Extraction and TLC Desitometric Determination of Triterpenoid Acids (Arjungenin, Arjunolic Acid) from Terminalia arjuna Stem Bark Without Interference of Tannins

Abstract

The stem bark of Terminalia arjuna Linn. (fam: Combretaceae), commonly known as Arjuna in Indian systems of medicine, is a reputed drug used for various cardiac disorders. T. arjuna stem bark is reported to contain different groups of chemical constituents including phenolics, tannins, saponins and triterpenoid acids. From our earlier experience with tannin containing herbal drugs, we are aware that tannins interfere in the extraction of certain compounds and hence in their quantification. In the present experiment, we report a sample preparation method to overcome the interference of the tannins by adsorbing them with carboxy methyl cellulose, which facilitates the efficient extraction of the triterpenoid acids. Further we established TLC densitometric methods for the quantification of two of the triterpenoid acids of T. arjuna stem bark viz., arjungenin and arjunolic acid using HPTLC. The methods were validated in terms of accuracy, precision and repeatability. The calibration curve showed linearity in the range of 160–480 ng spot−1 and 160–560 ng spot−1 for arjungenin and arjunolic acid respectively. The percentage of arjungenin and arjunolic acid were found to be 0.324% w/w and 0.524% w/w in the stem bark by this modified method of extraction, which was many times higher than when compared to that using the extraction method without CMC (0.018% and 0.049% respectively). The study reiterates the importance of sample preparation in the quantification of non polar phytochemicals from herbal raw materials, such that the compounds of interest are extracted efficiently, overcoming the interference of other compounds like tannins in the matrix of plant material.