Obtaining thymoquinone and thymohydroquinone from Wild bergamot (Monarda fistulosa L.)

Abstract

Background: Thymoquinone (TQ) and thymohydroquinone (THQ) are natural substances with antibacterial, antimycotic, antiviral, anticancer, antioxidant activity. Previously, was developed the method for obtaining Wild bergamot essential oil with high TQ content. The objective of this study was to create methods for obtaining individual substances TQ and THQ from Wild bergamot herb. Material and methods: Aerial parts of Wild bergamot have been collected from the plantation of the Scientific Practical Centre of Nicolae Testemitanu State University of Medicine and Pharmacy. The hydrodistillation method has been used for essential oil isolation and fractionation, and purification of individual substances. The analytical part of study has been performed by the HPLC method. Results: THQ was obtained in crystalline form by reducing TQ directly in the essential oil with ascorbic acid, sulphurous acid, or natural components of the Wild bergamot essential oil. Subsequent oxidation of THQ with hydrogen peroxide or nitrous acid gave TQ. Additionally, the yield of TQ was increased by optimising the parameters of plant material fermentation and using two-stage hydrodistillation with intermediate oxidation of the THQ formed at the first stage. Conclusions: Several technological procedures were created to obtain THQ from the Wild bergamot essential oil with a yield from 68-74% to 93-97% and TQ from THQ with a yield of 87-92%. The procedure of plant material processing has been optimised also to obtain essential oil with 48-56% TQ and not more than 12% residual phenols.