Comprehensive quality assessment of peppermint oils and commercial products: An integrated approach involving conventional and chiral GC/MS coupled with chemometrics

Authors: Wang, Mei; LEE, JOSEPH - University Of Mississippi; ZHAO, JIANPING - University Of Mississippi; LEE, JOSEPH - University Of Mississippi; CHATTERJEE, SHAMBA - University Of Mississippi; CHITTIBOYINA, AMAR - University Of Mississippi; ALI, ZULFIQAR - University Of Mississippi; KHAN, IKHLAS - University Of Mississippi

Submitted to: Journal of Chromatography B
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2023
Publication Date: 12/8/2023
Citation: Wang, M., Lee, J., Zhao, J., Lee, J., Chatterjee, S., Chittiboyina, A.G., Ali, Z., Khan, I.A. 2023. Comprehensive quality assessment of peppermint oils and commercial products: An integrated approach involving conventional and chiral GC/MS coupled with chemometrics. Journal of Chromatography B. 1232:123953. https://doi.org/10.1016/j.jchromb.2023.123953.
DOI: https://doi.org/10.1016/j.jchromb.2023.123953

Interpretive Summary: Peppermint essential oil (EO) is a versatile and aromatic EO derived from leaves of the peppermint plant, scientifically known as Mentha x piperita. With its invigorating minty scent and a myriad of potential benefits, peppermint EO has earned a prominent place in traditional herbal medicine, contemporary wellness practices, and even the food and beverage industry. Despite its popularity and economic significance, peppermint EO is one of the most frequently adulterated EOs. Although ISO standards for peppermint EO exist, detecting sophisticated forms of adulteration remains challenging. To address this issue, a combination of techniques including both conventional and chiral GC/MS, along with chemometrics was utilized to evaluate an extensive set of authentic and commercial peppermint EOs. A comparison of the conventional GC/MS data with the ISO standard indicated that 27 out of the 36 commercial samples were not qualified to be ISO peppermint EO. Chiral methods provide a relatively simple, robust, and cost-effective means to investigate the authenticity of peppermint EO based on the enantiomeric distributions of eight specific terpenes. In this investigation, the outliers identified by chiral analysis coincided with those identified by the conventional GC/MS analysis. Furthermore, chemometric analysis was also used to isolate outliers in commercial samples. This investigation illustrates the utility of combining multiple techniques to assess the quality and authenticity of peppermint EO, as well as detecting potential adulteration.

Technical Abstract: Peppermint essential oil (EO) has a multitude of applications, such as a fragrance in cosmetics, personal care and industrial products, or as a flavoring ingredient in food and beverages. Despite its popularity and economic significance, peppermint EO is often adulterated to reduce production costs and to increase profits. Although the ISO standard for peppermint EO exists, detecting sophisticated forms of adulteration remains challenging. The current study used conventional and chiral GC/MS analysis of volatiles compounds, and chemometric techniques to evaluate an extensive set of authentic peppermint EO (n = 22) and commercial products (n = 36) purported to contain peppermint EO. Specifically, thirty-six terpenoids were examined in each sample and compared with the ISO standard. Seventy-five percent of the selected commercial products did not meet the ISO specifications and the ratio between menthone/isomenthone was proven to be a good indicator for authentication and adulteration detection. Chiral GC/MS was further employed to measure eight terpenoids: a-pinene, ß-pinene, limonene, menthol menthone, isomenthone, pulegone, and menthyl acetate. The enantiomeric compositions of 28 commercial products were above or below the norm measured from authentic peppermint EOs. Of the 28 samples, one met the ISO standard. A class prediction model based on partial least squares-discriminant analysis (PLS-DA) of conventional GC/MS data was constructed using authentic peppermint EOs. The model can distinguish the most common types of peppermint EOs (US, India, and US/India blend) sold in the US market and was then used to analyze commercial samples. The results from chemometric analysis were consistent with ISO and chiral GC/MS analysis. Overall, the applicability of combining conventional, chiral GC/MS and chemometric tools has been successfully demonstrated to address the overall quality of peppermint EOs in commerce and may help combat sophisticated adulteration.