Evaluation of the antimicrobial activities and biopreservative potentials of Alstonia boonei stem bark and Euphorbia hirta leaves crude extracts in minced meat

Abstract

The antimicrobial activities and preservative potentials of crude extracts of Alstonia boonei stem bark and Euphorbia hirta leaves were studied in minced meat. Soxhlet extraction and cold ethanol extraction methods were used for the extraction of the dried and ground samples. Well-in-Agar diffusion method was used for antimicrobial screening at different concentrations on E. coli, B. subtilis, S. aureus, S. typhi and S. cerevisiae. The preservative effects at 0.1%, 0.2% and 0.3% alone and in combination were determined in minced meat using E. coli and B. subtilis as test isolates. E. hirta cold and A. boonei cold extracts gave the highest zone of growth inhibition on E. coli and B. subtilis with 20 mm zone diameter at 200 mg/ml concentration. Phytochemical analysis revealed the presence of alkaloids, flavonoids, tannins, saponins and cardiac glycosides. A. boonei at 0.1, 0.2 and 0.3% produced a log cycle reduction on the growth of E. coli while the mixture of A. boonei and E. hirta extracts (1:1) at 0.1% and 0.2% produced a log cycle reduction on the growth of E. coli and B. subtilis in the minced meat at the end of storage. However, the A. boonei extracts had more significant effect on the isolates. The results revealed the potentials of the plant extracts as natural antimicrobial preservatives in meat. The observed antimicrobial activities may be attributed to the phytochemicals identified in the extracts.

Keywords: Antimicrobial preservative, Alstonia boonei, Euphorbia hirta, crude extracts, minced meat, phytochemicals.