4

CANAVANINE

The extensive use of plants as medicines has pointed out that herbal
medicines are not as safe as frequently claimed. Instances of efficacy and
toxicity have recently surfaced with several commercially available herbal
medicines. It can be harmful to take herbal medicines without being aware of
their potential adverse effects. Many plants produce toxic substances that
discourage consumption by animals. Herbal preparations may come from plants
that are not eaten by other animals, so it is not surprising that particular
risks of toxicity are associated with the use of herbs that contain
potentially toxic constituents. Herbal medicines can also be harmful if they
delay or replace a more effective form of treatment, since many products are
sold as dietary supplements but lack scientific information about their safe
and effective use, because toxicological data and support of clinical
studies is lacking. Both users and practitioners should be enabled to make
the risk-benefit assessment before using any herbal medicine. Adverse
effects that may occur with some herbal products include systemic lupus
erythematous syndrome, due to the responsible constituent, L-canavanine.
(Capasso R, et al, Fitoterapia, 71:1001, 2000)

Let us examine the immediately foregoing thesis as it pertains to
canavanine-rich plants, in a loose chrono-subject order, abstracted directly
from the published scientific literature so as to share various investigator's
own perspectives on their research, as they pertain to the subject matter of
the safety and efficacy of canavanine plants.

Nature's pesticides are one important subset of natural chemicals. Plants
produce toxins to protect themselves against fungi, insects and animal
predators. Many Leguminosae (now the Family: Fabaceae) contain canavanine, a
toxic arginine analog that, after being eaten, is incorporated into protein
in place of arginine. (Ames B, et al, Dietary Pesticides, Proc Natl Acad
Sci, USA, July 17, 1990) Canavanine-rich plants have even been specifically
investigated for their pesticidal properties (Koul O, Phytoparasitica,
13(3-4), 1985); (Rosenthal G, J Chem Ecol, 12(5), 1986); (Rosenthal G,
Dahlman D, Food Agric Food Chem, 39(5), 1991); (Rosenthal G, et al, J Agric
Food Chem, 43(10), 1995); (Rosenthal G & Harper L, Insect Biochem Mol Biol,
26(4), 1996); (Rosenthal G, et al, J Agric Food Chem, 46(1), 1998).
Canavanine is a potentially deleterious arginine antimetabolite whose
toxicity is expressed in canavanine-sensitive organisms ranging from viruses
to humans. (Rosenthal G, et al, J Biol Chem, 264(23), 1989) Many
anti-nutritional and toxic factors abound in seeds, which are generally rich
in nutrients and therefore more prone to attack from herbivores. These
factors, including canavanine, defend plants against destruction and though
good for the plant, cause deleterious effects or are even toxic to insects,
animals and man. (Makkar H & Becker K, Asian-Austral J Animal Sci, 12(3),
1999); (Siddhuraju P & Becker K, Nahrung, 45(4), 2001)

Nonprotein amino acids in plants are often intermediates in the synthesis
and catabolism of the protein amino acids and many of these amino acids may
play roles as defensive agents. The best-characterized examples of
nonprotein amino acids in plants are L-canavanine and L-canaline. Massive
accumulation of canavanine, a structural analog of L-arginine, occurs in the
seeds and leaves of many legumes, offering protection against predation.
(Nonprotein amino acids, Purdue University School Agriculture, undated) Some
herbivores, which are mixed feeders, have developed several survival
defences of their own. A number of canavanine-degrading bacteria may break
down sufficient of the dietary canavanine so that the toxic effects of this
compound are reduced when ruminants eat canavanine-containing foods.
(Dominguez-Bello M, Stewart C, Syst Appl Microbiol, 13(4), 1990); (G
Rosenthal & E Bell, in G Rosenthal & D Janzen (Eds), Herbivores: Their
Interaction With Secondary Plant Metabolites, pp 353-386, Academic Press,
1979) Some herbivores evade canavanine poisoning because their enzymes, like
canavanine-producing plants, do not use canavanine by mistake (W Purves, G
Orians & H Hellar, Life: the Science of Biology, WH Freeman & Co, 1995)
Rodents, which are traditional seed-eaters, and the usual toxicological
surrogate for humans, are fairly susceptible to canavanine poisoning, whilst
primates and humans are least successfully adapted to the toxicity of
canavanine in plants, as shall be attested to in the pages which follow.

