Chemical Composition of the Essential Oil and Nitrogen Metabolism of Menthol Mint under Different Phosphorus Levels

Abstract

The purpose of this work was to evaluate the effects of different phosphorus levels (0.05, 0.5, 1 and 2 mM) under nitrogen metabolism and the essential oil profile of menthol mint (Mentha arvensis L.). The relationship between the leaf maturity and the essential oil profile was also explored. The experiment was conducted in a hydroponic system located in a grow chamber during 41 days and after the harvest, nitrate reductase activity, and the NO− -N, amino-N, and soluble sugars levels of each plant part were evaluated. Also the essential oil from young leaves (6th to 8th node) and adult leaves (3rd to the 5th node) was analyzed. An uptake mechanism related to the increase in fresh weight of the roots was promoted with the use of low P levels (0.05 and 0.50 mmol•L −1 ). With 1 mmol•L −1 P plants showed in all parts an increased nitrate reductase activity and high levels of nitrate and amino-N in leaves. Plants submitted to the lowest P level (0.05 mmol•L −1 ) presented high levels of menthol. In leaves from 6th to 8th node (mature leaves) menthol level was approximately 87% of the essential oil however leaves from the 3rd to the 5th node (young leaves) showed high levels of pulegone, that can be toxic for humans. The results indicate that the essential oil quality in menthol mint is influenced by the leaf maturity and the P levels. Also it was showed that the oil extracted from mature leaves of plants under low P levels has the best commercial profile.

Production and Quality of Menthol Mint Essential Oil and Antifungal and Antigerminative Activity

“…However, between the young and adult leaves, it was observed increased concentrations of menthol (9%) and menthyl acetate (330%) in mature leaves and a decrease of menthone (71%) in young leaves ( Table 1). Similar results were showed by others authors [26] [28] [30].…”

“…The results showed that the young leaves are associated with higher content of limonene and ketone monoterpenes, intermediates in the biosynthesis of menthol, on the other hand, the adult leaves presented higher contents of alcohols and esters monoterpene (Note in Figure 2 the numbers marked with asterisk) [30]. Table 2 shows that essential oil affected partially the development of the fungus F. oxysporum, R. solani and S. rolsii.…”