Bromelain is a crude extract from the pineapple that contains, among other components, various closely related proteinases, demonstrating, in vitro and in
vivo, antiedematous, antiinflammatory, antithrombotic
and fibrinolytic activities. The active factors involved are
biochemically characterized only in part. Due to its efficacy
after oral administration, its safety and lack of undesired
side effects, bromelain has earned growing acceptance
and compliance among patients as a phytotherapeutical
drug. A wide range of therapeutic benefits has
been claimed for bromelain, such as reversible inhibition
of platelet aggregation, angina pectoris, bronchitis, sinusitis,
surgical traumas, thrombophlebitis, pyelonephritis
and enhanced absorption of drugs, particularly of antibiotics.
Biochemical experiments indicate that these
pharmacological properties depend on the proteolytic activity
only partly, suggesting the presence of nonprotein
factors in bromelain. Recent results from preclinical and
pharmacological studies recommend bromelain as an
orally given drug for complementary tumor therapy: brofrom
animal organs such as trypsin and chymotrypsin.
These enzymes offer a wide spectrum of therapeutic efficacies:
they demonstrate, in vitro and in vivo, antiedemateous,
antiinflammatory, antithrombotic and fibrinolytic
activities. They modulate the functions of adhesion
molecules on blood and endothelial cells, and also regulate
and activate various immune cells and their cytokine
production.
Bromelain acts as an immunomodulator by raising the impaired
immunocytotoxicity of monocytes against tumor
cells from patients and by inducing the production of distinct
cytokines such as tumor necrosis factor-a, interleukin
(Il)-1b, Il-6, and Il-8. In a recent clinical study
with mammary tumor patients, these findings could be
partially confirmed. Especially promising are reports on
animal experiments claiming an antimetastatic efficacy
and inhibition of metastasis-associated platelet aggregation
as well as inhibition of growth and invasiveness of tumor
cells. Apparently, the antiinvasive activity does not
depend on the proteolytic activity. This is also true for
bromelain effects on the modulation of immune functions,
its potential to eliminate burn debris and to accelerate
wound healing. Whether bromelain will gain wide
acceptance as a drug that inhibits platelet aggregation, is
antimetastatic and facilitates skin debridement, among
other indications, will be determined by further clinical
trials. The claim that bromelain cannot be effective after
oral administration is definitely refuted at this time.
Introduction
The role of proteolytic enzymes for therapeutic use
Bromelain belongs to a group of proteolytic enzymes
which are used as drugs for the oral systemic treatment of
inflammatory, blood-coagulation-related and malignant
diseases. Apart from the plant cysteine-proteinases
bromelain and papain, the group comprises proteinases
CMLS, Cell. Mol. Life Sci. Vol. 58, 2001 Review Article 1235
medication to glucocorticoids, nonsteroidal antirheumatics
and immunomodulatory agents. Their very low toxicity
makes them suitable tools for controlling chronic inflammatory
diseases.
For the therapy of inflammatory and malignant disorders,
these proteinases are employed as
– additives for chemotherapy (to reduce side effects of
drugs and to improve quality of life);
– additives for radiotherapy (to reduce inflammation and
edema);
– additives in surgery (to reduce edema and to improve
wound healing);
– additives to prevent lymphedema by reducing lymphocongestion,
detritus, viscosity of the exsudate and stimulation
of phagocytosis of associated leukocytes.
It should be added that clinical studies support these recommended
indications only to a limited extent. Yet the
large body of preclinical, pharmacological and daily experience
offers an important and worthwhile field for
well-designed clinical studies in order to evaluate evidence-
based medical indications.
Biochemistry of bromelain
Bromelain is a crude, aqueous extract from the stems and
immature fruits of pineapples (Ananas comosus Merr.,
mainly var. Cayenne from the family of bromeliaceae),
constituting an unusually complex mixture of different
thiol-endopeptidases and other not yet completely characterized
components such as phosphatases, glucosidases,
peroxidases, cellulases, glycoproteins and carbohydrates,
among others [1, 2]. In addition, bromelain contains
several proteinase inhibitors [3, 4]. Stem-bromelain
(EC. 3.4.22.32) is distinguished from fruit-bromelain
(EC. 3.4.22.33), previously called bromelin [2]. Today
bromelain is prepared from cooled pineapple juice by
centrifugation, ultrafiltration and lyophilization. The process
yields a yellowish powder, the enzyme activity of
which is determined with different substrates such as
casein (FIP units), gelatine (gelatine digestion units) or
chromogenic tripeptides [1, 5, 6]. In aqueous solution,
bromelain rapidly deteriorates through self-digestion.