In addition to the amino acids, which are the building blocks of proteins,
living systems also produce nonprotein amino acids. These compounds possess
a rich structural diversity and often elicit deleterious biological effects
in viruses and all living systems (Rosenthal GA. Q Rev Biol 52: 155, 1977);
(G Rosenthal, Plant Nonprotein Amino and Amino Acids, Academic Press, San
Diego, 1982). L-Canavanine, the L-2-amino-4- (guanidinoxy) butyric acid
structural analog of L-arginine, is such a higher plant toxicant, produced
and stored by leguminous plants, as part of their chemical defense, where it
functions as a barrier against a wide array of insects and other pests (G
Rosenthal, in: Insecticides: Mechanism of Action and Resistance, D Otto & B
Weber, (Eds), Intercept Ltd., 1982), (G Rosenthal, in: Frontiers and New
Horizons in Amino Acid Research, K Takai, (Ed), Elsevier, 1992). [This data
set is extracted from a much publicised cancer patent: (Crooks P & G
Rosenthal, Use of canavanine as a therapeutic agent for the treatment of
pancreatic cancer, US Patent 5,552,440, 3 September 1996)]

Based on toxicological data, in terms of modern toxicology, canavanine is
accordingly rated as "very toxic", ie between extremely toxic and moderately
toxic, but relatively closer to the former than to the latter (Rodricks J,
Calculated Risks: The Toxicity and Human Health Risks of Chemicals in Our
Environment, Cambridge University Press, 1992). This classification,
however, does not take into consideration the irresponsibly suggested
chronic use of canavanine by malnourished and/or already ill persons as
commercially and media hyped with Sutherlandia.

AP

5

The earliest toxicity reports were of observed effects in rats fed
canavanine-containing meal (Orru A, Cesaris-Demel V, Quanderni Nutrizone, 7,
273, 1941). Later experiments quantified the mammalian toxicity of
canavanine, with 20mg/kg (body weight) having no effect, 200mg/kg showing
clear damage and 2g/kg leading to death, all within 24hrs! When 1g/kg of
arginine was fed together with 200mg/kg canavanine, no toxicity was
observed. Boiling and ethanol extraction did not reduce toxicity. An
explanation for the toxic effects was disturbance of protein metabolism
related to disturbance of arginine functions. Lethal dose poisonings are
only reached in exceptional cases. However, even small doses allow
recognition of clear toxic effects. (Tschiersch B, Pharmazie, 17, 621, 1962)
Relatively moderate canavanine feeding was observed to lead to a reduction
in normal weight gain (Jaffe W, Arnzie-mittle-Forsch, 10, 1012, 1960). Milk
reduction was markedly reduced after feeding canavanine to dairy cows. When
feed was given with protein-rich fodder, little ill-effects were noted.
Canavanine is rapidly metabolized in the liver, yet damage is reported for
this and other organs (Shone D, Rhodesia Agric J, 58, 18, 1961).

Nuclear alterations in mammalian cell-induced by L-cananavine, were observed
in quite early research (Hare J, J Cell Physiol, 75:129, 1970).
L-Canavanine, the guanidinooxy structural analog of L-arginine, can lead to
the production of canavanine-containing proteins, which ultimately can
disrupt critical reactions of RNA and DNA metabolism and protein synthesis.
Canavanine also affects regulatory and catalytic reactions of arginine
metabolism, arginine uptake, formation of structural components and other
cellular processes. In these ways, canavanine alters essential biochemical
reactions and becomes a potent antimetabolite of arginine. These deleterious
properties of canavanine render it a highly toxic secondary plant
constituent. (Rosenthal G, Q Rev Biol, 52(2), 1977) Canavanine, following
prolonged administration, can result in toxic effects in various mammalian
tissues. Some features of the deleterious effects of this compound are
interference with the metabolism of the normal protein amino acids and
involvement of specific tissues such as the liver. (M Hegarty, Toxic amino
acids of plant origin, in: R Keeler et al (Eds): Effects of poisonous plants
on livestock. Academic, pp. 575-585, 1978); (Kay D, Crop and Product Digest
No. 3 - Food legumes, Tropical Products Institute, pp 200-201, 1979)

Post mortem of animals allowed to free range on canavanine-rich plants have
revealed lesions and hemorrhages of the lymph glands (M Clarke, D Harvey and
D Humphreys, Veterinary Toxicology, Bailliere Tindall, p236, 1981).
Canavanine has furthermore been determined to be a Vitamin B6 antagonist (H
Klosterman, in R Ory (Ed), Anti-nutrients and Natural Toxicants in Foods,
Chap 16, 1981). The toxicity and pharmacokinetics of canavanine have been
determined in laboratory rat studies. Twenty-one percent of the administered
canavanine remained in the gastrointestinal tract 24 hr after an oral dose.
Less than 1% was incorporated into the proteins of adult and neonatal rats 4
or 24 hr following administration. Repeated administration resulted in far
greater uptake and more severe toxicity. Weight loss and alopecia were
observed in rats given canavanine daily for 7 days. Food intake was
decreased by 80% in adult rats subjected to this dosing regimen. (Thomas D &
Rosenthal G, Toxicol Appl Pharmacol, 91(395), 1987); (Thomas D & Rosenthal
G, Toxicol Appl Pharmacol, 91(406), (1987)

