Salvadora persica L. is a popular chewing stick commonly known as “miswak”. During our ongoing research activities on the chemical constituents of Salvadora persica roots, which is a new sulphur-containing imidazoline alkaloid 1,3-Dibenzyl-4-(1,2,3,4-tetrahydroxy-butyl)-1,3-dihydro-imidazole-2-thione, persicaline, (1) along with five known compounds (2–6) are identified. Compounds (2, 3) were reported for the first time from the family Salvadoraeceae. The structure of the new compound was established by extensive spectroscopic data and HR-MS. The antioxidant activities of the fractions and isolates were evaluated using different in vitro methods, such as DPPH, superoxide anion and nitric oxide radicals scavenging assays. Compound (1) showed a promising antioxidant activity with IC50 0.1, 0.08, and 0.09 µM in the three assays, respectively, comparable to ascorbic acid.