Bromelain- Biochemistry, Pharmacology and Medical Use

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  • Review

    Bromelain: biochemistry, pharmacology and medical useH. R. Maurer

    Department of Biochemistry, Molecular Biology and Biotechnology, Institute of Pharmacy, Freie Universitt Berlin,Kelchstrasse 31, 12169 Berlin (Germany), Fax + 49 30 838 5 06 23, e-mail: hrmaurer@zedat.fu-berlin.de

    Received 25 August 2000; received after revision 29 March 2001; accepted 30 March 2001

    Abstract. Bromelain is a crude extract from the pineap-ple that contains, among other components, various clo-sely related proteinases, demonstrating, in vitro and invivo, antiedematous, antiinflammatory, antithromboticand fibrinolytic activities. The active factors involved arebiochemically characterized only in part. Due to its effi-cacy after oral administration, its safety and lack of un-desired side effects, bromelain has earned growing ac-ceptance and compliance among patients as a phytothera-peutical drug. A wide range of therapeutic benefits hasbeen claimed for bromelain, such as reversible inhibitionof platelet aggregation, angina pectoris, bronchitis, si-nusitis, surgical traumas, thrombophlebitis, pyelonephri-tis and enhanced absorption of drugs, particularly of anti-biotics. Biochemical experiments indicate that thesepharmacological properties depend on the proteolytic ac-tivity only partly, suggesting the presence of nonproteinfactors in bromelain. Recent results from preclinical andpharmacological studies recommend bromelain as anorally given drug for complementary tumor therapy: bro-

    from animal organs such as trypsin and chymotrypsin.These enzymes offer a wide spectrum of therapeutic effi-cacies: they demonstrate, in vitro and in vivo, antiede-mateous, antiinflammatory, antithrombotic and fibrinoly-tic activities. They modulate the functions of adhesionmolecules on blood and endothelial cells, and also regu-late and activate various immune cells and their cytokineproduction. Indeed, these enzymes are used in the UnitedStates and Europe as an alternative or complementary

    CMLS, Cell. Mol. Life Sci. 58 (2001) 123412451420-682X/01/091234-12 $ 1.50 + 0.20/0 Birkhuser Verlag, Basel, 2001 CMLS Cellular and Molecular Life Sciences

    melain acts as an immunomodulator by raising the im-paired immunocytotoxicity of monocytes against tumorcells from patients and by inducing the production of di-stinct cytokines such as tumor necrosis factor-a, inter-leukin (Il)-1b, Il-6, and Il-8. In a recent clinical studywith mammary tumor patients, these findings could bepartially confirmed. Especially promising are reports onanimal experiments claiming an antimetastatic efficacyand inhibition of metastasis-associated platelet aggrega-tion as well as inhibition of growth and invasiveness of tu-mor cells. Apparently, the antiinvasive activity does notdepend on the proteolytic activity. This is also true forbromelain effects on the modulation of immune func-tions, its potential to eliminate burn debris and to accele-rate wound healing. Whether bromelain will gain wideacceptance as a drug that inhibits platelet aggregation, isantimetastatic and facilitates skin debridement, amongother indications, will be determined by further clinicaltrials. The claim that bromelain cannot be effective afteroral administration is definitely refuted at this time.

    Key words. Bromelain; proteinases; antiinflammation; edema prevention and destruction; fibrinolysis; thrombosisand metastasis prophylaxis; immunomodulation; skin debridement; complementary tumor therapy.

