The anti-inflammatory potential of hydrophilic polyphenolic-rich extracts obtained from native Australian herbs: anise myrtle, lemon myrtle and Tasmannia pepper leaf, and a reference sample bay leaf, was evaluated using the lipopolysaccharide (LPS)-activated murine macrophage RAW 264.7 model. Pretreatment with all herbal extracts at non-cytotoxic concentrations reduced the LPS-induced protein levels of pro-inflammatory enzymes, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). Concomitant decrease in accumulation of their products, prostaglandin E2 (PGE2) and nitric oxide (NO), respectively, was observed. A suppression of LPS-induced expression of COX-2 and iNOS and decrease of NO and PGE2 levels suggests potential anti-inflammatory properties of the extracts. Anise myrtle, lemon myrtle and bay leaf selectively inhibited COX-2 and iNOS enzymes, while Tasmannia pepper leaf extract exhibited a pronounced inhibitory activity toward COX-1 and was the least effective inhibitor of iNOS. Anise myrtle and lemon myrtle are potentially more efficient anti-inflammatory agents than Tasmannia pepper leaf.
Keywords: Anise myrtle; COX-1; COX-2; Herbs; Lemon myrtle; Polyphenols; Tasmannia pepper leaf; iNOS.