HPTLC Analysis and Chemical Composition of Selected Melaleuca Essential Oils

Abstract

Tea tree oil (TTO) is a volatile essential oil obtained by distillation, mainly from the Australian native plant Melaleuca alternifolia (Maiden & Betche) Cheel (Myrtaceae). In this study, a comparative analysis of the chemical constituents of seven tea tree oils (M. alternifolia) and four other Melaleuca spp. oils (M. cajuputi, (MCa), two chemotypes of M. quinquenervia, (MNe and MNi), and M. ericifolia (MRo)) was carried out using gas chromatography–mass spectrometry (GC-MS) and high-performance thin-layer chromatography (HPTLC). Among the seven TTOs, terpinen-4-ol (37.66–44.28%), γ-terpinene (16.42–20.75%), α-terpinene (3.47–12.62%), α-terpineol (3.11–4.66%), and terpinolene (2.75–4.19%) were the most abundant compounds. On the other hand, the most abundant compounds of the other Melaleuca oils varied, such as 1,8-cineole (64.63%) in MCa oil, (E)-nerolidol (48.40%) and linalool (33.30%) in MNe oil, 1,8-cineole (52.20%) in MNi oil, and linalool (38.19%) and 1,8-cineole (27.57%) in MRo oil. HPTLC fingerprinting of Melaleuca oils enabled the discrimination of TTO oils from other Melaleuca spp. oils. Variation was observed in the profile of the Rf values among EOs. The present study shows that HPTLC is one of the best ways to identify and evaluate the quality control in authenticating TTOs, other Melaleuca EOs, or EOs from other species within the Myrtaceae.

Comparison of Approaches for Authentication of Commercial Terpinen-4-ol-type Tea Tree Oils Using Chiral GC/MS

“…A summary of all 114 peaks initially identified in the TTO library ( n = 88) and oxidized TTO samples ( n = 12) is provided in Supporting Information Table S6. The peaks were then further identified by comparison to analytical standards, mass spectra in the NIST 17.0 MS library, SpectraBase, and PubChem, published RI on both chiral β-cyclodextrin and nonpolar columns ,,− and also considering the concentration and frequency of detection in unoxidized and oxidized TTO (Supporting Information Table S7). Twenty-five peaks were matched to analytical standards, 28 peaks were identified using both mass spectra and RI data, 14 peaks were identified by either RI or mass spectra data, 31 peaks were not identified, and 7 peaks were not considered further due to the low frequency of detection above 0.01% (Supporting Information Table S6).…”

“…Constituent identification was based on comparison of retention time to selected authentic standards (Supporting Information Table S1) and comparison of the spectra with mass spectral databases (NIST 17) using a probability-based matching algorithm. Additional identification was undertaken for TTO components previously reported, particularly considering relative retention indices (RIs) reported for chiral β-cyclodextrin and nonpolar columns. ,,− RIs were determined by comparing the retention time of identified components with the retention time of nearby n -alkanes in diesel fuel, using the generalized linear equation developed for temperature-programmed GC . In addition to measuring RI on the β-cyclodextrin column used in the reported e GC–MS method, RIs were also determined on a nonpolar HP-5MS column with the same parameters as the e GC–MS method except for a different He carrier gas flow (1.1 mL/min) and temperature program (Supporting Information Table S4).…”

Consort allergic contact dermatitis due to propolis in eardrops

“…6 This case report includes Propoxol ear drops as a source of consort dermatitis, in which not only propolis but also Melaleuca essential oils containing mainly terpenoids constitute the main sensitising constituents. 7 AUTHOR CONTRIBUTIONS Kerre Stefan: Conceptualization; data curation; formal analysis; investigation; writingoriginal draft. Goossens An: Writingreview and editing.…”