Evaluation of Antimicrobial Potential of Carica papaya Seed Extracts

INTRODUCTION

Medicinal plants are an important source of secondary metabolites such as alkaloids, tannins, terpenoids, flavonoids, and steroids, which possess significant antimicrobial properties. Across the world, researchers have studied various medicinal plants as therapeutic alternatives for effectively treating bacterial infections with fewer side effects on humans. The World Health Organization recognizes phytochemicals from medicinal plants as excellent resources for novel drug discovery, as these compounds exhibit antioxidant, anticancer, antimicrobial, anti-inflammatory, and antifungal activities.

Antimicrobial agents are substances that either kill or inhibit the growth of microorganisms. Carica papaya, an herbaceous plant belonging to the family Caricaceae, has been traditionally used to manage a variety of health conditions due to its nutraceutical and pharmaceutical properties. The plant is rich in nutrients and minerals like potassium and magnesium, along with antioxidants such as vitamins A, C, and E. Different parts of the papaya plant—including seeds, roots, stems, leaves, flowers, and fruit—possess significant medicinal value. For instance, papaya fruit contains proteolytic enzymes that aid in treating injuries, trauma, and allergies.

Papaya flowers have been traditionally used to treat cancer, cardiovascular diseases, inflammation, and indigestion. Additionally, they help neutralize free radicals and support the immune system. Previous studies have investigated the antimicrobial properties of papaya root extracts against pathogens such as P. vesicularis, S. faecalis, A. hydrophila, S. typhimurium, and E. coli using the well diffusion method.

The antibacterial activity of ethanolic extracts of papaya leaves has been tested against clinical isolates of E. coli, K. pneumoniae, and P. mirabilis. Phytochemical analyses have confirmed the presence of alkaloids, flavonoids, steroids, and tannins in papaya, along with enzymes like papain and chymopapain. Moreover, papaya leaves have demonstrated antimalarial and antiplasmodial activity and are used to treat conditions like malaria, liver diseases, constipation, tuberculosis, arthritis, mental disorders, and various other ailments.

Papaya seeds, which have a peppery flavor, exhibit antibacterial properties and have been used to manage conditions such as kidney failure, piles, typhoid, urogenital disorders, and chronic skin ulcers. Numerous researchers have explored the phytochemical content, antioxidant activity, and antibacterial properties of Carica papaya seed extracts.

Building on this research, the present study aimed to evaluate the antimicrobial efficacy of Carica papaya seed extracts against specific pathogenic bacteria, thereby exploring their potential as treatments for bacterial infections with minimal side effects.

MATERIALS AND METHODS

Collection and Preparation of Plant Material

Plant materials were obtained from local markets and residential gardens. The collected materials were thoroughly washed with distilled water and dried in an incubator for approximately 24 hours. The dried materials were then ground into fine powder using a mortar and pestle. Methanol and ethanol were used as solvents to prepare the respective extracts. For each extraction, 10 grams of powdered material were placed in Soxhlet apparatus with 100 ml of either absolute methanol, ethanol, or distilled water for 3–4 hours until the extracts accumulated in the flasks. The extracts were then filtered through muslin cloth followed by Whatman filter paper. Concentration of the filtrates was achieved by heating at 70°C in a hot air oven. The dried extracts were stored in screw-capped bottles at 4°C until further analysis.

Determination of Antimicrobial Activity

The antimicrobial activity of the methanolic, ethanolic, and aqueous extracts was assessed using the agar well diffusion method. Bacterial strains were subcultured on nutrient agar plates and incubated for 24 hours. Sterile Petri dishes were prepared with autoclaved nutrient agar, and wells of 5 mm diameter were created using a cork borer. After solidification, bacterial suspensions were swabbed uniformly across the plates. Test extracts were dissolved in dimethyl sulfoxide (DMSO) at concentrations of 25, 50, and 100 mg/ml. Defined volumes of each concentration were added to the wells. DMSO served as the negative control, and amoxicillin was used as the positive control. Plates were incubated for 24 hours at 37°C, and zones of inhibition were measured to assess antimicrobial activity.

