Comparative evaluation of antidiabetic potential of partially purified bioactive fractions from four medicinal plants in alloxan-induced diabetic rats

Self-recovery in diabetic Sprague Dawley rats induced by intraperitoneal alloxan and streptozotocin

Alloxan and streptozotocin are the most popular diabetogenic agents in assessing antidiabetic activity. Self-recovery, indicated by unstable hyperglycemia conditions in animals induced by those agents, becomes a significant disturbance to accurate examination. This study aimed to evaluate and reveal the self-recovery incidence in Sprague Dawley rats induced with alloxan and streptozotocin. Each dose of alloxan (120, 150, 180 mg/kg) and streptozotocin (40, 50, 60 mg/kg) was administered through intraperitoneal injection. The results showed that each dose of alloxan induced self-recovery incidence. In rats given streptozotocin, self-recovery only occurred at a dose of 40 mg/kg. The other higher doses of streptozotocin induced stable hyperglycemia. Furthermore, this study revealed two types of self-recovery, namely temporary recovery and end recovery. Temporary recovery occurred in rats given alloxan, during end recovery in alloxan and streptozotocin. The examination of insulin levels showed a significant reduction in the temporary recovery and stable diabetic rats compared to the end recovery rats. Besides, the bodyweight of rats was also affected by different incidences of self-recovery. This study recommends paying more attention to the possibility of self-recovery in obtaining animal models of diabetes, emphasizing the determination of suitable diabetogenic agents and proper doses to reduce self-recovery incidences. The finding of temporary recovery in rats receiving alloxan indicates that alloxan induced delayed diabetes in rats.

Evaluating Peptides of Picrorhiza kurroa and Their Inhibitory Potential against ACE, DPP-IV, and Oxidative Stress

Picrorhiza kurroa Royle ex Benth. is a high-altitude plant having great medicinal value. However, its medicinal value at the peptide level is still unknown, which limits its utility in the development of peptide-based therapeutics. Here, we identify 65 peptides fromP. kurroa hydrolysate. Sequence analysis suggests that one novel bioactive peptide, ASGLCPEEAVPRR (BP1), has antioxidant potential and shows angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibitory activities. The molecular docking study showed that BP1 has a lower binding energy and strong affinity toward active pockets of ACE and DPP-IV, which explains its higher ACE [IC₅₀ = 59.90 ± 9.52 μg/mL (43.40 μM)] and DPP-IV [IC₅₀ = 3.04 ± 0.26 μg/mL (2.2 μM)] inhibitory activities. BP1 protects HEK293 cells from H₂O₂-induced oxidative damage by inhibiting intracellular reactive oxygen species (ROS) and malondialdehyde accumulation and activating the intrinsic antioxidant defense system. Additionally, phase-contrast microscopy studies revealed that pre-treatment of BP1 to HEK293 cells before exposure to H₂O₂ retains the normal morphology and blocks apoptosis. Furthermore, it also suppresses ROS-induced mitochondrial apoptosis via restoring the mitochondrial membrane potential (ΔΨm) and inhibiting caspase 3/7 activity. Therefore, BP1 has antioxidant potential and ACE and DPP-IV inhibitory activities that could be used for peptide-based formulation(s) in pharmaceuticals to treat diabetes, cardiovascular diseases, and other diseases associated with ROS.