Present study deals with the biochemical analysis of different parts of Cassia occidentalis L. and its correlation with their allopathic potential. Growth studies on Echinochloa crus-galli, a common agricultural weed of rice ecosystems showed significant reduction with flower and leaf extracts as compared to root and stem extracts of C. occidentalis. Metabolic fingerprinting was achieved by using Fourier Transform Technique (FTIR) to understand differential distribution of different phytochemicals in root, stem, flower and leaf tissues. Presence of different functional groups C=O, C–H, C=C, C–O, C–C and N–H were identified which indicated the presence of alkyl groups, methyl groups, alcohols, ethers, esters, carboxylic acid and anhydrides in different tissues. The results showed that flower and leaf tissues were rich in lipids, proteins, amides (aromatic compounds) corresponding tomany sharp bands in the region of 1700-1500 cm-1. Thus, FTIR studies not only provided the bio-molecular profile of C. occidentalis but also established a correlation of allopathic potential of different tissues with relative distribution of different phytochemicals