Antioxidant and antimicrobial properties of methanolic extract of green walnut skin

In recent years, the use of natural substances such as essential oils and extracts has been emphasized in place of chemical preservatives in the food industry. green walnut skin is an agricultural waste that, due to its phenolic compounds, can be considered as a natural combination containing biological properties, and it reduces many of the incurable diseases and prevents the oxidation of lipids and is used as antimicrobial factors. In this study, the content of phenolic compounds, antioxidant and anti - bacterial properties of methanolic extracts of green walnut skin was investigated.

Extraction was carried out using both soaking and soxhelt methods in  60% and 80% methanol solvent. The amount of phenolic compounds of the extract was determined by spectrophotometric method.
The anti-radical activity of the extract was evaluated by DPPH radical inhibitory test. Antibacterial activity of the extract was investigated by disc diffusion method against Salmonella typhimurium, Shigella dysentery and Listeria monocytogenes. Collected data were analyzed using SPSS software and Duncan test.

The total phenol content for soaking and soxhlet methods was respectively 17.81 and 89.07, according to Gallic acid equivalent, based on mg / g of sample. EC50 amount of green walnut skin was 0.15 mg / ml. The  Remarkable antimicrobial activity was observed against all studied bacteria. MIC was between 1.625 and 1.25 and MBC between 1.2 and 2.5 mg / ml.

The results of this study showed that methanolic extracts of green walnut skin are a potential source of bioactive compounds with antioxidant and antimicrobial properties that can be used in the food and medicine industry to protect human health.