Author: Laura Cordero
Date: 05/07/2014



The papaya is the fruit of the plant Carica Papaya native from southern Mexico, Central America, and northern South America. The papaya is now cultivated in most tropical countries.

The papaya seed, juice, leave and fruit are known for their high nutritional value and the presence of antioxidants. The stem and leaves are of particular medicinal significance and are commonly used in traditional folk therapy both as medicine and as food. They are primarily used to fight infection and aid digestion. The papaya fruit is a source of nutrients such as provitamin A, carotenoids, vitamin C, folate and dietary fibre. Along with these nutrients, the papaya is rich of the digestive enzyme, papain. Papain exhibits proteolytic, analgesic and anti-inflammatory properties and has numerous health benefits. Most of the research is based on Fermented Papaya Preparation (FPP) also sold under the commercial name Immun'Âge.

The fresh papaya leaves and papaya fruits are allowed to age slowly over a period of a few months, until the fermented papaya is obtained. The fermented pieces are then dried and ground to fine powder.


There are three main health benefits associated to FPP.


The fermented papaya is known for its antioxidant effect as assessed by several studies.

Oxidative stress-induced cell damage has been implicated in a variety of haematological diseases, cancer, diabetes, cardiovascular dysfunctions and neurodegenerative disorders such as stroke, Alzheimer's disease and Parkinson's disease, prompting the suggestion that the disease pathology can potentially be modulated by treatment with free-radical scavengers and antioxidants. The free radicals have important physiological functions, but if in excess they are cytotoxic due to their interactions with the DNA, the proteins and mainly with the membrane lipids, promoting lipid peroxidation. Normally, their level is tightly balanced by antioxidant systems, like the Glutathione which regulates the rate of ROS generation and scavenges excess ROS.

Many nutrients act as antioxidant thereby counteracting the increased formation of free radicals generated by the toxicants. The underlying mechanisms by which FPP contrasts oxidative stress in biological systems are not completely understood. Antioxidant action can be exerted through different mechanisms: metal chelation, radical scavenging, as well as, electron donation.

In order to get further insights into FPP's mode of action, Rimbach et al. (Rimbach, G., Guo, Q., Akiyama, T., Matsugo, S., Moini, H., Virgili, F., & Packer, L. (2000). Ferric nitrilotriacetate induced DNA and protein damage: inhibitory effect of a fermented papaya preparation. Anticancer research, 20(5A), 2907) generate hydroxyl radicals with both iron-dependent and iron-independent systems. The iron is redox active and it participates in the generation of ROS. The iron acts like a catalyst in the formation of ROS by Fenton's reaction.

(1) Fe2+ + H2O2 → Fe3+ + HO• + OH
(2) Fe3+ + H2O2 → Fe2+ + HOO• + H+

The authors used the photosensitive organic hydroperoxide NP-III to generate hydroxyl radicals in the absence of iron. NP-III is a compound that generates hydroxyl radicals upon irradiation with UV under controllable experimental conditions. Also they used NitriloTriacetic Acid (NTA):, a synthetic aminotricarboxilic acid, which forms water-soluble complexes with iron at neutral pH (Fe-NTA). Under the conditions investigated, FPP acted as an antioxidant due to both hydroxyl scavenging, as well as, iron chelation. By comparing the hydroxyl radical scavenging activity of FPP between Fenton and NP-III systems, it can be concluded that iron chelation is an important mechanism, which significantly contributes to the antioxidant mode of action of FPP. The iron binding affinity of FPP might prevent that Fe3+ is being reduced back to Fe2+, which in turn promotes the formation of hydroxyl radicals via Fenton's reaction. Removal of Fe3+ by FPP would thus further reduce hydroxyl radical generation. The study specifies that relatively high concentrations of FPP were necessary to combat Fe-NTA induced oxidative damage. Moreover, it has not been clarified yet which particular constituents of FPP are mainly responsible for its antioxidant activity. However, it is certain that FPP significantly blocked oxidative damage to DNA and proteins probably both due to hydroxyl radical scavenging, as well as, iron chelation.