Besides the potential to cause a lupus erythematosus-like syndrome, general
medical science and toxicological cautionary reports have been ongoing
(Shqueir A, et al, Anim Feed Sci Technol, 25(1-2), 1989); (J D'Mello, Toxic
Amino Acids, in: J D'Mello, C Duffus & J Duffus (Eds), Toxic Substances in
Crop Plants, Royal Soc Chem, pp 21-28, 1991); (Rosenthal G, Phytochem,
30(4), 1991); (Garcia-Bibao J, Alimentaria, 29(229), 1992); (J Chen, in A
Tu, (Ed), Toxin-Related Diseases: Poisons Originating from Plants, Animals
and Spoilage, Intercept Ltd, pp 55-99, 1993); (Gregory S, et al, Cell
Immunol, 153(2), 1994); (Leporatti M, Fitoterapia, 67(6), 1996); (Rosenthal
G & Nkomo P, Pharmaceut Biol, 38(1), 2000); (Tsirigotis M, et al, J Biol
Chem, 276(49), 2001). In particular, the paradoxical effect of slightly
increased lifespan (restricted only to high protein diets) but decreased
reproduction due to teratogenic effects, have intrigued and concerned
researchers (Brown D, J Animal Sci, 72(Suppl 1), 1994); (Schardein J, J
Toxicol Rev, 15(4), 1996); (Brown D, et al, J Nutr Immunol, 5(3), 1998).
Studies evaluating cell aging in human diploid fibroblast cells however,
have led to the lifespan being slightly shortened in canavanine-treated
cells (as also with aspartame-treated cells) (Kasamaki A, Urasawa S, J
Toxicol Sci, 18(3), 1993).

The major toxicological concerns with canavanine-rich plants, as far as
human poisoning is concerned, are immune system effects, particularly
auto-immunity, where the body turns upon itself, via inappropriate oxidative
free radical attack. A number of clinical reports and experimental studies
have shown that autoimmune responses and/or autoimmune diseases and
disorders are frequently chemically induced in humans by xenobiotics,
including by canavanine (Morimoto I, Kobe J Med Sci, 35(5-6), 1989);
(Morimoto I, et al, Clin Immunol Immunopathol, 55(1), 1990); (Yoshida S &
Gershwin M, Semin Arthritis Rheum, 22(6), 1993); (Bigazzi P, Toxicology,
119(1), 1997). Autoimmune disorders result from a breakdown of immunologic
tolerance leading to an immune response against self-molecules. In most
instances the events that initiate the immune response to self-molecules are
unknown, but a number of studies suggest associations with environmental and
genetic factors and certain types of infections. There have been
associations of a number of xenobiotics with human autoimmune disease,
including canavanine. Xenobiotics may also exacerbate an existing autoimmune
disorder. (Powell J, et al, Environ Health Perspectives, 107(Suppl 5),
1999); (Gebbers O, Schweiz Rundsch Med Prax, 90(44), 2001)

6

The first signs of auto-immune problems in humans arose from observations
that regular consumption of large quantities of canavanine-containing
alfalfa seeds, often as sprouts, caused symptoms of toxicity. Amongst the
first symptoms noted in humans was that of pancytopenia with splenomegaly
(Manilow M, et al, Lancet, 1, 615, 1981). Canavanine also induced certain
hematologic and serologic abnormalities in monkeys test fed on alfalfa
sprouts, causing a severe lupus erythematosus-like syndrome (SLE), which in
man is characterised by a defect in the immune system, which is associated
with anti-immunity, antinuclear antibodies, chromosome breaks and various
other types of pathology. (Manilow M, et al, Science, 216, 415, 1982) The
chromosome breaks appear to be due to oxygen radicals as they are prevented
by superoxide dismutase (Emerit I, et al, Hum Genet, 55, 341, 1980). The
canavanine pathology was considered to be due, in part, to the production of
oxygen radicals during phagocytization of antibody complexes with
canavanine-containing protein (Ames B, Science, 221, 4617, 1983). SLE has
been exacerbated in humans and caused experimentally in monkeys through the
regular ingestion of quantities of canavanine-containing alfalfa sprouts
(Roberts J, et al, (letter), N Engl J Med, 308, 1361, 1983).

