An Ultrahigh-Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry (UHPLC-MS/MS) Method for...

Oxygen heterocyclic compounds (OHCs) like polymethoxyflavones (PMFs), coumarins (CMNs), furanocoumarins (FCMNs), and terpenes like nootkatone (NKT) are key secondary metabolites in grapefruit essential oils (GEOs). While these compounds exhibit a plethora of promising bioactivities (e.g., antioxidant, antiallergic, anti-inflammatory, and antibacterial), potential adverse effects, such as CMN toxicity at high concentrations and FCMN phototoxicity exacerbated by UVA exposure and interactions with certain over-the-counter medications, warrant a sensitive and selective analytical method for determining their levels in GEO-based products intended for topical and oral use. To address these analytical needs, a rapid 16 min ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) method was developed for the simultaneous identification and quantification of 25 OHCs (three PMFs, seven CMNs, and 15 FCMNs) and NKT in cold-pressed GEOs. The method exhibited excellent linearity (R ² > 0.99 for all analytes), low limits of detection (LODs, 6 × 10^-8 to 1.5 × 10^-6 mg g^-1), and limits of quantification (LOQs, 2 × 10^-7 to 5 × 10^-6 mg g^-1). Intra- and interday precision (% RSD) ranged from 1.43 to 3.59% and from 2.16 to 6.90%, respectively. The resulting quantitative data will be essential for establishing safe levels of OHCs in cold-pressed GEOs, thereby minimizing phototoxicity and drug interaction risks. Furthermore, this validated method can also be applied to various GEO-based products to ensure the quality of raw materials and inform the reduction or elimination of specific OHCs.