Abesingha, J.M.I.K.Premathilake, S.N.2021-12-162021-12-1620169789550481095http://www.erepo.lib.uwu.ac.lk/bitstream/handle/123456789/8039/68-2016-Antimicrobial%20Activity%20and%20Toxicity%20Effect%20of%20Adiantum%20Capillus-Veneris.pdf?sequence=1&isAllowed=yMedicinal herbs are important natural resources that can be used against various infections. Adiantum capillus-veneris has been used in traditional medicine for centuries against various infections. The objectives of the present study were to study the antibacterial activity against Staphylococcus aureus and the toxicity effect of A. capillus¬veneris. Leaf extraction of A. capillus-veneris was prepared using the Soxhlet apparatus with absolute methanol as solvent and then concentrated using a rotary vacuumed evaporator. Using a stock solution of 100 mg/mL four different concentrations of crude extracts were prepared (50 mg/mL, 25 mg/mL, 12.5 mg/mL, and 6.25 mg/mL) for the antibacterial test. Well diffusion method was employed to study the antimicrobial activity and inhibitory zone diameter was also measured. Absolute methanol was used as negative control. For the toxicity test crude extract was reconstituted using distilled water. A stock solution of 1000 1..tg/mL was prepared and 500 tg/mL, 100 ps/mL, 10 tg/mL and 1 lig/mL solutions were prepared using this solution. Zebrafish (Danio rerio) embryos were used as toxicological model and their coagulation, lack of somite formation, lack of detachment of the tail and lack of heart beat was used as the lethality indicators. The results indicated that methanol extract of the A. capillus-veneris have antibacterial activity against S. aureus and the Minimum Inhibitory Concentration (MIC) was 12.5 mg/mL (One way ANOVA, p<0.05 and Dunnett's test by 95% confident level). According to the Probit analysis the lowest LD 50 value received for toxicity test was 102 .tg/mL after 96 hours by 95% confident level. According to the results it could be concluded that leaf extracts of the A. capillus-veneris shows antibacterial activity against S. aureus at a very low concentration and they could be toxic with the increasing time duration. Keywords: Adiantum capillus veneris, Staphylococcus aureus, MIC, Zebrafish embryo, LD 50enHerbal PlantIndigenous MedicinePlantNatural ResourcesOther