The use of drug substances derived from plants, fungi, bacteria, and marine organisms are ‘‘Mother Nature Gift’’ for diseases of mankind. Many of these are discovered serendipitously and have a long tradition in medicine. Till date, the use of natural products, their semi synthetic and synthetic derivatives have been mostly confined to their ethnic use. But it has been well known that each substance has a wide spectrum of biological activities as evident from some new uses of many old drugs. PASS (Prediction of Activity Spectra for Substances) has been employed as a strong potential tool to predict the biological activity spectrum of synthetic substances for the discovery of new drugs. But the potential of PASS to predict the biological activity spectra of natural products is still underestimated. The present study was therefore undertaken to investigate and correlate the biological activity spectrum of the main phytoconstituent of Azadirachta indica with their reported biological activities in order to evaluate the applicability of PASS.