The addition of serum containing a2-macroglobulin will
prevent self-digestion (see below). By high-resolution
fast protein liquid chromatography (FPLC) and other
biochemical methods, basic (stem bromelain, ananain,
comosain) and acidic thiol-proteinases have been isolated
from crude bromelain, partially or fully sequenced and
characterized in more detail [6–8]. They mainly comprise
glycosylated multiple enzyme species of the papain
superfamily with different proteolytic activities, molecular
masses between 20 and 31 kDa, and isoelectric points
between > 10 and 4.8. Two major basic proteinases, F4
and F5, were further characterized and showed molecular
masses of 24,397 and 24,472 Da, respectively [6] (Table
1). In addition, numerous, different protein fractions were
obtained by means of various biochemical methods
[SDS-polyacrylamide gel electrophoresis (PAGE), isoelectric
focusing (IEF), multicathodal-PAGE]. Among the
basic proteinases, one fraction (F9, ananain) reveals the
highest specific proteinase activity, is not glycosylated
and has a molecular mass of 23,427 Da [6, 8, 9]. The enzymatic
activities comprise a wide spectrum with pH optima
between 5.5 and 8.0 [10]. The substrate spectrum is
similarly broad, extending from synthetic low molecular
mass amides and dipeptides up to high molecular substrates
such as fibrin, albumin, casein, angiotensin II,
bradykinin. Bromelain preferentially cleaves glycyl,
alanyl and leucyl bonds.
Commercial bromelain preparations are evaluated according
to their proteolytic activity. The platelet aggrega-
Table 1. Cysteine proteinases (bromelains) from pineapples (Ananas comosus).
Name Abbreviation Molecular mass Isoelectric point Sequences Glycosylation Reference
(EC number) according to [6, 7] (Dalton)
accordimg to [2, 8]
From pineapple stems:
Stem bromelain F4 and F5 23,800 > 10 completely glycosylated 6
(EC 3.4.22.32) (sequence + sugar) sequenced
(212 amino acids)
Ananain F9 23,464 > 10 completely not glycosylated 6, 9
(EC 3.4.22.31) (sequence) sequenced
(216 amino acids)
Comosain F9/b 24,509 and 23,569 > 10 N-term. sequence glycosylated 6, 8
(esms)
SBA/a and SBA/b 23,550 and 23,560 4.8 and 4.9 N-term. sequence highly glycosylated 7
(esms)
From pineapple fruits:
Fruit bromelain 23,000 4,6 N-term. sequence not glycosylated 1
(EC 3.4.22.33)
tion inhibitory and antiinflammatory action seem to be
related to the protease activity. However, other effects
such as inhibition of tumor cell growth and metastasis as
well as debridement of burns are associated with other
nonproteinolytic components contained in bromelain.
Thus, the determination of the proteolytic activity alone
may not be sufficient to completely characterize the pharmacological
properties of bromelain [11].
Pharmacology of bromelain: preclinical studies
Pharmacodynamics of bromelain
From a variety of in vitro and animal experiments, mainly
with rodents, as well as from clinical observations, based
on uncontrolled and controlled studies, the general properties
of bromelain may be summarized as follows
[11–14] Bromelain
– prevents edema formation and reduces existing edemas
– reduces the blood level of fibrinogen
– supports fibrinolysis
– activates plasmin
– prolongs the prothrombin and partial thromboplastin
time (after relatively high doses)
– prevents aggregation of blood platelets
– prevents adhesion of platelets to endothelial cells of
blood vessels
– reduces the blood level of plasmakinins
– reduces the level of prostaglandine E2 and of thromboxane
A2 in exsudates during acute inflammation
– acts as an antiinflammatory agent
– induces the secretion of interleukin (Il)-1, Il-6, Il-8 and
tumor necrosis factor (TNF)-a from blood monocytes
and granulocytes
– supports the oxidative burst and the cytotoxicity of
granulocytes against tumor cells
– increases the tissue permeability of antibiotic drugs
– prevents metastases in a mouse model
– supports skin debridement of burns
Some effects of bromelain may result from its capacity to
alter and modulate distinct cell surface structures by cleaving
off peptides [15]. Thus, the bromelain-mediated modification
of adhesion molecules on platelets and on other
normal and malignant tumor cells may inhibit their aggregation.
The dissolution of cell membrane constituents
and the effects on components of hemostatic processes
may explain antiedemateous and fibrinolytic phenomena.
