Abstract:
Metrosideros robusta (Northern Rata) is a flowering tree endemic to New Zealand. Very few
studies have investigated the chemical composition of the tree. A prior study found it to be
high in monoterpenes and sesquiterpenes. This likely suggests that the essential oil could be
high in anti-microbial and anti-oxidant properties. This study hopes to examine chemical
composition of the essential oil of the leaves, and identify if there are any bioactive
properties. Water steam distillation (WSE) and Solvent extraction (SE) were investigated to
extract three different essential oils from the Rata tree leaves; fresh plant solvent extraction
(FP SE), dried plant solvent extraction (DP SE), and fresh plant steam distillation (FP SD).
Solvent extraction produced high essential oil yields with more volatile compounds present.
The primary volatile compounds discovered δ-Cadinene, Naphthalene,
1,2,3,4a,5,6,7-hexahydro-1,6 -dimethyl1 4-(1 -methylethyl)-, Myrtenyl acetate, Copaene, and
β-Eudesmene by gas chromatography-mass spectrometry. All of these compounds are
terpenes. FPSE essential oil demonstrated the lowest bactericidal concentration against both
Escherichia coli (2.4% w/v) and Staphylococcus aureus. (0.6% w/v). DPSE EO demonstrated
the lowest fungicidal concentration again Candida albicans (2.5% w/v). All EO’s showed
antimicrobial activity. FPSE and DPSE both showed similar antioxidant activity. In summary
the results show the identification of volatile compounds in the Northern Rata lead and
suggest that it could have applications therapeutically. Future in vitro investigation into the
purification and bioactivity of the northern rata leaf would be worth conducting.