Fruit of the Angels
Nutrition | Binu Kularathne
Papaya/pawpaw is also known as the “fruit of angels’’ by Christopher Columbus due to their unique and pleasant flavour. Mainly grown in tropical areas, papaya fruit and the plant as a whole have been subjected to study in the last few decades due to their potential medicinal and commercial use, considering their antioxidant properties, anticancer properties, and enzyme activity.
Image 1. The smallest ones are the wild papaya, followed by the hybrid between wild and domesticated papaya followed by the domesticated papaya fruit with its seeds (Maradol variety) [9].
What Exactly is the “Fruit of the Angels”?
Carica papaya L., widely known as papaya, is an orange/yellow/ red sweet fruit, and one fruit has hundreds of seeds. Papaya pulp can be eaten raw after removing the peel. It is also found in jams, juice, and other food products in the market. The pulp of the fruit is rich in vitamins A, C, E, and B, minerals (magnesium and potassium), and food fibres. The seeds are rich in phenolic compounds and fatty acids, but they aren’t usually eaten directly like the pulp. The leaves are rich in food fibres and polyphenolic compounds [1].
Fighting Dengue Fever
Carica papaya L. leaf extract has been used for centuries to treat dengue fever, mainly by Ayurvedic doctors. Much research has recently been conducted to prove the efficacy and science behind how Carica papaya L. leaf extract fights dengue fever.
Dengue is caused by the Flavivirus. The papaya leaf extract is known to increase the platelet count. This is due to a compound in papaya leaf extract, which is thought to stabilise the plasma membrane of the platelets and thus prevent it from being degraded due to stress induction by the dengue virus. However, the dose-and-effect relationship is not linear. This hemolysis inhibition was greatest when blood was treated with the extract from partially mature leaves [2].
Papaya and the Heart
The nutrients contained in papaya are known to be beneficial against cardiovascular illnesses. This is likely due to its anti-platelet cohesion, anti-hypertensive, hypoglycemic, and hypolipidemic actions. This reduces the chance of atherosclerotic plaque, thrombi, and emboli formation and hence minimises the chances of ischemia and/or myocardial infarction [1, 3-4]. Also, papaya aids in preventing damage caused by free radicals [1].
Papaya and its Anticancer Properties
Research have found that papaya has compounds with many anticancer properties against a variety of cancers [6]. Considering how papaya is a plant found in nature, its extracts can be a very effective way to treat many cancers or at least decrease the tumour size until properly targeted treatments can be used for patients.
α-tocopherol, lycopene, and benzyl isothiocyanate are compounds found in papaya that were found to have potential anti-cancer properties due to the exhibition of anti-proliferative activity [6]. Anticancer activity includes TH1 formation, which results in cytokine secretion of IL-12, IFN, and TNF-α, which cause cytotoxicity against the tumour cells of cervical carcinoma, breast adenocarcinoma (MCF-7), hepatocellular carcinoma (HepG2), lung adenocarcinoma (PC14), pancreatic epithelioid carcinoma (Panc1), and mesothelioma (H2452). Also, genes for PBMC are upregulated, causing the antitumor effects [6].
There are many compounds in papaya with anticancer properties.
These include the chlorogenic acid compound of papaya. Chlorogenic acid is also a dietary polyphenol. It exhibits anti-cancer properties such as cytotoxicity against tumour cells, induction of apoptosis by caspase-3 activation, reduction of BCL-2 activity, preventing progression of G0/G1 cell cycle phase in colon cancer (Caco-2 Cells), some breast cancers, lung cancer (A549 cells), promyelocytic leukaemia (HL-60 cells) and other leukaemias [6].
Caffeic acid, which mainly increases apoptosis rates, reduces new blood formation in cancer cells, and decreases tumour cell viability, ultimately decreasing cell proliferation. This compound is best against colon cancer (HT-29 and HCT-150), breast cancer (MCF-7 and T47D), skin cancer (A431), some cervical cancers, fibrosarcoma (HT-1080), hepatocarcinoma (HepG2 Huh70) and cervical cancer (HeLa ME180) [6].