Bromelain prevents edema formation and reduces
existing edema
Several groups have provided significant evidence for
both the edema-protective and edema-reducing efficacy
of bromelain in a variety of classical animal experiments
[16–20]. Among them, the data by Netti et al. [17] are
particularly interesting, since papain, another cysteine
proteinase, was ineffective in all experimental models,
whereas bromelain induced 41% (carrageenin) and 45%
(dextran) inhibition of edema formation. In addition, bromelain
showed the strongest edema-protective efficacy of
all drugs tested, such as indometacin, acetylsalicylic acid,
aescin, oxyphenbutazon, and so on [18]. Moreover, both
intraperitoneal (i. p.) and orally applied bromelain proved
significantly capable of reducing edema (induced by cotton
tissue, carrageenin, croton oil) in various animal models
. It was concluded that bromelain increases tissue
permeability by fibrinolysis and promotes reabsorption
of edema fluid into blood circulation. Uhlig and
Seifert [18] compared enteral and i. p. application of bromelain
and demonstrated a highly significant edema reduction
(by 50%) 12 h after oral application, whereas i. p.
administration was effective during the first hours only.
Bromelain promotes the absorption of antibiotic drugs
It has been known for a number of years that bromelain is
capable of enhancing the tissue permeability of penicillins
and tetracyclins after oral administration. This increases
absorption and leads to an improved diffusion after
subcutaneous and intramuscular application of the antibiotics.
Higher serum and tissue levels are obtained, and
side effects are reduced [21–23].
Among others, Neubauer evaluated the combined bromelain
and antibiotic therapy of 53 hospitalized patients
with pneumonia, bronchitis, staphylococcus infections,
thrombophlebitis, pyelonephritis and rectal abscesses
. Twenty-three of the patients had been on antibiotic
therapy without success. Twenty-two of these patients responded
favorably to the combined treatment of bromelain
and antibiotics. In every disease state significant reduction
in morbidity was noted as opposed to antibiotics
alone. Similarly, Ryan concluded from his double-blind
clinical study on acute sinusitis that of the patients receiving
bromelain, 83% showed complete resolution of
nasal mucosal inflammation versus 52% in the placebo
group [25].
Bromelain affects blood coagulation and fibrinolysis
The data on the edema-protective and -reducing efficacy
of bromelain suggest that hemostatic processes are
involved, such as prolongation of the prothrombin time,
partial thromboplastin time and decrease of the fibrinogen
blood level.
In the inflammatory animal models of Pirotta et al. [26],
bromelain increased the fibrinolytic activity in a dose-dependent
manner. Livio et al. [27] found an increase of
prothrombin and partial thromboplastin time as well as a
decrease of ADP-induced platelet aggregation. All these
effects were clearly dose dependent and related to the
1236 H. R. Maurer Bromelain: biochemistry, pharmacology and medical use
CMLS, Cell. Mol. Life Sci. Vol. 58, 2001 Review Article 1237
proteolytic activity of bromelain, since inactivation of the
enzyme abolished the effects [28].
Bromelain prevents platelet aggregation
In 1972 Heinicke et al. [29] observed that oral administration
of bromelain to healthy persons, particularly
those with high platelet counts, significantly lowers the
ADP-induced aggregation of platelets. Morita et al. [28]
attempted to isolate and characterize platelet aggregation
inhibitory factors from bromelain. At about the same
time, other authors reported on fibrinolytic activities of
bromelain and experiments to isolate fractions by means
of biochemical methods [26, 30].
Aggregation and adhesion of platelets to endothelial cells
have recently been studied in more detail [31]. When the
platelets were incubated with bromelain prior to activation
with thrombin, aggregation was completely prevented.
Papain was less effective. Bromelain reduced, in vitro,
the adhesion of thrombin-activated, fluorescent-labelled
platelets onto bovine aorta endothelial cells. Using an
in vivo laser thrombosis model, oral administration of
bromelain to rats could significantly decrease the thrombus
formation in mesenterial arterioles by 11%, in venols
by 6%.
Bromelain effects on plasminogen,
Quick- and partial thromboplastin time
In vitro, bromelain was able to activate plasminogen to
yield plasmin, which is known to cleave fibrin [32]. This
property is shared with streptokinase. In addition, bromelain
inhibited the thrombin-induced formation of blood
plasma fibrin in vitro; the other cysteineproteinase papain
was less effective in this respect. In contrast to
streptokinase, bromelain was not able to dissolve fibrin
aggregates. After oral administration [3000 Fédération
International Pharmaceutique (FIP) units daily for 10
days] to healthy persons, no significant influence was
determined as to thromboplastin (Quick) time and plasmin
formation, yet a moderate increase of the partial
thromboplastin time (a PTT) still within normal range
.
