ISSN:
0739-4462
Keywords:
phytosterol dealkylation
;
ecdysteroids
;
makisterone A
;
Heteroptera
;
Dysdercus
;
gas-liquid chromatography/mass spectrometry
;
cotton stainer bug
;
ecdysone
;
20-hydroxyecdysone
;
Chemistry
;
Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
The absence of phytosterol dealkylation in the cotton stainer bug, Dysdercus fasciatus, has been established and the major ecdysteroid in the fifth-stage larvae identified. The demonstration that the free and esterified sterols in D fasciatus consisted of 95-96% sitosterol and 4-5% campesterol, a similar composition to the cottonseed diet, together with the lack of conversion of [14C]sitosterol into cholesterol, establishes that phytosterol dealkylation does not occur in this insect species. The ecdysteroid titer determined by radioimmunoassay in the fifth instar of D fasciatus shows a distinct peak at day 6, the instar lasting for 7 days. Makisterone A was purified by HPLC from insects at a time of high ecdysteroid titer and identified as a major component by both fast atom bombardment and electron impact mass spectrometry. Gas-liquid chromatography/mass spectrometry (selected ion monitoring) confirmed the occurrence of makisterone A and revealed the presence of two unidentified compounds. One of these occurs in a similar amount to makisterone A and may be 26-hydroxymakisterone A, whereas only a minute amount of the other compound, which may be 20-deoxymakisterone A, was present; further identification of the latter compounds is necessary. C27 ecdysteroids (eg, ecdysone and 20-hydroxyecdysone) and C29 ecdysteroids (eg, podecdysone A) were undetectable. The specificity of the enzymes of ecdysteroid biosynthesis is discussed.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/arch.940010111
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