10 research outputs found
Structure–Activity Relationship Studies of Flavonol Analogues on Pollen Germination
Flavonoids are polyphenolic compounds
required in the fertilization
process in many, if not all, plants. However, the exact biological
mechanism(s) and the interacting proteins are unknown. To determine
the characteristics important in activating or inhibiting the pollination
sequence, a structure–activity relationship analysis of natural
and synthetic flavonols was conducted. Flavonol analogues were synthesized
through a modified “one-pot” procedure that utilized
a Baker–Venkataraman type rearrangement and a Suzuki–Miyaura
cross-coupling of a halo-flavonol with an organotrifluoroborate. Of
the flavonols tested, kaempferol was the only compound to act as a
full agonist. The other smaller, less sterically hindered flavonols
(galangin, kaempferide, and 4′-methyl flavonol) acted as partial
agonists. Larger more hydrophobic flavonol analogues (3′- and
4′-benzoyl, 3′- and 4′-phenyl, and 3′-
and 4′-iodo flavonols) had minimal or no agonist activity.
Competition assays between kaempferol and these minimally activating
flavonols showed that these analogues inhibited the action of kaempferol
in a manner consistent with noncompetitive antagonism. The results
suggest that steric hindrance is the most important factor in determining
a good agonist. Hydrogen bonding also had a positive effect as long
as the substituent did not cause any steric hindrance