Mechanism of action of bromelain, apparently due
to its proteolytic activity
The antiedematous, antiinflammatory, antithrombotic
and fibrinolytic efficacy of bromelain reported so far
suggests that several mechanisms of action are involved
on different levels: The blood clotting, complement and
kinin systems interconnect and mutually influence each
other. Generally, they regulate cascade systems of proteinase-
mediated reactions.
Besides interactions with plasmakinins, prostaglandins
and the fibrinogen/fibrin system the reaction with the
plasmaprotein a2-macroglobulin plays a significant role
(see below). Like most endoproteinases, bromelain circulates
in blood, bound to this high molecular mass proteinase
inhibitor [35]. However, binding does not completely
inactivate the enzyme; the capacity to hydrolyze
small substrates is still preserved [36].
Bromelain is an effective fibrinolytic agent in vitro and in
vivo. However, this property is more evident in purified
fibrinogen solutions than in plasma, probably due to proteinase
inhibitors present in plasma. Despite this limitation,
an increase of the fibrinolytic activity was observed
Protease Parameter Effect Signifiance Ref.
Bromelain POS extrinsic blood coagulation = blood coagulation, dependent on factor II, V 31
Bromelain F9 (Quick-test) = VII, X and fibrinogen 33
Bromelain POS intrinsic blood coagulation Ø blood coagulation, dependent on plasmatic 31
Bromelain F9 (PTT-Test) = factors except factor VII 33
Bromelain POS activation of plasminogen = activation causes fibrin degradation 31
Bromelain BP to plasmin ≠ (fibrinolysis) 33
Bromelain F9 d 26, 27
Bromelain BP thrombin-dependent fibrin Ø reduction of blood clotting 34
Bromelain F4, F9 formation
Bromelain BP thrombin-stimulated platelet Ø reduction of thrombus formation 31
aggregation
Bromelain BP thrombin-stimulated platelet Ø reduction of thrombus formation 31
adhesion onto endothelial cells
Bromelain BP in vivo thrombus formation in Ø reduction of thrombus formation 31
arterioles and venoles after oral
administration
Bromelain BP (base powder), commercial crude extract; POS, BP given orally; F4, F9, bromelain fractions.
after bromelain administration [26]. Besides direct cleavage
of fibrin, activation of fibrinolytic factors was discussed
, e. g. by increasing the plasmin concentration
. The fibrinolytic activity of bromelain has been attributed
to the enhanced conversion of plasminogen to plasmin,
which limits the spread of the coagulation reaction
by degrading fibrin [38].
By means of these reactions the vascular permeability
may be enhanced and edematous fluid may again be absorbed
by tissues. This is in agreemant with clinical findings
in that bromelain administration may lead to an increased
concentration of concomitantly given antibiotics
in body fluids as well as in tissues (see above).
Plasmakinins and prostaglandins play important roles as
mediators of pain and vascular phenomena associated
with acute inflammation. Animal experiments demonstrated
that bromelain lowers the plasmakinin level [39].
Similarly, bromelain injections caused a dose- dependent
decrease of bradykinin levels at inflammatory sites and a
parallel decrease of the prekallikrein levels in sera [40].
Studies of prostaglandin metabolism during acute inflammation
showed that orally administered bromelain
reduces the level of both PGE2 and of thromboxane B2
dose-dependently [41].
Nonsteroidal antiinflammatory drugs inhibit the enzyme
cyclooxigenase, resulting in a decrease of both pro- and
antiinflammatory prostaglandins. In contrast, bromelain
may, according to Taussig, selectively inhibit the proinflammatory
thromboxane generation and shift the ratio of
thromboxane/prostacyclin (PGI2 ) in favor of the antiinflammatory
prostacyclin. The mechanism of action of the
recently introduced ‘superaspirins’ and of bromelain
were suggested to be identical [11].
Effects of bromelain on malignant growth
First observations on the effects of bromelain
on cancer patients
Gerard in 1972 [42] and Nieper in 1976 [43] reported on
beneficial effects following oral administration of bromelain
to cancer patients. After treatments with relatively
high doses for several weeks and months, respectively,
they noted remarkable remissions of malignant tumors
with negligible side effects. However, these reports must
be considered to be anectodal by and large.
Bromelain inhibits tumor cell growth in vitro
Bromelain inhibits the proliferation of different tumor
cells in vitro. The inhibitory activity can be traced neither
to the proteolytic nor to the peroxidase activity or to the
platelet aggregation-inhibitory activity [44]. Later, Garbin
et al. [45] as well as Grabowska et al. [46] confirmed
the concentration-dependent inhibitory activity of bromelain
crude extract and bromelain fractions on various
tumor cells in vitro. Maurer et al. [47] found that bromelain
may induce differentiation of leukemic cells in vitro
and proposed this phenomenon as a possible mechanism
of action. Apoptosis of tumor cells may result from induction
of differentiation, a process by which many
cytostatic drugs may eliminate tumor cells.
