Inhibitory effects of baeomycesic acid from the lichen Thamnolia subuliformis on 5-lipoxygenase in vitro

Baeomycesic acid (1), a β-orcinol depside isolated from the lichen Thamnolia subuliformis (Ehrh.) W. Culb. was tested for in vitro inhibitory effects on arachidonate metabolism. Results showed that baeomycesic acid has potent dose-dependent inhibitory effects on 5-lipoxygenase isolated from porcine leucocytes, with an IC(50) value of 8.3 μM. Structure-activity relationships are discussed in comparison to other phenolic lichen constituents. Baeomycesic was inactive when tested for in vitro inhibitory effects against cyclooxygenase isolated from sheep seminal vesicle microsomes.