Ent-2′-epi-Orobanchol and Its Acetate, As Germination Stimulants for Striga gesnerioides Seeds Isolated from Cowpea and Red Clover

Abstract

Striga gesnerioides is a root parasitic weed of economic significance to cowpea (Vigna unguiculata) crops in Western Africa. Seeds of the parasite germinate in response to cowpea root exudates. Germination stimulants for the seeds were isolated from the hydroponic culture filtrate of cowpea, and their structures were unambiguously determined as (-)-(3aR,4R,8bR,2'R)-ent-2'-epi-orobanchol and (+)-(3aR,4R,8bR,2'R)-ent-2'-epi-orobanchyl acetate, on the basis of mass, CD, and (1)H NMR spectra; optical rotatory power; and chromatographic behavior on HPLC. The alcohol was first isolated and identified from the cowpea root exudates, and the acetate may be the same compound that had been previously isolated from the exudates and designated as alectrol. Identity of the stimulants produced by cowpea to those produced by red clover (Trifolium pratense) was confirmed.

Tomato strigolactones

“…The abundance of most of these near future are likely. Further research and structure identification will be needed to prove this and confirm the postulated to several revisions to proposed structures of naturally occurring strigolactones already 23,24 and additional revisions in the pathway. A better understanding of this will in the near future prove instrumental for designing strategies to fine-tune the strigolactone composition in a plant.…”

“…In addition, the stereochemistry of the revised solanacol structure 22,23 matches the stereochemistry of orobanchol which was recently unambiguously determined. 24 The configuration of these two compounds does, however, not match the proposed stereochemistry of 7-oxoorobanchol 21 and 7-hydroxyorobanchol. 13,16 However, in these reports the stereochemistry of the latter compound was not unambiguously determined.…”

Structure-Activity Relationship Studies of Strigolactone-Related Molecules for Branching Inhibition in Garden Pea: Molecule Design for Shoot Branching

“…The results are inverted for aromatic A-ring analogs of orobanchol for seeds of parasitic weeds (Malik et al, 2011). The C29-(R) stereochemistry was also reported to be an important structural feature for potent germination stimulation activity for strigol, sorgolactone, orobanchol, orobanchyl acetate, and GR24 derivatives Ueno et al, 2011aUeno et al, , 2011b. Recently, it was demonstrated that A-ring dimethyl substitution on GR24 lowers the germination activity (Malik et al, 2010).…”

“…1). The first analysis of the distribution of SLs in different species suggests that 5-deoxystrigol is generally shared by both monocots and dicots, while orobanchol and orobanchyl acetate, for which structural revisions were recently proposed (Ueno et al, 2011b;Vurro and Yoneyama, 2012), seem to be found in dicots but not in monocots. Solanacol Chen et al, 2010), identified in tobacco (Nicotiana tabacum), is the only SL having an aromatic A-ring.…”

Striga

“…The development of highly advanced analytical methods, for example the high performance liquid chromatography (HPLC) connected to tandem mass spectrometry (LC-MS/MS) (Sato et al, 2003), has allowed new SLs to be surveyed in the root exudates of many different plant species, including few millet species (Akiyama et al, 2005;Awad et al, 2006;Xie et al, 2007;Matsuura et al, 2008;Xie et al, 2008;Xie et al, 2009a;Xie et al, 2009b;Yoneyama et al, 2010;Kohlen et al, 2011;Ueno et al, 2011;Jamil et al, 2012). …”