The systemic lupus erythematosus (SLE) inducing property of alfalfa sprouts
in monkeys has been attributed to their non-protein amino acid constituent,
canavanine. Occurrence of autoimmune hemolytic anemia and exacerbation of
SLE have been linked to ingestion of plant products containing canavanine.
Researchers have reported the results of investigations into the effects of
canavanine on T-cells. Canavanine has shown dose-related effects in vitro on
human immunoregulatory cells, which could explain its SLE-inducing
potential. These effects include: 1) diminution of the mitogenic response to
both phytohemagglutinin and concanavalin A, as determined in both thymidine
incorporation and cell cycle studies; and 2) abrogation of concanavalin
A-induced suppressor cell function, which results in increased release of
both IgG and DNA binding activity into supernatants by cells from normal
subjects and SLE patients. These immunoregulatory effects of canavanine may
explain the induction or exacerbation of SLE. (Alcocer-Varela J, et al,
Arthritis Rheum, 28(1), 1985)

One report of a study of the effects in vitro and in vivo of canavanine on
immune function in normal and autoimmune mice showed that Canavanine in high
doses effectively blocks all DNA synthesis in vitro within 24 h. At lower
doses, canavanine affected B-cell function of autoimmune mice, inhibiting
[3H]thymidine incorporation in response to B-cell mitogens, and
pokeweed-induced intracytoplasmic immunoglobulin synthesis, but stimulated
intracytoplasmic immunoglobulin. The decrease in survival in
canavanine-treated autoimmune mice correlated with an increase in
spontaneous immunoglobulin-secreting cells (IgG greater than IgM) and
antinuclear and double-stranded DNA antibodies. Histopathological analyses
revealed increased glomerular damage and immunoglobulin deposition in the
kidneys of the canavanine-treated autoimmune and normal mice. Ten percent of
normal mice developed high titers of autoantibodies after 24 weeks of the
diet. These data suggest that the dietary amino acid, canavanine, affects
B-cell function resulting in autoimmune phenomena and providing a new animal
model of autoimmunity, a diet-induced SLE syndrome. (Prete P, Can J Physiol
Pharmacol, 63(7), 1985)

Professor Varro Tyler, a pharmacognosy authority at Purdue University,
respected by both allopathic and complementary alternative medicine
fraternities alike, warned that reports appeared noting that patients with
clinically and serologically quiescent systemic lupus erythematosus (SLE)
had even had the disease reactivated by ingesting canavanine-containing
alfalfa tablets and he postulated that the canavanine present in all parts
of the plant was replacing arginine in vital metabolic processes in the
body, thus causing recurrence of SLE. (Tyler V, et al, (Eds), Pharmacognosy,
Lea and Febiger, 1988) Reports on the alfalfa sprout / canavanine toxicity
phenomenon were not restricted to the scientific press. By way of example,
popular natural health author, Dr Andrew Weil, MD, of the University of
Arizona, as a health columnist wrote that: "canavanine in alfalfa sprouts
can harm the immune system, possibly 'increasing' the risk of cancer and
degenerative diseases" (Weil A, Are Sprouts Health Foods?:
Naturally-occurring toxins create doubts, Natural Health, Nov/Dec, 1992).
Many lay publications followed suite.

Systemic lupus erythematosus (SLE) in humans is characterized by a defect in
the immune system that is associated with autoimmunity, antinuclear
antibodies, chromosome breaks, and various types of pathology (Ames B, et
al, Proc. Natl. Acad. Sci. USA, July 17, 1990). Canavanine induced SLE is
characterised by an auto-immune hemolytic anemia with low complement levels,
positive antinuclear antibodies, anti-DNA, positive lupus cell preparations,
and deposition of immunoglobulin and complement. (D Metcalf, in: Food
Allergy: adverse reactions to foods, D Metcalf, et al (Eds), Blackwell
Scientific Publications, 1991); (A Mongey & E Hess, in D Wallace & B Hahn,
Dubois' Lupus Erythematosus and Associated Disorders, Lea and Febiger,
1993); (Herbert V, et al, Amer J Clin Nutr, 60: 639, 1994); (Brinker F, Herb
Contraindications and Drug Interactions, Eclectic Medical Publications, pp
27-28, 1998); (Brown A, J Renal Nutr, 10(4), 2000) For anyone considering
using a canavanine-containing product, eg Sutherlandia, for treatment of
AIDS, consider that the SLE which it causes, often accompanies AIDS, is a
complex disorder sharing similarities with AIDS as regards affecting a
predominately young population, its propensity for multiple organ
involvement and for causing potentially life-threatening episodes (Schattner
A & Rager-Zisman B, Rev Inf Dis, 12:204, 1991); (Morrow W, et al, Clin
Immunol Immunopathol, 58:163, 1991); (J Levy, HIV and the Pathogenesis of
AIDS, ASM Press, 1998). (See Appendix 2)

