The thin layer chromatographic examination of the isolated compound L 2 from the petroleum ether (40-60 °C) extract of the leaves of Lagerstroemia speciosa was visualized as brown spot and a violet spot was observed on the thin layer chromatographic plate when the vanillin-sulphuric acid reagents was sprayed on it followed by heating at 110 °C for about 10 min. It was completely soluble in chloroform. The steroidal nature of the compound was observed from the Salkowski and Liebermann Burchard’s test [12]. Isomer of β-sitosterol was obtained as white needle shaped crystals m.p. 100-102 °C. It had the molecular formula C29H46O2 as determined by HREIMS and confirmed by 1HNMR and 13C-NMR (Table-1) and DEPT analysis. The UV spectra displayed characteristic absorption bands for a conjugated double bond at 232 nm. Its IR spectrum showed absorption band at 3510 cm-1 was an indicative of -OH group where as the absorption band at 2900 cm-1 was assigned to -CH of aliphatic asymmetric stretching. The absorption peaks at 1660 cm-1 and 1600 cm-1 were indicating the presence of >C=C< skeletal unit whereas the absorption band at 1460 cm-1 and 1340 cm-1 were suggested the -CH2- and -CH3 bending vibration, respectively. The other two absorption bands at 1250 cm-1 and 1190 cm-1 indicated the presence of -CH bending for -CH3 group. The absorption peak at 1060 cm-1 was demonstrated the presence of -C-O stretching of secondary alcohol while the band at 980 cm-1 supported the steroidal nature [12] and the other absorption band at 800 cm-1 indicated the presence of proton attached to C=C. The 1H-NMR spectrum showed three singlets at δ 1.13, 1.12 and 0.91 for the methyl protons at positions C-27, C-26 and C-21, respectively. A broad singlet at δ 4.48 was accounted for methyl protons at position C-29 that attached through methylene group. Two different singlets at δ 1.80 and 3.52 were suggested due to the presence of methyl protons of C-18 and C-19. The 13C-NMR spectrum of the compound L2 revealed the presence of 29 carbons for a steroidal skeleton. From the proton, carbon thirteen and DEPT 1HNMR chemical shift value it was assigned that there were two double bonds in the in the structural position at C-5 and C-9. All the 13C-NMR signals were in agreement with the data for sterol with the exception of 13C chemical shift value at δ 171.7 ppm. This value is usually considered for the presence of carbonyl carbon. But there was no absorption band was monitored in the IR spectral analysis of the compound L2 between the region 1680 cm-1 to 1850 cm-1 typically for >C=O group. Comparing the 13C-NMR spectroscopic data with the reported data of the identical steroid compound along with the IR, 1H-NMR and DEPT NMR spectral analysis and physical properties the identity of the isolated compound L2 was established as the isomer of βsitosterol.