Changes in essential oil composition of peppermint (Mentha x piperita L.) affected by yeast extract and salicylic acid foliar application

Objective: This study was planned to investigate the effects of foliar application of salicylic acid and yeast extract on production of valuable essential oil components in peppermint. Methods: A completely randomized design experiment with nine treatments consisting salicylic acid (40, 80, 160 and 320 mg/l), yeast extract (0.25, 0.75, 1 and 1.5 g/l) and distilled water (control) with three replications was carried out under greenhouse conditions. Results: In total, forty compounds were identified in the essential oils of the plant aerial parts. Menthone, menthol, piperitone, isopulegol and γ -terpinene were the major compounds of the oils studied. Menthone and menthol were 16.69 % and 14.39 % of the essential oils, respectively. Salicylic acid and yeast extract were increased menthone, neomenthol, piperitone, γ -terpinene and isomenthol acetate production 42, 60, 39, 59 and 34 % higher than control plants, respectively. Foliar application with 320 mg/l salicylic acid gave the best result in the enhancement of the major essential oil components of treated plants. The results of correlation between essential oil constituents showed that the neomenthol content had a significant positive correlation with menthone (r = 0.865 ** ), γ -terpinene (r = 0.848 ** ) and negative correlation with isopulegol (r = -0.886 ** ). Conclusion: The quality of essential oil of M. piperita were influenced by the foliar application of salicylic acid and yeast extract at the appropriate concentrations. Elicitation by 320 mg/l salicylic acid was the optimum treatment for menthone, neomenthol, γ -terpinene and piperitone production.