Multifunctional Biological Activities of Luteolin and Rosmarinic Acid Isolated From Perilla Frutescens.

Luteolin and rosmarinic acid isolated from the seed of Perilla frutescens (L.) was found to possess preventive antioxidant activities. These two phenolic compounds prevent generation of influenza virions by inhibiting rvH1N1 neuraminidase (EC 3.2.1.18). Notably, the inhibition kinetics analyzed by Dixon plots indicates that luteolin and rosmarinic acid are noncompetitive inhibitor and inhibition constant, K_i, were estimated as 14.3 and 43.9 μM, respectively. Luteolin inhibited the soybean lipoxygenase-1 (EC 1.13.11.12, Type 1) catalyzed oxidation of linoleic acid with an IC₅₀ of 5.0 μM. The inhibition kinetics indicate that luteolin is a simple reversible noncompetitive slow-binding inhibition against soybean lipoxygenase-1 with kinetic parameter (k₃ = 0.056 μM^-1min^-1, k₄ = 0.006 μM^-1min^-1, K_i^app = 0.106 μM). Subsequently, luteolin also inhibited α-glucosidase and recombinant human aldose reductase with IC₅₀ of 45.4 and 0.6 μM, respectively. In the α-glucosidase inhibition kinetics analyzed by Dixon plot indicates that luteolin is a noncompetitive inhibitor, and the inhibition constant, K_I was obtained as 45.0 μM. Notably, the inhibition kinetics of luteolin does follow hyperbolic dependence of aldose reductase inhibition on Dixon plots. Thus inhibition kinetics indicated that luteolin is a mixed type inhibitor.