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Current textbooks give an inaccurate picture of the occurrence of cholesterol in plants and also of the role of plant sterols in the mammalian uptake of cholesterol. Keywords (Audience): General Public Vol. XX No. XX Month 200X Journal of Chemical Education 1
There is a widespread belief among the public and even
among chemists that plants do not contain cholesterol. This
error is the result (in part) of the fact that plants generally
contain only small quantities of cholesterol and that analyti-
cal methods for the detection of cholesterol in this range were
not well developed until recently (1). Another reason has to
do with the legalities of food labeling that allow small quan-
tities of cholesterol in foods to be called zero (2). The fact is
that cholesterol is widespread in the plant kingdom although
other related sterols, such as β-sitosterol (henceforth referred
to as sitosterol), generally occur in larger quantities. No cur-
rent biochemistry text that we have examined provides an
accurate account of cholesterol in plants. Here is a suggested
paragraph for the next generation of biochemistry texts:
More than 250 steroids have been described in plants (3).
Of these, perhaps sitosterol, which differs from choles-
terol by an ethyl substituent at position 24, is the most
common. But plants also contain cholesterol both free
and esterified. Cholesterol occurs as a component of plant
membranes and as part of the surface lipids of leaves
where it is sometimes the major sterol. The quantity of
cholesterol is generally small when expressed as percent
of total lipid. While cholesterol averages perhaps 50
mgkg total lipid in plants, it can be as high as 5 gkg
(or more) in animals.
A sample of current biochemistry textbooks shows that the
question of cholesterol in plants is, at best, treated in a mis-
leading way.
“ only rarely found in plants.” (4) (False)
“Similar [to cholesterol] sterols are found in other eu-
caryotes: stigmasterol in plants.” (5) (True , but mislead-
Plant cell membranes have no cholesterol. (6) (False)
Related [to cholesterol] sterols are present in plant mem-
branes. (7) (True, but misleading)
Cholesterol is absent from prokaryotes but is found to
varying degrees in virtually all animal membranes. (8)
(True, but why are plants not even mentioned?)
Plants contain little cholesterol. (True) Rather, the most
common sterol components of their membranes are stig-
masterol and beta-sitosterol. (Not quite right, see Table
1). (12)
In addition, only Garrett and Grisham (13) discuss the
interesting question of the effects of plant steroids on cho-
lesterol levels in humans. Although evidence for these effects
has been in the literature for some time, a number of other
commonly used textbooks make no mention either of the
occurrence of cholesterol in plants nor of the effects of plant
sterols on cholesterol metabolism in humans.
Cholesterol and Plants
E. J. Behrman* and Venkat Gopalan
Department of Biochemistry, The Ohio State University, Columbus, OH 43210; *
Concepts in Biochemistry edited by
William M. Scovell
Bowling Green State University
Bowling Green, OH 43403
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2Journal of Chemical Education Vol. XX No. XX Month 200X
Data and Discussion
The quantity of cholesterol in a number of common veg-
etable (plant) oils is given in Table 2. According to FDA rules,
cholesterol quantities less than 2 mgserving may be labeled
as zero (19). The reader should check the label on whatever
oil is currently on the shelf. Caveat emptor. It is clear that
cholesterol and its esters are important constituents of plant
membranes and that this has been known for more than thirty
years. Table 2 also gives some data on the sterol fraction of
some plant organelles.
While cholesterol is usually a minor constituent of the
sterol fraction in plants, it is the major constituent of some
plant surfaces. The cholesterol and sitosterol makeup of the
sterol fraction of various canola surfaces is shown in Table 3.
The proportion of cholesterol in the sterol fraction of the
genera Liliaceae, Solanaceae, and Scrophulariaceae is espe-
cially large (Itoh et al. in refs 3 and 22)
Cholesterol and Plant Sterols
There is considerable interest in plant sterols owing to
their cholesterol-lowering effects. While Garrett and Grisham
(13) are to be commended for elaborating on this matter in
their textbook, their descriptions are incorrect and likely to
cause misunderstanding.
Despite their [plant sterols] structural similarity to cho-
lesterol, minor isomeric differences and/or presence of
methyl and ethyl groups in the side chains of these sub-
stances result in their poor absorption by intestinal mu-
cosal cells. Interestingly, although plant sterols are not
effectively absorbed by the body, they nonetheless are
highly effective in blocking the absorption of cholesterol
itself by intestinal cells.
This paradox is attributable to inaccuracies in the above state-
A typical western diet contains 400–600 mg cholesterol
and 200–400 mg plant sterols (sitosterol and campesterol)
per day. While 40–60% of the cholesterol is absorbed, less
than 20% of campesterol and less than 5% of sitosterol are
absorbed (23). Current models (24) propose the initial up-
take of cholesterol and plant sterols from the intestine into
the enterocyte (intestinal mucosal cell) by a common trans-
porter (called NPC1L1) expressed at the lumenal surface.
