The present work aimed to determine the changes in nitrogen concentration and the variation of alkaloid types during the development of Erythrina americana fruit from flower to dry seed. The protein nitrogen, non-protein nitrogen content, and alkaloid types in flowers, string beans, mature seeds, mature pods (without seeds), dry seeds, and dry pods at different developmental stages were studied. The protein nitrogen increased from flowers to mature seeds, while non-protein nitrogen decreased with maturation. Alkaloids accumulated not only at the end of seed maturation but also in young tissues like flowers. On a dried basis, high alkaloid content was observed in flowers and dry seeds compared to low levels in dry pods, with the highest concentration in mature seeds. GC/MS analysis showed that â-erythroidine was the major alkaloid in all tissues examined. Erysodine and erysovine were found in mature and dry tissues but not in flowers. N-oxide alkaloids were only found in mature tissues. The results confirmed that alkaloids and proteins increased simultaneously during fruit maturation, showing an inverse relationship with non-protein nitrogen content.