Densitometric HPTLC Quantification of 2-Azaanthraquinone Isolated from Mitracarpus scaber and Antimicrobial Activity against Dermatophilus congolensis

摘要

2-Azaanthraquinone (benzo[g]isoquinoline) isolated from Mitracarpus scaber has been found to have in-vitro antimicrobial activity against Dermatophilus congolensis (MIC 7.5mug mL_(-1)), the causative agent of bovine dermatophilosis. To quantify this compound in Mitracarpus scaber, a new, simple and rapid high-performance thin-layer chromatographic (HPTLC) method was developed and validated for selectivity, recovery, and repeatability. Compounds were separated on silica gel 60F_(254) plates with toluene-ethyl acetate-methanol, 80 + 18 + 2, as mobile phase. Detection was performed by densitometric scanning at A = 310 nm and calibration plots showed the response was linearly dependent on concentration in the range 10-100mug mL_(-1), with good values of R~2. The method was repeatable and precise with relative standard deviations between 0.98 and 1.59% intra-day and between 3.41 and 5.56% inter-day for concentrations from 10 to 100mug mL_(-1). Limits of detection and quantification were 3 and 6mug mL_(-1), respectively (corresponding to 15 and 30 ng, respectively, on the plate). Concentrations of azaanthra-quinone were found to be 0.009% in Mitracarpus scaber aerial parts, 0.057% in the alcoholic extract, and 1.95% in the alkaloid extract. Azaanthraquinone may explain the antimicrobial activity of this last extract and part of the effect of the alcoholic extract.