Relationships between risk of thrombosis and
risk of metastases
An association between venous thromboembolism (VTE)
and cancer has been recognized since at least 1865 [48].
Patients with clinically evident malignant diseases or occult
cancer have an increased risk of VTE, and necropsy
studies document an increased prevalence of thrombosis
among patients with visceral cancer. Conversely, two recent
studies have shown that the risk of revealing malignancy
one year after a VTE is increased three to four
times [49, 50]. We know by now that upon contact with
platelets, tumor cells release a variety of factors (growth
factors such as platelet-derived growth factor (PDGF),
transforming growth factor-b (TGF-b), thrombin, thrombospondin,
prostaglandins, cathepsins, among others)
that promote platelet aggregate formation. They are also
capable of damaging the vascular wall, thereby inducing
congestion, which in turn causes coagulation. Platelets
may form aggregates with tumor cells that can adhere to
the endothelium and stimulate initial processes of metastases
[51–55].
Taussig et al. [11] deserve the credit for recognizing the
significance of bromelain as an anticoagulant and as a
potential antimetastatic drug. In 1988, he and co-workers
reported that bromelain fed to C57bl/6 mice would
dramatically lower the take of subcutaneous (s.c.)-injected
Lewis lung tumor cells, leading to 77–98% reduction,
and that this effect was due neither to the proteolytical
anticoagulant nor to the peroxidase activity of bromelain.
Similarly, Grabowska et al. [46] found that B16F10
mouse melanoma cells, preincubated in vitro with bromelain,
significantly reduced lung metastatic tumor
weight about three times. However, no survival benefit
was seen. Furthermore, bromelain diminished the capacity
of these cells to migrate through an extracellular matrix
layer in an in vitro invasion assay and inhibited the
growth of the tumor cells in a concentration-dependent
manner, whereas the antiproliferation effect did not correlate
with the proteolytic activity. Finally, human platelets
pretreated in vitro with bromelain lost their capacity
to stimulate the invasiveness of several metastatic tumor
cells in the in vitro invasion assay.
Metastasized tumor cells, while migrating through the vessels,
carry CD44 adhesion molecules on their surface, by
which they adhere to endothelial cells via the ligand hyaluron.
Bromelain preferentially cleaves off CD44 molecules
by virtue of its proteolytic activity, thus inhibiting
one of the first steps of the metastatic process (shown at
the upper right).
In addition, metastasized tumor cells carry the receptor
(uPAR) for the urokinase plasminogen activator (uPA),
which generates plasmin from plasminogen. Plasmin degrades
the extracellular matrix (ECM), composed of
collagen type IV, laminin and fibronectin. Tumor cells
also secrete matrix metalloproteinases (MMPs), enabling
the malignant cells to invade through the ECM. Bromelain
diminishes uPAR expression and uPA activity, thus
inhibiting the invasion step of metastasis (shown at the
upper left).
Recently, relevant interactions between tumor cells and
platelets were elucidated in more detail. They take place
on different levels: intravasal distribution, adhesion on
endothelial cells, invasion and extravasation. Platelets
directly bind to tumor cells, a process promoted by the release
of factors such as platelet factor 4, thrombospondin,
thrombin and gelatinase A from platelets, which facilitate
thrombus formation.
TGF-b, produced by both platelets and tumor cells, plays
an important role: it induces the synthesis of ECM proteins
and stimulates the activity of uPA, MMPs and angiogenesis.
Thus, disturbance of the blood coagulation
system may lead to the formation of thrombi by aggregating
platelets and tumor cells. Bromelain is capable of inhibiting
both platelet aggregation in vitro and in vivo, as
well as platelet-stimulated invasiveness of tumor cells
(shown at the lower endothelium).
Protease Parameter Effect Signifiance Ref.
Bromelain BP tumor cell proliferation Ø reduction of tumor cell growth 44, 45
Bromelain F9 46
Bromelain BP tumor cell invasion through Ø reduction of the invasive potential of 46
Bromelain F4, F9 extracellular matrix = tumor cells
Bromelain F5
Bromelain POS growth of lung metastases in mice Ø reduction of the metastatic potential of 44
tumor cells
Bromelain BP CD44 expression on metastatic cells Ø reduction of tumor cell adhesion to 46, 57
Bromelain F9 endothelial cells 58
Bromelain BP growth of lung metastasis in mice Ø reduction of the metastatic potential of 46
tumor cells
Bromelain BP survival time of mice bearing lung = mouse survival time 46
metastases (in vitro Æ in vivo)
Bromelain BP (base powder), commercial crude extract; POS, BP given orally; F4, F9, Bromelain fractions.
