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Phytomedicine 17 (2010) 862–867
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Phytomedicine
journal homepage: www.elsevier.de/phymed
Modulation of the immune system by Boswellia serrata extracts
and boswellic acids
H.P.T. Ammon ∗
Department of Pharmacology, Institute of Pharmaceutical Sciences, University of Tuebingen, Auf der Morgenstelle 8, 72076 Tuebingen, Germany
a r t i c l e
i n f o
Article history:
Dedicated to Prof. Dr. hc mult. Wagner for
his 80th birthday.
Keywords:
Boswellia serrata extracts
Boswellic acids
Immune system
a b s t r a c t
Extracts from the gum resin of Boswellia serrata and some of is constituents including boswellic acids
affect the immune system in different ways. Among the various boswellic acids 11-keto-␤-boswellic
acid (KBA) and acetyl-11-keto-␤-boswellic acid have been observed to be active. However, also other
boswellic acids may exhibit actions in the immune system.
In the humoral defence system a mixture of boswellic acis at higher doses reduced primary antibody
titres; on the other hand lower doses enhanced secondary antibody titres following treatment with sheep
erythrocytes.
In the cellular defence boswellic acides appear to increase lymphocyte proliferation whereas higher
concentrations are even inhibitory. Moreover, BAs increase phagocytosis of macrophages.
BAs affect the cellular defence system by interaction with production/release of cytokines. Thus, BAs
inhibit activation of NF␬B which is a product of neutrophile granulocytes. Consequently a down regulation
of TNF-␣ and decrease of IL-1, IL-2, IL-4, IL-6 and IFN-␥, which are proinflammatory cytokines by BEs and
BAs has been reported.
Suppressions of the classic way of the complement system was found to be due to inhibition of the
conversion of C3 into C3a and C3b. However, which of these pharmacological actions contribute to the
therapeutic effects and which is finally the best dosage of a standardized extract needs further examination. And it is also a question whether or not a single BA will have the same therapeutic effect as a
standardized extract.
Among the mediators of inflammatory reaction, mast cell stabilisation has been described by a BE.
Inhibition of prostaglandin synthesis appears to play only a minor role as far as the anti-inflammatory
effect is concerned.
On the other hand the inhibitory action of BAs on 5-LO leading to a decreased production of leukotrienes
has received high attention by the scientific community since a variety of chronic inflammatory diseases
is associatied with increased leukotriene activity.
At the end of the cascade of events in the cellular immune system as far as it directs to various tissues of
the body – i.e. autoimmune diseases – formation of oxygen radicals and proteases (for example elastase)
play an important destructive role. Here, BEs as well as BAs have been found to be inhibitory.
From the pharmacological properties of BEs and BAs it is not surprising that positive effects of BEs
in some chronic inflammatory diseases including rheumatoid arthritis, bronchial asthma, osteoarthritis,
ulcerative colitis and Crohn’s disease have been reported.
© 2010 Published by Elsevier GmbH.
Abbreviations: BS, Boswellia serrata; BE, Boswellic extract; BA, Boswellic acid; PFC, plaque-forming cell; LPS, lipopolysaccharides; PHA, phytohaemagglutinin; ConA,
concanavalin A; NF␬B, neutrophil factor ␬B; AKBA, acetyl-11-keto-␤-boswellic acid; KBA, 11-keto-␤-boswellic acid; TNF-␣, tumor necrosis factor ␣; IL (1-12), interleukines
1-12; INF-␥, interferon-␥; PBMCs , peripheral blood monocuclear cells; NK-cells, natural killer cells; C3 , complement 3; H1 -receptor, histamin 1-receptor; H2 -receptor,
histamin 2-receptor; COX, cyclooxigenase; IKK, I␬B␣kinases; 5-HETE, 5-hydroxyeicosatetraenoic acid; 5-LO, 5-lipoxigenase; 12-HHT, 12-hydroxyheptadecatrienoic acid;
fMLP, n-formyl-methionyl-leucyl-phenyl-alanin; FLAP, 5-lipoxigenase activating protein; HLE, human leucocyte elastase; LTB4 , leukotrien B4 ; LTC4 , leukotrien C4 ; LTD4 ,
leukotrien D4 ; LTE4 , leukotrien E4 ; NADPH, nicotinamid-adenin-dinucleotid-phosphat-hydrogen; PGF1␣ , prostaglandin F 1␣; PMA, phorbol 12-myristate 13 acetate; PMN,
polymorphnuclear neutrophils; SOD, superoxiddismutase; TH1, T-helper cells.
∗ Tel.: +49 07071 2974675; fax: +49 07071 292476.
E-mail address: [email protected].
0944-7113/$ – see front matter © 2010 Published by Elsevier GmbH.
doi:10.1016/j.phymed.2010.03.003
H.P.T. Ammon / Phytomedicine 17 (2010) 862–867
Introduction
Extracts from oleo gum resin of Boswellia serrata, in India called
salai guggal, have been described in Ayurvedic text books (Charaka
Samhita, 1st–2nd century AD and Astangahrdaya Samhita 7th
century AD) as a remedy for the treatment of a variety of inflammatory diseases. In 1986 Singh and Atal reported anti-inflammatory
activity of an extract of the gum resin of B. serrata in animal
experiments. Wagner et al. (1987) observed inhibition of guinea
pig complement system by ␣- and ␤-boswellic acids and in 1992
anti-complementary activity of a mixture of boswellic acids was
described by Kapil and Moza (1991).
