Targeted LC–MS/MS Phytochemical Profiling and Synergistic Anti-Urease Activity of Limoniastrum guyonianum Extracts Supported by Molecular Docking and In Silico ADME and Drug-Likeness Assessment

Limoniastrum guyonianum Durieu ex Boiss. is an endemic halophyte native to the semi-arid regions of North Africa and represents an under-explored source of bioactive phytochemicals. This study investigated the phytochemical composition and anti-urease potential of L. guyonianum aerial parts through an integrated experimental and computational approach. Plant material was subjected to sequential organic extraction and an additional independent aqueous extract was prepared from the raw plant; the resulting organic fractions were characterized using a targeted LC–MS/MS method validated for 53 phytochemicals. Overall, 21 compounds, mainly flavonoids and phenolic acids, were quantified, 11 of which are quantitatively reported in this species for the first time. The hydromethanolic and methanolic extracts showed the greatest phytochemical diversity, containing 17 and 16 compounds, respectively, together with high total phenolic contents (222.39 ± 0.61 and 157.65 ± 4.40 µg GAE/mg) and flavonoid contents (114.34 ± 16.82 and 223.62 ± 10.64 µg QE/mg). The anti-urease activity of L. guyonianum was evaluated for the first time; the combination of polar extracts showed substantial inhibitory activity (IC50 = 44.66 ± 1.21 µg/mL) compared with the reference inhibitor thiourea (IC50 = 19.62 ± 0.34 µg/mL). Combination analysis yielded CI point estimations below 1 across the non-extrapolated effect range (CI = 0.52–0.69 at Fa = 0.10–0.40), together with substantial dose-reduction effects (DRI ≥ 8.24 for ME and ≥1.75 for MEW). The hydromethanolic extract also exhibited preliminary antibacterial activity against Bacillus cereus and Staphylococcus aureus, with inhibition zones of 18.50 ± 0.07 and 19.50 ± 0.07 mm, respectively. Molecular docking against three urease structures (PDB IDs: 1E9Y, 4H9M, and 4UBP) identified epigallocatechin as the highest-ranked phytochemical according to the composite CNN_VS metric (3.80 ± 0.31), with an average predicted binding energy of −7.55 kcal·mol−1. In silico ADME and drug-likeness assessment further revealed marked differences in predicted oral pharmacokinetic properties among the quantified phytochemicals, with lower-molecular-weight aglycones generally showing more favorable profiles than glycosylated and highly hydroxylated compounds. These findings provide the first evidence of the anti-urease potential of L. guyonianum and highlight the synergistic activity of its polar extracts, supporting further investigation of this North African halophyte as a source of bioactive phytochemicals.