In Vitro Antileishmanial Potential of Glycyrrhiza glabra (L.) (Licorice): An Integrated Study of Its Antioxidant and Antibacterial Activities

Abstract

This study aimed to assess the antileishmanial potential of the roots Glycyrrhiza glabra L. (licorice) a medicinal plant widely used in traditional phytotherapy and recognized for the richness of its secondary metabolites. However, scientific data on Moroccan licorice extracts remain limited, especially on phytochemistry and antileishmanial, antioxidant, antibacterial activities. In this study, G. glabra roots obtained from herbalists in the Fez region (Morocco) were used to prepare a hydroethanolic extract by Soxhlet extraction (ethanol/water 80:20, v/v). The total contents of phenolic compounds, flavonoids, and condensed tannins were determined using the Folin–Ciocalteu, AlCl₃, and vanillin–HCl methods, respectively. Antioxidant activity was evaluated using DPPH and ABTS assays and expressed as IC₅₀ values. Antileishmanial activity was assessed in vitro against promastigote forms of Leishmania tropica, Leishmania infantum, and Leishmania major using the MTT assay, while antibacterial activity was evaluated by the disk diffusion method against nine bacterial strains in comparison with ceftriaxone. The extract exhibited a high content of phenolic compounds (346.8 ± 0.11 mg GAE/g) and flavonoids (131.4 ± 0.01 mg QE/g), but a low tannin content (0.44 ± 0.04 mg CE/g). It showed notable antioxidant activity (IC₅₀ = 182.5 ± 0.13 µg/mL (DPPH) and 17 ± 0.3 µg/mL (ABTS), dose-dependent inhibition of promastigotes with marked sensitivity of L. major (IC₅₀ = 116.81 ± 2.42 µg/mL) and moderate sensitivity of L. infantum (309.21 ± 5.31 µg/mL) and L. tropica (345.38 ± 6.88 µg/mL), as well as selective antibacterial activity mainly directed against Gram-positive bacteria.