Pinoresinol: A lignol of plant origin serving for defense in a caterpillar

Abstract

Pinoresinol, a lignan of wide distribution in plants, is found to occur as a minor component in the defensive secretion produced by glandular hairs of caterpillars of the cabbage butterfly, Pieris rapae. The compound or a derivative is appropriated by the larva from its normal food plant (the cabbage, Brassica oleracea). Pinoresinol was shown to be absent from the secretion if the larva was given a cabbage-free diet but present in the effluent if that diet was supplemented with pinoresinol. Pinoresinol is shown to be a feeding deterrent to ants (Formica exsectoides), indicating that it can complement the defensive action of the primary components of the secretion, a set of previously reported lipids called mayolenes. In the test with F. exsectoides, pinoresinol proved to be more potent than concomitantly tested mayolene-16.ignans comprise a large class of secondary metabolites in vascular plants. Derived from the three phenyl-propanoid precursors, p-coumaryl alcohol (1 in Fig. 1), coniferyl alcohol (2 in Fig. 1) and sinapyl alcohol (3 in Fig. 1), they fulfill important physiological functions in plants (1) and are of considerable pharmaceutical interest (2). For example, podophyllotoxin (4 in Fig. 1) derivatives are used extensively in anticancer treatments and have been shown recently to possess antiviral properties as well (3). Pinoresinol (5 in Fig. 1) is one of the structurally simplest lignans, being a dimer of coniferyl alcohol, and its frequent presence in woody or fibrous plants should come as no surprise [the Beilstein database (MDL Information Systems, San Leandro, CA) revealed 46 and 8 references, respectively, for the isolation of (ϩ)-pinoresinol and (Ϫ)-pinoresinol from plants] (4). Virtually any plant capable of producing lignin can be presumed to have the enzymes necessary to link two units of coniferyl alcohol (2 in Fig. 1) in a fashion leading to the bicyclic ring core of pinoresinol (5 in Fig. 1).The amount of pinoresinol produced by plants varies widely. Particularly high concentrations of pinoresinol have been found in young foliage, for example of Forsythia spp., as well as in the reproductive organs and seeds of many plants (5). The compound is therefore generally presumed to be a defensive agent, as is suggested also by its antihelminthic and antifungal activity (6-9). Animals are not known to produce pinoresinol or other dimeric lignols, nor have they been shown to acquire such compounds from plants. We here report the presence of pinoresinol in the defensive secretion of a caterpillar, the larva of Pieris rapae, the cabbage butterfly, one of the world's most familiar lepidopterans (10). We had earlier reported on the composition of this secretion, produced as droplets by glandular hairs on the back and flanks of the larva (11) (Fig. 2). We had noted the fluid to contain a series of structurally labile linolenic acid derivatives, the mayolenes (6 in Fig. 3), which we demonstrated to be protective against ants (Crematogaster lineolata) (11). We have found pinoresinol itself to also be dete...

Inducible direct plant defense against insect herbivores: A review

“…Lignin and other phenolics can strengthen cell walls and therefore can be anti-nutritional (BrodeurCampbell et al, 2006;Schroeder et al, 2006). Some phenolics and sesquiterpenes along with other volatiles can repel herbivores from oviposition on host plants (Henzell & Hall, 1974;DeMoraes et al, 2001;Huber et al, 2006).…”

Metabolomic analysis of the interaction between plants and herbivores

“…Caterpillars of P. rapae do take up pinoresinol from B. oleracea plants to excrete them from their glandular hairs: whether it is present in the fat body as well is unknown (Schroeder et al 2006). A different study showed P. brassica caterpillars take up flavonoids (Ferreres et al 2007).…”

“…It also receives increasing interest in the field of plant-host interactions (Allwood et al 2006(Allwood et al , 2008Choi et al 2004Choi et al , 2006. In both the aforementioned studies into the uptake of pinoresinol and of flavonoids by Pieris caterpillars a broad-spectrum metabolomics-type analysis was essential to discover the compounds (Ferreres et al 2007;Schroeder et al 2006).…”

Small Glycosylated Lignin Oligomers Are Stored in Arabidopsis Leaf Vacuoles

“…4CL, p-coumarate:CoA ligase; C3H, p-coumarate 3-hydroxylase; CA, caffeic acid; CAD, cinnamyl alcohol dehydrogenase; CCR, cinnamoyl-CoA reductase; CSE, caffeoyl shikimate esterase; F5H, ferulate 5-hydroxylase; Fer-CoA, feruloyl-CoA; HCT, p-hydroxycinnamoyl-CoA:quinate/shikimate p-hydroxycinnamoyl transferase; PAL, phenylalanine ammonia-lyase; pCA, p-coumaric acid; POX, peroxidase; LAC, laccase. of these coupling products is not well understood, but they have been postulated to serve as antioxidants (Kitts et al, 1999) or to play a role in plant defense (Harmatha and Nawrot, 2002;Hano et al, 2006;Schroeder et al, 2006). In contrast to the free-radical lignin polymerization, the monolignol cross-coupling toward (neo)lignans is guided by dirigent proteins (Davin et al, 1997) that have a "dirigent domain" that acts as a scaffold that orients two monolignol radicals during dimerization, leading to the formation of a specific stereoisomer.…”