Determination of Enantiomeric Distribution of Terpenes for Quality Assessment of Australian Tea Tree Oil

Abstract

A number of papers have appeared in recent years proposing the use of enantiomeric ratios of key monoterpenes in Australian tea tree oil (TTO) for detection of adulterated oils. There are however a range of reported values, even from exactly the same suite of authentic oils, and we address here probable reasons for these differences and stress the importance of establishing reference ratios within each laboratory based on oils of known provenance. Any biological variation in the ratio for the key terpene terpinen-4-ol has been demonstrated to be effectively unmeasurable, because the standard deviation on multiple measurements of the same oil is of the same order as that of multiple authentic oils.

TLC-Based Bioassay to Isolate Kairomones from Tea Tree Essential Oil That Attract Male Mediterranean Fruit Flies, Ceratitis capitata (Wiedemann)

“…Enantiomeric distribution has provided a powerful tool for quality and authenticity control of essential oils [68][69][70][71]. The ISO 4730:2017 (oil of Melaleuca, terpinen-4-ol type) addressed the enantiomeric distribution of (+)-terpinen-4-ol (67−71%) in authenticated TTOs [65].…”

Pulmonary delivery of tea tree oil-β-cyclodextrin inclusion complexes for the treatment of fungal and bacterial pneumonia

“…It is worth in the order of AU$ 29 million per year in Australia. In 2015, more than 800 tonnes of TTO were produced . TTO is a promising natural non‐toxic, non‐contaminating, biodegradable and seldom resistant antimicrobial material.…”

“…In 2015, more than 800 tonnes of TTO were produced. [9] TTO is a promising natural non-toxic, non-contaminating, biodegradable and seldom resistant antimicrobial material. However, its strong stimulation, allergic reactions, volatilization, instability under light or oxygen and poor water solubility restrict the therapeutic potential of TTO.…”

Piper nigrum Oil – Determination of Selected Terpenes for Quality Evaluation

“…Terpinene-4-ol is an important component of many essential oils. This compound has recently been included in the revised international standard, ISO 4730-2017: Essential Oil of Melaleuca, terpinen-4-ol type (tea tree oil) [29] because of the consistent chiral ratio signature observed in authenticated oils that could aid in distinguishing oils of high purity for the terpine-4-ol chemotype from oils adulterated with other compounds [18,32]. The chiral ratio of this compound was also measured in P. nigrum.…”

“…Interestingly, consistency in enantiomeric distribution of these four levorotatory terpenes indicates possible stereocontrolled biogenesis in P. nigrum plants regardless of the geographical origin of the black pepper. An investigation very similar to the one described herein was carried out with a large set of tea tree oils from Australian M. alternifolia plants [32]. The enantiomeric compositions of limonene, terpinene-4-ol, and α-terpineol in tea tree oils were determined.…”