To understand mechanisms of osmoprotection, the composition of sugars and related compounds were analyzed in extracts of fully hydrated and desiccated leaves of the desiccation‐tolerant resurrection plant Myrothamnus flabellifolia. During the dehydration process the concentrations of fructose and glucose decrease, whereas sucrose, arbutin and glucopyranosyl‐β‐glycerol increase. The substances were identified by GC‐MS and NMR‐analyses. This is the first report of large amounts of glucopyranosyl‐β‐glycerol in higher plants which may act as an osmoprotectant. Significant levels of the nonreducing sugar trehalose were present in all samples tested.
In this work free phenolics and phenolic glucosides present in the water
content (vegetation water,
VW) of olive fruits of the three Italian cultivars (cvs.) Cipressino,
Dritta, and Leccino were identified
by 1H NMR. The phenolic metabolite content of the
three cultivars was studied at three fruit growth
stages. The major phenolic compounds, common to all three
cultivars, were 4-hydroxyphenylethanol
(tyrosol) (1), 4-hydroxyphenylethanol glucoside
(2), and oleuropein (3). Considerable
differences in
the content of compounds (1−3) were found to
occur in the fruits during growth and maturation of
the drupe. Glucoside (4), a major component of the low
molecular weight solutes of Dritta and
Leccino cvs., was not detected in Cipressino fruits. The quinol
glucoside (4) was thought to derive
from oxidation of the glucoside of 4-hydroxyphenylethanol
(2). Hydrolysis of (4) followed
by
cyclization yielded the bicyclic compound halleridone
(5).
Keywords: Olea europaea; Oleaceae; 1H NMR; free and conjugated
phenolics; metabolite monitoring
in olives
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