In Vivo Studies of Inoculated Plants and In Vitro Studies Utilizing Methanolic Extracts of Endophytic Streptomyces sp. Strain DBT34 Obtained from Mirabilis jalapa L. Exhibit ROS-Scavenging and Other Bioactive Properties.

Reactive oxygen species (ROS) and other free radicals cause oxidative damage in cells under biotic and abiotic stress. Endophytic microorganisms reside in the internal tissues of plants and contribute to the mitigation of such stresses by the production of antioxidant enzymes and compounds. We hypothesized that the endophytic actinobacterium Streptomyces sp. strain DBT34, which was previously demonstrated to have plant growth-promoting (PGP) and antimicrobial properties, may also have a role in protecting plants against several stresses through the production of antioxidants. The present study was designed to characterize catalase and superoxide dismutase (SOD), two enzymes involved in the detoxification of ROS, in methanolic extracts derived from six endophytic actinobacterial isolates obtained from the traditional medicinal plant Mirabilis jalapa. The results of a preliminary screen indicated that Streptomyces sp. strain DBT34 was the best overall strain and was therefore used in subsequent detailed analyses. A methanolic extract of DBT34 exhibited significant antioxidant potential in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) assays. The cytotoxicity of DBT34 against liver hepatocellular cells (HepG2) was also determined. Results indicated that methanolic extract of Streptomyces sp. strain DBT34 exhibited significant catalase and SOD-like activity with 158.21 U resulting in a 55.15% reduction in ROS. The IC50 values of a crude methanolic extract of strain DBT34 on DPPH radical scavenging and ABTS radical cation decolorization were 41.5 µg/mL and 47.8 µg/mL, respectively. Volatile compounds (VOC) were also detected in the methanolic extract of Streptomyces sp. strain DBT34 using GC-MS analysis to correlate their presence with bioactive potential. Treatments of rats with DBT34 extract and sitagliptin resulted in a significant (p ≤ 0.001) reduction in total cholesterol, LDL-cholesterol, and VLDL-cholesterol, relative to the vehicle control and a standard diabetic medicine. The pancreatic histoarchitecture of vehicle control rats exhibited a compact volume of isolated clusters of Langerhans cells surrounded by acinies with proper vaculation. An in-vivo study of Streptomyces sp. strain DBT34 on chickpea seedlings revealed an enhancement in its antioxidant potential as denoted by lower IC50 values for DPPH and ABTS radical scavenging activity under greenhouse conditions in relative comparison to control plants. Results of the study indicate that strain DBT34 provides a defense mechanism to its host through the production of antioxidant therapeutic agents that mitigate ROS in hosts subjected to biotic and abiotic stresses.

Phytotherapeutic efficacy of the medicinal plant Terminalia catappa L.

Diabetes is a chronic, lifelong condition due to inadequate production of insulin or the cells does not properly respond it. Recently, the significance and effectiveness of herbal drugs associated with diabetes has emerged. The aim of the present study was to determine the anti-diabetic effects of Terminalia catappa L. leaves on streptozotocin (STZ)-treated rats. Two different concentrations of ethanolic leaf extract (300 and 500 mg/kg) of T. catappa were used to treat diabetic rats, and biochemical parameters were analyzed in blood samples. The results of herbal treatments were compared with the standard drug, glibenclamide. The ethanol extract (500 mg/kg) had significant anti-diabetic activity by altering blood glucose, glycosylated hemoglobin, liver glycogen, glucose 6-phosphatase, fructose 1,6-bisphosphatase, glucokinase, aspartate transaminase, alanine transaminase, alkaline phosphatase, urea, uric acid and creatinine levels while increasing insulin levels. Thus, the present study suggests that the supplementation of the diabetic patients with T. catappa leaves can lead to recovery from diabetic effects.