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Despite the existence of various therapeutic approaches, diabetes mellitus and its complications have been an increasing burden of mortality and disability globally. Hence, it is necessary to evaluate the efficacy and safety of medicinal plants to support existing drugs in treating diabetes. Xanthones, the main secondary metabolites found in Gentiana dinarica and Gentiana utriculosa , display various biological activities. In in vitro cultured and particularly in genetically transformed G. dinarica and G. utriculosa roots, there is a higher content of xanthones. The aim of this study was to investigate and compare antidiabetic properties of secondary metabolites (extracts) prepared from these two Gentiana species, cultured in vitro and genetically transformed with those collected from nature. We compare HPLC secondary metabolite profiles and the content of the main extract compounds of G. dinarica and G. utriculosa methanol extracts with their ability to scavenge DPPH free radicals and inhibit intestinal α-glucosidase in vitro. Anti-hyperglycemic activity of selected extracts was tested further in vivo on glucose-loaded Wistar rats. Our findings reveal that the most prominent radical scavenging potential and potential to control the rise in glucose level, detected in xanthone-rich extracts, were in direct correlation with an accumulation of xanthones norswertianin and norswertianin-1- O -primeveroside in G. dinarica and decussatin and decussatin-1- O -primeveroside in G. utriculosa .

Silibinin has considerable therapeutic potential for the treatment of diabetes through anti-inflammatory, antioxidant, and immunomodulatory properties. However, the therapeutic application of silibinin is quite limited due to its poor bioavailability. In the present study, an attempt was made to improve the antidiabetic efficacy of silibinin by its encapsulation in liposomal vesicles. The liposomes with a high encapsulation efficiency of silibinin (96%) and a zeta potential of −26.2 ± 0.6 mV were developed and studied using nicotinamide/streptozotocin-induced diabetic rats. Administration of silibinin-loaded liposomes to diabetic rats lowered glucose levels, increased insulin levels, and improved pancreatic islet architecture. The anti-inflammatory effect of silibinin-loaded liposomes was demonstrated by a decrease in serum C-reactive protein (CRP) levels and a reduced deposition of collagen fibers in the islets of diabetic rats. Furthermore, silibinin-loaded liposomes were more efficient in lowering glucose, alanine transaminase, triglyceride, and creatinine levels in diabetic rats than pure silibinin. In addition, silibinin-loaded liposomes had a significantly better effect on beta-cell mass and Glut2 glucose receptor distribution in diabetic islets than pure silibinin. The present results clearly show that liposome encapsulation of silibinin enhances its antidiabetic efficacy, which may contribute to the therapeutic benefit of silibinin in the treatment of diabetes and its complications. [ABSTRACT FROM AUTHOR]