Syringin from stem bark of Fraxinus rhynchophylla protects Aβ(25–35)-induced toxicity in neuronal cells

The medicinal herb Jinpi , derived from the dried stem barks of Fraxinus rhynchophylla belonging to Oleaceae is widely used as a variety of Korean folk remedies for anti-inflammatory, febricide, antidiarrhea, and antileukorrhea diseases. In the course of screening antidementia agents from natural products, F. rhynchophylla showed significant inhibitory activity toward Aβ (25–35) -induced neuronal cell death. An active principle was isolated and identified as syringin. When the neuroblastoma cells were exposed to 50 μM Aβ (25–35) , 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction rate (survival rate) decreased to 60.21 ± 2.16% over control while syringin treated ones recovered cell viability up to 79.12 ± 1.39% at 20 μM. In addition, 20 μM syringin almost completely removed Aβ (25–35) -induced reactive oxygen species. The neuroprotective effect of syringin seemed to be originated from the reduction of apoptosis since decrease in caspase-3 activity and expression, reduction in cleaved PARP, and DNA fragmentation were observed. These results suggest that F. rhynchophylla and syringin are expected to be useful for preventing Aβ (25–35) -induced neuronal cell damage.