7

Canavanine is a genotoxic mutagen in yeast cells, animals and humans, and is
often used to induce and study mutagenesis in laboratory cultures and
animals (Morollo A, Ttroczi J, Environ Mutagen, 8(Suppl 6), 1986); (Davies P
& Parry J, Mol Gen Genet, 162(2), 1978); (Gocke E & Manney T, Genetics,
91(1), 1979); (McDougall K & Lemontt J, Mutat Res, 63(1), 1979); (Larimer F,
et al, Mutat Res, 77(2), 1980); (Suiko M, et al, Daigaku Nogakubu, Kenkyu
Hokoko, 29(2), 1982); (Bender E & Brendel M, Mutat Res, 197(1), 1988);
(Fedorova I, et al, Genetika, 28(5), 1992); (Fedorova I, et al, Genetics,
148(3), 1998). The potential of canavanine to induce mutagenesis (and by
implication, possibly cancer), intrigues researchers, who for example, using
data in mathematical models which predict the stability of protein
synthesizing systems, have found that if a single compound, eg the arginine
analog canavanine, is discriminated very poorly from the cognate substrate,
an "error catastrophe" must be envisaged (Freist W, et al, J Theoret Biol,
193(1), 1998). Researchers have recently pointed out that while the negative
effect of permanent contamination of populations because of spontaneous
mutations does not appear to be very high for humans and animals when the
environment was benign, a very different outcome was seen when environmental
stress was induced in the laboratory, using canavanine (Szafraniec K, et al,
Proc Natl Acad Sci, 98(3), 2001).

Seeing as canavanine containing substances have been suggested as treatment
for cancers, let us examine its potential in his regard directly from
synopsis of the published works of a world authority on canavanine and
cancer.

Canavanine is a potent arginine antimetabolite that bears strong structural
analogy to its protein amino acid counterpart, arginine. As a subtle
structural mimic of L-arginine, canavanine can function in all enzymic
reactions for which arginine is a substrate. Therefore, canavanine
potentially can inhibit any enzyme-directed reaction employing arginine as
the preferred substrate. Canavanine assimilation can alter protein
conformation and adversely affect normal biological function and biochemical
activities. Exposure to canavanine adversely affects a basic property or
functional parameter of one or more enzymes. Several studies of canavanine's
antineoplastic activity have been conducted, demonstrating that canavanine
could mediate its toxic effect not only at the level of protein function,
but also through its ability to disrupt DNA replication. Canavanine's lethal
effect was manifested preferentially in rapidly proliferating cells - a
property essential to chemotherapeutic efficacy. These promising findings
with canavanine had the drawback that canavanine's cumulative toxicity
resulted in about a 15% diminution in body weight after 5 treatment days.
Analysis of canavanine catabolism in the adult rat demonstrated that hepatic
arginase fostered the hydrolysis of canavanine to yield L-canaline and urea;
this reaction pathway was the principal basis for canavanine catabolism in
this mammal. Thus, it is reasonable to propose that administration of
L-canavanine to a human would result in the formation of L-canaline, a
highly toxic nonprotein amino acid that is a powerful inhibitor of pyridoxal
phosphate-dependent enzymes via a direct reaction between canaline and the
vitamin B6 moiety of an enzyme. The intrinsic toxicity of canavanine is as a
substrate for hepatic degradation via the action of arginine. Certain ester
derivatives of canavanine (synthetic drug development) might provide an
efficacious drug capable of eliciting little if any bodyweight loss while
enhancing the therapeutic index for canavanine. (Rosenthal G, L-canavanine:
A Novel Chemotherapeutic Agent for Human Pancreatic Cancer, 2001)

Canavanine has been shown to enhance human tumor cell killing in combination
with radiation (Green M & Ward J, Cancer Research, 43(9), 1983), but this
finding has not led to any practical improvements in toxic radiation
therapy.

From another source, is a (limited result) report of an interesting
L-arginine / L-canavanine comparative equivalent controlled study. Some
guanidino compounds have been found to inhibit spontaneous mammary
tumorigenesis in mice. Chronic treatment with Lilium auratum or Astragalus
sinicus, which contains L-arginine or L-canavanine on spontaneous mammary
tumorigenesis significantly inhibited the development but not the growth of
mammary tumors, with no significant long-term deleterious side-effects with
either product, estimating from body weight change and plasma component
levels. These findings suggest that these natural products may act as
prophylactic agents for mammary and possibly other types of tumors.
(Nagasawa H, et al, Anticancer Res, 21(4A), 2001)

