Phytochemical constituent and antimicrobial properties of guava extracts of east Hararghe of Oromia, Ethiopia

Abstract

Abstract Background There is a need for the screening more effective, affordable and readily available antimicrobial substances from local medicinal plants or herbs as the pathogenic bacteria are developing the resistance to common antibiotics. Guava (Psidium guajava L.) has antimicrobial activities and it is easily accessible to local populace in tropical region. Antimicrobial properties of guava extracts are attributed to the presence of different phytochemical constituents. The fact that phytochemicals’ constituents vary as a result of geographical locations and literatures about Ethiopian guava with respect to phytochemicals’ composition and content, and antimicrobial activities are hardly available, there is a need to analyze phytochemicals and antimicrobial properties of the Ethiopian guava from Oromia Regional State, Babile and Gursum Districts against Salmonella Typhi, Shigella boydii, Staphylococcus aureus and Enterococcus faecalis. Methods Extraction was done by maceration. Qualitative analysis of phytochemicals was carried out using standard protocol and quantitative phytochemical determination was conducted using spectrophotometric and gravimetric methods. Antimicrobial activities were determined by disc diffusion and broth dilution method. Results Qualitative phytochemical analysis revealed the presence of alkaloids, saponin, steroids and tannin, but the absence of flavonoid and phlobatannin in all Babile and Gursum leaf and bark extracts. Gravimetric measurement showed the highest terpenoid content of 105.00 ± 8.66 mg extract/g of powder in Gursum leaf extract. Similarly, spectrophotometric measurement showed the highest total phenol content of 0.205 ± 0.01 mg/g of the extracts as Tannic Acid Equivalent in Gursum leaf extract. Antimicrobial activity tests revealed that Babile leaf extract showed the highest 13.0 ± 6.79 mm zone of inhibition against Shigella boydii compared to that of other guava extracts. Babile leaf extract showed the lowest 2.375 ± 0.177 mg/ml minimum inhibitory concentration against Shigella boydii, while Gursum leaf extract showed the lowest 1.875 ± 0.884 mg/ml MIC against Salmonella Typhi. Phytochemical analysis showed the presence of alkaloids, saponins, steroids and tannins in the all extracts, but the absence of flavonoids and phlobatannins in the all extracts and terpenoids in Babile extracts. The highest content of alkaloid and terpenoid (98.67 ± 14.43, 93.33 ± 8.82 mg extract/g of powder, respectively) were found in Babile leaf and Gursum bark extracts, respectively. Antimicrobial activity tests revealed that Babile leaf extracts showed higher zone of inhibition against all clinical isolates than that of Gursum leaf extracts, but Babile bark extracts showed lower zone of inhibition against all clinical isolates than that of Gursum bark extracts. Babile leaf extracts showed the highest zone of inhibition (13.0 ± 6.79 mm) against S. boydii, and Babile bark extracts showed the lowest Minimum Inhibitory Concentration (1.250 ± 0.001 mg/ml) against S. Typhi. Conclusion Guava extracts from different location could be source of natural antimicrobial agents with different composition and content. In vivo antimicrobial activity, and isolation, identification and synergy of specific active compound that responsible for the antibacterial activity should be evaluated.

Keywords

• Antimicrobial activity
• Ethiopia
• Psidium guajava
• Phytochemical analysis
• Shigella boydii