Table: Zones of Inhibition (mm) of Carica papaya Seed Extracts Against Pathogens

Bacteria	Concentration (mg/ml)	Methanolic	Ethanolic	Aqueous
Staphylococcus aureus	25	3.6	3.8	2.9
	50	5.2	6.5	4.2
	100	9.8	10.7	8.0
Pseudomonas aeruginosa	25	3.2	3.0	2.4
	50	4.7	5.4	3.3
	100	10.2	9.3	6.8
Escherichia coli	25	3.6	3.2	2.6
	50	4.9	4.5	4.0
	100	8.0	8.4	7.2

RESULTS AND DISCUSSION

Quantitative analysis of the inhibition zones indicated that Carica papaya seed extracts exhibited notable antimicrobial activity against the tested gram-positive and gram-negative bacteria. Specifically, ethanolic extracts produced the largest inhibition zone of 10.7 mm at 100 mg/ml against Staphylococcus aureus, while methanolic extracts showed the highest inhibition of 10.2 mm against Pseudomonas aeruginosa. Aqueous extracts consistently displayed lower antimicrobial activity, with a maximum inhibition zone of 8.0 mm at 100 mg/ml against S. aureus.

The data suggest that increasing the concentration of papaya seed extracts enhanced their antimicrobial efficacy across all bacterial strains tested. Furthermore, organic solvent extracts (methanolic and ethanolic) demonstrated greater antimicrobial potential compared to aqueous extracts. This might be attributed to better solubility of active phytochemical compounds in organic solvents. Comparing the organic extracts, ethanolic extracts were generally more effective than methanolic extracts against S. aureus, indicating ethanol as a superior solvent for extracting antimicrobial compounds targeting gram-positive bacteria.

Previous studies corroborate these findings, highlighting the significant antibacterial properties of various parts of Carica papaya, including seeds, roots, leaves, and fruits. These results further validate the potential use of Carica papaya seed extracts as effective antimicrobial agents.

CONCLUSION

This study demonstrated that methanolic and ethanolic extracts of Carica papaya seeds possess strong antimicrobial activity against both gram-positive and gram-negative bacteria, especially Staphylococcus aureus, whereas aqueous extracts exhibited moderate efficacy. The findings support the potential application of Carica papaya seeds as a natural source of antimicrobial agents for the treatment of bacterial infections.

REFERENCES:

