| Summary: | This study identified new compounds with pest control activities. The two
sources of candidates that were followed here were the main heartwood extract of
Alaska Yellow Cedar (AYC) constituents and several semi-synthetic counterparts.
Five compounds were isolated and identified for the first time in AYC
heartwood in this research: two monoterpenes, two sesquiterpenes, and one
lignan. The two monoterpenes were (1S)-2-oxo-3-p-menthenol (41) and (4R)-4-hydroxy-4-isopropyl-cyclohex-1-enecarboxylic acid (63). The two sesquiterpenes
were (5S,7R,10R,11R)-eudesm-4(14)-ene-11,12-diol (46) and (4R,5S,7R)-1(10)-
eremohpilen-11,12-diol (59). The lignan was (1R,2S,5R,6S)-2,6-bis-(3,5-
dimethoxy-4-hydroxyphenyl)-3,7-dioxabicyclo-[3.3.0]octane,(67). Structures for
these compounds were confirmed on the basis of spectroscopic techniques such as
1- and 2-D NMR, high resolution MS and IR.
The pest control activity studies of 15 compounds isolated or semi-synthesized
from AYC heartwood were conducted at the Centers for Disease
Control and Prevention (CDC). Two types of studies were conducted--short-term
(24h) and residual (over 1-4 weeks) activity for application against three types of
pests related to human health - nymphal I. scapularis ticks, adult X cheopis fleas
and adult Ae. eagypti mosquitoes.
The 24 h studies revealed that nootkatone, valencene-13-aldehyde and
valencene-13-ol were the most active among the studied compounds against the
three pests. They exhibited highly improved pest control activities compared to
valencene. This suggests that oxidation on both positions C-2 and C-13 of the
eremophilane ring structure has an important effect on the activity. For
compounds where the conformation of the eremophilane bicyclic ring has been
altered, the activity seemed to diminish greatly. The above mentioned three
compounds can be good candidates as pest control lead compounds.
The residual studies revealed that the most active compounds exhibited
activity profiles that generally decreased with time. Although the long-term safety
of these compounds has yet to be evaluated, the natural origin and the long history
of use of these compounds suggest that they can be promising candidates. This
study revealed that the three most promising compounds in the 24 h study exhibited reasonably promising behavior, which makes them even stronger as pest
control candidates. === Graduation date: 2004
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