Total polyphenols and tannin concentration and DPPH-radical scavenging activity in olive varieties from Montenegro

The interest in the biological effects of dietary antioxidants of phenolic nature is underlined by various reports [1,2]. These indicate that the daily intake of small amounts of plant phenolics reduce the risk of coronary heart disease in large population groups. Oxidative injury is assumed to play a crucial role in the development of several diseases, e.g. coronary heart disease and cancer, and the probability that antioxidants may protect against oxidative injury and low-density lipoprotein (LDL) oxidation has gained growing evidence in the past years.

Olives (Olea europaea L.) are rich in simple and complex phenolic compounds with potent antioxidant properties, which may have a protective action on human health. Olive fruit and oil contain significant quantities of phenolic compounds. They include simple compounds such as vanillic, gallic, coumaric and caffeic acid, tyrosol etc. Furthermore, olive oil contains secoiridoids such as oleuropein or more complex molecules such as lignans and flavonoids, e.g. apigenin or luteolin. Beside this, olive oil is rich in α-tocopherol, which has the highest vitamin E activity.

Thus, total polyphenols and tannin concentration in leaves and fruits of 22 indigenous and introduced olive varieties growing in Montenegro, were investigated for the first time. Concentration of total polyphenols ranged, depending on locality, from 15.2 to 76.1, and tannin from 2.6 to 54.5mg catehine/g dry weight, being significantly higher in leaves compared to fruits. Fruit EtOH extracts showed different level of DPPH-radical scavenging activity which ranged from 2.6 to 61.7% of neutralised radicals.

References:1. Owen, RW. et al. (2000) Food Chem Toxicol. 38:647–659.

2. Gašić, O. et al. (1999) Acta Hort 474:469–472.