Activity of the extracts and indole alkaloids from Alstonia scholaris against Mycobacterium tuberculosis Hsub37Rv
2008
Macabeo, A.P.G. | Aguinaldo, M.A.M., University of Sto. Tomas, Espania, Manila 1008 (Philippines). Phytochemistry Lab. | Krohn, K. | Gehle, D., University of Paderborn, Warbuger Str. 100, 33098 Paderborn (Germany). Dept. of Chemistry | Read, R.W. | Brophy, J.J., University of New South Wales, Sydney 2052 (Australia) | Franzblau, S.G., University of Illinois at Chicago 8335, Wood Wl. Chicago, Illinois (USA) 60612-7231. Inst. for Tuberculosis Research
The crude methanolic extracts of Alstonia scholaris (L.) R. Brown demonstrated in vitro antituberculosis activity (89% inhibition against Myobacterium tuberculosis Hsub37Rv at 50 ug/mL) using Microplate Alamar Blue Assay (MABA). Gradient pH fractionation of the alkaloids gave three alkaloid extracts, AsA, AsB and AsC, which exhibited 69%, 99% and 99% inhibition, respectively. Group separation by silica gel vacuum liquid chromatography (VLC) of extracts AsA and AsB afforded fractions that showed 69-99% inhibition against the test myobacterium. The previously reported indole alkaloids -19, 20E-vallesamine (1), a mixture of angustilobine B N4-oxide (2) and n4- methyl angustilobine B (3), 20S-tubotaiwine (4), 6,7-seco-angustilobine B(5) and (+)-manilamine (6) from the most bioactive alkaloid fractions with 98-99% inhibition- showed weak activities. Among the six compounds, only alkaloid 4 demonstrated the highest activity with a minimum inhibitory concentration (MIC) of 100 ug/mL. Compared with the standard rifampin (MIC 0.125 ug/mL), all alkaloids were considered inactive.
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