Anti‐skin ageing activities of rice (Oryza sativa) bran soft and hard waxes in cultured skin cells

Abstract Objective Rice ( Oryza sativa ) bran waxes, the by‐products of rice bran oil manufacturing, are widely used as inactive components in several preparations. Nevertheless, the function of rice bran waxes against skin ageing has never been reported. This study aimed to investigate thermal property and fatty acid profile of rice bran waxes, including rice bran soft (RBS) and hard (RBH) waxes, and the activities against skin ageing in cultured skin cells. Methods Thermal property and fatty acid profile of rice bran waxes were analysed by differential scanning calorimetry and gas chromatography–mass spectrometry, respectively. The cytotoxicity assay of waxes was performed in B16F10 melanoma cells, human skin fibroblasts and co‐culture cells of HaCaT cells and human skin fibroblasts. The non‐cytotoxic concentrations of waxes were evaluated for their activities against skin ageing, including melanogenesis assay, antioxidant activity, collagen content analysis, matrix metalloproteinase‐1 and matrix metalloproteinase‐2 inhibitory assay and anti‐inflammatory activity. Results Thermal property indicated the endotherm peaks with melting temperatures at 40.89 ± 0.27°C and 69.64 ± 0.34°C for RBS and RBH, respectively. The main fatty acids in RBS were oleic (31.68 ± 0.75%) and linoleic acids (27.19 ± 0.40%), whereas those in RBH were palmitic (36.24 ± 1.08%) and stearic acids (35.21 ± 4.51%). The cytotoxicity assay in single cells and co‐culture cells showed the non‐cytotoxicity of RBS (0.0001–1 mg/mL) and RBH (0.0001–0.1 mg/mL). The anti‐skin ageing activities of 1 mg/mL RBS and 0.1 mg/mL RBH included the melanogenesis inhibition by suppression of tyrosinase and tyrosinase‐related protein‐2 enzymes, the antioxidant activity by cellular protection against cell damage and cell death, the collagen stimulation, the matrix metalloproteinase‐1 and matrix metalloproteinase‐2 suppression and the anti‐inflammation. Conclusions The study results suggest that RBS and RBH can potentially be applied as the functional ingredients in formulations against skin ageing as well as provide the superior benefit on skin moisturization.