The Antimicrobial Activity of Black Sour Cherry (Prunus cerasus L.) Extracts: I. Measurement of Sensitivity and Attenuation of Gram-Positive and Gram-Negative Bacteria and C. albicans in Culture

We have previously examined the antimicrobial activity of sweet cherry (Prunus avium L.) extracts on a wide spectrum of gram-positive and gram-negative bacteria in addition to the fungus, Candida albicans. To further understand the effect of a variety of extracts of a related family of sour, tart cherries (Prunus cerasus L.) on bacterial and fungus growth, the antimicrobial activities of black sour cherry extracts (SCE) were measured in culture. SCEs were subdivided into variables: Whole juice extracts (WJE), methanol-extracted juice (MEJ), ddH2O-extracted pomace (dPOM), and methanol-extracted pomace (mPOM). Bacteria and fungus were culturally grown on Mueller-Hinton agar suitable for disk-diffusion method. WJE showed prominent inhibition of Enterococcus Group D (EGD), Staphylococcus aureus, Citrobacter koseri, Enterobacter cloacae, and Klebsiella pneumoniae, with minor attenuation of Bacillus subtilis, Escherichia coli ESBL, Proteus vulgaris, and C. albicans. By contrast, MEJ exhibited substantial inhibition of EGD, S. aureus, Streptococcus Group A (GAS), Streptococcus Group B (GBS), E. cloacae, E. coli, E. coli ESBL, and K. pneumoniae, with minor attenuation of B. subtilis, P. vulgaris, and C. albicans. Interestingly, prominent inhibitory/attenuation effect was reported with dPOM on EGD, S. aureus, GAS, C. koseri, K. pneumoniae, and P. vulgaris, with minor effect on E. cloacae, E. coli, E. coli ESBL, and C. albicans. Furthermore, mPOM exhibited substantial inhibition of EGD, S. aureus, E. coli, K. pneumoniae, and P. vulgaris, with attenuation of GAS, and E. coli ESBL. Of note, whilst WJE, MEJ, and dPOM had no tangible, measurable effect on P. aeruginosa, mPOM significantly inhibited this pathogen. These results confirm the attenuating effect of black sour P. cerasus extracts on the differential growth of gram-positive and gramnegative bacteria, and fungus. Since many of the aforementioned are pathogenic in their nature, sour cherry extracts are interestingly of value in regulating and attenuating the growth of microorganisms of medical importance.