Anti-inflammatory activity and secondary metabolite profiling of Eucalyptus camaldulensis (Myrtaceae)

Aim: This study investigated the anti-inflammatory effect of the extract and fractions of Eucalyptus camaldulensis and also profiled the secondary metabolites of its most active fraction. Methods: The leaves of E. camaldulensis were collected, authenticated and extracted with methanol. The extract (100, 200, and 400 mg/kg), normal saline (negative control), and aspirin (positive control) were administered orally to egg-induced paw oedema rats of five groups of five rats each. The extract was partitioned, and each of the solvent fractions was assayed for its anti-inflammatory activity. The results obtained were subjected to one-way analysis of variance (ANOVA) followed by Bonferroni post hoc tests, and p < 0.05 was considered significant. Also, the most active fraction was subjected to gas chromatography-mass spectrometry (GC-MS) analysis. Results: The extract at 100 mg/kg demonstrated the best anti-inflammatory effect at 29%, while the n-hexane (N-HEX) fraction gave the highest inflammatory inhibition at 43%. α-Phellandrene, o-cymene, n-hexadecanoic acid, and beta-sitosterol were identified as the most abundant compounds in the N-HEX fraction. Conclusions: The study concluded that the methanol extract of E. camaldulensis possesses good anti-inflammatory properties, and its non-polar fraction was responsible for the observed activity. Bioassay-guided purification of anti-inflammatory constituents of the N-HEX fraction is recommended for future studies.