# Is Curzerene Responsible for the Bioactive Properties of Eugenia uniflora? A Possible Misinterpretation of Bioactive Markers

## TL;DR

This study shows that the bioactive properties of Eugenia uniflora's essential oil may be misattributed to Curzerene due to chemical changes during analysis.

## Contribution

The study demonstrates that Curzerene may be misidentified due to thermal rearrangements during gas chromatography.

## Key findings

- Curzerene may result from thermal rearrangement of Furanodiene during GC analysis.
- NMR analysis identified fewer compounds compared to GC-MS, suggesting misidentification in GC.
- Thermal treatment revealed the presence of Elemene-type compounds from rearrangement.

## Abstract

Essential oils are a complex matrix of volatile compounds
produced
by many plants of different families with diverse bioactivities. Eugenia uniflora (Myrtaceae), popularly known as the pitangueira,
is native to Brazil and a source of essential oils, mainly composed
of sesquiterpenes such as Furanodiene. Curzerene is the major contributor
to most of the bioactive properties assigned to E. uniflora. Gas chromatography (GC) is the primary technique for characterizing
essential oils. However, sesquiterpenes of the germacrene type may
undergo a [3,3]-sigmatropic rearrangement in GC, converting into Elemene-type,
leading to these compounds’ misidentification. Curzerene is
an Elemene-type compound known to result from the sigmatropic rearrangement
of furanodiene. Aiming to demonstrate this evidence, the objective
of this study was to perform a thermal treatment of the essential
oil from E. uniflora, to simulate
the heating conditions during GC to identify the chemical transformations
in this essential oil. Essential oil from E. uniflora leaves were obtained by hidrodistillation and was characterized
by GC-MS. Nine major sesquiterpenes were identified in the GC-MS analysis
of the oil, with the most prevalent being Germacrene B (16.19%), Curzerene
(13.28%), and Germacrene D (12.64%). Additionally, β-Elemene
and β-Elemenone were identified in lower concentrations. In
the NMR analysis, it was possible to identify only four germacrene-type
compounds and a small amount of Curzerene. After thermal treatment
(240 °C), the Elemenes resulting from the sigmatropic rearrangement
were identified. These results suggest that most of the properties
assigned to Curzerene throughout the years, which do not combine cold
techniques, such as NMR spectroscopy, to characterize the essential
oil of E. uniflora, were incorrectly assigned and
likely belong to furanodiene, evidencing the importance of apply different
methods of analysis in some situations.