Densitometric HPTLC Quantification
of 2-Azaanthraquinone Isolated from Mitracarpus scaber
and Antimicrobial Activity against Dermatophilus
congolensis
Fernand Gbaguidi, Giulio Muccioli, Georges Accrombessi, Mansour Moudachirou, and Joëlle Quetin-Leclercq*

Summary
2-Azaanthraquinone (benzo[g]isoquinoline) isolated from Mitracarpus
scaber has been found to have in-vitro antimicrobial activity
against Dermatophilus congolensis (MIC 7.5 µg mL–1), the causative
agent of bovine dermatophilosis. To quantify this compound in
Mitracarpus scaber, a new, simple and rapid high-performance thinlayer
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 ë= 310 nm and calibration plots showed
the response was linearly dependent on concentration in the range
10–100 µg 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 100 µg mL–1. Limits of detection and quantification
were 3 and 6 µg mL–1, respectively (corresponding to 15 and
30 ng, respectively, on the plate). Concentrations of azaanthraquinone
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.