Any inflammation is the response of the body to damages of
tissues. Its final target is healing and restauration. There are three
kinds of inflammations:
• Acute inflammations are mostly related to infections or injuries.
• Chronic inflammations are the consequence of continuation of
acute inflammations due to inadequate immune defence.
• Primary chronic inflammations which develop chronically just
from the begin of the disease. They are mostly caused through
derangements of the immune system i.e. auto-immune diseases.
The organisation of any inflammation includes a variety of
factors deriving from the immune systems i. e., immune cells, complements, cytokines, mediators of inflammation, enzymes etc.
In the last decades extracts from the oleo gum resin of B. serrata
(BEs ), some boswellic acids (BAs) and other compounds have been
studied for their effects on different steps/factors of the immune
system and on the cascades of events finally leading to inflammation.
This review deals with the effects of BEs and active constituents
on factors related to the immune system and mediators of inflammation.
Effects of B. serrata extracts (BEs ), boswellic acids (BAs ) and
other compounds of BEs on parameters of immune defence
Humoral defence
Antibody titres
Humoral defence is related to the activation of B-cells. After contact with antigens B-cells differentiate to plasma cells. These cells
produce antibodies which belong to the family of immunoglobulins.
Humoral antibody synthesis was tested by Sharma et al. (1996)
in the serum from mice treated with sheep erythrocytes by determining the hemagglutinating antibody titres. It was found that a
single oral dose of a mixture of BAs (50–200 mg/kg) on the day
of sensitisation produced a dose related reduction (10.4–32.8%)
in primary hemagglutinating antibody titres on day 4. A significant reduction in antibody production was obtained with 100
and 200 mg/kg doses. On the other hand the secondary antibody
titres were significantly enhanced at lower doses, the effect being
more prominent at 50 mg/kg. Azathioprine as a reference compound (200 mg/kg p.o.) administered following the same schedule
resulted in only 10.4% inhibition of primary antibody synthesis and
had no effect on the secondary antibody production.
Using the technique of complement fixing, a method for analyzing antigen and antibody titres, oral administration of a mixture
containing BAs (25, 50, 100 mg/kg) for 5 days around the time of
immunization resulted in a significant decrease in primary and secondary complement fixing antibody titres at 100 mg/kg (Sharma et
al. 1996).
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A marked increase (15.38–26.92%) in antibody production on
day +7 was observed when a BA mixture (25–100 mg/kg) was
given orally for 5 days around immunization. The effect was more
pronounced at a dose of 25 mg/kg than at 50 or 100 mg/kg. The
secondary antibody titres were only marginally increased. Azathioprine treatment (100 mg/kg) had no significant effects on primary
as well as on secondary antibody titres.
In mice in which treatment was initiated 7 days prior to
immunization, BAs (25–100 mg/kg) elicited a dose related increase
(37.93–63.79%) in the primary humoral response without significantly affecting the expression of the secondary response.
Levamisole (2.5 mg/kg, p.o.), an immunopotentiating agent, displayed only a 25% increase in primary and a 6.66% increase in
secondary antibody titres.
Immunglobulines
Previously it was shown by Khajuria et al. (2008) that oral
administration of a biopolymeric fraction (BOS 2000) from B. serrata (1–10 mg/kg) elicted a dose related increase in the delayed
hypersensitivity reaction (early 24h and delayed 48h ) in mice. It also
stimulated the IgM and IgG titre expressed in the form of plaques
(PFC) and complement fixing antibody titre.
From these studies where either a mixture of different boswellic
acids or a biopolymeric extract of BS has been employed, it appears
that lower doses exhibit a humoral immunstimulating action,
whereas this effect is attenuated or even reversed with increasing
the dose.
Cellular defence
Cellular defence includes proliferation and activation of lymphocytes as well as induction of phagocytosis of macrophages and
neutrophile granulocytes.
From the lymphocytes T1-lymphocytes cause cytotoxic actions
to living cells (i.e. microorganisms and tumor cells). In case of
autoimmune diseases T1-cells also attack and damage a variety of
single tissues in the body, leading among others to allergic reactions, rheumatoid arthritis, psoriasis, type 1-diabetes, bronchial
asthma, multiple sclerosis, neurodermitis, lupus erythematodes,
Huntington thyreoiditis and others. In most cases the autoimmune
diseases concentrate on specific cells/tissues inducing a chronic
inflammatory process which ends with the destruction of the
cells/tissues in question.
The treatment of these diseases at present consists in the
applications of glucocorticoides, nonsteroideal antiphlogistics,
immunosuppressives and others, their disadvantages being in part
severe side effects.
Lymphocyte proliferation
Two studies investigated the effect of an extract of Boswellia
carterii Birdw. and of BAs in the lymphocyte proliferation assay.