Bromelain modulates the function of
cell adhesion molecules
In 1992, Hale and Haynes [15] reported that in vitro treatment
of T lymphocytes with bromelain removes distinct
surface molecules, thereby enhancing CD2-mediated T
cell stimulation. The adhesion molecule CD44 has attracted
particular interest since it was recognized as a marker
for circulating cells, especially metastasizing tumor cells
. Harrach et al. [57] showed that bromelain diminished
CD44 expression on Molt 4/8 leukemia and SK-Mel
28 melanoma cells, the effect being most pronounced
with bromelain fraction F9, with its high proteolytical activity.
Yet the proteinase activity of the bromelain fractions
tested did not correlate with the manner in which
CD44 expression could be modulated. Bromelain was
more effective than chymotrypsin, papain and trypsin.
Treatment of human lymphocytes with bromelain F9 reduced
the expression of CD44, yet did not affect CD11a
(LFA-1) molecules; the adhesion of lymphocytes onto
umbilical vein endothelial cells was also lowered [60].
In addition, selective influences of bromelain on the expression
of other surface molecules on lymphocytes were
observed by Kleef et al. [61]. It is still an open question
whether the modulation of CD44 molecules is a prerequisite
for the inhibition of metastasis by bromelain. Oral
administration of bromelain (3000 FIP units daily for 10
days) did cause a moderate reduction of CD44 expression
on the lymphocytes from mammary tumor patients. Conversely,
the expression of CD11a and CD62L molecules
was weakly increased; CD16 molecules remained unchanged
.
Bromelain modulates functions of immune cells
Bromelain and papain stimulate, in vitro, mononuclear
blood leukocytes to produce considerable quantities of
TNF-a, Il-1b and Il-6, particularly in monocytes [62, 63].
The production of these cytokines by leukocytes could also
be demonstrated after oral administration of a polyenzyme
drug containing bromelain [64]. Moreover, granulocytes
reacted to the same drug by forming reactive oxygen radicals
known to exert antimicrobial and antitumor inhibitory
effects [65]. Garbin et al. [45] found that purified bromelain
fraction F9 augments, in vitro, at suboptimal concentrations
of Il-2, the lymphocyte-mediated inhibition of proliferation
of various tumor cells. It remains to be shown in
clinical studies whether bromelain can be used for unspecific
immunostimulation to treat distinct disorders.
Mynott et al. recently suggested that bromelain may be a
novel inhibitor of T cell signal transduction [66]. However,
since bromelain contains different biological activities,
these findings need confirmation with purified factors.
In a study with 15 healthy donors and 15 mammary tumor
patients, orally given bromelain (3000 FIP units daily for
10 days) doubled the capacity of patient’s blood monocytes
to kill tumor cells in vitro [33]. Among both patients
and healthy donors, individual monocyte responses varied
to a great extent. Bromelain responders (>10% increase
in immunocytotoxicity) showed a significantly
weaker cytotoxicity than those grouped as nonresponders.
This weakness could be overcome by bromelain.
The effects were reversible. NK- and LAK-cell activities
dropped during bromelain administration, but normalized
again afterwards.
Table 4 summarizes immune-cell-mediated effects of
bromelain against tumor cells.
Bromelain achieves debridement of burns
Rapid debridement of third-degree burns considerably reduces
the morbidity and mortality of severely burned patients.
It permits early skin grafting and lessens the problem
of sepsis, thus abbreviating the convalescence
period.
Topical bromelain (35% in a lipid base) has
achieved complete debridement on experimental burns in
rats in about 2 days, as compared with collagenase, which
required about 10 days, with no side effects or damage to
adjacent burned tissue [67]. A debridement agent apparently
free of proteolytic activity was extracted from commercial
bromelain; it was called escharase [68]. Morever,
the use of topical bromelain for frostbite eschar removal
was investigated: no debridement other than that of the
superficial eschar layers was noted; after two topical applications
of bromelain, frostbite injuries remained unaffected
.
Pharmacokinetics of bromelain
Is bromelain absorbed following oral application?
