Evaluation of the α-Amylase, α-Glucosidase, Tyrosinase Inhibitory and Photoprotective Activities of Organic Solvent and Aqueous Extracts of Retama monosperma Stem

Abstract

Retama monosperma is a medicinal plant widely used in traditional medicine across the Mediterranean region to treat various conditions, including diabetes, rheumatism, hyperlipidemia, and hypertension. The present study aimed to investigate the enzyme (α-amylase, α-glucosidase, and tyrosinase) inhibitory activity as well as the photoprotective effect of the extracts of R. monosperma stem. Organic solvent (hexane, ethyl acetate, and ethanol) extracts of R. monosperma stem were obtained by Soxhlet extraction, while aqueous extract was obtained by maceration. The α-amylase and α-glucosidase inhibitory activities of the extracts were investigated in vitro using the spectrophotometric method. Furthermore, the efficacy of the extracts as dermo-protective and photoprotective agents were evaluated by tyrosinase inhibitory activity and by ultraviolet absorbance test. The results showed that the hexane extract exhibited the highest α-amylase inhibitory activity (IC50 = 273.91 ± 0.61 µg/mL), for the α-glucosidase inhibitory activity, the aqueous extract demonstrated the highest potency (IC50 = 2331.12 ± 2.69 µg/mL). The ethyl acetate extract showed the highest tyrosinase inhibitory activity (313.68 ± 0.88 µg QE/mg extract). Additionally, the 10 mg/mL aqueous extract displayed significant photoprotective activity, with high UVA (1.810 ± 0.031) and UVB (2.112 ± 0.008) absorbance values. The results of this study have highlighted the therapeutic potential of R. monosperma, and established a solid foundation for future research on natural therapies and the development of innovative drugs for the treatment of hyperglycemia and pigmentation disorders.