Chemotype variations in Melaleuca cajuputi Powell essential oils from Peninsular Malaysia using GC-MS and chemometric analysis

Melaleuca cajuputi Powell (MC), locally known as ‘Gelam’, is a native Malaysian species valued for its essential oils and therapeutic uses. While 1,8-cineole-rich chemotypes from Indonesia and Australia are well described under subsp. cajuputi, the Malaysian populations remain poorly documented. Twenty MC oil samples from Peninsular Malaysia were analysed using GC-MS and chemometric analysis to tentatively determine their major chemical constituents and chemotypic variations, revealing three distinct chemotypes: Chemotype 1 (β-caryophyllene and humulene-rich); Chemotype 2 (mixed β-caryophyllene/β-elemene/terpinen-4-ol/p-cymen-8-ol profile); and Chemotype 3 (p-cymene-rich). Compared to published reports, Malaysian oils contained significantly lower 1,8-cineole levels but higher contents of β-caryophyllene, humulene, p-cymene, β-elemene and terpinene-4-ol. These chemical patterns show similarities to characteristics previously reported for subsp. cumingiana, although further validation is needed. This study provides the first chemotype-based pattern recognition of Malaysian MC and demonstrates the value of chemometric approaches for essential oil classification and preliminary chemotaxonomic investigation.