This in vitro test utilizes sensibilized lymphocytes, especially Tlymphocytes and is used to establish immunomodulatory activity.
In 1996 Sharma et al. reported that, if spleen cells from nonimmunized mice were used, a mixture of various BAs in the range of
1.95–125.0 ␮g/ml showed no spontaneous mitogenic activity and
the cell viability was comparable to controls. When the test was
performed in the presence of mitogen stimulating lipopolysaccharides (LPS), phytohaemagglutinin (PHA), concanavalin A (ConA) and
alloantigen, a concentration dependent inhibition of lymphocyte
proliferation was observed.
These data are in contrast to the observations of Badria et al.
(2003) who used this assay with isolated lymphocytes from venous
human blood. In this study, a methylene chloride extract from
the oleo gum resin of Boswellia carterii Birdw. at 1 mg/ml stimulated lymphocyte transformation by 90% (EC50 = 0.55 mg/ml) in
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the presence of PHA or Con A. Various compounds of the essential oil were also active. The different BAs and tirucalic acids
(TAs) tested, including acetyl-␤-boswellic acid, acetyl-␣-boswellic
acid, 3-oxo-TA, acetyl-11-keto-␤-boswellic acid, ␤-boswellic acid,
3-hydroxy-TA, and 11-keto-␤-boswellic acid, showed a similar
activity with EC50 values from 0.001 to 0.005 ␮M.
From these studies it may be concluded, that in addition to BAs
also other compounds of an extract from Boswellia resins are effective in stimulating lymphocyte proliferation.
Though the data of both studies as far as quantitative terms are
concerned are not comparable it appears, that low concentrations
of BAs increase stimulated proliferation of lymphocytes whereas
higher concentrations are even inhibitory. This is in line with the
observations that in vivo lower doses of BAs increase antibody titers
whereas higher doses show even the opposite.
Phagocytosis
The effect of an undefined mixture of BAs on phagocytosis was also studied by Sharma et al. (1996). Preincubation
of peritoneal macrophages with different concentrations of BAs
(1.95–125 ␮g/ml) resulted in an enhanced phagocytotic function
of adherent macrophages with a maximal effect occurring at
62.25 ␮g/ml.
NFB/cytokines/chemokines
The function of cellular defense is regulated by a variety of
compounds released from leukococytes, macrophages and T-cells
including NF␬B, cytokines and chemokines.
NFB
The transcriptionsfactor NFk B, which usually is present in the
cytosol is produced by neutrophil granulocytes and activates
numerous genes which are related to the defence against infectious
diseases and induction of inflammatory processes. Its presence is a
prerequisite for the formation/action of cytokines/chemokines and
thus any inhibitor of NF␬B by will result in a decrease of cellular
defence and inflammatory reactions.
As far as possible effects of BEs and BAs are concerned; AKBA
has turned out to be a natural inhibitor of NF␬B (Cuaz-Pérolin et al.
2008). Thus AKBA applied in vivo in mice (100 ␮mol/kg) for 1 week
inhibited the NF-␬B activation. This may be one explanation why
BAs inhibit production of cytokines.
However, inhibition of NFk B is not only related to the action
of BAs. Previously Moussaieff et al. (2007) reported that incensole acetate a compound isolated from Boswellia resins also
inhibits NFk B activation. This action was combined with an antiinflammatory effect in the inflamed mouse paw model.
From these studies it appears possible that the antiinflammatory action of BAs or other constituents of BEs starts with
the inhibition of NF␬-B activation.
Cytokines
Cytokines are produced by macrophages and T-cells following
the recognition of a pathogen.
The cytokines studied so far in connection with the antiiflammatory actions of BAs are TNF␣ and various interleukines. TNF␣,
IL-1, IL-2, IL-6 and others are involved in antibacterial and proinflammatory reactions.
TNF-˛. TNF-␣ is released from macrophages. It activates vascular endothel, increases permeability of vessels, entry of IgG, and
complement into tissues. It induces fever and shock.
Inhibition of TNF-␣ and its signaling has been recognized as
a highly successful strategy for the treatment of chronic inflammatory diseases such as rheumatoid arthritis. Previously it has
been shown by Syrovets et al. (2005) that acetyl-␣-BA and AKBA
inhibited the generation of TNF-␣ in concentrations between 1
and 10 ␮M in lipopolysaccharide-stimulated human monocytes.
AKBA was found to be the most active compound. The effect was
mediated by a direct inhibitory action on IK B␣ kinases (IKK)
conveyed inhibition of NFk B and subsequent down regulation of
TNF-␣ expression in human monocytes. In human monocytes,
Borsches and Grim (personal communication 2000) observed a
concentration-dependent inhibition of TNF-␣ and IL-1␤ production
in a concentration range of 5–20 ␮M.
Roy et al. (2005) tested the genetic basis of the antiinflammatory effects of a standardized BE in a system of
TNF-␣-induced gene expression in human micro vascular endothelial cells. Acutely, TNF-␣ induced 522 genes and down regulated
141. 133 genes were clearly sensitive to BE treatment. Such genes
are directly related to inflammation, cell adhesion and proteolysis. DNA micro array analysis in connection with Remap, gene
ontology data mining tool and others led to the recognition of
primary BE-sensitive and others led to the recognition of primary
BE-sensitive TNF␣-inducible pathways. BE was found to prevent
TNF-␣-induced expression of matrix metalloproteinases and
mediators of apoptosis.
