Rapid Spectrophotometric Method for Assessing Hydroperoxide Formation from Terpenes in Essential Oils upon Oxidative Conditions

Abstract

Essential oils are widely used in the food and cosmetics industry as natural flavoring and fragrance substances. For this reason, a thorough quality control applying selected analytical methods is required. Oxidation along with hydroperoxide formation is an important drawback during production and storage of essential oils. Hydroperoxides constitute the main products formed upon photo-oxidation of essential oils. Due to hydroperoxide instability, gas chromatography (GC) and high-performance liquid chromatography (HPLC) analyses are required. According to the European Pharmacopoeia, titration is the official method for oxidation assessment. However, this analysis is time-consuming, and large sample quantities are required. Here, we present a simple and accurate spectrophotometric method for the detection of peroxide trace amounts in essential oils and terpenes. The principle is based on the formation of Wurster’s red, which is enforced by the peroxide-driven oxidation of N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD). The method was validated using dibenzoyl peroxide (DBP) and cumene hydroperoxide (CHP). To demonstrate the suitability of the method for routine analysis, various oxidized terpenes and essential oils were chosen. Moreover, photo- and thermal oxidation experiments were compared and evaluated using gas chromatography/mass spectrometry (GC/MS) and a synthesized limonene-2-hydroperoxide (Lim-2-OOH) reference standard to gather detailed information on the structural changes of the respective terpenes.

An Optimized Terpene Profile for a New Medical Cannabis Oil

“…Remarkably, the final composition of MCO-2 and MCO-3 was further varied. In particular, they were deprived of oxidized terpenes, thus free of secondary thermal oxidation's products as aldehydes and ketones [30,38]. The formation of these compounds could significantly affect the quality of a product being a marker of aging [38].…”

“…In particular, they were deprived of oxidized terpenes, thus free of secondary thermal oxidation's products as aldehydes and ketones [30,38]. The formation of these compounds could significantly affect the quality of a product being a marker of aging [38]. For example, the presence of oxidized terpenes in essential oils has been associated with shifting colors, unpleasant smell, unpalatable taste, and consistency alterations [39].…”

“…For example, limonene acute toxicity is reported associated with its oxidized product that is limonene hydroperoxide [44]. Thus, the absence of oxidized components in MCOs is an important requisite both for the quality control of the product and the safety of the patients [38].…”

Copper Hexacyanoferrate as a Novel Electrode Material in Electrochemical Detection of Cumene Hydroperoxide

“…Organic peroxides such as CHP can be detected by mass spectrometry, 18 gas chromatography, 19 high-performance liquid chromatography, 20 fluorescence, 21 spectrophotometry, 22 and electrochemistry. [23][24][25] The focus of this work lies in the electrochemical methods which allow low-cost analysis of CHP at fast speed.…”