Phytochemical Profiling and Biological Activities of Moroccan Rhus pentaphylla

Abstract

Rhus pentaphylla Desf., a medicinal plant traditionally used in North Africa, remains insufficiently investigated with respect to its glycoconjugate composition and biological properties. This study investigated the influence of extraction solvent on the LC–ESI–MS/MS profiles and biological activities of aqueous, ethanolic (EtOH100), and hydroethanolic (EtOH50) extracts of Moroccan R. pentaphylla, with particular emphasis on glycosylated metabolites. LC–ESI–MS/MS profiling resulted in the annotation of 39 metabolites belonging to several phytochemical classes, including phenolic acids, flavan-3-ols, coumarins, and numerous phenolic and flavonoid glycoconjugates. Citric acid, gallic acid, chlorogenic acid, esculetin, and caffeic acid were confirmed by comparison with in-house reference standards, whereas the remaining compounds were tentatively annotated based on their precursor ions and MS/MS fragmentation patterns through comparison with published literature and an in-house database. Several glycoconjugates, including caffeic acid glucoside, coumaric acid glycosides, and flavonoid glycosides, were tentatively annotated. Differences in the relative chromatographic responses of individual compounds were observed among the three extracts, highlighting the influence of extraction solvent on their phytochemical profiles. The hydroethanolic extract exhibited the highest total phenolic content and the strongest antioxidant activity (DPPH IC50 = 32.00 µg mL−1; ferric-reducing capacity = 81.56 mM FeSO4 equivalents g−1 extract), whereas the aqueous and ethanolic extracts showed greater tyrosinase inhibitory activity. All three extracts displayed comparable α-amylase inhibitory activity, with no statistically significant differences among them. Antibacterial activity was generally limited; however, the ethanolic extract produced the largest inhibition zone against Pseudomonas aeruginosa (14.01 ± 0.62 mm) and showed an MIC of 100 mg mL−1, whereas the MIC of the hydroethanolic extract was >100 mg mL−1. At the tested concentrations of 12.5 and 25 mg mL−1, the ethanolic extract significantly reduced P. aeruginosa biofilm biomass, whereas the hydroethanolic extract produced a significant reduction only at 25 mg mL−1. Both extracts significantly reduced the measured extracellular protein levels, while their effects on EPS-associated carbohydrates were more limited. Overall, extraction solvent influenced both the glycoconjugate-containing phytochemical profiles and the in vitro biological responses of R. pentaphylla extracts. The observed effects may reflect the combined contributions of multiple constituents rather than the activity of individual metabolites. Further bioassay-guided fractionation, structural confirmation, compound-specific quantitative analysis, and mechanistic investigations are required to identify the constituents contributing to these biological effects.