This frequently asked question can now be answered in
the affirmative. In 1992, Smyth et al. [20] showed that
bromelain given orally to rabbits increases the plasmin
serum level and prolongs the prothrombin and antithrombin
times. Seifert et al. [70] found that up to 40% of 125Jlabelled
bromelain is absorbed from the intestine in high
molecular form. Later, by means of different methods, a
large body of direct and indirect evidence supported the
conclusion that bromelain is absorbed from the intestine
[36,71]. Similarly, other enzymes, such as kallikrein [72],
known to lower arterial blood pressure, and several cytokines
such as, IL-2, -5 and -6 [73] reveal pharmacological
effects following oral application, thus strongly suggesting
intestinal absorption of these proteins. However,
one question still remains to be answered: How much
bromelain is absorbed and in which form does it circulate
in the blood? Proteinases similar to bromelain are rapidly
complexed with antiproteinases, mainly with a2-macroglobulin
(AMG) and a1-antitrypsin. This fact creates difficulties
for the quantitative determination of bromelain
in serum. Consequently, the recovery of bromelain considerably
varied depending on the analytical method
used. In any case, the protective AMG molecule leaves
the proteolytical activity of bromelain intact but reduced
. Three days after oral administration of 8.6 g of bromelain,
Castell [71] determined a mean half-life of 6–9 h
and a plasma concentration (AUC) of 2.5–4 ng/ml.
AMG, the main complexing agent for bromelain in blood,
is secreted by macrophages and consists of four identical
subunits (or two identical halves) in the so-called slow
form [36]. After entrapping the bromelain molecule, the
slow form will undergo a conformational change in order
to yield the AMG fast form, causing an increased affinity
to LDL or other AMG receptors, yet retaining proteolytic
activity. The plasma half-life of the AMG slow form is reduced
from its original 8 days to 10–30 min in the fast
form. The latter can still interact with additional cytokines
(Il-1b, Il-6, IFNg, TNFa, TGFb, PDGF etc.) and
hormones and is known as activated AMG. The immunogenic
determinants of the entrapped enzyme molecules
are covered by AMG, which prevents determination using
antibodies.
In a remarkable clinical study meeting all requirements of
good clinical practice (randomized, double-blind, crossover-
design), the bioavailability of a polyenzyme drug
(combining bromelain, trypsin, and rutosid) was examined
in 21 healthy males [75–78]. Following oral administration
of 400-mg and 800-mg tablets (corresponding to
1.94 and 3.88 ¥ 104 FIP units) four times daily up to 4
days, the specific activities of bromelain and trypsin were
determined in plasma. The activities and AUC values
proportionally correlated with the respective dosage. In
addition, quantitative studies by means of enzyme immunoassays
and Western blot analyses confirmed these findings.
Moreover, plasma concentrations of trypsin and
specific proteinase activities correlated as well. These results
support the notion that the enzymes are absorbed
from the gastrointestinal tract in a functionally intact
form. The relatively high doses were well tolerated, with
few side effects such as pasty faeces, flatulence, and
fullness. This is consistent with observations in athletes
taking as much as 1.2 ¥ 104 FIP units of bromelain daily.
Toxicology of bromelain
Acute toxicology
According to Moss et al. [16] no LD50 could be determined
with oral doses up to 10 g/kg in mice, rats or rabbits.
Lethal doses (LD50) after i.p. administration: mice 37 mg/
kg, rats 85 mg/kg; after intravenous (i.v.) administration:
mice 30 mg/ kg, rabbits 20 mg/kg. No immediate toxic
reactions were seen. These relatively high doses exceed
those normally given to human by far.
Chronic toxicology
Five hundred milligrams of bromelain per kilogram per
day given orally to rats did not provoke any alteration in
food intake, growth, histology of the heart, kidney and
spleen, or hematological parameters [16]. Normal doses
of 3000 FIP units/day given to human over a period of
10 days did not significantly affect blood coagulation
parameters [33].
Drug safety
In 12 placebo-controlled studies, very few side effects
were observed; one study noted a 1.8% incidence of
diarrhea, nausea, occasional gastric disorders and allergic
reactions. One company registered only eight cases of
side effects such as exanthema and urticaria out of >3.5
million bromelain tablets (500 FIP units each) sold over 7
years [79]. Bromelain is considered to be nontoxic and
without side effects; therefore it can be used without concern
in daily doses from 200 up to 2000 mg (500–5000
FIP units) for prolonged periods of time [13]. Bromelain
has shown therapeutic benefit in doses as small as 160 mg/
day, but the best results occur when starting at a dose of
750 mg/day. It is generally recommended that bromelain
be taken at least 1 h before meals. To minimize trauma
from sporting activities or tooth extractions, administration
should begin 48 h prior to event. Tablets must be
coated in such a way that they resist stomach digestion.
Clinical efficacy of bromelain
Medical use of drugs containing
bromelain and other proteinases such as papain, trypsin
and chymotrypsin (to mention the most frequently
used) is a matter of dispute: Many medical doctors are
still sceptical about findings that proteinases are absorbed
from the gastrointestinal tract in a functionally intact
form, and consequently deny any efficacy of orally applied
enzymes. On the other hand, a remarkable list of
clinical studies, conforming to GCP rules and mainly performed
with polyenzyme drugs, clearly makes a case for
evidence-based pharmacological efficacy of proteinases
.
