Skin Anti-aging Assays of Proanthocyanidin Rich Red Rice Extract, Oryzanol and Other Phenolic Compounds

Abstract

Red rice is a variety of rice that has more nutritious than white or brown rice. It is also a good source of many potent anti-aging phytochemicals. However, the compounds in red rice extract that exhibit skin anti-aging properties have not been investigated. In this study, the main bioactive compounds in red rice extract (RRE) including proanthocyanidin, catechin, hydroxybenzoic acid, vanillic acid and oryzanol were studied in order to determine their anti-skin aging properties. The effects on skin degradation were assessed by inhibitory enzymatic activity against collagenase and matrixmetalloproteinase-2 (MMP-2). The production levels of collagen and hyaluronic acid obtained from human skin fibroblasts were determined by ELISA. Anti-melanogenesis activity of the bioactive compounds were investigated in B16-F10 mouse melanoma cells. The activity of collagenase and MMP-2 was strongly inhibited by proanthocyanidin and catechin, while hydroxybenzoic acid, vanillic acid and oryzanol had no effect. Moreover, proanthocyanindin and catechin significantly induced collagen and hyaluronic acid synthesis in human fibroblast cells. Proanthocyanidin and oryzanol reduced the melanin content in B16-F10 mouse melanoma cells. Proanthocyanidin, but not oryzanol, significantly decreased cellular tyrosinase activity. However, the bioactive compounds obtained from red rice extract had no effect on mushroom tyrosinase activity. In addition, proanthocynidin and catechin, exhibited strong DPPH radical scavenging activity, whereas oryzanol slightly inhibited this action. Taken together, these results suggest that proanthocyanidin, catechin, and oryzanol are the bioactive compounds in red rice that exhibit the greatest levels of anti-skin aging properties.