Isolation and identification of succinic semialdehyde dehydrogenase inhibitory compound from the rhizome of Gastrodia elata Blume

In our search for the anticonvulsant constituent of Gastrodia elata repeate d column chromatographies guided by activity assay led to isolation of an a ctive compound, which was identified as gastrodin on the basis of spectral data. Brain succinic semialdehyde dehydrogenase (SSADH) was inactivated by preincubation with gastrodin in a time-dependent manner and the reaction wa s monitored by absorption and fluorescence spectroscopic methods. The inact ivation followed pseudo-first-order kinetics with the second-rate order con stant of 1.2x10(3) M(-1)min(-1). The time course of the reaction was signif icantly affected by the coenzyme NAD(+), which affected complete protection against the loss of the catalytic activity, whereas substrate succinic sem ialdehyde failed to prevent the inactivation of the enzyme. It is postulate d that the gastrodin is able to elevate the neurotransmitter GABA levels in central nervous system by inhibitory action on one of the GABA degradative enzymes, SSADH.