Please note that the implication arising from this last study abstract is
that plant constituents other than canavanine are responsible for the
positive effects, including simply L-arginine itself, for which L-canavanine
is merely a mimic, which is mischievously substituted with positive, but
potentially far more severe adverse-effects at any probable therapeutic (as
opposed to prophylactic) doses. Consider briefly, research into arginine
itself. Arginine is conditionally essential to most mammals and to humans. A
high content is found only in high protein foods, with little in cereals and
grains (but plenty in nuts). Arginine has been used to successfully treat
depression (nitric oxide is synthesized from L-arginine) (Yildiz F, et al,
Psychopharmacology (Berl), 149(1), 2000) and a variety of cancers (R
Braverman, with C Pfeiffer, et al, The Healing Nutrients Within: Facts,
Findings and New Research on Amino Acids, Keats Publishing, 1997); (Takeda
Y, et al, Cancer Res, 35, 390, 1975); (Critselis A, et al, Federat Proc, 36,
1163, 1977); (Pryme H, Cancer Lett, 5, 19, 1978); (Milner J, et al, J Nutr,
109, 489, 1979); (Barbul A, et al, Surg, 90(2), 1981); (Tayek J, et al, Clin
Res, 33(1), 1985); (Reynolds J, et al, J Surg Res, 45, 513, 1988); (Reynolds
J, et al, Surg, 104(2), 1988); (Park K, Proc Nutr Soc, 52:387, 1993);
(Brittenden J, et al, Surgery, 115:205, 1994); (Ma, Q et al, World J Surg
20:1087, 1996); (Van Bokhorst-de van der Schueren M, et al Amer J Clin Nutr,
7(2), 2001). Arginine enhances in vivo immune responses in mice (Lewis B &
Langkamp-Henken B, J Nutr, 130:1827, 2000).

8

In healthy adult humans, eight amino acids are indispensable (ie not
synthesised in the body). Studies have revealed that that in certain
nutritional or disease states or in certain stages of development, otherwise
dispensable amino acids such as arginine may become indispensable and hence
a classification has been proposed whereby the indispensability of amino
acids be based on clinical and therapeutic considerations. (Laidlaw S &
Kopple J, Am J Clin Nutr, 46: 593, 1987) Arginine is a precursor for three
pathways, the products of which are involved in tissue injury and repair:
nitric oxide, an effector molecule in inflammatory and immunological tissue
injury; polyamines, required for DNA synthesis and cell growth; and proline,
required for collagen production. L-arginine is a key component in and may
mediate the beneficial effects of low protein diet. (Narita I, et al, Proc
Natl Acad Sci, 92, 4552, 1995) The activation of macrophages by cytokines
secreted by armed inflammatory CD4 T-cells is central to the host response
to pathogens. Activated macrophages undergo changes that greatly increase
their antimicrobial effectiveness and amplify immune responses, in
particular by inducing the production of hydrogen peroxide and nitric oxide.
These antimicrobial products can also damage host cells and so a series of
enzymes, including catalase and superoxide dismutase (SOD) are produced
during phagocytosis to control the action to act primarily on pathogens.
(Janeway C & Travers P, Immunobiology, Blackwell Scientific Publications,
1994) SOD stabilises NO, whilst processes generating superoxide, conversely
inactivate NO, itself having anti-oxidant function (E Cadenas, Ch 1, in:
Oxidative Stress and Antioxidant Defenses in Biology, S Ahmad (Ed), Chapman
& Hall, 1995).

Just a decade ago, conventional wisdom held that mammals could not produce
immunological reactive nitrogen intermediates (RNI) because they would be
toxic. Recent studies into the role of reactive oxygen intermediates (ROI)
and RNI in mammalian immunity show that in combination, the contribution of
two enzymes, phagocyte oxidase (phox) and inducible nitric oxide synthase
(NOS) to preventing microbial resistance to RNI, appears to be greater than
previously appreciated, with each appearing to compensate in large part for
isolated deficiency of the other. Animals deficient in the phox, the major
source of pathogen-triggered ROI production, are susceptible to several
inoculated pathogens. High output production of RNI is the specialty of
mammalian phagocytes and is also attainable by many mammalian cells in
response appropriate inflammatory stimuli. Even RNI of dietary origin are
put to use as antimicrobial agents in gastric juice, a key component of the
innate immune system of epithelium. Host defense epithelia with their
antimicrobial armament, including T-cells and natural killer cells, are
apparently incapable of ensuring the survival of the host against commensal
organisms in the combined absence of phox and NOS, or medical intervention.
(Nathan C & Shiloh M, Proc Natl Acad Sci, USA, 97(16), 2000) Nitric oxide
plays a key role in neurotransmission, control of blood pressure and
cellular defense mechanisms. Nitric oxide synthases catalyze the oxidation
of L-arginine to NO. (Boucher J, et al, Cell Molec Life Sci, 55(8/9), 1999)

