Potential of Green Synthesis Using a Nanotechnology Approach to Enhance the Biological Properties of Onion Extracts

The use of onions as a natural source of medicinal compounds is on the rise globally. However, its therapeutic effectiveness is limited by several factors, including poor solubility, low bioavailability, etc. Hence, developing strategies to overcome these limitations and enhance their therapeutic potential is justified. This study therefore investigates the potential of green synthesis using a nanotechnology approach to enhance the biological properties of onion extracts. Three different onion varieties were used. The bulbs of each onion were sliced, air-dried, and separately extracted using an ethyl acetate and ethanol solvent mixture (1:1 v/v). Each extract obtained was divided into two: plain onion extract and synthesised silver nanoparticles (Ag-NPs) onion extract. This was obtained by mixing the extract with a solution of silver nitrate and heating for 5 hours at 60oC. DPPH (1,1 difenyl-2-picryl-hydrazyl) and hydrogen peroxide scavenging, total antioxidant capacity, red blood cell membrane stabilisation, protein denaturation, and heat-induced hemolysis were assayed. The results of the study showed enhanced DPPH scavenging abilities by the synthesised silver nanoparticles of onion extracts at ≤ 81.01% in comparison to the value exerted by the plain onion extracts at ≤ 75.61%. The total antioxidant capacities of the synthesised Ag-NPs ranged from 0.46±0.6 to 0.85±0.06 mg AAE/g dry extract, while the plain onion extracts ranged from 0.76±0.3 to 0.96±0.09 mg AAE/g dry extract. The synthesised Ag-NPs inhibited protein denaturation at 61.80±0.09–73.34±0.16%, compared to 42.25±0.20–55.08±0.12% by the plain onion extract. The study suggests that green synthesis using nanotechnology approaches can enhance the antioxidant and anti-inflammatory potential of onion extract, leading to improved therapeutic efficacy.