In this context it is important to note that most TNF␣-induced
genes are NFk B-dependent and it appears that down regulation
of TNF-␣ in response to BAs may be the consequence of their
inhibitory action on NF␬B.
Interleukines. A variety of interleukines is produced by
macrophages and T-cells. They are related to different actions. In
brief:
• IL-1 produced from macrophages activates lymphocytes, local
tissue destruction and fever.
• IL-2 from TH –O and TH -1 cells controls proliferation and differentiation of T-cells.
• IL-4 produced by TH -2 cells activates B-cells and T-cells, but
inhibits activation of macrophages.
• IL-6 from macrophages activates lymphocytes, antibody production and generates fever.
• IL-10 a product of TH -2 cells reduces developement of TH -1 cells.
• IL-12 which is produced by macrophages activates natural killer
cells (NK -cells).
• INF-␥ from TH -1 can prevent activation of TH -2 cells.
As far as the actions of T-cells on other cells is concerned TH -1
cells activate macrophages whereas TH -2-cells activate B-cells.
The effect of an extract from Boswellic carterii on the production
of TH -1 and TH -2 cytokines by murine splenocytes was studied by
Chervier et al. (2005). In these in vitro experiments, application of
the resin extract, using ethanol as a solvent, showed significant cellular toxicity not seen with ethanol alone. Interestingly, the use of
an extract with sesame oil as solvent resulted in a dose dependent
inhibition of IL-2 and IFN-gamma and a dose-dependent potentiation of IL-4 and IL-10.
Gayathri et al. (2007) observed that a crude methanolic extract
from BS and 12-ursine-2-diketone, a pure compound of BS, inhibited TNF-␣, IL-1 ␤ and IL-6 in cultured PBMCs .
Observations on Th1/Th2 cytokines revealed marked down
regulation of IFN-␥ and IL-12 whereas IL-4 and IL-10 were
upregulated upon treatment with a crude extract and the pure
compound 12-ursene-2-diketone indicating that both are capable
of carrying out anti-inflammatory activity at sites where chronic
inflammation is present by switching off the proinflammatory
cytokines.
In addition, in the study of Khajuria et al. (2008) the authors
demonstrated that oral administration of 1–10 mg/kg of a poly-
H.P.T. Ammon / Phytomedicine 17 (2010) 862–867
meric fraction (BOS 2000) from BS decreased levels of IL-4, IFN-␥
and TNF-␣ in the serum.
Taking in vitro results together it appears possible that—if
transferable to the in vivo situation, BEs and constituents of BEs
may decrease the cellular activity of the immunesystem through
inhibiton of activation, proliferation and differentiation of B- and Tlymphocytes (IL-1, IL-2, IL-4, IL-6), tissue destruction (IL-1), action
of NK-cells (IL-12), antibody production (IL-6) and fever (IL-1, IL-6).
That this seems to be possible is evidenced by the vivo experiments of Khajuria et al. (2008).
Complement system
The complement system consists of a variety of plasma proteins
which together attack extracellular pathogens.
Activation of the complement system by antigens (classic way)
or by surface pathogens finally leads to taxis of inflammatory cells,
opsonisation of pathogens and destroy of pathogens.
Inhibition of the guinea pig complement system by ␣-boswellic
acid and ␤-boswellic acid in a concentration range between 5 and
100 ␮M has been reported by Wagner et al. (1987). Anticomplementary activities of a mixture of BAs were also described by Kapil
and Moza (1991). Here BAs inhibited the in vitro immunohaemolysis of antibody-coated sheep erythrocytes by pooled guinea-pig
serum. The reduced immunohaemolysis was found to be due to
inhibition of C3-convertase of the classical complement pathway.
The threshold concentration for inhibiting C3-convertase was
100 ␮g per 0.1 ml dilutent buffer added to the assay. BAs also
weakly inhibited individual components of the complement
system.
Thus at least in vitro BAs can suppress the conversion of C3 into
C3a and C3b and therefore its proinflammatory/lytic actions.
Mediators of inflammation
Mediators of inflammation are produced and released by mast
cells, granulocytes, macrophages, thrombocytes, red blood cells,
endothelial cells and fibroblasts.
They transport specific informations to related tissues and
finally produce the inflammatory symptoms. Studies with BEs
and/or BAs have focused so far on histamine, prostaglandins,
leukotrienes and oxigen radicals.
Histamine
Histamin is a vasoactive amin stored in mast cells and is released
when antigens bind to IgE molecules on the surface of mast cells.
Histamine causes vasodilatation, constriction of bronchial smooth
muscle, secretion of gastric acid and interacts with nociceptors.
