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.