Arctiin, a lignin isolated from Arctium lappa, exhibits a variety of biological effects, including anti‑viral, anti‑inflammatory, and anti‑proliferative actions, in mammalian cells. In a previous study, arctiin was demonstrated to induce procollagen type I synthesis and exhibited protective effects against ultraviolet B (UVB) radiation in normal human dermal fibroblasts (nHDFs). However, the underlying molecular mechanism of arctiin‑mediated collagen synthesis remains unknown. In the present study, the mechanism for increased expression of collagen type 1α 1 chain (COL1A1) mRNA in arctiin‑induced nHDFs was identified. The expression of microRNA‑378b (miR‑378b), downregulated by arctiin, was correlated with the expression of sirtuin‑6 (SIRT6) mRNA, a regulator of COL1A1 mRNA. Furthermore, it was revealed that arctiin protected the UVB radiation‑mediated decrease in COL1A1 mRNA expression, through the miR‑378b/SIRT6 signaling pathway. In conclusion, these results suggest that arctiin regulates COL1A1 through the miR‑378b‑SIRT6 axis.