Characterisation of volatile organic compounds of kanuka (Kunzea ericoides) subcritical water extract: A comparative analysis

Kānuka (Kunzea ericoides) is a traditional medicinal plant enriched with volatile organic compounds (VOCs) with known antimicrobial, anti-inflammatory, myorelaxant, antiviral, and insecticidal properties. Despite its known bioactive properties, a comprehensive VOCs profile of kānuka remains unexplored. This study evaluated the efficiency of subcritical water extraction (SWE) in profiling kānuka leaf VOCs, using gas chromatography-mass spectrometry (GC-MS), and compared the results conventional extraction methodologies, including steam distillation (SD) and solvent extraction (SE). The data revealed that kānuka contains diverse compounds, including terpenes, alkanes, esters, ketones, and alkenes. SWE was more efficient due to its wide range of selectivity in recovering a large number of VOCs (103 compounds) at a lower temperature (120°C) and time (20 min). SD was more effective in recovering terpenes, whereas SE exhibited limited selectivity for alkane groups. SWE facilitated the chemical transformation of compounds, including decarboxylation and hydroxylation, as the temperature increased and the recovery of oxygenated terpenes, alkanes, and ester derivatives. It indicates that SWE provides efficient extraction and induces structural modifications, which are beneficial for enhancing the biological properties. This study highlights the broad compound selectivity of SWE and its compatibility with GC-MS analysis. Additionally, it provides insights into method optimisation for chromatographic profiling of VOCs and supports the development of sustainable extraction methodologies for bioactive compound characterisation that focuses on industrial applications in the pharmaceutical, cosmetic, and food sectors.