Bioactivity of Neem (Azadirachta indica) callus extract

This study was conducted in order to explore the possibility of utilizing plant tissue culture techniques for production of secondary metabolites from callus culture of Azadirachta indica (Neem) and to investigate the bioactivity of the established callus extract in comparison with the extract from the intact leaves. The presence of secondary metabolites in the extracts was detected by Thin Layer Chromatography (TLC). Both the callus and leaf extracts eluted five fraction of compounds and it were observed that callus extract had a good resolution. various extract concentration (5.10. and 20 mg/ml) were determined for the rate and extent of inhibition kinetics against staphylococcus aureus. Escherichia coli, and candida albicans. Results showed that callus extract of A. indica wiped out all viable cells of C. albicans within 18 hours and the subsequent concentration 5 and 10 mg/ m1 retard the growth after 24 h. A higher concentration of 20 mg/ ml had the same effect on S. aureus after 6 h and the E. coli cells were completely inhibited by the extracts after 24 h. Similar kinetics were showed by leaf extract but in slight rate as compared to the callus extract. In general both extract posses antimicrobial activity with notable efficient rates. For assaying of the inhibitory effect on some phyto pathogens the effect of different concentrations of the callus and leaf extracts on the radial growth of Drechslera rostrata. Fusarium oxysporum and Alterneria alternata were in vitro assessed. Obvious inhibitory effect was observed on the mycelia radial growth of the three treated fungi. The level of inhibition increased with the increase of te extract concentration. The maximum inhibitory effect (84%) was recorded with Drechslera rostrata when inoculated in media contain 20 mg/ ml of callus while the inhibition rate of mycelia growth of the same species reaches 61% when inoculated in a medium contain the same concentration of the neem leaf extract. The subsequent concentrations of the callus and leaf extracts gave similar trends of inhibition on the fungi cultured on extract amended agar plates. As for seed-borne fungi obvious inhibitory rates observed upon the treatment of sorghum seeds when compared with control, the high concentration of callus extracts (20 mg/ ml) completely inhibit the fungal growth, while the inhibition rate was reached 75% when the leaf extract was used. The study of the efficiency against fresh water snails Biomphlaria glabrata which is the vector of Schistosoma mansonil showed molluscicidal activity against the snails of B. glabrata. Different concentration (5. 10. 15 nd 20 mg/ ml) of the callus and leaf extract were used and both of them showed excellent mortality responses at high concentrations after 24 h. However there was clear difference in the efficiency between the callus extract and the leaf extract and the callus extracts proved to be more effective than that of the leaves. The highest and more rapidly mortality rate (100%) was obtained by adding 20 ml of the callus extract to the rearing medium. Decreasing the amount of the extract to 15. 10 and 5 ml, reduced the mortality to 97,92 and 85% respectively. Similar concentrations of the leaf extract found to be less effective.(Author)