Breadfruit (Artocarpus altilis L.) is an abundant crop originating from the pacific islands, cultivated for over 3000 years in the Caribbean West Indies. Several studies have been published about breadfruit, but few have described its leaves. However, Artocarpus altilis (L.) leaves, which are largely underutilized, are increasingly being consumed in juice, for example. They are thought to have beneficial health effects but there is no research to confirm this. This study presents a comparative analysis of the dietary and pharmacological compounds found in the leaves of Artocarpus altilis (L.) at two different stages of maturity: green and yellow. We performed analyses of total proteins, polyphenols and flavonoids contents in both types of leaves. Qualitative and quantitative analyses of the polyphenolic compounds were achieved using an HPLC-UV method. Biological properties such as antimicrobial and antiradical activities were studied. The results indicate that the total protein content of the yellow leaves is significantly lower than that found in the green leaves. Conversely, the yellow leaves have significantly higher total polyphenol and flavonoid contents than the green leaves. Antioxidant activity tests were carried out on the leaves using the DPPH method, which revealed similar values for both types of leaves. These results suggest that yellow leaves may represent a richer source of phenolic compounds than green leaves, with potential applications as a natural source of antioxidants and other bioactive compounds. While the green leaves show very interesting total protein content compared to many other plant sources, suggesting they could be used to develop new protein sources. In the antimicrobial assay, Artocarpus altilis leaf extracts demonstrated efficient activities against bacteria. Further analysis is necessary to determine the precise nature of the pharmacological compounds and biological properties, such as anti-cancer and anti-inflammatory activities, in Artocarpus altilis (L.) leaves at these two stages of maturity.