Active macrophages can produce superoxide in addition to NO. When L-arginine
is limited, a high-output isoform of NOS can favor formation of a joint and
particularly destructive cytotoxic product peroxynitrite (Xia Y & Zweier J,
Proc Natl Acad Sci, USA, 94: 6954, 1997), implicated in stroke, heart
disease and immune complex-mediated pulmonary edema (D Laskin & C Gardner,
Ch 9, in: Toxicology of the Liver, G Plaa & W Hewitt (Eds), Taylor &
Francis, 1998). The oxidative, inflammatory, mutagenic and cytotoxic
potential of peroxynitrite contrasts with the antioxidant, anti-inflammatory
and tissue-protective properties ascribed to NO itself (Bryk R, et al,
Nature, 14; 407, 2000). Phox and NOS 'inhibitors' are reportedly toxic in
experimental animals, but L-arginine analogs (of which canavanine is one) in
contrast, because of their similarity to arginine, are considered to be
phox-sparing, nontoxic NOS inhibitors (with the obvious exclusion of
canavanine). NOS is most readily observed in macrophages from patients with
infectious or inflammatory diseases. Sustained production of NO endows
macrophages with cytotoxic activity against viruses, bacteria, fungi,
protozoa, helminths, and tumor cells (MacMicking J, et al, Annu Rev Immunol,
15: 323, 1997); (Nathan C & Shiloh M, Proc Natl Acad Sci, USA, 97(16), 2000)
Immunocompetent cells rely on amino acids as energy substrates. Arginine in
particular is a modulator of immunity and a greater availability improves
the nonspecific immune response. (Walrand S, et al, Am J Clin Nutr, 72(3),
2000)

Nitric oxide is synthesised from L-arginine by NOS, of which there are two
types, constitutive and inducible, and both of which are inhibited by
L-arginine analogues. The NO released by the constitutive enzyme acts as a
transduction mechanism underlying a large number of physiological responses.
The inducible NOS is expressed after the activation of endothelial cells,
macrophages and several other cells by cytokines. The only role for NO
released by the inducible enzyme is as a cytotoxic molecule for invading
micro-organisms and tumour cells. (T Fan & M Dale, Ch 8 in: Textbook of
Immunopharmacology, M Dale, et al (Eds), Blackwell Scientific Publications,
1994) Dietary protein or arginine deficiency impairs constitutive and
inducible NO synthesis (Wu G, et al, J Nutr 129: 1347, 1999). A recent
review of the literature indicates that NOS inhibitors (of which canavanine
is one) have exacerbated infection by 80 species of viruses, bacteria,
fungi, and protozoa (M DeGroote & F Fang, in: Nitric Oxide and Infection, F
Fang (Ed), Kluwer/Plenum, pp. 231-264, 1999); (Nathan C & Shiloh M, Proc
Natl Acad Sci, USA, 97(16), 2000) Nitric oxide-mediated regulation of
mitochondrial respiration represents a primary line of defense against
oxidative and other stresses (Paxinou E, et al, Proc Natl Acad Sci USA,
98(20), 2001), but aberrant production of NO contributes to the pathogenesis
of diseases. Sustained NO production via NOS requires extracellular arginine
uptake. (Nicholson B, et al, J Biol Chem, 276(19), 2001) Sutherlandia is a
NOS inhibitor.

9

The production of NO represents an important component of the host immune
response against viral infections, including retroviruses. Antiviral effects
occur through its microbiostatic and microbicidal activity and probably also
through its pro-inflammatory and immunoregulatory properties. AIDS is
associated with activation of the immune system. Macrophages are suspected
to play a major role in human immunodeficiency virus (HIV) infection. The
impact of nitric oxide production on HIV-1 infection is still difficult to
predict. HIV-1 stimulates NO production by human macrophages and NO
concentration is increased in the sera of patients with AIDS, especially in
those with neurological disorders and pulmonary disease caused by
intracellular opportunistic pathogens. In vivo, human macrophages may
synthesize detectable but very low production of NO during HIV infection,
evidenced in AIDS patients, and in particular in individuals with
opportunistic infections. The molecular mechanisms involved remain unclear,
but the unusual low production of NO by HIV-infected human monocytes could
explain the lack of antiviral activity against HIV. (Blond D, et al, J
Virol, 74(19), 2000) Increased expression of NOS might be expected in HIV
infections, yet elevated NO levels in serum are related only to active
AIDS-related bacterial, protozoan, and fungal infections, rather than
chronic viral infection with HIV alone. NO may play a role in the local
control of chronic viral infections at tissue level, but this is not
reflected in serum levels. (Lake-Bakaar G, et al, Dig Dis Sci, 46(5), 2001)

