To evaluate the phytochemistry, HPTLC fingerprint profile and antimicrobial activity of Cassia fistula L. bark, preliminary phytochemical screening was done by the methods of Treas and Evans and Sofowora. The HPTLC analysis were carried out as Harbone and Wagnar et al. described. The in vitro antimicrobial activity were performed by agar well diffusion method of Perez et al.The phytochemical screening showed the presence of alkaloids, glycosides, fats, tannins, flavonoids in methanol extract of bark, where as alkaloids, glycosides, saponins, tannins, flavonoids, photobatalines and anthraqunonine were found in the aqueous extract. The HPTLC finger printing of the methanolic extract of bark showed 8 compounds with different Rf values. The highest values are 0.86 (79.20%), 0.27 (5.14%) and 0.92 (4.23%) respectively. The compound with 79.20% area appeared to be the major compound. The HPTLC results confirmed that the alkaloids are the major constituents in bark of C. fistula L. This was followed by the glycosides, tannins and flavonoids in trace amount. The purity of sample was confirmed by comparing the absorption spectra at start, middle and end position of the band. It can be concluded that HPTLC finger printing of Cassia fistula L. bark may be useful in differentiating the species from the adulterant and act as a biochemical marker for this medicinally important plant in the pharmaceutical industry. Among the different extracts methanol and aqueous extracts showed significant antimicrobial activity against test microbes and gram negative bacteria P.aeruginosa and S.aureus also.