It binds to H1 and H2 receptors. Its effects in allergic reactions
type I are very well known. In addition, mast cell activation results
in release of leukotrienes and platelet activating factors. In 2003,
Pungle et al. (2003) evaluated an extract of the oleo gum resin of
BS consisting of AKBA along with other constituents such as KBA
and acetyl-␤-boswellic acid for antianaphylactic and mast cell stabilising activity. Passive paw anaphylaxis and compound 48/80 as
inducer of mast cell degranulation were used as model. The extract
inhibited passive paw anaphylaxis in rats in a dose-dependent
manner (20, 40 and 80 mg/kg, p.o.). However, dexamethasone
(0.27 mg/kg, p.o.) serving as positive control for the extract proved
to be superior. A significant, dose-dependent inhibition (20, 40 and
80 mg/kg, p.o.) in compound 48/80-induced degranulation of mast
cells was also observed, thus showing a mast cell stabilising activity. The positive control disodium cromoglycate (50 mg/kg, i.p.)
afforded maximum protection against degranulation as compared
to the extract containing 60% AKBA.
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The results suggest promising antianaphylactic and mast cell
stabilising activity of the extract of BS.
Prostaglandins
Prostaglandins are produced from arachidonic acid (a constituent of cell membrane phospholipids) either by action of the
constitutive cyclooxygenase 1 (COX-1) or the inducible cyclooxigenase 2 (COX-2) enzymes. Prostaglandin production appears to
depend mainly on the COX-2 products, which are responsible for
inflammatory symptoms, including vasodilatation, permeability
and sensitization of nociceptors.
Two types of drugs were used to treat pains/inflammation. One
type (acetylsalicylic acid) does not distinguish between COX-1
and COX-2 whereas compounds such as celecoxib preferentially
inhibit COX-2. In polymorphous nuclear leukocytes (PMNL) stimulated with the calcium ionophore A23187 an alcoholic extract
from BS inhibited 6-keto-PGF1␣ formation, which was substantial
at 100 ␮g/ml being, however, two to tree times higher than the
level needed for inhibition of leukotriene synthesis (Ammon et al.
1991).
Acetyl boswellic acids were tested in human platelets which
contain COX1 but no 5-LO. In concentrations up to 400 ␮M they
showed no effect on 12-HHT-COX formation (Safayhi et al. 1992;
Ammon et al. 1993). This is in line with data of Gupta et al. (1992)
who observed little effect of BAs in the carrageenan (aspirin) model
compared to the latex papaya model in which prednisolone and
levamisole were effective and in which “aspirin” compounds were
not active.
On the other hand Siemoneit et al. (2008) showed that BAs , especially AKBA inhibited COX-1 formation in intact human platelets
(IC50 = 6 ␮M) in a reversible manner which is in according with
unpublished observations of our laboratory. In the study of
Siemoneit et al. (2008) COX-2 was less efficiently inhibited by BAs .
Thus, it appears that inhibition of prostaglandin synthesis by
BEs and BAs as far as their anti-inflammatory actions are concerned
play only a minor role. It is therefore not surprising, as discussed
above, that there are differences in the anti-inflammatory actions
between BAs and “aspirin” like drugs.
Leukotriens
Leukotriens are produced in neutrophils, eosinophils,
macrophages and mast cells by 5-lipoxigenase (5-LO) after
activation through the membrane protein five-lipoxigenase activating protein (FLAP). Their functions include: chemotaxis, plasma
exudation (oedema), stimulation of oxigen radical formation and
phagocytosis (partially mediated by LTB4 ) as well as bronchoconstriction, mucus secretion and vasoconstriction (partially mediated
by LTC4 , LTD4 and LTE4 ).
Based on the observations of Singh and Atal (1986), Ammon et
al. (1991) studied the effect of an ethanolic extract of the oleo gum
resin of BS on leukotrien B4 formation in rat PMN. After stimulation
of the leukotrien synthesis in PMN with calcium and ionophore
A231876 the extract inhibited LTB4 and 5-HETE (a metabolite of the
5-LO-cascade) formation in a concentration-dependent manner in
the range between 10 and 80 ␮g/ml. In this assay, prednisolone was
without any effect, suggesting that the pharmacodynamic target
was not phospholipase A2 .
In 1992, BAs were reported to be specific, non-redox inhibitors
of 5-LO (Safayhi et al. 1992). In this study, isomers (␣-and ␤-) of BAs,
i.e., 11-keto-␤-boswellic acid and their acetyl derivatives were isolated from the oleo gum resin of BS. BAs and derivatives decreased
the formation of LTB4 in calcium-stimulated PMN in a concetrationdependent manner. Acetyl-11-keto-␤-boswellic acid (AKBA) was
most effective with an IC50 value of 1.5 ␮M (Safayhi et al. 1992).
To find out whether or not the inhibitory action of BAs depends on
specific chemical structures, Sailer et al. (1996) studied the effect
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of a variety of derivatives of BAs on leukotrien synthesis in Caionophore-stimulated PMN. From the IC50 value, it was obvious
that not all of the compounds tested inhibited leukotrien synthesis
and that some exhibited only a partial effect. The findings revealed
that a hydrophilic funcion at C-4 in combination with an 11-keto
group is essential for the inhibition of leukotrien synthesis by BAs .
