Changes in the contents and composition of polyphenolics and resulting antioxidant activities of S. verbenaca by-products were investigated at three phenological stages (flowering, early fruiting and late fruiting stages). The highest accumulation of total phenolics was detected at the flowering stage (58.36 mg GAE/g DW). HPLC analysis of methanolic extracts showed the prevalence of methyl carnosate (821.45-919.82 μg/g DW) and rosmarinic acid (544.51-649.26 μg/g DW). Phenolic diterpenes (1056.90-1148.42 μg/g DW) was the most represented class of compounds. Three complementary tests namely, DPPH(•) (IC50 value, 49.22 μg/mL) and ABTS(•+)-radical scavenging assays (146.86 μM TE/mg) and FRAP reducing power test (188.93 mM Fe(II)/mg) were used to evaluate the antioxidant capacity and showed the best performance at the early fruiting period. The current study evidenced the significant effect of phenophase on antioxidants and contributed to valorize S. verbenaca extracts as a source of functional phenolic compounds.