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Title: A Rare Excitatory Amino Acid from Flowers of Zonal Geranium responsible for Paralyzing the Japanese Beetle

Author
item Ranger, Christopher
item WINTER, RUDOLPH - University Of Missouri
item SINGH, MICHAEL - Rutgers University
item Reding, Michael - Mike
item Frantz, Jonathan
item Locke, James
item Krause, Charles

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2010
Publication Date: 1/25/2011
Citation: Ranger, C.M., Winter, R.E., Singh, M.E., Reding, M.E., Frantz, J., Locke, J.C., Krause, C.R. 2011. A rare excitatory amino acid from flowers of zonal geranium responsible for paralyzing the Japanese beetle. Proceedings of the National Academy of Sciences. 108(4):1217-1221.

Interpretive Summary: The Japanese beetle (Popillia japonica) exhibits rapid paralysis after consuming flowers from zonal geranium (Pelargonium × hortorum). Symptoms of paralysis first appear in the hind legs and progress anteriorly until the specimen eventually lies on its back or side with the legs extended rigidly outward. The phenomenon was first described in 1920, but since then no attempts to isolate and identify the paralytic compounds have been reported in the literature. To determine the phytochemical basis for paralysis, extracts of the flower petals from Pelargonium × hortorum cv. Nittany Lion Red were fractionated and subsequently tested for activity on adult Japanese beetles. The activity-guided fractionations ultimately resulted in the isolation of a purified compound. Structural analysis determined the compound was quisqualic acid, a known but rare excitatory amino acid previously known from only one plant genus (Quisqualis). Quisqualic acid mimics L-glutamic acid, which is a neurotransmitter in the insect neuromuscular junction and mammalian central nervous system. Quisqualic acid is an exceptionally potent agonist of excitatory amino acid receptors. These findings demonstrate zonal geranium is a previously unknown source of quisqualic acid. In addition, isolation of a neurotoxic, excitatory amino acid from zonal geranium establishes the phytochemical basis for induced paralysis of P. japonica, which had remained uncharacterized since the phenomenon was first described in 1920. Such information could assist with developing botanically-based formulations for controlling the Japanese beetle.

Technical Abstract: e Japanese beetle (Popillia japonica) exhibits rapid paralysis after consuming flowers from zonal geranium (Pelargonium × hortorum). Activity-guided fractionations were conducted with polar flower petal extracts from Pelargonium × hortorum cv. Nittany Lion Red, which led to the isolation of a paralysis inducing compound. HR-MS and NMR (1H, 13C, COSY, HSQC, HMBC) analyses identified the paralytic compound as quisqualic acid, a known but rare agonist of excitatory amino acid receptors. Geranium-derived and commercially available, synthetic quisqualic acid demonstrated a positive paralytic dose response. Isolation of a neurotoxic, excitatory amino acid from zonal geranium establishes the phytochemical basis for induced paralysis of P. japonica, which had remained uncharacterized since the phenomenon was first described in 1920.