The antioxidant effect of fermented papaya preparation through iron chelation was analysed also by Prus and Fibach (Prus, E., & Fibach, E. (2012). The antioxidant effect of fermented papaya preparation involves iron chelation. Journal of biological regulators and homeostatic agents, 26(2), 203). Iron overload is a major clinical problem associated with various haematological diseases, such as thalassemia, paroxysmal noctural haemoglobinuria and myelodysplastic syndrome. Normally, iron is transported in the circulation and transferred into the cells through binding to transferrin. In cells, iron is bound to various components such as haemoglobin, heme and cytochrome C, while the excess is stored in ferritin. In addition, all cells contain some unbound, chelatable iron, termed Labile Iron Pool (LIP) or Labile Cellular Iron (LCI). LCI is the major culprit in iron-mediated cytotoxicity.

In iron overload, serum iron exceeds the binding capacity of transferrin and it is present in the form of non-transferrin bound iron. This leads to increased ROS, with concomitant decrease in anti-oxidants and results in oxidative stress. Prus and Fibach investigated the ability of FPP to prevent and revert cellular accumulation of LIP and thereby reduce ROS generation. Liver-, heart- derived cells and RBCs were exposed to serum iron excesses in the form of ferrous ammonium sulphate and the effects of FPP on their LIP and ROS were measured by flow cytometry. The results indicate that FPP reduced the cytosolic LIP in RBCs and both the cytosolic and mitochondrial LIPs in the heart- and liver- derived cells. The study suggests that components of FPP can enter cells and chelate intra-cellular LIP. According to this, the FPP treatment may be preventive as well as therapeutic in the sense of being able to actively reverse iron overloads.

Amer et al. (Amer, J., Goldfarb, A., Rachmilewitz, E.A., & Fibach, E. (2008). Fermented papaya preparation as redox regulator in blood cells of beta-thalassemic mice and patients. Phytother. Res. 22, 820-828) and Fibach et al. (Fibach, E., Tan, E.S., Jamuar, S., Ng I., Amer J., & Rachmilewitz E.A. (2010). Amelioration of oxidative stress in red blood cells from patients with beta-thalassemia major and intermedia and E-beta-thalassemia following administration of a fermented papaya preparation. Phytother. Res. 24(9), 1334-8) consider specifically the ß-thalassemia where the oxidative stress is primarily caused by the RBC abnormalities – degradation of unstable Hb which results in free globin chains. Another contributing factor is iron overload due to increased intestinal absorption and regular blood transfusions. The two studies tested the in vivo effects of FPP by treating two groups of patients affected by ß-thalassemia major and intermedia from different countries. They showed a significant reduction in all the tested parameters of oxidative stress in their blood cells, without a significant improvement in the haematological parameters. Since the turnover of the erythron is relatively slow, it is possible that longer treatment duration is required in order to achieve the latter goals. In addition, a combination treatment with both FPP and an iron chelator might yield better results.

The antioxidant effect of FPP has also been evaluated in vivo by Marotta et al. (Marotta, F., Naito, Y., Padrini, F., Xuewei, X., Jain, S., Soresi, V., Zhou l., Catanzaro R., Zhong k., Polimeni A., & Chui, D. H. (2011). Redox balance signalling in occupational stress: modification by nutraceutical intervention. Journal of biological regulators and homeostatic agents, 25(2), 221) using healthy subjects having a work perceived as stressful. The first evidence that psychological stress may induce damage to nuclear DNA by means of oxidative stress, was shown in the liver cells of rats exposed to conditioned emotional stimuli. The rats subject to such stimuli exhibited increased 8-hydroxy-2' -deoxyguanosine (8-OHdG) in nuclear DNA of the liver after repeated exposures, with a return to baseline levels one hour after stopping the acute stressor. 8-OHdG is one of the predominant forms of free radical-induced oxidative lesions and has therefore been widely used as a biomarker for oxidative stress and carcinogenesis. The authors used the heme oxygenase system and its products as test parameter to evaluate the effect of FPP to reduce the oxidative stress. Heme oxygenase includes the inducible (HO-1) and the constitutive (HO-2) isoenzymes. These isoenzymes cleave the tetrapyrrolic ring of cellular heme releasing carbon monoxide and equimolar amounts of free iron and biliverdin. Biliverdin is in turn converted into bilirubin which acts as an antioxidant. Indeed, the bilirubin scavenges nitric oxide (NO) radicals directly and quenches excess oxidants. Furthermore, high levels of bilirubin react with ROS, producing several species of Bilirubin Oxidative Metabolites (BOMs). The level of BOMs excreted with the urines reflects the level of free radical in tissues.