Arguments for the use of bromelain for medical indications
– Bromelain belongs to a group of proteolytical enzymes
that have found a wide range of applications
for the indications mentioned above.
– Bromelain is a phytotherapeutic drug that can be given
orally and reveals few toxic side effects, thus favoring
acceptance and compliance by patients.
– Bromelain is orally absorbed and generates various
pharmacological systemic effects: prevention and reCMLS,
Cell. Mol. Life Sci. Vol. 58, 2001 Review Article 1243
duction of edema antiinflammation, stimulation of
monocytes to secrete cytokines such as Il-1b and
TNF-a, induction of phagocytosis and cytotoxicity by
granulocytes, inhibition of platelet aggregation and
stimulation of fibrinolysis, immunomodulatory effects
promoting antigen-unspecific tumor cytotoxicity,
among others.
– In vitro and in vivo data suggest that bromelain may
act as a prophylactic drug to prevent metastases. However,
clinical data to support this suggestion are still
lacking.
– There are satisfactory prescriptions for quality control
and production of a standardized pharmaceutical drug.
These arguments may recommend bromelain as a suitable
model substance for further scientific evaluation of
the class of proteinases to which bromelain belongs. The
reversible platelet aggregation inhibitory property of
bromelain may attract interest in cardiovascular surgery.
Bromelain’s potential for debridement of skin burns may
be beneficial for early skin grafting. For applications in
oncology, further preclinical and well-designed clinical
studies are undoubtedly required. Bromelain effects on
lymphedema in mammary tumor patients, and the prophylaxis
of metastases and antiangiogenic phenomena
with respect to tumor growth should be worthwhile subjects
for further, more detailed investigations.
Finally:Why do pineapple plants produce and
need bromelain?
The significance of bromelain proteinases for pineapples
has been a mystery for a long time. The most compelling
hypothesis is based on the well-known fact that carnivorous
plants derive their supply of nitrogen and phosphorus
from degradation of organic material (foliage, insects,
microbes) by means of highly active proteinases
and other digesting enzymes. In the tropical jungle, the
pineapple plant is an epiphytic bromeliad, growing on
other plants which offer hardly any nutrients. The rosettelike
arrangement of the pineapple plant’s leaves forms
funnel-type rainwater reservoirs, so-called phytotelmata,
that are always filled with water, as well as with nitrogen
and phosphorus suppliers. This hypothesis is supported
by recent findings that leaves react to mechanical stimuli
of only 2 s by producing proteinkinases [86]. Moreover,
the carnivorous pitcher plant Sarracenia purpurea was
shown to respond to various chemical signals (nucleic
acids, proteins, ammonia) by secreting hydrolytic enzymes
. In order to digest as many proteins from insects
and microorganisms as possible, enzyme ‘families’
with a broad spectrum of pH optima, such as the ‘papain
superfamily’, have evolved.
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Diagnosis Design n Drug, Critical parameters, Ref.
of study daily dosage results, observations
Acute sinusitis r, db, P1 V : 23 4 ¥ 40 mg Br inflammation, secretion, breathing, 25
Pl : 25 disturbance, pain.
V significantly better than Pl
Face and head trauma db, Pl V : 20 4 ¥ 40 mg Br edema, ecchymoses; reduction by V 19
Pl : 21 highly significant
Trauma of lower extremity r, b, Cd V : 18 3 ¥ 40 mg Br pain, edema, hematoma. V significantly 80
3 ¥ 1000 mg Cd better than oxyphenbutazone (Cd)
Posttraumatic inflammation r, b, Cd V : 60 3 ¥ 40 mg Br hematoma, edema, flexibility, pain; 81
and swelling Cd : 60 3 ¥ 1000 mg Cd equivalence of V and oxyphenbutazone (Cd)
Postoperative tumefactions r, db, PI V : 50 3 ¥ 80 mg Br girth of ball of forefoot, smallest girth 82
Pl : 50 of forefoot pain intensity; significant
improvement of all parameters by V
Mediolateral episiotomy r, db, Pl V : 80 4 ¥ 40 mg Br edema, inflammation, pain; 83
Pl : 80 V significantly better than Pl
Oral surgery r, db, cr 16 4 ¥ 40 mg Br swelling, pain; 84
(teeth extraction) less inflammation and pain by V
n, number of patients; r, randomized; db, double-blind; cr, cross-over; Pl, placebo; Cd, control drug; Br, bromelain; V, verum.
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