Subsequently, by mechanisms that are still unknown, sort-
ing of these various sterols takes place inside the enterocyte
with the majority of cholesterol being transferred to chylo-
microns and most of the plant sterols selectively pumped back
into the intestine by two ATP-dependent transporters (called
ABCG5 and ABCG8). This means that the discrimination
is by a selectivity of egress not ingress. This provides a basis
for understanding sitosterolemia, a rare inherited disease in
which there is hyper-absorption of plant sterols from the small
intestine. Sitosterolemic individuals absorb cholesterol and
plant sterols (presumably using NPC1L1) but are unable to
re-transport sitosterol into the intestine owing to mutations
in ABCG5 or ABCG8 (24).
Although plant sterols are not absorbed by the body as
effectively as cholesterol, they are absorbed (23). The choles-
terol-lowering effects of plant sterols (and their esters) are due
in part to their competition with cholesterol for packaging
into mixed micelles that are taken up by NPC1L1.
We thank Melvin Pascall for ref 19 and Wesley Harnish
for an essential stimulus.
Literature Cited
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chemistry; W. C. Brown: Dubuque, IA, 1995; p 385.
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ego, 2001; Vol. 1, p 392.
8. Berg, J. M.; Tymoczko, J. L.; Stryer, L. Biochemistry, 5th ed.;
Freeman: New York, 2002; p 325.
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10. Kemp, R. J.; Mercer, E. I. Biochem. J. 1968, 110, 119–125.
11. Mudd, J. B. In The Biochemistry of Plants, Stumpf, P. K.;
Conn, E. E. Eds.; Vol. 4, Academic Press, New York, 1980,
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NETO :ehtnoataD.sloretslatotfotnecrepsanevigsiataD ,hsidar,keel,egabbacfosdipilecafrusehtfotnetnocloretselohc elbaliavaoslareppepneergdna,arko,hcanips .)02( oslaeraerehT tnalpgnirudoitarloretsotis/loretselohcehtnisegnahcegral fer(tnempoleved 12 .)nierehtsecnereferdna Vol. XX No. XX Month 200X Journal of Chemical Education 3
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30, 687–695.
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19. Title 21 of the Code of Federal Regulations (21 CFR), sec-
tion 101.62(d).
(accessed Aug 2005).
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1998, 23, 439–444.
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Phytochem. 1996, 42, 335–339.
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esis; Daum, G., Ed.; Springer: Berlin, 2004; Chapter 5.
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K. E.; Tian, H.; Graf, G. A.; Yu, Y.; Grishin, N. V.; Schultz,
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ence 2000, 290, 1771–1775.
24. Lutjohann, D.; Bjorkhem, I.; Beil, U. F.; von Bergmann, K.
J. Lipid Res. 1995, 36, 1763–1773.
... Foods of plant origin have lower calorie density than foods of animal origin (Table 1). In addition, food from plant sources contains no cholesterol [23,67] or only traces of cholesterol [68]. In the article "Cholesterol and Plants", E. J. Behrman and Venkat Gopalan explain that plants may contain not only phytosterols but also cholesterol (which is considered a zoosterol). ...
... Moreover, according to FDA rules, cholesterol quantities <2 mg per serving may be labeled as "no cholesterol" or "zero cholesterol". E. J. Behrman and Venkat Gopalan also give a very good explanation for the cholesterol-lowering effects of phytosterols (plant sterols): phytosterols compete with cholesterol for packaging into the mixed micelles that are taken up by the polytopic transmembrane protein, Niemann-Pick C1-Like 1 (NPC1L1) [68]. Vegan diets are also associated with improved gut microbiota symbiosis, increased insulin sensitivity, reduced trimethylamine-N-oxide (TMAO), activation of peroxisome proliferator-activated receptors (PPARs), and overexpression of mitochondrial uncoupling proteins [16,24,48]. ...
... The consumption of raw fruits, vegetables, roots, nuts, and germinated seeds provides an intake of carotenoids, vitamin C, vitamin E, and other compounds that have an antioxidant effect. 3. Lipid-lowering effects-the absence [23,67] or limited intake of dietary cholesterol [68]. Moreover, some plants that are rich in sterols and stanols may lower serum low- [37,38]. ...
