VDR and rheumatoid arthritis: By analyzing the forecast targets and active RA genes, 16 potential targets of purpurin against RA were acquired, including VDR, LGALS2, CCL5, CSK, CTSS, LCK, MMP3, CFB, EGFR, TYMS, TAP1, AR, HSP90AB1, PPARG, MMP1 and STAT1, of which MMP3 was considered as the key target as it has the highest fit score with purpurin (Figure 6C, Table S1).