1. Sundar, S.; Padmalatha, K.; Helasri, G.; Vasanthi, M.; Narmada, B.S.; Lekhya, B.; Naga Jyothi, R. and Sravani, T. Anti-microbial activity of aqueous extract of natural preservatives-Cumin, Cinnamon, Coriander and Mint. Research Journal of Pharmacy and Technology. 2016; 9(7): 843-847.
2. Chandra, G.; Ghosh, A.; Chatterjee, S.K. and Bhattacharjee, I. Antibacterial activities of some plant extracts used in Indian traditional folk medicine. Asian Pacific Journal of Tropical Biomedicine. 2011; S165-S169.
3. Malik, N and Ahmed, S.  Anti-microbial activity of Carica papaya, Piper nigrum and Datura stramonium plants on drug resistant pathogens isolated from clinical specimens. IOSR Journal of Biotechnology and Biochemistry. 2016; 2(6): 01-06.
4. Alabi, O.A.; Haruna, M.T.; Anokwuru, C.P.; Jegede, T.; Abia, H.; Okegbe, V. and Esan, E. Comparative studies on antimicrobial properties of extracts of fresh and dried leaves of Carica papaya (L) on clinical bacterial and fungal isolates. Pelagia Research Libarary. 2012; 3(5): 3107-3114.
5. Aravind, G.; Bhowmik, D..; Duraivel, S. and Harish, G. Traditional and medical uses of Carica papaya. Journal of Medicinal Plants Studies. 2013; 1(1): 7-15.
6. Ekaiko, M.U.; Arinze, A.G.; John, W.O. and Ajah, O. Effect of the leaf extract of Psidiumguajava L. and Carica papaya L. International Journal of Life Sciences Research 2015; 3(4): 55-60.
7. Dwivedi, M.K.; Sonter, S.; Mishra, S.; Patel, D.K. and Singh, P.K. Antioxidant, antibacterial activity and phytochemical characterization of Carica papaya flowers. Beni-Suef University Journal of Basic and Applied Sciences 2020; 9(23): 1-11.
8. Vijay, Y.; Goyal, P.K. and Chauhan, C.S. Carica papaya linn. An Overview. Int. J. Harbal Med. 2014; 2(5): 1-8.
9. Tiwari, P.; Kumar, K.; Panik, R.; Pandey, A. and Sahu, P.K. Antimicrobial activity evaluation of the root of Carica papaya linn. Int. J. pharm. Tech. Res. 2011; 3(3): 1641-1648.
10. Adejuwon, A.O.; Agbaje, E.O. and Idika, N. Antifungal and antibacterial activities of aqueous and methanolic root extracts of Carica papaya linn. (Caricaceae). International Research Journal of Microbiology. 2011; 2(8): 270-277.
11. Yusha’s, M.; Onuorah, F.C. and Murtala, Y. In vitro sensitivity pattern of some urinary tract isolates to Carica papaya extracts. Bayero J. Pure Appl. Sci. 2009; 2(2): 75-78.
12. Romasi, E.F.; Krina, J. and Parhusip, A.J.N. Antibacterial activity of papaya leaf extracts against pathogenic bacteria. Makara. Tcknologi. 2011; 15(2): 173-177.
13. Peter, J.K.; Kumar, Y.; Pandey, P. and Masih, H. Antibacterial activity of seed and leaf extract of Carica papaya var. Pusa dwarf Linn. IOSR Journal of Pharmacy and Biological Sciences. 2014; 9(2) Ver. VII: 29-37.
14. Sharma, A.; Bachheti, A.; Sharma, P.; Bachheti, R.K. and Husen, A. Phytochemistry, pharmacological activities, nanoparticle fabrication, commercial products and waste utilization of Carica papaya L.: A comprehensive review. Current Research in Biotechnology. 2020; 2: 145-160.
15. Yismaw, G.; Tessema, B.; Mulu, A. and Tiruneh, M. The in-vitro assessment of antibacterial effect of papaya seed extract against bacterial pathogens isolated from urine, wound and stool. Ethiop. Med. J. 2008; 46(1): 71-77.
16. Ying, C.K.J.; Praveen, N.; Paliwal, N. and Khan, N.H. Phytochemical analysis, antioxidant and antibacterial activities of ethanolic extract of  Carica papaya seeds. Biomed. J. Sci. & Tech. Res. 2021; 33(5): 26175-26187.
17. Ukaegbu-Obi, K.M.; Anyaegbunam, C.P. and Enya, E. Antibacterial activity of Carica papaya seeds on some human pathogens. Annals of West University of Timisoara, Ser. Biology. 2018; 21(1): 11-16.
18. Baskaran, C.; Ratha bai, V.; Velu, S. and Kumran, K. The efficiency of Carica papaya leaf extract on some bacterial and a fungal strain by well diffusion method. Asian Pacific Journal of Tropical Disease. 2012; 2(S2): 658-662.
19. Yahaya, K.H. and Abdullahi, M.A. Antibacterial activity of Carica papaya (Leaf and Seed) extracts on Methicillin resistant Staphylococcus aureus (MRSA) from wound. International Journal of Research Publication and Reviews. 2022; 3(12): 1399-1406.
20. Nirosha, N. and Mangalanayaki, R. Antibacterial activity of leaves and stem extract of Carica papaya. International Journal of Advanced Pharmacy and Biochemistry. 2013; 2(3): 473-476.
21. Prabhu, A.K.; Devadas, S.M.; Lobo, R.; Udupa, P.; Chawla, K. and Ballal, M. Antidiarrheal activity and phytochemical analysis of Carica papaya fruit extract. J. Pharm. Sci. Res. 2017; 9: 1151-1155.
22. Dagne, E.; Dobo, B. and Bedewi, Z. Antibacterial activity of papaya (Carica papaya) leaf and seed extract against some selected gram-positive and gram-negative bacteria. Pharmacogn. J. 2021; 13(6s): 1727-1733.