1021-4437/01/4802- $25.00 © 2001
Russian Journal of Plant Physiology, Vol. 48, No. 2, 2001, pp. 160–164. Translated from Fiziologiya Rastenii, Vol. 48, No. 2, 2001, pp. 191–195.
Original Russian Text Copyright © 2001 by Stakhova, Ladygin, Stakhov.
Numerous publications are devoted to the effects of
exogenous synthetic and natural physiologically active
compounds on carbohydrate and amino acid metabo-
lism [1–4]. In particular, the possibility of carbon rep-
artition between the early products of photosynthesis,
amino acids and sugars, was demonstrated [5, 6]. In
addition, the binding of physiologically active com-
pounds to enzymes involved in the metabolism of
amino acids and carbohydrates, thus affecting the
direction of metabolism, was detected [6–8].
Flavonoids (quercetin, rutin, ﬂoridzin, and others)
are natural physiologically active substances. Such ﬂa-
vonoids as quercetin, catechol, and coumarin are evi-
dently synthesized in chloroplasts [9, 10]; they can
interact with the components of the electron-transport
chain [11–14]. Quercetin is known to affect enzyme
activities, in particular, the carboxylase and oxygenase
activity of ribuloso-1, 5-bisphosphate carboxylase/oxy-
Thus, from the published data, we expect that plant
treatment with ﬂavonoids can change the metabolism
of carbohydrates and amino acids  via ﬂavonoid
action on the rates of accumulation of reducing agents,
photophosphorylation [11–14], and the modulation of
enzyme activities [6–8]. Keeping in mind the nutri-
tional signiﬁcance of carbohydrates and amino acids, it
is important to increase their content in crop fruits.
The objective of this work was to study the effect of
tomato plant treatment with quercetin on the contents
of carbohydrates and amino acids in the ripe fruits.
MATERIALS AND METHODS
The following cultivars of tomato (
Mill.) plants were used: Ukrainskii tepli-
chnyi, Malinovye, Vinogradnye, Tallalikhinskie, Perts-
evidnye, Zomok slivovidnyi, Galla, K-226 (Korean),
Korean, Kechkemet, Bibor, and Star shtambovyi. Most
experiments were run with cv. Ukrainskii teplichnyi.
Plants were grown in a greenhouse under natural
illumination. At various developmental phases (most
frequently during the formation of the ﬁrst fruits),
tomato shoots were treated with quercetin using an OP-1
portable sprayer (MZTO, Russia). Quercetin concen-
trations ranged from 1.5 to 5.0 mg/l at the rates of 50–
, depending on the plant size.
Quercetin was ﬁrst dissolved in ethanol (100 mg per
10 ml) and then diluted to a ﬁnal concentration with
water. For better wetting, a surfactant was added to the
solution (usually 1 g per 1 l of the solution).
Ripe fruits were squeezed through a sieve to remove
seeds, and the pulp was lyophilized and used for esti-
mating the composition and content of carbohydrates
and amino acids.
To determine the content of sugars, lyophilized sam-
ples were hydrolyzed with 4 N HCl at 100
drates were subjected to column chromatography using
an LC-6000 analyzer (Biotronik, Germany); a copper
salt of 2,2'-bicinchoninic acid supplemented with
aspartic acid was applied as a dye reagent . In
amino acid assay, the material was ﬁrst hydrolyzed
with 6 N HCl , and then the content and composi-
tion of amino acids were determined using a LC-5000
amino acid analyzer (Biotronik, Germany). The con-
tents of amino acids and carbohydrates were calculated
with a C-R3A Chromatopac (Shimadzu, Japan). The
The Effect of Quercetin on the Accumulation of Carbohydrates
and Amino Acids in Tomato Fruits
L. N. Stakhova, V. G. Ladygin, and L. F. Stakhov
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow oblast, 142292 Russia;
fax: 7 (0967) 79-0532; e-mail: email@example.com
Received January 28, 2000
—We studied the effects of low concentrations of quercetin on the contents of sugars and amino acids
in ripe tomato (
Mill.) fruits. In treated plants, the content of glucose increased by 1.5–
4.5 times, whereas the total content of amino acids decreased by 1.5 times. The glucogenic amino acids,
glutamic and aspartic acid, decreased most substantially, viz. by 1.7 and 1.6 times, respectively. The mechanism
of the quercetin-induced enhancement of gluconeogenesis and suppression of glycolysis, both resulting in the
accumulation of glucose, are discussed.
Key words: Lycopersicon esculentum - amino acids - glucose - carbohydrates - tomato fruits - quercetin - glu-