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

• Published in: Ciência rural 2018-01, Vol.48 (11)
• Main Authors: Queiroz, Giovanna Alcântara, Silva, Pedro Henrique Lopes, Oliveira, Rosilene Aparecida de, Sodré, George Andrade, Costa, Larissa Corrêa do Bomfim
• Format: Article
• Language: English
• Subjects: AGRONOMY; Chemical composition; Commercialization; Design of experiments; Distillation; Drying; Drying oils; Drying ovens; Economic importance; Essential oils; Experimental design; Gas chromatography; Herbal medicine; Integrity; Leaves; Lippia; Lippia origanoides; Mass spectrometry; Mass spectroscopy; medicinal plant; Medicinal plants; Oils & fats; Pharmaceutical industry; Quality standards; Scanning electron microscopy; secretory structures; Thymol; Trichomes; Ventilation
• ISSN: 0103-8478; 1678-4596; 1678-4596
• DOI: 10.1590/0103-8478cr20180283

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. RESUMO: As plantas medicinais são geralmente comercializadas secas, no entanto, as temperaturas utilizadas nos processos de secagem podem interferir no teor e composição química dos óleos essenciais destas plantas. A Lippia origanoides possui timol em seu óleo essencial, que se encontra armazenado em tricomas glandulares. O timol é um componente majoritário de importância econômica na indústria química e farmacêutica. O objetivo do trabalho foi estudar o efeito das temperaturas de secagem de folhas de L. origanoides na integridade dos tricomas, teor e composição química do óleo essencial. O delineamento experimental foi inteiramente casualizado, com quatro tratamentos definidos por temperaturas de secagem em estufa (40ºC, 50ºC, 60ºC e 70ºC) e quatro repetições. Foram realizadas extrações por hidrodestilação e determinação dos teores dos óleos essenciais (%), análise de composição química do óleo por cromatografia gasosa acoplada à espectrometria de massas e microscopia eletrônica de varredura para determinação da integridade dos tricomas. A secagem das folhas de L. origanoides em estufa de ventilação forçada a 40ºC minimizou a pe