Qualitative And Quantitative Properties Of Essential Oil Of Mentha Pulegium L. And Mentha Suaveolens Ehrh. Affected By Harvest date

Omer, Elsayed; Aziz, Eman E.; Fouad, Rasha; Fouad, Hend

doi:10.21608/ejchem.2021.109391.5002

Qualitative And Quantitative Properties Of Essential Oil Of Mentha Pulegium L. And Mentha Suaveolens Ehrh. Affected By Harvest date

Document Type : Original Article

Authors

¹ Medicinal and Aromatic Plants Department, National Research Centre

² National Research Center, Dokki, Cairo, Egypt

³ Medicinal and Aromatic Plants Research Department, National Research Centre, Egypt

10.21608/ejchem.2021.109391.5002

Abstract

The variation in the content of secondary metabolites of medicinal and aromatic plants can be influenced by harvest date and climatic conditions. The objectives of this study were to evaluate the effect of seven harvest dates every two weeks (4th May, 17th May, 31st May, 14th June, 28th June, 12th July and 26th July) on the productivity of the essential oil content and composition of pennyroyal (Mentha pulegium L.) and apple mint (Mentha suaveolens Ehrh.) grown under environmental conditions of Egypt. Essential oils were extracted and the chemical composition was determined by gas chromatography - mass spectrophotometer (GC-MS).The fresh and dry biomass yields plant-1 of the two mint species increased with the delay in harvesting date up to 12th and 26th July. Essential oil percentage ranged from 0.26 to 0.41% in pennyroyal and from 0.07 to 0.22 % in apple mint. The major constituents of pennyroyal oil were found to be pulegone (46.91 to 94.89%) and ρ-menthan-3-one,cis (0.38 to 48.14%). The highest relative concentration of pulegone (94.89%) was obtained at the 2nd harvest date on17th May. The late harvest date on 26th July produced the highest relative concentration of ρ-menthan-3-one,cis (48.14 %.) and the lowest concentration of pulegone (46.91%). In apple mint, the major constituents were l-linalool (58.18 to73.27%) followed by linalyl acetate (6.10 to 24.56%), then α-terpineol (4.57 to7.81%) and 1,8-cineole (1.72 to 4.68%). The highest relative concentrations of l-linalool (73.27%) and1,8-cineole (4.68%) were produced from the 2nd harvest date on 17th May, while the lowest relative percentage (58.18 and 1.72 %) were recorded at the 5th harvest on 28th June. On the other hand, the highest amount of linalyl acetate (24.56%) was recorded in the 5th harvest date. It might be concluded that, the 2nd harvest date on 17th May was found to be suitable for producing the highest relative concentration of pulegone (94.89%) and l- linalool (73.27%) for pennyroyal and apple mint, respectively. While the delay in harvesting date up to 26th July increased the biosynthesis of ρ-menthan-3-one,cis (48.14 %.) and linalyl acetate (24.56%) in pennyroyal and apple mint, respectively. The harvest date affects the rate of transformation of the major constituents of the essential oil of pennyroyal and apple mint plants.

Keywords