Antimicrobial Assessment of Annona muricata Fruits and Its Chemical Compositions

Aim: To determine the antibacterial activity of Annona muricata fruits against some human pathogens, the fungi associated with deterioration of Annona muricata fruits and the chemical compositions of the fruits.

Study Design: The study was designed to test the inhibitory ability of the plant extract on human pathogens, to identify the fungi associated with deterioration of Annona muricata fruits and determine its chemical compositions by GC-MS.

Place and Duration of Study: Department of Chemistry, Alvan Ikoku Federal College of Education, Owerri and Department of Plant Science and Biotechnology, Imo State University, Owerri, Nigeria, between June to November 2016.

Methodology: The antibacterial activity of Annona muricata fruits was performed by filter paper disc diffusion technique. Pieces of the sour sop sections were plated on potato dextrose agar (PDA) plates each and incubated at 27ºC and the plates examined daily for the development of fungal growth. The chemicals from Annona muricata fruits were extracted with ethanol and subjected to GC/MS analysis and the identification of compounds was done by comparing spectrum of the unknown component with the spectrum of the known components stored in the NIST library.

Results: The results of the bacterial analysis showed that the ethanol extract inhibited all the tested organisms S. aureus, P. mirabilis, K. pneumoniae, Salmonella and E. coli. which justified the use of the plant in the treatment of diarrhea and other infections by Herbalists. The fungal pathogens found to be associated with the rotting of A. muricata fruit included Aspergillus niger (Tiegh), Aspergillus flavus (Link), Rhizopus stolonifer (Ehrenb.), Fusarium oxysporium (Schlech), and Botryodiplodia theobromae (Pat.). The most pathogenic fungi was B. theobromae which caused rot of 11.48 mm2, followed by R. stolonifer that caused rot of 4.03 mm2. The least pathogenic fungus was A. niger causing rot area of 2.51 mm2. The GC-MS analysis revealed that ethanolic extract of Annona muricata fruits contains seven compounds with 5-Hydroxymethylfurfurole constituting the bulk of the oil (29.95%), followed by 3,5-Dihydroxy-6-methyl-2,3-dihydro-4-H-pyran-4-one (28.57%). The oil contains an ester, Butanoic acid,2-methyl-3-oxo-ethyl ester (5.35%) which may be responsible for the sweet aroma of the fruit. Other compounds present were Furfural (6.25%), 4- Hydroxy-2,5-dimethyl-3-hexanone (13.84%), 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (3.13%) and Oleic acid (12.95%). These compounds possessing a wide spectrum of pharmacological activities justified the use of this plant for the treatment of ailments traditionally.