Pittosporum angustifolium (Gumbi Gumbi) is a culturally significant Australian native species widely used in traditional medicine. While recent studies have confirmed its rich phenolic composition and strong antioxidant capacity, limited attention has been given to chemotaxonomic variation linked to provenance, which remains a key barrier to authentication, standardization, and responsible commercial development.

This study investigated phytochemical variability in P. angustifolium leaves collected from multiple locations across Central Queensland, Australia. A multi-tiered analytical framework was employed, integrating total phenolic (TPC), flavonoid (TFC), and monomeric anthocyanin (TMA) contents, alongside antioxidant capacity assessed by FRAP and CUPRAC assays. Targeted LC–MS analysis of chlorogenic acids (CGAs), together with selected phenolics of interest, was undertaken and supported by acid and enzymatic hydrolysis to resolve esterified and free phenolic fractions. Antimicrobial activity was also evaluated to link chemical composition with functional bioactivity.

Strong and consistent associations were observed between total CGA content and antioxidant capacity, supporting CGAs as dominant contributors to functional activity. On this basis, the study hypothesizes that relative CGA isomer distributions may vary with provenance, reflecting the influence of environmental conditions and underlying genetic diversity on phytochemical accumulation. This work, therefore, establishes an initial CGA-centered chemotaxonomic framework for Gumbi Gumbi in Central Queensland, providing a foundation for future provenance verification and material authentication.

Beyond documenting natural variability, this study demonstrates how targeted, marker-based chemotaxonomy can support quality assurance, functional standardization, and evidence-based cultivation strategies for culturally important medicinal plants. As interest grows in Indigenous-led agronomic production of Gumbi Gumbi, these findings provide a scientifically rigorous and culturally respectful platform for linking provenance, bioactivity, and translational outcomes.

Keywords: Gumbi Gumbi; Pittosporum angustifolium; chemotaxonomy; provenance authentication; chlorogenic acids; LC–MS; antioxidant activity