,6174, (stem bark)-828.9, calondenum capense stem bark-1021.
The results above show that Zanthoxylum usambarense is the most potent among the plants having the lowest LC50 value of 1.047.On the other hand, the aerial part of Olinia rochetiana had the highest LC50 value hence has the least biological activity .In comparing parts of the same plant, Warbugia ugadensis stem bark showed more biological activity compared to its leaves also the stem bark of Teclea trichorcapa showed more activity than its leaves. Rawsonia lucida also showed varying activity of its parts where the stem bark had much more activity than the leaves. The other plants like Clausena anisata, Calondenum capense, Markhamia lutea showed moderate activity.
The study gives credence to the traditional medicinal uses of the above plants for example, Zanthoxylum usambarense bark decoction serves as an emetic and in cure of malaria and other ailments. Such compounds that exhibit biological activity can undergo bioassay guided fractions in order to isolate the active compounds. These active compounds may later serve as lead compounds for the synthetic modifications by pharmaceutical industries.