The Distribution of Two Major Iridoids in Different Organs of Antirrhinum majus L. at Selected Stages of Development

Abstract

Two iridoid glucosides isolated from leaves of Antirrhinum majus L. were identified as the known compounds antirrhinoside and antirrhide. Plants grown hydroponically demonstrated that antirrhinoside is present in all plant organs including the roots. In contrast, antirrhide is found only in leaves. Furthermore, both iridoids were identified in the main stem axillary leaves and leaves on the lateral branches. The highest concentrations of antirrhinoside were found in the main and lateral stems as well as the buds and flowers. As leaves age, for both cultivars, the levels of antirrhinoside drop significantly, and there is a corresponding increase in antirrhide. In spite of the different genetic backgrounds of the two cultivars, the overall distribution of the iridoids was similar during vegetative and flowering development. Radiolabeling of recently expanded axillary leaves with (14)CO(2) showed that both antirrhinoside and antirrhide were prominently labeled in the laminar tissue. However, only (14)C-antirrhinoside was recovered in the subtending petiole tissue, consistent with the suggestion that it is a phloem mobile compound.

A Comparison of Antirrhinoside Distribution in the Organs of Two Related Plantaginaceae Species with Different Reproductive Strategies

“…However, for A. majus, we have found that antirrhinoside is the predominant iridoid in all plant tissues except for older leaves that contain mainly antirrhide (Beninger et al 2007). Similarly, for L. vulgaris, antirrhinoside is the major iridoid found in all plant tissues (this paper).…”

“…Penn. (Gowan et al 1995), and recent research has shown that this also is likely the case for antirrhinoside in A. majus (Beninger et al 2007). Other possible defensive secondary metabolites such as the alkaloids choline (Harkiss 1974) and linarinic acid (Hua et al 2002) have been found in A. majus and L. vulgaris, but their concentrations are extremely low (9.7×10 −4 % and 2.5×10 −6 %, respectively).…”

“…Whether they have biological activity at these concentrations is unknown. However, antirrhinoside, can be found in concentrations ranging from 5 to 23% dry weight of plant tissue in A. majus (Beninger et al 2007), and is known to inhibit growth of larval gypsy moth significantly at a concentration of only 3.3% in artificial diet (Beninger et al 2008).…”

Changes in plant chemical defenses and nutritional quality as a function of ontogeny in Plantago lanceolata (Plantaginaceae)

“…shoots vs. roots), these carbon-based defenses are synthesized through the isoprenoid biosynthetic pathway and are usually stored in cell vacuoles (Croteau 1987). They are also likely phloem mobile (Gowan et al 1995;Beninger et al 2007), and concentrations in leaves and roots in P. lanceolata were found to be positively correlated (De Deyn et al 2009). Previous studies have identiWed plant age as an important intrinsic factor aVecting P. lanceolata chemistry (e.g., Bowers and Stamp 1993;Fuchs and Bowers 2004;Barton 2007); and these ontogenetic trajectories in IG production signiWcantly vary among both maternal families and populations (Bowers and Stamp 1993;Barton 2007).…”

Monoterpenoid Indole Alkaloid Biosynthesis

“…Snapdragon (Antirrhinum majus) contains two major iridoids, antirrhide and antirrhinoside (Guiso and Scarpati, 1969). When photosynthesising leaves were fed with 14 CO 2 , the partitioning of 14 C between the leaf and petiole was monitored and it was shown that 47% of the phloem mobile 14 Cphotoassimilate was antirrhinoside while the rest was sucrose (Beninger et al, 2007) This suggests that in snapdragon, and perhaps in other plants, iridoids may partially replace sucrose in the translocation of photoassimilates. In this context iridoids can function as osmoregulators, playing a similar role to sucrose, but their toxicity will have the advantage of deterring herbivores.…”