Phytochemical Profiling and In Vitro/In Silico Evaluation of α-Glucosidase Inhibition, Antimicrobial and Antioxidant Activities in Retama monosperma Decoctions

The current study aimed to investigate the phytochemical composition of R. monosperma's decoction by UHPLC/DAD/ESI-MS, and to evaluate its antidiabetic, antioxidant, and antibacterial effects. Quinolizidine alkaloids and flavonoids were identified. Vitexin, saponarin, vicenin-2, and pinocembrin have never been found before in R. monosperma. Hydroxylupanine was also identified in R. monosperma L. for the first time. Antioxidant capacity was evaluated through four assays: DPPH radical scavenging, hydrogen peroxide scavenging, conjugated diene, and TBARS. Antibacterial activity was determined by disc diffusion and MIC assays, while α-glucosidase inhibition was used to examine the antidiabetic potential of the decoction. In silico studies were also performed to investigate the antioxidant affinity of R. monosperma metabolites. The SAE (seeds aqueous extract) and CAE (cladodes aqueous extract) exhibited strong antioxidant activity, while FAE (flowers aqueous extract) showed moderate activity overall. SAE demonstrated a higher inhibitory effect on α-glucosidase followed by FAE and CAE surpassing acarbose. Molecular docking showed that saponarin and vicenin-2, followed by vitexin and genistin, are the key flavonoids contributing to the high antioxidant potency of seed decoction. Saponarin and vicenin-2 are highly active against the NADPH oxidase protein initiating the antioxidant phenomenon. The ADME-Tox profiling study showed that the four active compounds are well metabolized and are neither toxic nor carcinogenic. When using a decoction of R. monosperma in traditional medicine, particular attention should be paid to the fact that in addition to their pharmacological properties, quinolizodine alkaloids herein identified exhibit toxicological activities, including hallucinogenic properties.