DHFR and endothelial dysfunction: Stachydrine (alkaloid found in L. cardiaca) was proven by Xie et al. [20] to ameliorate homocysteine- (Hcy-) induced endothelial dysfunction via nuclear factor erythroid 2–related factor 2 (Nrf2) dependent upregulation of guanosine triphosphate cyclohydrolase I (GTPCH1) and dihydrofolate reductase (DHFR) enzymes and increase in bioavailabilities of tetrahydrobiopterin (BH4) and nitric oxide (NO), thus protecting endothelial function.