Also, β-carotene in papaya is known to have anti-tumour activity by inducing cell apoptosis and arresting the cell cycle in some prostate cancers [6].
Image 3. Home-grown papaya in Sri Lanka covered with a plastic bag to protect it from wild insects and birds. Photo by Nadeeka Kularathne.
Quinic acid, isorhamnetin and protocatechuic acid, ferulic acid, butyric acid, and linalool are best against certain colon cancers. Kaempferol was the best compound against breast cancer (MDA-MB453/MCF-7). Stearic acid and Linoleic acid against leukaemia (HL-60). Apigenin against colorectal cancer (SW480) and breast cancer (BT-474). Violaxanthin against breast cancer (MCF-7). Zeaxanthin against human uveal melanoma (SP6.5 and C918). Myricetin against bladder cancer (T24). Quercetin against liver cancer (HepG2). Rutin against colon cancer (HCT116), Keratinocyte cell line (HeCaT), lung cancer (A459), colon cancer (HT29, CaCo-2). Catechin against breast cancer (MCF-7), naringenin against breast cancer (SKBR3, MDA-MB-231), liver cancer (Human hepatocellular carcinoma HepG2 Cells), prostate cancer (PC3, LNCaP), melanoma (B16F10), and Gliomas-brain cancer (U118-MG). Vaccenic acid against nasopharyngeal carcinoma (5- 8F and CNE-2). Xylitol against certain lung cancers. α-Tocopherol against oral squamous carcinoma (ORL-48). Lycopene against colon cancer (HT29) and breast cancer (MCF-7 and BrdU). 5,7-Dimethoxycoumarin against some human adenocarcinoma types [6]. In rats, up to 2000 mg/kg of body weight was considered to be a safe daily dose. However, the exact safe dose is yet to be studied for humans [6].
Papaya and its Antimicrobial Activity
The organic extracts of the roots of the papaya tree were found to be effective against all the tested gram-positive bacteria, such as Pseudomonas aeruginosa (Highest activity), as well as against some gram-negative bacteria, such as Proteus mirabilis. However, the aqueous leaf extracts showed stronger inhibition. The leaf extract consisted of alkaloids, tannins, saponins, glycosides, and phenols, according to phytochemical analysis [5].
The minimum inhibitory concentration of papaya plant extract for S. aureus was very low compared to other bacteria, meaning the extract is potentially effective in treating boils, breast abscesses, and surgical wound infections that involve S. aureus.
Image 2. Home-grown papaya tree in Sri Lanka with raw papaya. Photo by Nadeeka Kularathne.
The Use of the Papain Enzyme from Papaya
The enzyme, papain, is a cysteine protease, and proteases are the major enzymes that are commercially used [7]. Papain is used as a meat tenderizer in the food industry, to support the immune system in the healthcare industry, as a food preservative, and for tooth-removing purposes in the medical/pharmaceutical industry. Chemically modified versions are used as detergents and also used as a compound in exfoliators in the skin care industry [8].
However, papain is immobilised by a variety of methods to improve its activity and to help it thrive under many different conditions. The methods of immobilisation include the immobilisation of papain using organic supports such as agarose beads, cellulose beads, cotton fabric, chitosan, and alginate. The immobilisation of papain enzymes on synthetic organic support beads, such as nylon combined with polyacrylamide, are also widely used. Also, papain is immobilised using smart polymers, polymeric membranes, inorganic supports, mesoporous silicate, inorganic oxide support, magnetic particles, micro-magnetic porous particles, magnetic nanoparticles, and hybrid materials [7].
Conclusion
In conclusion, papaya is a valuable fruit with many medicinal properties. These properties include anti-dengue properties, cancer-fighting properties, antimicrobial properties, and heartfriendly properties. The papain enzyme from papaya is also recognised as an important enzyme that is used by many industries around the world.
