Phagocytosis is a primary and an essential step of host defense, and is triggered by the interaction of particles with specific receptor of macrophages. In this study, we investigated the effect of extracts of Rudbeckia laciniata (RLE) on the phagocytic activity of macrophage, by monitoring the phagocytosis-associated signal transduction. RLE markedly increased phagocytosis of serum-opsonized zymosan particles (SOZ), while phagocytosis of IgG-opsonized zymosan particles (IOZ) or none-opsonized zymosan particles (NOZ) remained unaffected. However, RLE did not affect the binding of opsonized zymosan particles (OZ) with the cell surface of macrophage. This suggests that RLE may regulate SOZ-induced intracellular signaling during phagocytosis of macrophage. To confirm this hypothesis, we investigated whether RLE was involved in the RhoA-mediated signal transduction during phagocytosis of SOZ. Inhibitors of the RhoA-mediated signaling pathway, such as Y-27632 (for ROCK), ML-7 (for MLCK), and Tat-C3 (for RhoA), totally blocked phagocytosis of SOZ enhanced by RLE, as well as phagocytosis of SOZ. Additionally, RhoA activity was markedly increased when cells were treated with RLE, suggesting that RLE could increase the phagocytic activity of macrophage via RhoA-ROCK/MLCK signal pathway. Thus, RLE may be used to develop functional foods for immunity.

The objective of the present investigation was to obtain vitamin, mineral, flavonoid, and polyphenol profiles of Rudbeckia laciniata (RL), and to examine the effects of extract of RL (RLE) on various physiological activities of HaCaT keratinocyte for the utilization of RL as natural raw materials to develop functional food. To accomplish this purpose, we checked the contents of the general nutrients of RL. The contents of vitamin A, vitamin B1 and vitamin B2 were 7.49 μg/g, 51.96 μg/g, and 132 μg/g respectively, while vitamin C and vitamin D3 were not detected. The contents of mineral such as Ca, K and Fe were 2.01 mg/g, 6.06 mg/g and 0.03 mg/g respectively. Total flavonoid contents of RLE were 0.25 mg/g, and total polyphenol were estimated as 1.43 mg/g. Because RL contains high levels of vitamin A which is associated with skin aging, we investigated the effect of RLE on physiological function of keratinocytes with respect to skin aging. We found that RLE significantly increased the growth rate of HaCaT cells and reduced ultraviolet radiation B (UVB)-induced cellular toxicity. Also, the extract of Rudbeckia laciniata attenuated the UVB-induced reactive oxygen species (ROS) generation in a dose-dependent manner in HaCaT cells. In addition, treatment with the extract dose-dependently increased migration activity of HaCaT cells. Thus, these findings indicated that RLE could regulate the physiological activity of keratinocytes, and may be used to develop functional foods.