The clinical trail observed that the excretion of BOMs was significantly elevated in stressed subjects. The oxidative stress has been evaluated through the analysis of the blood levels of 8-OHdG, SOD, GPX and MDA. The stressed subjects showed a significant increased level of erythrocyte SOD and MDA, a decreased level of erythrocyte GPX, and an increased level of 8-OHdG in leukocytes.

Supplementing all the study subjects with FPP for four weeks resulted in normalized blood levels of SOD, GPX and MDA.

Bilirubin synthesis is regulated by the rate-limiting enzyme, HO-1, which is rapidly induced by oxidative stress and inflammatory reactions. Hence, the authors in Marotta et al. (Marotta, F., Yoshida, C., Barreto, R., Naito, Y., & Packer, L. (2007). Oxidative-inflammatory damage in cirrhosis: effect of vitamin E and a fermented papaya preparation. Journal of gastroenterology and hepatology, 22(5), 697) noted a significant correlation between BOMs and HO-1 over-expression. These results suggest that FPP supplementation can be a good support to reduce the oxidative stress by modulating the cellular metabolism of the redox processes and generating variations of the genomic regulation.

The anti-oxidant effect of FPP has been proven valid also in subjects affected by gastrointestinal and hepatic diseases. Recent gastroenterology studies showed that FPP was able to significantly decrease the oxidative stress in gastric mucosa affected by longstanding chronic atrophic gastritis associated with metaplasia and important to curb the mucosal concentration of 8-OhdG. With regard to the liver, oxidative DNA damage, namely 8-OHdG generation, has been indicated as an early event in Hepatitis C Virus (HCV) infection and as a marker of liver damage. Persistent genomic changes are factors giving rise to carcinogenesis. The therapeutic armamentarium is enriched by new effective antiviral drugs and regimens in recent years but there is a substantial percentage of non-responders whose cirrhotic transformation cannot be prevented. Moreover, patients with established HCV-related cirrhosis are often not eligible for antiviral treatment. Marotta et al. showed that the antioxidant supplementation with FPP significantly improved the oxidant/antioxidant balance observed as a partial restoration of glutathione status and decreased lipid peroxidation. Although the ultimate therapeutic target is to eradicate HCV, antioxidant therapy might offer a worthwhile adjunctive tool. Indeed, it has been suggested that the generation of ROS even at such low levels that are unable to bring about overt parenchymal cell death, when chronically occurring for a long time, can lead to accumulation of 8-OHdG in DNA and such genomic abnormalities have been described even at a stage of chronic hepatitis. However, such complementary support still deserves further studies.


FPP has been reported to induce natural killer cell activity and to enhance the capacity of respiratory burst in neutrophils in vitro supporting the hypothesis that FPP acts as an immune modulator. In particular, Collard et al. (Rimbach, G., Park, Y.C., Guo, Q., Moini, H., Qureshi, N., Saliou, C., Takayama, K., Virgili, F., & Packer, L. (2000). Nitric oxide synthesis and TNF-alpha secretion in RAW 264.7 macrophages: mode of action of a fermented papaya preparation. Life Sci, 67(6), 679-94) demonstrated that FPP affects Nitric Oxide (NO) synthesis, and TNF secretion in macrophages. NO is a multiple regulatory molecule involved in a wide range of physiological and pathophysiological processes. Appropriate stimuli for the expression of the inducible form of NO synthase in monocyte-macrophages are the exposure to the bacterial wall components LipoPolySaccharide (LPS) and various cytokines such as IFN, TNF-α and IL-1. Macrophage inducible Nitric Oxide Synthase (iNOS) is able to generate massive amounts of NO which contributes to the host immune defence against virus and bacteria. However, high NO production has been associated with oxidative stress.