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Absorption of dietary cholesterol, campesterol, and sitosterol, cholesterol balance, and fecal excretion of plant sterols were determined in three unrelated patients with phytosterolemia and three healthy volunteers during constant intake of cholesterol and plant sterols using accurate gas-liquid chromatography-mass spectrometry techniques. Each subject received a mixture of [26,26,26,27,27,27-2H6]cholesterol, [6,7,7-2H3]sitostanol, and [6,7,7-2H3]campesterol together with two non-absorbable markers, [5,6,22,23-2H4]sitostanol and chromic oxide. Feces were collected from days 5 to 7 and absorption of different sterols was calculated from the intestinal disappearance of the different sterols relative to [5,6,22,23-2H4]sitostanol and chromic oxide. The results obtained by the two markers were not different and the absorption of cholesterol averaged 53 +/- 4% for the patients (mean +/- SD) and 43 +/- 3% for the volunteers. Campesterol absorption averaged 24 +/- 4% in patients and 16 +/- 3% in healthy volunteers, whereas sitosterol absorption averaged 16 +/- 1% and 5 +/- 1%, respectively. Cholesterol synthesis expressed by body weight varied considerably in the two groups but appeared to be about 5 times lower in patients than in controls. Administration of a high dose of sitostanol (0.5 g t.i.d.) to two patients was followed by a reduction in cholesterol absorption by 24% and 44%, an increase in fecal output of cholesterol and steroids derived from cholesterol and plant steroids, and a marked reduction of serum cholesterol, campesterol, and sitosterol. Under the conditions used, inhibition of cholesterol absorption by sitostanol was not followed by a significant rise in cholesterol synthesis. The time of observation was, however, too short to allow final conclusion on this. The results show that the absolute difference in absorption rate of different sterols between the patients and healthy volunteers was about the same. As a consequence, increasing hydrophobicity causes a relative decrease of absorption rates. Thus, patients with phytosterolemia seem to have a generally increased absorption of sterols rather than a loss of a specific discriminatory mechanism, and oral administration of sitostanol seems to be an interesting new approach for treatment of phytosterolemia.
Apical tissues of Brassica campestris, grown under controlled environmental conditions, were analysed for their lipid content. The principal lipids were sterols, phospholipids and sphingolipids. The major sterols were identified as sitosterol, stigmasterol, campesterol and cholesterol, the phospholipids as phosphatidylethanolamine (PE) and phosphatidylcholine (PC), and the sphingolipids as cerebrosides. In the early stages of apical development, unusually high proportions of cholesterol and cerebrosides were found. However, their relative proportions gradually decreased as the apex developed; a concomitant increase in sitosterol was observed. These results suggested a specific association between these lipids and the development of the shoot apex. PE increased steadily during apical development, whereas PC increased more rapidly, but then declined at the later stage. The relative proportion of campesterol increased in the apex during the late stages of development and appeared to be involved in petal formation, which coincided with the decrease in PC.
Cholesterol has been detected as one of the major sterols in the surface lipids of higher plant leaves. It was widely distributed among the plant leaves of various species as a common main sterol component with a few exceptions. The content of cholesterol amounted to 71.5% of the total sterols in the surface lipids of rape leaves. However, the proportion of cholesterol in the intracellular lipids of rape leaves was lower than that in the surface lipids, and the seed lipids contained only a trace amount of cholesterol, as reported in the literature. In the leaf surface lipids examined, a minor amount of cholestanol associated with cholesterol often was detected by capillary gas chromatography and gas chromatography-mass spectrometry. The related analysis for the surface lipids of fruits showed that cholesterol was one of the major component sterols also in those lipids of several species.
Chloroplasts, mitochondria and microsomes were isolated from a cell-free extract of green and etiolated leaves of bean, by differential and sucrose or ficoll gradient centrifugation. The sterols and sterol esters of whole leaves and subcellular fractions were compared. The following sterols were identified from the leaves: cholesterol (cholest-5-en-3β-ol), Δ7-cholestenol (cholest-7-en-3β-ol), campesterol (), stigmasterol (), sitosterol (stigmast-5-en-3β-ol) and isofucosterol (). These sterols are present in all subcellular fractions but their concentrations differ significantly; in particular the chloroplasts and the mitochondria are much richer in cholesterol (24%) compared to the leaves (1%).The amount of sterols per mg of proteins in the fractions varied as follows: reticulum. Sterol esters were generally enriched in cholesterol (25–75%) and poor in stigmasterol (10%).These results are discussed in terms of the role of the sterols in the structure and function of plant cell membranes.
1. The composition of the esterified and unesterified sterols of the nuclear, chloroplastidic, mitochondrial and microsomal fractions of 21-day-old maize shoots was examined. 2. The microsomal and mitochondrial fractions contain the bulk of the sterols of the tissue. 3. Only 1% of the sterol isolated from all the organelles is esterified. 4. The nuclear fraction has the greatest proportion of esterified sterol and the microsomal fraction the least. 5. 4-Demethyl sterols constitute the bulk of both esterified and unesterified sterols in all organelle fractions. 6. Cholesterol is the major esterified 4-demethyl sterol of the nuclear and chloroplastidic fractions, but only the nuclear fraction has an appreciable proportion of unesterified cholesterol. 7. Sterol esters of linolenic acid are more abundant in the mitochondrial and microsomal fractions than in the other two fractions.