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Drying temperature changes trichome integrity, chemical content and composition of the essential oil of pepper-rosmarin

ABSTRACT: Medicinal plants are generally commercialized dried. However, temperatures used in their drying processes may interfere with the content and chemical composition of their essential oils. The Lippia origanoides possesses thymol in the essential oil that is stored in glandular trichomes. Thymol is a major component of economic importance in the chemical and pharmaceutical industry. The objective of this study was to evaluate the effect of the drying temperatures of L. origanoides leaves regarding trichome integrity, content, and chemical composition of the essential oil. The experimental design was completely randomized with four treatments defined by oven drying temperatures (40, 50, 60, and 70ºC) and four replications. Essential oil was extracted by hydro distillation and the essential oil contents were determined (%). Chemical composition of the oil was analyzed by gas chromatography coupled to mass spectrometry. Scanning electron microscopy was carried out to determine trichome integrity. Drying the L. origanoides leaves in a forced ventilation oven at 40°C minimized the loss of extracted essential oil content (17.5g kg-1) and relative thymol percentage. Leaves dried at the temperatures of 60 and 70ºC exhibited a higher percentage of ruptured trichomes and reduced essential oil content to 13.7g kg-1 and 11.8g kg-1, respectively.