The study showed that the treatment of macrophages with a low and a high molecular weight fraction (LMF and HMF, respectively) of FPP alone failed to induce appreciable levels of NO production. However, significant increases of NO production occurred after cells treated with a combination of IFN-γ with either LMF or HMF. Starting from this observation, the authors were able to characterize the mechanism by which FPP changes IFN-γ-induced NO production in macrophages. The expression of the *iNOS gene* is regulated by endotoxin and cytokines such as IFN-γ and IL-2.

Two upstream DNA regions of the iNOS promoter, the RI and RII domains, are required for the maximal promoter activation by LPS and the RII domain mediates promoter trans-activation of IFN-γ. Both domains comprise multiple sequences involved in transcription activation, such as NF-kB binding sites, IFN-γ response elements and IFN-γ-activated factor binding sequence. The FPP affects NF-kB DNA binding, which accounts for the observed augmentation of the iNOS gene transcription. Hence it is likely that FPP modulates IFN-γ-induced induction of iNOS by up regulating the rate of gene transcription through a yet unknown mechanism.

FPP acts also on the secretion of TNF-α which elicits a number of physiological effects including septic shock, inflammation, cachexia and cytotoxicity. Both LMF and HMF caused a significant increase in TNF-α secretion when IFN-γ was present. This elevated TNF-α secretion due to FPP might finally result in further augmentation of iNOS synthesis thereby possibly potentiating the microbicidal activity of macrophages.

The immune modulating action of FPP was subject to studies also for the treatment of diabetes. In Collard et al. (Collard, E., & Roy, S. (2010). Improved function of diabetic wound-site macrophages and accelerated wound closure in response to oral supplementation of a fermented papaya preparation. Antioxidants & redox signaling, 13(5), 599) the authors sought to establish if there is improved function of diabetic wound-site macrophages and accelerated wound closure in response to oral supplementation of FPP to diabetic mice. The study on viable macrophages isolated from the wound site demonstrated that FPP supplementation improved respiratory burst function, as well as, inducible NO production. NO availability in diabetic wounds is compromised. Diabetic mice supplemented with FPP showed a higher abundance of CD68 as well as CD31 at the wound site, suggesting effective recruitment of monocytes and an improved pro-angiogenic response. Macrophages from diabetic mice produced higher levels of the pro-inflammatory cytokines, like TNF-α, and it can be envisaged that FPP could affect the genes for these proteins.


Beyond acting as immune modulator, FPP has been proven to be also an efficient mean to control the blood sugar level Dabes et al. (Danese, C., Esposito, D., D'Alfonso, V., Cirene, M., Ambrosino, M., & Colotto, M. (2006). Plasma glucose level decreases as collateral effect of fermented papaya preparation use. La Clinica terapeutica, 157(3), 195). Indeed, the use of FPP is able to lower the circulating levels of glucose in fasting and post meal conditions. This happens in both healthy subjects and subjects affected with type 2 diabetes mellitus. Hence, FPP could be used as an adjuvant drug in the treatment of type 2 diabetes mellitus.

Somanah et al. (Somanah, J., Bourdon, E., Rondeau, P., Bahorun, T., & Aruoma, O. I. (2014). Relationship between fermented papaya preparation supplementation, erythrocyte integrity and antioxidant status in pre-diabetics. Food and Chemical Toxicology, 65, 12-1) conducted a randomized controlled clinical trial to determine the effect of a short term supplementation of FPP on the antioxidant status of a multi-ethnical population predisposed to type 2 diabetes mellitus. This study shows that a daily intake of 6g FPP could positively alter diabetes-related risk factors, including a significant decrease in systemic inflammation and mean arterial blood pressure, and an improvement of the lipid profile, the liver and the kidney functionalities, Moreover the study suggests that the process of fermentation can greatly modify the ratio of free amino acids which may contribute to the functional qualities of FPP. Beyond being rich in amino acids, oligosaccharides and vitamin B6, FPP also contains a variable amount of citric and malic acid both known to possess hydroxyl groups that may greatly influence its free radical scavenging.


FPP may have other powerful health benefits such as a reduced risk of heart diseases. There are other ongoing studies to analyse the exact nature of the FPP mechanism and its future use especially in cancer treatments.

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