Oven and Conventional Drying Methods Affect Volatile Oil Content and Composition of Mentha pulegium L.

Abstract

: The principal aim of the present experiment was to study the effects of different drying methods (shade drying, sun drying and oven drying at 40°C and 60°C) on essential oil compositional variation of pennyroyal (Mentha pulegium L.). Flowering tops of the plants were dried till constant weight balance via different methods. Volatile oil quantity and quality of plants were traced by Clevenger type apparatus and GC- MS, respectively. The results revealed that the drying method imposed meaningful effects on essential oil content as; shade drying (1.1 %)>oven drying at 40°C (1 %)>sun drying (0.8 %)>oven drying at 60°C (0.7 %), respectively. Volatile oil profile and their proportional percentage were also greatly affected by the drying type. Menthone (29.1-48.1 %), menthol (11.5-24.6 %), neomenthol (10.1-14.3 %), (E)-caryophyllene (3.1-8.9 %) and pulegone (4-6.9 %) were the predominant common constituents for all the drying methods with wide degree of variation. Germacrene D (4-5.1 %), menthyl acetate (1.8-8.6 %) and isopulegol (0.5-4.9 %) were the other common constituents again with the broader distribution amongst the drying methods. β-Cubebene (2.1 %) and alloocimene (1.4 %) contained the highest amount with shade drying. In contrast, piperitenone oxide (1.4-1.6 %) was exclusive of oven drying methods. Overall, considering the volatile oil major constituents, the decision on the appropriate drying method depends upon the compounds of interest.