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Olive vari­eties with dif­fer­ent polyphe­nol pro­files have dif­fer­ent antibac­te­r­ial prop­er­ties, accord­ing to new research out of Italy.

Researchers at the National Research Council’s insti­tute of food sci­ences (ISA-CNR) and the University of Salerno tested the antibac­te­r­ial activ­ity of three olive vari­eties. Their find­ings now pave the way for the explo­ration of new nat­ural med­ica­tion.

“We first con­ducted a study con­cern­ing the bio­chem­i­cal pro­file, includ­ing volatile com­pounds, and the rela­tion­ship between the antiox­i­dant activ­ity and polyphe­nols of extra vir­gin olive oils obtained by autochtho­nous vari­eties of Campania, Ruvea Antica, Ravece, and Ogliarola,” Filomena Nazzaro, a sci­en­tist at the ISA-CNR, told Olive Oil Times. ​“Then, in a sec­ond exper­i­ment, we ana­lyzed the antibac­te­r­ial activ­ity cor­re­lated to the polyphe­nol pro­files of the above-men­tioned vari­eties.”

“This last research, in par­tic­u­lar, exam­ined the inhibitory effect of the polyphe­no­lic extracts against sev­eral gram-pos­i­tive and gram-neg­a­tive bac­te­r­ial strains,” she added. ​“They gave us remark­able results in terms of their activ­ity against path­o­genic species, namely those that are respon­si­ble for the for­ma­tion of biofilms, which are very inter­est­ing when it comes to human health since they increase the resis­tance of bac­te­ria to syn­thetic antibi­otics.”

The analy­sis of the polyphe­nol frac­tions of the extra vir­gin olive oils con­firmed well-known antibac­te­r­ial prop­er­ties, show­ing that the qual­i­ta­tive and quan­ti­ta­tive pro­file of polyphe­nols can affect those prop­er­ties in dif­fer­ent ways.

The researchers applied a sta­tis­ti­cal method to pre­dict the syn­er­gis­tic effect of polyphe­nols and the influ­ence of each of them, based also on their amount, on the activ­ity of the whole extract.

The tests were per­formed using 2.5 and 4.9 micro­grams of the three polyphe­nol extracts against dif­fer­ent pathogens. The results showed that the min­i­mum con­cen­tra­tion nec­es­sary to inhibit the growth of the path­o­genic tester strains was low for all the polyphe­no­lic extracts, and this con­firmed their gen­eral capac­ity to inhibit the growth of path­o­genic or unwanted microor­gan­isms.

“In par­tic­u­lar, all three extracts were effec­tive in inhibit­ing the growth of Escherichia coli [with 4.9 micro­grams of polyphe­no­lic extracts from Ravece and Ogliarola],” Nazzaro said. ​“In our opin­ion, this result could find an inter­est­ing prac­ti­cal appli­ca­tion, since this bac­terium is one of the causes of uri­nary tract infec­tions. Research on polyphe­no­lic extracts, as well as essen­tial oils, are actu­ally open­ing new hori­zons in the treat­ment of, for exam­ple, com­mon catheter infec­tions, which are painful and dif­fi­cult to erad­i­cate.”

The three extracts also were found to be capa­ble of inhibit­ing the growth of Pseudomonas Aeruginosa, a well-known pathogen that is respon­si­ble for the for­ma­tion of the afore­men­tioned biofilms.

The extracts of Ogliarola and Ravece were more effec­tive than those of Ruvea Antica in inhibit­ing the growth of the strain; in par­tic­u­lar, 2.5 micro­grams of polyphe­nols extract of Ravece were twice as effec­tive as that of Ruvea Antica against Pseudomonas Aeruginosa; 4.9 micro­grams of Ravece polyphe­nols extract were three times more effec­tive than those of Ruvea Antica.

The researchers stud­ied the antiox­i­dant activ­ity of the extracts fol­low­ing the same method­ol­ogy, with extra vir­gin olive oils from vari­eties grown in the same plot of land at the same time. This lim­ited the vari­ables involved and led to the find­ing that Ruvea Antica con­tained the great­est amount of total polyphe­nols, show­ing the high­est antiox­i­dant activ­ity.

The research team also sug­gested that it would be inter­est­ing to con­duct this research on sev­eral vari­eties, in dif­fer­ent years.

“This could be a basis of com­ple­men­tary stud­ies to for­mu­late ideal drugs of nat­ural ori­gin, com­posed of opti­mal mix­tures of polyphe­nols, which are able to exer­cise with the min­i­mum effort, in terms of quan­tity, and the max­i­mum result, namely against the great­est num­ber of pathogens, their antibac­te­r­ial effi­cacy,” Nazzaro said. ​“Future research should also take into account the use of the extra vir­gin olive oil by-prod­ucts, which are rich in polyphe­nols.”

“Moreover, this makes us under­stand the impor­tance of assum­ing that every day a fair amount of extra vir­gin olive oil, which is digested and trans­formed into mol­e­cules that are ben­e­fi­cial for our micro­biome, also coun­ter­acts the growth of path­o­genic species,” Nazzaro con­cluded.

• Food Science and Nutrition


• Microorganisms