Antifungal activity of ethanolic Psidium guajava L. leaf extract against food spoilage fungi

Aims: This study was aimed to determine the antifungal activity of ethanolic Psidium guajava L. leaf extract against food spoilage fungi.Methodology and results: The ethanolic P. guajava L. leaf extract was tested for antifungal activity against Candida albicans ATCC10231, C. glabrata ATCC2001, C. krusei ATCC32196, C. parapsilosis ATCC22019, Aspergillus fumigatus ATCC26430, A. niger ATCC9029, Rhizopus oligosporus ATCC22959, and R. oryzae ATCC22580 in terms of well diffusion assay, minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and timekill curve assay, using Clinical and Laboratory Standard Institute (CLSI) methods.The inhibition conidia germination assay was determined qualitatively and quantitatively.The well diffusion agar results showed the inhibition zones of extract at a concentration 1% against C. albicans ATCC10231, C. glabrata ATCC2001, C. krusei ATCC32196, C. parapsilosis ATCC22019, A. fumigatus ATCC26430, A. niger ATCC9029, R. oligosporus ATCC22959, and R. oryzae ATCC22580 in the range from 7.00 0.00 to 8.50 0.00 mm.The MICs and MFCs values ranged from 0.31 to 2.50 mg/mL and 5.00 to >5.00 mg/mL, respectively.The time-kill analysis was done for C. albicans ATCC10231, C. glabrata ATCC2001, C. krusei ATCC32196, and C. parapsilosis ATCC22019 with 0 MIC, 0.5 MIC, 1 MIC, 2 MIC and 4 MIC.The results revealed that the extract was only able to reduce 3 log10 CFU/mL at 4 MIC for all Candida strains.The inhibition of conidial germination assay was done with 0 MIC, 1 MIC, 2 MIC, 4 MIC, and 8 MIC.The results showed that A. fumigatus ATCC26430, R. oligosporus ATCC22959, and R. oryzae ATCC22580 were completely killed at 8 MIC, whereas A. niger ATCC9029 reduced conidia germination by 20%.In the qualitative assay, R. oligosporus ATCC22959 and R. oryzae ATCC22580 can be inhibited with the extract up to day 14.On the other hand, 8 MIC of extract only succeeds in inhibiting conidial germination of A. fumigatus ATCC26430 up to day 10, while A. niger ATCC9029 was inhibited up to day 5. Conclusion, significance and impact of study:The current study shows that ethanolic P. guajava L. leaf extract has antifungal activity and can inhibit germination of the spoilage fungi.Thus, it can be considered one of the candidates for natural food preservatives.