Bio-guided Studies of Lotus maritimus Aerial Parts and Investigation of their Antioxidant, Tyrosinase and Elastase Inhibitory Activities

Background: Lotus maritimus L. (Fabaceae) is a perennial herb species with yellow flowers, growing in Europe, Asia, Middle East and Maghreb. Some flavones and flavonols have been identified in their leaves and flowers. Their leaf extract was used as a cellulolytic and antiaging cosmetic ingredient. Objective: The aim of this work was to perform antioxidant, anti-tyrosinase and anti-elastase properties of L. maritimus aerial parts and their chemical profile. Methods: A ¹³C NMR-based dereplication method combined with a bio-guided purification was used for metabolite identification. Chemical structures were determined by NMR and ESI-MS spectroscopic methods. The antioxidant properties of the fractions and purified compounds were measured using CUPRAC, DPPH and hydroxyl radical scavenging assays. Their inhibitory activities against the fungal tyrosinase and human neutrophil elastase enzymes were also evaluated. Results: EtOAc and n-BF fractions were characterized as the most active parts. Twenty-two compounds were identified from these fractions by using a ¹³C NMR-based dereplication method. This process was completed by the purification of minor compounds in the n-BuOH fraction. Eight known compounds were isolated, including many mono-glycosylated flavonoids with variable substitutions on the B-ring, allowing structure-activity relationships. Conclusion: Twenty-two compounds, including phenolic acids, flavonoids and glycoside derivatives, were firstly described in L. maritimus. Three quercetin and myricetin-type flavonoids exhibited good antioxidant activities and all flavonoids tested have moderate effects on elastase inhibition.