These data are in favour that as far as mediators of inflammation
deriving from the arachidonic acid cascade are concerned the inhibition of leukotrien synthesis by BEs and/or BAs plays the major role
in their anti-inflammatory action.As far as the clinical relevance of
the in vitro data showing inhibition of leukotrien synthesis by BE
and BAs is concerned, Siemoneit et al. (2009) denied such a possibility, since they could not find a decrease of leucotriens in the plasma
of healthy subjects after oral administration of 800 mg of an extract
of the gum resins. On the other hand Th. Simmeth (personal communication) observed inhibition of cystein-leucotrien formation in
granulocytes ex vivo stimulated with Ca2+ and calcium ionephore
from healthy subjects who have taken 1200 mg of the commercial
product H 15 (Gufic, Ltd. Mumbai). The inhibitor effect was more
than 90% with a maximum 6 h after intake which corresponds to
pharmacokinetic data received from humans treated orally with
a BE showing maximal blood levels of KBA after 4 h, (Sterk et al.,
2004), suggesting that BE/BAs exert their therapeutic useful effect
mainly during stimulation of leucotrien synthesis.
Oxygen radicals. Oxygen radicals are also factors involved in tissue destruction, for instance in rheumatoid arthritis. Heil et al.
(2001) studied the effects of BEs and AKBA on SOD-quenchable O2 radical formation in intact PMNs and in a cell-free system. AKBA
(IC50 = 10 ␮M) and extracts (IC50 = 13 ␮g/ml) consistently inhibited
the phorbolester PMA-stimulated NADPH oxidase activity in rat
peritoneal PMNs and reduced fMLP and PMA-induced oxidative
burst in stimulator-sensitive human blood PMN preparations, but
failed to block the NADPH-oxidase activity in the membrane fraction of PMA-prestimulated PMNs.
These data suggest direct inhibitory effects of BEs and AKBA on
oxygen radical formation in PMNs .
Human leukocyte elastase (HLE). HLE is a serine protease produced
and released by PMN, and because of its aggressive destructive
properties, some investigators have suggested that HLE may play
a role in several diseases, such as pulmonary emphysema, cystic
fibrosis, chronic bronchitis, acute respiratory distress syndrome,
glomerulonephritis and rheumatic arthritis. In 1995, it was demonstrated that granulocyte-mediated hepatotoxicity after endotoxin
stimulation depends on elastase release (Sauer et al. 1995).
Using pure HLE Safayhi et al. (1997) screened several pentacyclic
triterpenes for inhibitory actions on HLE. This is of therapeutic
interest, since leukotrien formation and HLE release are increased
simultaneously during neutrophile stimulation in a variety of
inflammatory and hypersensitivity based human diseases. Thus,
decrease of chemotaxis together with inhibition of this enzyme,
would lower the destructing actions of HLE, especially at the locus
of diseases.
In the study of Safayhi et al. (1997) AKBA decreased the activity
of HLE in vitro with an IC50 value of roughly 15 ␮M. Among the
pentacyclic triterpenes tested in concentrations up to 20 ␮M, they
also observed substantial inhibition by ␤-boswellic acid, amyrin
and ursolic acid, but not by 18-␤-glycyrrhetinic acid. The data show,
that the dual inhibition of 5-lipoxygenase and HLE is unique to BAs:
other pentacyclic triterpenes with HLE inhibitory activities (e.g.,
ursolic acid and amyrin) did not inhibit 5-LO.
When an extract was employed in the enzyme test (H15TM Gufic
Ltd. Mumbai) half maximal inhibition occurred at ∼7.5 ␮g/ml (personal observation).
In addition to the inhibitory action on oxygen radical formation
in PMNs , BEs , AKBA and some other constituents of BEs produced
direct inhibiton of human leukocyte elastase, an enzyme which is
responsible for destruction of functional tissues including cartilage
in joints.
Clinical studies
There are variety of clinical studies dealing with the effects
of BEs in chronic inflammatory diseases including rheumatoid
arthritis (Etzel 1996), bronchial asthma (Gupta et al. 1998) ulcerative colitis (Gupta et al. 1997), Crohn’s disease (Gerhardt et al.
2001), Osteoarthritis (Kimmatkar et al. 2003; Sengupta et al. 2008;
Sontakke et al. 2007) suggesting improvement. It is possible that
this is due to different actions of BEs /BAs on factors/mediators of
the immune system.
Summary
Extracts from the gum resin of B. serrata and other Boswellia
species as well as some of its constituents including boswellic acids
and others have been shown to affect parameters of the immune
system in different ways.
As far as the humoral defence system is concerned boswellic
extracts and boswellic acids affect antibody titres and immunglobines. Here, it appears that in mice oral doses of 50 mg/kg and
less are stimulatory whereas higher doses tend to show the opposite. The same holds for the proliferation of lymphocytes.
A further target of BEs and BAs in the immune system is the complement system where inhibiton of C3-convertase was reported.
Many studies deal with the effects of BEs, BAs and other constituents of BEs on NF␬ B and cytokines. The activation of the
transcription factor NF␬ B was shown to be inhibited by AKBA
and probably also of other compounds including incensole acetate
and 12-ursene-2-diketone suggesting decreased transcription of
factors related to inflammation including a variety of cytokines.
