Liriomyza trifolii is one of the leaf mining flies native to North America and well characterized by its high degree of polyphagy. However, Momordica charantia leaves (commonly known as bitter gourd) are rarely attacked by these insects. Therefore, the present study was undertaken to isolate and characterize some of M. charantia leaf's constituent (s), which are responsible for the oviposition deterrency against L. trifolii insects. It is noted that L. trifolii insects deter from ovipositing by the M. charantia leaves due to the presence of momordicine I and II and its newly identified related compounds, 7, 23-dihydroxy-3-O-malonylcucurbita-5, 24-dien-19-al and 7-O-beta-D-glucopyranosyl-3, 23-dihydro xycucurbita-5, 24-dien-19-al. Therefore, M. charantia leaf extract and its constituents may be used as an alternative control method in fight against L. trifolii insects.