Abstract : First introduced as a therapeutic compound in 1957, bromelain’s actions include: (1) inhibition of platelet aggregation; (2) fibrinolytic activity; (3) anti-inflammatory action; (4) anti-tumor action; (5) modulation of cytokines and immunity; (6) skin debridement properties; (7) enhanced absorption of other drugs; (8) mucolytic properties; (9) digestive assistance; (10) enhanced wound healing; and (11) cardiovascular and circulatory improvement. Bromelain is well absorbed orally and available evidence indicates that it’s therapeutic effects are enhanced with higher doses. Although all of its mechanisms of action are still not completely resolved, it has been demonstrated to be a safe and effective supplement.
Bromelain has been used for a variety of clinical applications for more than 35 years. Although its mechanisms of action has not been completed resolved, bromelain has demonstrated a beneficial effect on the kinin system, the coagulation cascade, the cytokine system, and prostaglandin synthesis. Bromelain is believed to enhance the absorption of flavonoids and has been shown to increase absorption of glucosamine, so bromelain supplemention should be considered when these nutrients are given. It may also enhance absorption and utilization of many other substances; however, to date research in this area has focused primarily on antibiotics. Bromelain has been shown to exert a beneficial effect at doses as low as 160 mg/day, however, there is a general consensus among researchers that the best results occur when bromelain is given in doses above 500 mg per day and that results improve in a dose-dependent manner with higher levels of bromelain supplementation. Bromelain has been demonstrated to be well absorbed after an oral dose and has been shown to be safe at high doses for prolonged periods of time. For the conditions discussed in this review, bromelain has shown itself to be an effective supplement.
Bromelain: A Literature Review and Discussion of its Therapeutic Applications, Gregory S. Kelly, N.D. - Alternative Medicine Review Volume 1, Number 4 - 1996

Bromelain is a general name for a family of sulfhydryl-containing proteolytic enzymes obtained from Ananas comosus, the pineapple plant.
Although bromelain’s primary constituent is a sulfhydryl proteolytic fraction, it also contains escharase (a non-proteolytic component in bromelain thought to be important in the action of topical bromelain), peroxidase, acid phosphatase, several protease inhibitors, and organically-bound calcium.1 The beneficial effects of bromelain are due to multiple constituents apart from its proteolytic fraction.
A variety of designations have been used to indicate the activity of bromelain, with published research varying in the designation utilized. Rorer units (r.u.), gelatin dissolving units (g.d.u.), and milk clotting units (m.c.u.) are the most commonly used measures of activity. One gram of bromelain standardized to 2,000 m.c.u is approximately equal to 1 gram with 1,200 g.d.u. activity or 8 grams with 100,000 r.u. activity.
Key words: bromelain, pineapple, Ananas, proteolytic, protease, anti-inflammatory, surgery, inflammation, wound, injury, intestinal pathogens, platelet aggregation, fibrinolytic, blood thinner, antibiotic, diarrhea, cancer, antimicrobial, circulation, cardiovascular, angina, prostatitis, arthritis, digestion, IBD, renal, kidney, sinusitis
Bromelain Monograph - Alternative Medicine Review Volume 15, Number 4

Bromelain belongs to a group of protein digesting enzymes obtained commercially from the fruit or stem of pineapple.
Fruit bromelain and stem bromelainare prepared differently and they contain different enzymatic composition. “Bromelain” refers usually to the “stem bromelain.” Bromelain is a mixture of different thiol endopeptidases and other components like phosphatase, glucosidase, peroxidase, cellulase, escharase, and several protease inhibitors. In vitro and in vivo studies demonstrate that bromelain exhibits various fibrinolytic, antiedematous, antithrombotic, and anti-inflammatory activities. Bromelain is considerably absorbable in the body without losing its proteolytic activity and without producing any major side effects.
Bromelain accounts for many therapeutic benefits like the treatment of angina pectoris, bronchitis, sinusitis, surgical trauma, and thrombophlebitis, debridement of wounds, and enhanced absorption of drugs, particularly antibiotics. It also relieves osteoarthritis, diarrhea, and various cardiovascular disorders. Bromelain also possesses some anticancerous activities and promotes apoptotic cell death. This paper reviews the important properties and therapeutic applications of bromelain, along with the possible mode of action.
Bromelain has a wide range of therapeutic benefits, but the mode of its action is not properly understood. It is proved that bromelain is well absorbed in body after oral administration and it has no major side effects, even after prolonged use. All the evidences reviewed in this paper suggest that bromelain can be used as an effective health supplement to prevent cancer, diabetes, and various cardiovascular diseases in the long run.
Properties and Therapeutic Application of Bromelain: A Review - Hindawi Publishing Corporation Biotechnology Research International - Volume 2012, Article ID 976203, Rajendra Pavan, Sapna Jain, Shraddha, and Ajay Kumar

Abstract : The thiol protease, bromelain, an extract from pine apple stern, was suggested to have antuhrombotic and anticoagulant activities in vivo. We studied the effects of bromelain on cell size distribution of isolated human platelets in vitro by Coulter Counter measurements. Preincubation of platelets 'with bromelain (10 ug/mL) completely prevented the thrombin (0.2 U/mL) induced platelet aggregation. Papain was less active in pi-eventing platelet aggregation. In vitro, bromelain (0.1 ug/mL) reduced the adhesion of bound, thrombin stimulated, fluorescent labeled platelets to bovine aorta endolhelial cells. In addition, preincubation of platelets with bromelain, prior to thrombin activation, reduced the platelet adhesion to the endothelial cells to the low binding value of unstimulated platelets. On the basis of mass concentrations, the proteases papain and tiypsin were as effective as bromelain.
Using a laser thrombosis model, the in vivo effects of orally and intraveneousfy applied bromelain on thrombus formation in rat mesenteric vessels were studied. Bromelain, orally applied at 60 mg/kg body weight, inhibited the thrombus formation in a time dependent manner, the maximum being after 2 hours in 11% of arterioles and 6% of venoles. Intmveneous application at 30 mg/kg was slightly more active in reducing thrombus formation in aiterioles (13%) and venoles (5%), suggesting that oralfy applied bromelain is biologically active. These results may help to explain some of the clinical effects absented after bromelain treatment in patients with thrombosis and related diseases.
Bromelain Proteases Reduce Human Platelet Aggregation in Vitro, Adhesion to Bovine Endothelial Cells and Thrombus Formation in Rat Vessels in Vivo - in vivo 71-7-12 (1999), Metzig C, Grabowska E, Eckert K, Rehse K, Maurer HR