Sinhala Summary
පැපොල්, විද්යාත්මකව කරිකා පාපායා එල්., ලෙස හැඳින්වේ. එය ක්රිස්ටෝපර් කොලම්බස් විසින් හඳුන්වනු ලැබුවේ දේවදූතයන්ගේ ඵල ලෙසිනි. පැපොල් පලතුරු විටමින් A, C, E සහ B, ඛනිජ (මැග්නීසියම් සහ පොටෑසියම්) සහ ආහාර තන්තු වලින් පොහොසත් ය. බීජ, ෆීනෝලික් සංයෝග සහ මේද අම්ල වලින් පොහොසත් නමුත් මේවා සාමාන්යයෙන් කෙලින්ම අනුභව නොකෙරේ. කොළ, ආහාර තන්තු සහ පොලිෆෙනොලික් සංයෝග වලින් පොහොසත් ය. පැපොල් වල පැපේන් එන්සයිමය වාණිජමය වශයෙන් භාවිතා වේ උදා: ආහාර කල් තබා ගන්නා ද්රව්ය සහ සම ආරක්ෂණ නිෂ්පාදන ලෙස. පැපොල් වල අඩංගු පෝෂ්ය පදාර්ථ හෘද වාහිනී රෝග වලට, පිළිකා වලට එරෙහිව සහ ප්රති-ක්ෂුද්ර ජීවී ක්රියාකාරකම් වලට එරෙහිව ගුණදායකය. එසේම, ඩෙංගු රෝගයට එරෙහිව ගස්ලබු කොළ සාරය භාවිතා කරයි.
[1] L. F. Santana et al., “Nutraceutical Potential of Carica papaya in Metabolic Syndrome,” Nutrients, vol. 11, no. 7, p. 1608, Jul. 2019, doi: https://doi.org/10.3390/nu11071608.
[2] P. Ranasinghe et al., “In vitro erythrocyte membrane stabilization properties of Carica papaya L. leaf extracts,” Pharmacognosy Research, vol. 4, no. 4, p. 196, 2012, doi: https://doi. org/10.4103/0974-8490.102261.
[3] L. G. Teixeira et al., “White tea (Camellia sinensis) extract reduces oxidative stress and triacylglycerols in obese mice,” Food Science and Technology, vol. 32, no. 4, pp. 733–741, Sep. 2012, doi: https://doi. org/10.1590/s0101-20612012005000099.
[4] T. Vij and Y. Prashar, “A review on medicinal properties of Carica papaya Linn.,” Asian Pacific Journal of Tropical Disease, vol. 5, no. 1, pp. 1–6, Jan. 2015, doi: https://doi. org/10.1016/s2222-1808(14)60617-4.
[5] A. O. Udeze, “Antimicrobial Activity of Carica Papaya (Pawpaw Leaf) on Some Pathogenic Organisms of Clinical Origin from South-Western Nigeria,” vol. 2009, no. 7, p. 4, Jan. 2009.
[6] V. L. Maruthanila, R. Elancheran, and S. Mirunalini, “Carica papaya leaves and cancer prevention: An overview,” MiniReviews in Medicinal Chemistry, vol. 20, Aug. 2020, doi: https://doi.org/10.2174/138 9557520666200811102622.
[7] V. G. Tacias-Pascacio et al., “Immobilization of papain: A review,” International Journal of Biological Macromolecules, vol. 188, pp. 94–113, Oct. 2021, doi: https://doi. org/10.1016/j.ijbiomac.2021.08.016.
[8] H. A. Shouket et al., “Study on industrial applications of papain: A succinct review,” IOP Conference Series: Earth and Environmental Science, vol. 614, p. 012171, Dec. 2020, doi: https://doi. org/10.1088/1755-1315/614/1/012171.
[9] M. Chávez-Pesqueira and J. NúñezFarfán, “Domestication and Genetics of Papaya: A Review,” Frontiers in Ecology and Evolution, vol. 5, Dec. 2017, doi: https://doi. org/10.3389/fevo.2017.00155.
Binu is a second-year Biomedical Science student and she is fascinated by the way the human body interacts with nutrients and diseases. In her free time, she enjoys playing chess and painting canvases.