|Sirvent, T - CORNELL UNIVERSITY|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 13, 2003
Publication Date: December 15, 2003
Citation: SIRVENT, T.M., GIBSON, D.M. INDUCTION OF HYPERICINS AND HYPERFORINS IN H. PERFORATUM (HYPERICACEAE) IN RESPONSE TO DAMAGE BY HERBIVORES. JOURNAL OF CHEMICAL ECOLOGY. 2003. V. 29. P. 2667-2681. Interpretive Summary: Hypericum perforatum L. (family Hypericaceae), commonly called St. John's wort, is considered to be an important dietary supplement, with worldwide sales of over $500 million annually. Much of the current market is being supplied from field grown material, although some is collected by wild harvesting. The aim of the present study was to determine whether the active biological principles, hypericins and hyperforin, are part of the inducible plant defense system of St. John's wort. We found that levels of both types of compounds were elevated when plants were subjected to insect damage by insects that feed on a wide variety of plants, but were not affected when damaged by Chrysolina quadrigemina, an insect that feeds exclusively on St. John's wort. Since the pricing of St. John's wort is based on the concentration of hypericins and hyperforin, this study may be useful in identifying factors that affect the production of the active ingredients.
Technical Abstract: Plants respond to herbivore and pathogen attack by a variety of direct and indirect mechanisms that can include induction of secondary metabolite production. The phytomedicinal plant Hypericum perforatum L. produces two different classes of secondary metabolites-hyperforins, a family of antimicrobial acylphloroglucinols, and hypericins, a family of phototoxin anthraquinones exhibiting anti-microbial, anti-viral, and anti-herbivore properties in vitro. To determine whether these secondary metabolites are part of the herbivore-specific inducible plant defense system, we used an in vitro detached assay to assess the effects of specialist and generalist herbivore damage on the levels of hypericins and hyperforin. Greenhouse-grown H. perforatum plant sections were challenged with the specialist, Chrysolina quadrigemina, or with the generalist feeders, Spilosoma virginica, Spilosoma congruta, and Sodoptera exigua. Feeding by the specialist beetle or mechanical wounding did not induce phytochemical levels in plant tissue whereas the small amount of feeding by the generalists did cause significant increases in hypericins and hyperforin, from 30-100% increases in levels. Although the leaf damage index of the specialist feeding was 2.7 times greater, C. quadrigemina does not appear to elicit H. perforatum chemical defenses in response to feeding damage.