Among the factors are proinflamatory interleukines TNF-␣, IL-1␤,
IL-2, INF-␥, IL-6, IL-12, but also upregulation (IL-4, IL-10) was
observed.
In addition to effects of BEs and BAs and other factors related to
the humoral and cellular immune system direct actions on peripheral mediators of inflammation have been reported. Thus BEs and
various BAs are inhibiting leukotrien biosynthesis by 5-LO. As far as
an action on prostaglandin synthesis is concerned BEs and a mixture
of acetyl boswellic acids showed no effect whereas prostaglandin
synthesis in human platelets which represent COX-1 was inhibited
by AKBA. On the other hand COX-2 appeared to be less sensitive to
AKBA.
Products of the inflammatory process which finally cause
destruction of tissues in chronic inflammatory diseases—are oxygen radicals and enzymes released by leukocytes and macrophages
including human leukocyte elastase (HLE). The action of both is
inhibited by BEs and AKBA.
Conclusion
Both BEs , BAs and probably also other constituents of BEs possess a variety of different actions in the immune system. Depending
on the dose they may be stimulating in formation of antibodies
(lower doses) or inhibitory in the cellular part by affecting the
action of NF␬B and a variety of cytokines and finally the executors for all damages. Most of the data discussed in this review have
been obtained in in vitro experiments in a wide range of concentrations. Whether or not the results obtained with BEs and BAs in every
case are relevant in the therapy of chronic inflammatory diseases
H.P.T. Ammon / Phytomedicine 17 (2010) 862–867
remains to be established. Nevertheless some clinical studies have
shown positive results in the treatment with boswellic extracts.
References
Ammon, H.P., Mack, T., Singh, G.B., Safayhi, H., 1991. Inhibition of leukotriene B4
formation in rat peritoneal neutrophils by an ethanolic extract of the gum resin
exudates of Boswellia serrata. Planta Med. 57, 203–207.
Ammon, H.P., Safayhi, H., Mack, T., Sabieraj, J., 1993. Mechanism of antiinflammatory
actions of curcumine and boswellic acids. J. Ethnopharmacol. 38, 113–119.
Badria, F.A., Mikhaeil, B.R., Maatooq, G.T., Amer, M.M., 2003. Immunmodulatory terpenoids from the oleogum resin of Boswellia carterii Birdwood. Z. Naturforsch.
58, 506–516.
Chervier, M.R., Ryan, A.E., Lee, D.Y., Zhongze, M., Wu-Yan, Z., Via, C.S., 2005. Boswellia
carterii extract inhibits TH1 cytokines and promotes TH2 cytokines in vitro. Clin.
Diagn. Lab. Immunol. 1, 575–580.
Cuaz-Pérolin, C., Billiet, L., Baugé, E., Copin, C., Scott-Algara, D., Genze, F., Büchele, B.,
Syrovets, T., Simmet, T., Rouis, M., 2008. Antiinflammatory and antiatherogenic
effects of NF-Kappa B inhibitor acetyl-11-beta-boswellic acid in LPS-challenged
ApoE −/− mice. Arterioscler. Thromb. Vasc. Biol. 28, 272–277.
Etzel, R., 1996. special extract of Boswellia serrata (H15) in the treatment of reumatoid arthritis. Phytomedicine 3, 91–94.
Gayathri, B., Manjula, N., Vinaykumar, K.S., Lakshmi, B.S., Balakrishnan, A., 2007. Pure
compound from Boswellia serrata extract exhibits anti-inflammatory property
in human PBMCs and mouse macrophages through inhibition of TNF alpha, IL1beta, NO and MAP kinases. Int. Immunopharmacol. 7, 473–482.
Gerhardt, H., Seifert, F., Buvari, P., Vogelsang, H., Repges, R.Z., 2001. Therapie des
aktiven Morbus Crohn mit Boswellia serrata extract H 15. Z. Gastroenterol. 39,
11–17.
Gupta, O.P., Sharma, N., Chand, D., 1992. A sensitive and relevant model for evaluating anti-inflammatory activity-papaya latex-induced rat paw inflammatione.
J. Pharmacol. Toxicol. 28, 15–19.
Gupta, I., Parihar, A., Malhotra, P., Singh, G.B., Ludtke, R., Safayhi, H., et al., 1997.
Effects of Boswellia serrata gum resin in patients with ulcerative colitis. Eur. J.
Med. Res. 2, 37–43.
Gupta, I., Gupta, V., Parihar, A., Gupta, S., Ludtke, R., Safayhi, H., et al., 1998. Effects
of Boswellia serrata gum resin in patients with bronchial asthma: results of
a double-blind, placebo-controlled, 6 week clinical study. Eur. J. Med. Res. 3,
511–514.
Heil, K., Ammon, H.P., Safayhi, H., 2001. Inhibition of NADPH-oxidase by AKBA in
intact PMNs. Naunyn Schmiedebergs Arch. Pharmacol. 363S, R14.
Kapil, A., Moza, N., 1991. Anticomplementary activity of Boswellia acids—an inhibitor
of C3-convertase of the classical complement pathway. Int. J. Immunopharmacol. 14, 1139–1143.
