Quantitative Analysis of Corosolic Acid, a Type-II Anti-Diabetic Agent, in Different Parts of Lagerstroemia speciosa Linn.

Abstract

An HPTLC method has been established for rapid and simple quantitative determination of corosolic acid, a type-II (non-insulin dependant) anti-diabetic agent found in the plant Lagerstroemia speciosa. To identify the high-yielding parts of the plant, different tissues, for example leaf, stem, stem bark, root, heartwood, calyx, and fruit were extracted with 80% ethanol. The extracts were chromatographed on aluminum plates coated with silica gel 60F(254), With chloroform-methanol 8.5:1.5 (nu/nu) as mobile phase. Densitometric quantification of corosolic acid Was performed in absorbance mode at 366 nm after derivatization. Amounts of corosolic acid in the different samples were calculated by use of the regression equations (r = 0.99603) of calibration plots, which showed there was a good linear relationship between peak area and amount of corosolic acid in the range 0.55-4.5 mu g. The limits of detection (LOD) and quantitation (LOQ) were 6 and 16 ng, respectively. The method was validated for precision, repeatability, and accuracy. Recovery was determined by spiking samples with corosolic acid standard before and after extraction and found to be in the range 95.80-97.13%. The maximum corosolic acid content (0.89%) was found in the leaves.