Medicinal compounds, chemically and biologically characterised from extracts of Australian 'Callitris endlicheri' and 'C. glaucophylla' (Cupressaceae): Used traditionally in Aboriginal and colonial pharmacopoeia

Abstract

Ethnopharmacological significance: 'Callitris endlicheri' and 'C. glaucophylla' were highly valued by Australian Aboriginal people for use in medicinal applications. Pine needles were prepared using modalities of either smoking or topical preparations, requiring either aqueous or lipophilic extraction into animal fat. Extracts treated various ailments consistent with pathogenic infection, or other topical or tracheal ailments not clearly elucidated in ethnopharmacological records. Aim of the study: Here we aim firstly to investigate antimicrobial activities of both smoke, essential oil and solvent extracts and secondly to chemically characterise significant volatile compounds potentially related to medicinal or antimicrobial activities. Materials and methods: Essential oils were produced using traditional hydrodistillation of pine needles collected from 'Callitris endlicheri' and 'C. glaucophylla'. From the same material, solvent extracts were produced separately, using acetone and methanol, and then smoke extracts were produced with separate methods described herein, using fresh needles. All extracts were screened for antimicrobial activity against a range of bacterial organisms and sporicidal activity against pathogenic fungi ('Trichophyton mentagrophytes', 'T. interdigitalis' and 'T. rubrum'). Results: Essential oils produced only modest antibacterial activity and the Callitris endlicheri essential oil had moderate antifungal activity. Smoke extracts demonstrated considerable broad spectrum antimicrobial activity, but solvent extracts demonstrated more selective activity against 'Pseudomonas aeruginosa', 'Staphylococcus aureus', 'Bacillus subtilis' and the yeast 'Candida albicans'. Chemical character of essential oils was consistent with previous studies; however, solvent and smoke extracts from fresh needles produced high concentrations of potentially medicinal abietane diterpenes, specifically pisiferal, pisiferol and ferruginol; well known from Japanese species with demonstrated bioactivity. Conclusion: The occurrence of these diterpenes and other phenolics, in conjunction with significant antimicrobial activities from the various extracts, is in alignment with the use of Australian 'Callitris' species in Aboriginal medicinal practice.