Khajuria, A., Gupta, A., Suden, P., Singh, S., Malik, F., Singh, J., Gupta, B.D., Suri, K.A., Srinavas, V.K., Ella, K., Quazi, G.N., 2008. Immunmodulatory activity of biopolymeric
fraction BOS 2000 from Boswellia serrata. Phytother. Res. 22, 340–348.
Kimmatkar, N., Thawani, V., Hingorani, L., Khiyani, R., 2003. Efficacy and tolerability
of Boswellia serrata extract in treatment of osteoarthritis of knee—a randomized
double blind placebo controlled trial. Phytomedicine 10, 3–7.
867
Moussaieff, A., Shohami, E., Kashman, Y., Fride, E., Schmitz, M.L., Renner, F., Fiebich,
B.L., Munoz, E., Ben-Neriah, Y., Mechoulam, R., 2007. Incensolate acetate, a novel
anti-inflammatory compound isolated from Boswellia resin, inhibits nuclear
factor-kappa B activation. Mol. Pharmacol. 72, 1657–1664.
Pungle, P., Banavalikar, M., Suthar, A., Biyani, M., Mengi, S., 2003. Immunomodulatory activity of boswellic acids of Boswellia serrata Roxb. Indian J. Exp. Biol.
41, 1460–1462.
Roy, S., Khanna, S., Shah, H., Rink, C., Phillips, C., Preuss, H., et al., 2005. Human
genome screen to identify the genetic basis of the anti-inflammatory effects of
Boswellia in microvascular endothelial cells. DNA Cell Biol. 24, 244–255.
Safayhi, H., Mack, Th., Sabieraj, J., Anazodo, M.I., Subramanian, L.R., Ammon, H.P.,
1992. Boswellic acids: novel, specific nonredox inhibitors of 5-lipoxygenase. J.
Pharmacol. Exp. Ther. 261, 1143–1146.
Safayhi, H., Rall, B., Sailer, E.R., Ammon, H.P., 1997. Inhibition by boswellic acids of
human leukocyte elastase. J. Pharmacol. Exp. Ther. 281, 460–463.
Sailer, E.R., Subramanian, L.R., Rall, B., Hoernlein, R.F., Ammon, H.P., Safayhi, H., 1996.
Acetyl-11-keto-beta-boswellic acid (AKBA): structure requirements for binding
and 5-lipoxygenase inhibitory activity. Br. J. Pharmacol. 117, 615–618.
Sauer, A., Aigner, J., Hartung, T., Minuth, W., Wendel, A., 1995. Granulocyte mediated
hepatotoxicity after endotoxin stimulation depends on adhesion and elastase
release. Naunyn Schmiedebergs Arch. Pharmacol. 351S, A 495.
Sengupta, K., Alluri, K.V., Satish, A.R., Mishra, S., Golakoti, T., Sarma, K.V., Dey, D.,
Raychaudhuri, S.P., 2008. A double blind, randomized, placebo controlled study
of the efficacy and safety of 5-Loxin® for treatment of osteoarthritis of the knee.
Arthritis Res. Ther. 10 (4), R 85.
Sharma, M.L., Kaul, A., Khajuria, A., Singh, S., Singh, G.B., 1996. Immunomodulatory
activity of boswellic acids (pentacyclic triterpene acids) from Boswellia serrata.
Phytother. Res. 10, 107–112.
Siemoneit, U., Hofmann, B., Kather, N., Lamkemeyer, T., Madlung, J., Franke, L.,
Schneider, G., Jauch, J., Poeckel, D., Werz, O., 2008. Identification and functional
analysis of cyclooxygenase-1 as a molecular target of boswellic acids. Biochem.
Pharmacol. 75, 503–513.
Siemoneit, U., Pergola, C., Jazzar, B., Northoff, H., Skarke, C., Jauch, J., Werz, O.,
2009. On the interference of boswellic acids with 5-lipoxygenase: Mechanistic studies in vitro and pharmacological relevance. Eur. J. Pharmacol. 606, 246–
254.
Singh, G.B., Atal, C.K., 1986. Pharmacology of an extract of salai guggal ex Boswellia
serrata, a new non-steroidal anti-inflammatory agent. Agents Actions 18,
407–412.
Sontakke, S., Thawani, V., Pimpalkhute, S., et al., 2007. Open, randomized, controlled clinical trial of Boswellia serrata extract as compared to valdecocib in
osteoarthritis of knee. Indian J. Pharmacol. 39, 27–29.
Sterk, V., Büchele, B., Simmet, T., 2004. Effect of food intake on the bioavailability
of boswellic acids from a herbal preparation in healthy volunteers. Planta. Med.
70, 1155–1160.
Syrovets, T., Buchele, B., Krauss, C., Laumonnier, Y., Simmet, T., 2005. Acetylboswellic acids inhibit lipopolysaccharide-mediated TNF-alpha induction in
monocytes by direct interaction with IkappaB kinase. J. Immunol. 174,
498–506.
Wagner, H., Knaus, W., Jordan, E., 1987. Pflanzeninhaltsstoffe mit Wirkung auf das
Komplementsystem. Z. Phytother. 8, 148–149.