Comparative Physicochemical and Biological Evaluation of Green-Synthesized Silver Nanoparticles from Four Traditionally Used Antidiabetic Medicinal Plants with in vitro Antidiabetic Assessment of their Combined Formulation

Abstract

Background: Diabetes mellitus is one of the important metabolic diseases linked to chronic hyperglycaemia and its long-term complications. These medicinal plants used traditionally for diabetes provide various phytochemicals which exhibit antioxidant and enzyme inhibitory properties. Medicinal plant extracts are used as eco-friendly supporting materials for green synthesis of silver nanoparticles (AgNPs) which may improve the physicochemical and biological properties of the AgNPs.

Aim: The present study was aimed to comparatively evaluate the physicochemical and biological characteristics of green-synthesized AgNPs prepared from Eugenia jambolana, Tinospora cordifolia, Boerhavia diffusa and Tephrosia purpurea and to assess the in-vitro antidiabetic potential of their combined polyherbal AgNP formulations.

Methods: The selected medicinal plants were extracted using Soxhlet extractor in ethanol, the extracts were further used to synthesize AgNPs by green synthesis method using 1 mM silver nitrate. The synthesized nanoparticles were characterized by UVvisible spectroscopy, FTIR, particle-size and PDI analysis, SEM, zeta-potential analysis, DSC and XRD. Antibacterial activity was observed against the E. coli and S. aureus bacteria and antioxidant activity was investigated by the DPPH assay. The four combined formulations (F1-F4) were tested for their α-amylase and α-glucosidase inhibitory effects.

Results and Discussion: The synthesized AgNPs exhibited characteristic nanoscale properties, negative surface charge and differences in morphology and particle-size distribution depending on the plant. The DPPH inhibition was significantly high for E. jambolana AgNPs with 84.6 ± 2.3% and IC5₀value of 36.2 µg/mL. Formulation F1 exhibited the maximum inhibitory activities of α-amylase (81.6 ± 1.9%) and α-glucosidase (85.4 ± 1.9%) at a concentration of 200 µg/mL.

Conclusion: It is concluded that plant mediated AgNPs seem to possess potential antioxidant, antimicrobial and in-vitro antidiabetic activity. F1 exhibited the highest enzyme-inhibitory activity and could be regarded a promising formulation for future mechanistic, toxicity and in-vivo studies.