The Antioxidant and Tyrosinase-inhibiting A ctivities of 8-O-4′ N eolignans from Crataegus pinnatifida S eeds

Many tyrosinase inhibitors have been alleged to have serious side effects. To search for relatively mild and safe tyrosinase inhibitors, two new 8-O-4′ neolignans, named huangnin A (1) and B (2), and four known analogs (3-6) were isolated from the seeds of Crataegus pinnatifida. Their structures were elucidated by spectroscopic analyses (1D, 2D NMR, HRESIMS, CD and Rh 2(OCOCF 3) 4-induced CD). In addition, the in vitroantioxidant and anti-tyrosinase activities of all isolates were evaluated. The results showed that compound 5 has good antioxidant and promising tyrosinase-inhibiting activities.