The present invention provides a use of Trifolium pratense extract for enhancing the expression of hyaluronan synthase gene. The Trifolium pratense extract can increase skin water content and reduce skin wrinkles, and so as to form more moisturizing factors on the skin and maintain the integrity of the stratum corneum to enhance the skin barrier function. The Trifolium pratense extract is prepared by extracting Trifolium pratense using water, alcohols, or mixtures of water and alcohols as solvents.本發明提供一種紅菽草萃取物用於提升尿酸合成酶之基因表現量的用途，能增加皮膚含水量及減少皮膚皺紋，以使皮膚形成更多保濕因子，並維持角質層結構完整，以提升皮膚屏障功能。其中該紅菽草萃取物係紅菽草以水、醇、或醇水混合物之溶劑所萃取而得。