    Introduction

    The role of proteolytic enzymes for therapeutic useBromelain belongs to a group of proteolytic enzymeswhich are used as drugs for the oral systemic treatment ofinflammatory, blood-coagulation-related and malignantdiseases. Apart from the plant cysteine-proteinasesbromelain and papain, the group comprises proteinases

  • CMLS, Cell. Mol. Life Sci. Vol. 58, 2001 Review Article 1235

    medication to glucocorticoids, nonsteroidal antirheuma-tics and immunomodulatory agents. Their very low toxi-city makes them suitable tools for controlling chronic in-flammatory diseases. For the therapy of inflammatory and malignant disorders,these proteinases are employed as

    additives for chemotherapy (to reduce side effects ofdrugs and to improve quality of life);

    additives for radiotherapy (to reduce inflammation andedema);

    additives in surgery (to reduce edema and to improvewound healing);

    additives to prevent lymphedema by reducing lympho-congestion, detritus, viscosity of the exsudate and sti-mulation of phagocytosis of associated leukocytes.

    It should be added that clinical studies support these re-commended indications only to a limited extent. Yet thelarge body of preclinical, pharmacological and daily ex-perience offers an important and worthwhile field forwell-designed clinical studies in order to evaluate evi-dence-based medical indications.

    Biochemistry of bromelain

    Bromelain is a crude, aqueous extract from the stems andimmature fruits of pineapples (Ananas comosus Merr.,mainly var. Cayenne from the family of bromeliaceae),constituting an unusually complex mixture of differentthiol-endopeptidases and other not yet completely char-acterized components such as phosphatases, glucosida-ses, peroxidases, cellulases, glycoproteins and carbohy-drates, among others [1, 2]. In addition, bromelain con-tains 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 bycentrifugation, ultrafiltration and lyophilization. The pro-cess yields a yellowish powder, the enzyme activity ofwhich is determined with different substrates such as casein (FIP units), gelatine (gelatine digestion units) orchromogenic tripeptides [1, 5, 6]. In aqueous solution,bromelain rapidly deteriorates through self-digestion.The addition of serum containing a2-macroglobulin willprevent self-digestion (see below). By high-resolutionfast protein liquid chromatography (FPLC) and otherbiochemical methods, basic (stem bromelain, ananain,comosain) and acidic thiol-proteinases have been isolatedfrom crude bromelain, partially or fully sequenced andcharacterized in more detail [68]. They mainly com-prise glycosylated multiple enzyme species of the papainsuperfamily with different proteolytic activities, molecu-lar masses between 20 and 31 kDa, and isoelectric pointsbetween > 10 and 4.8. Two major basic proteinases, F4and F5, were further characterized and showed molecularmasses of 24,397 and 24,472 Da, respectively [6] (Table1). In addition, numerous, different protein fractions wereobtained by means of various biochemical methods[SDS-polyacrylamide gel electrophoresis (PAGE), iso-electric focusing (IEF), multicathodal-PAGE]. Among thebasic proteinases, one fraction (F9, ananain) reveals thehighest specific proteinase activity, is not glycosylatedand has a molecular mass of 23,427 Da [6, 8, 9]. The en-zymatic activities comprise a wide spectrum with pH op-tima between 5.5 and 8.0 [10]. The substrate spectrum issimilarly broad, extending from synthetic low molecularmass amides and dipeptides up to high molecular sub-strates such as fibrin, albumin, casein, angiotensin II,bradykinin. Bromelain preferentially cleaves glycyl,alanyl and leucyl bonds.Commercial bromelain preparations are evaluated ac-cording 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 berelated to the protease activity. However, other effectssuch as inhibition of tumor cell growth and metastasis aswell as debridement of burns are associated with othernonproteinolytic components contained in bromelain.Thus, the determination of the proteolytic activity alonemay not be sufficient to completely characterize the phar-macological properties of bromelain [11].

    Pharmacology of bromelain: preclinical studies

    Pharmacodynamics of bromelainFrom a variety of in vitro and animal experiments, mainlywith rodents, as well as from clinical observations, basedon uncontrolled and controlled studies, the general pro-perties of bromelain may be summarized as follows[1114] Bromelain

    prevents edema formation and reduces existing ede-mas

    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 thrombo-

    xane 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 monocytesand granulocytes

    supports the oxidative burst and the cytotoxicity ofgranulocytes against tumor cells

    increases the tissue permeability of antibiotic drugs prevents metastases in a mouse model supports skin debr

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