In this study, leaf essential oil effects on glutamate toxicity model formed in cortex neurons and LN405 cell cultures were investigated. Antidiabetic activity was evaluated by & alpha;-amylase and & alpha;-glucosidase inhibitions. MIC was used for antimicrobial activity. Seven groups were examined with MTT. Glutamate 10-5 mM in cortex showed 62% viability whereas oil viability did not increase in a dose-dependent manner and the highest viability rate was observed. There are four types of glandular trichomes in leaf anatomy of walnut. The oil exhibited half as much & alpha;-glucosidase inhibitory activity with an IC50 value of 8105 & mu;g/mL, compared to positive control acarbose (IC50 = 4762 & mu;g/mL). MIC of oil was determined to be 625 & mu;g/mL against E. coli, C. albicans, and C. parapsilosis, whereas S. aureus exhibited a MIC of 1250 & mu;g/mL. Major compounds of oil were found as & beta;-pinene (17.6%), & alpha;-pinene (11.3%), & beta;-eudesmol (8.6%), and caryophyllene oxide (6.2%).