Myrica rubra leaves as a potential source of a dual 5-LOX/COX inhibitor

Myrica rubra Sieb. et Zucc. is a valuable fruit tree that is used in Chinese, Japanese and Taiwanese traditional medicine. We investigated the anti-inflammatory activity of M. rubra leaves extracted with four different solvents. Total phenolics were determined using the Folin–Ciocalteu method. Extracts were investigated for their inhibitory activity toward the pro-inflammatory enzymes cyclooxygenase-1 and -2 (COX-1, COX-2) and 5-lipoxygenase (5-LOX). The ethanol extract of M. rubra leaves demonstrated a strong inhibition of prostaglandin E2 (PGE2) biosynthesis catalyzed by both COX-1 (93.42%) and COX-2 (75.71%) and leukotriene B4 (LTB4) formation catalyzed by 5-LOX (82.72%). Further we identified selective COX-1 inhibition by the n-butanol and aqueous fractions of the ethanol extract (with an IC50 for COX-1 inhibition of 1.07 and 0.71 µg mL−1 , respectively) and dual 5-LOX/COX inhibition by the ethyl acetate fraction (with an IC50 of 3.29 for COX-1, 2.54 for COX-2 and 8.30 µg mL−1 for 5-LOX).