As part of our contribution to the development of the plant kingdom as a source of natural bioactive substances and to the discovery of new compounds of therapeutic interest, we focused on an Algerian Saharan species: Haplophyllum tuberculatum. We performed a polarity-increasing organic solvent extraction with quantification of total phenols and flavonoids. We studied the effect of these extracts on the enzyme α-amylase from two different sources, and assessed antioxidant potential using four chemical tests. Analysis of phenolic content revealed average levels of total phenols and flavonoids. All extracts showed inhibitory effects on the enzyme. Antioxidant activity results from the four chemical tests showed low antioxidant power compared with standard antioxidants. This work has provided new phytochemical knowledge about Algerian Saharan plants and constitutes a contribution to the study of the role of natural polyphenols in the regulation of oxidative stress and the normalization of glycemic disorders.