The high-output pathway of nitric oxide production helps protect mice from
infection by several pathogens, including Mycobacterium tuberculosis.
Macrophages in the lungs of people with clinically active Mycobacterium
tuberculosis (Mtb) infection also express catalytically competent NOS.
(Nicholson S, et al, J Exp Med, 183(5), 1996) Glucocorticoids regulate NO
production following cytokine exposure primarily by limiting L-arginine
availability (Simmons W, et al, 271(39), 1996). Since the
tuberculosis-exacerbating effect of corticosteroids is quantitatively
indistinguishable from the effect of NOS deficiency, and corticosteroids
suppress NOS, this may be an important mechanism for the
tuberculosis-promoting effects of corticosteroids. (Nathan C, J Clin Invest,
100(10), 1997) Tuberculosis, the leading cause of death from infectious
disease, poses an even greater threat as immunodeficiency spreads among the
host population and drug resistance rises. NOS is necessary to control
primary tuberculosis. In experimental mice, the absence of NOS leads to
rapid bacterial growth, necrotic granulomatous pneumonitis, and death. In
mice, as in people, the sterile eradication of Mtb is rarely achieved,
suggesting that long-term CD4+ memory T-cells must continually enlist the
aid of macrophages to maintain bacterial dormancy. A requirement for NOS
later during infection therefore could be expected if the host is to avoid
disease recrudescence. Specifically inhibiting NOS during the late phase of
clinical stability supports this hypothesis, because infection progresses
more quickly and leads to earlier mortality. The fact that NOS is necessary
to control mycobacterial growth, has implications for the global incidence
of human tuberculosis, because Mtb currently infects over one-third of the
world's population. (MacMicking J, et al, Proc Natl Acad Sci, USA, 94(94;
5243; 1997)

Any molecule whose expression is induced by signals associated with
inflammation is likely to be detected in a wide variety of disease states.
It is not surprising, then, that NOS has been detected in people at sites
involved by Alzheimer's disease, multiple sclerosis, AIDS-associated
dementia, asthma, lung cancer, pulmonary sarcoidosis, Crohn's disease,
ulcerative colitis, rheumatoid arthritis, osteoarthritis, and psoriasis. The
cytotoxic and pro-inflammatory potential of NOS advances the case for its
therapeutic inhibition in those of the above diseases that are not thought
to be infectious in etiology, or in those infectious diseases where the
inflammatory effect of NOS appears to outweigh its antimicrobial effect.
However, the anti-inflammatory role of NOS emphasizes the possibility of
adverse consequences attendant on its inhibition. Expression of NOS
sometimes makes a profound difference to the course of infection or
inflammation. In both infection and inflammation, NOS appears to act both as
a direct effector and as a regulator of other effectors. The impact of NOS
is potentially dichotomous, and the dichotomy is sometimes manifest at
different times or sites in the same experimental setting. These
complexities do not preclude experimental therapeutic intervention, but
demand caution when trials are with nitric oxide synthase inhibitors.
(Nathan C, J Clin Invest, 100(10), 1997) Inhibitors of NOS (agents that
prevent binding of substrate L-arginine) are potentially beneficial in the
treatment of conditions associated with an overproduction of NO, including
septic shock, neurodegenerative disorders, and inflammation. (Hobbs A, et
al, Annu Rev Pharmacol Toxicol, 39; 191, 1999)

Conclusion. Canavanine-containing plants do have medicinal properties, but
so do all plants, including common beverages, fruits, vegetables, nuts,
seeds, culinary herbs and spices, often with far more documented beneficial
properties and greater documented safety profiles. As a result, canavanine
Sutherlandia products cannot be responsibly recommended over, or even in
addition to and especially in the absence of good nutrition and it is
clearly criminal to advocate otherwise. There is no scientific data to
indicate that L-canavanine has any superiority over L-arginine as a health
substance, indeed the very opposite is the case, so why not feed rather than
poison?

1. My introduction to my Genocide and Ethnopiracy report is posted here:
http://www.gaiaresearch.co.za/trads.html

2. My full Genocide and Ethnopiracy report is downloadable here:
http://www.gaiaresearch.co.za/tramed.pdf

3. My recent letter to Mayeng is available here:
http://www.gaiaresearch.co.za/pharmapact/Ethnopiracy.html

4. My original recent published paper is downloadable here:
http://www.gaiaresearch.co.za/impila.pdf

5. My new PHARMAPACT health freedom website address is:
http://www.gaiaresearch.co.za/pharmapact/