Investigation of antioxidant and antihemolytic activities of Algerian defatted olive fruits (olea europaea L.) at two ripening stages
Résumé
BACKGROUND: Olive fruits have become extremely valuable because they have important nutrient properties and have shown positive benefits for human health. The chemical composition and organoleptic characteristics may be influenced by genotype and some agronomic factors like olive drupe harvesting date. OBJECTIVE: In this study, the greatest interest is to clarify and to give more information for Algerian Olea europaea L. by investigation of their total phenolic and flavonoid contents, phenolic compounds identification, total antioxidant capacity and antihemolytic activity at two levels of the olive ripening process. METHODS: Colorimetric methods were used to quantify total phenolic and flavonoid contents. The phenolic composition was done by HPLC technique. The antioxidant activity was assessed by measuring radical scavenging activity against 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) radical cation (ABTS(center dot+)) expressed as Trolox Equivalen t Antioxidant Capacity (TEAC), Ferric Reducing Antioxidant Power (FRAP) and antihemolytic activity. RESULTS: The harvesting time effect on HPLC analysis of olive fruits was significant. Interestingly, the phenolic composition of the olive fruits differed greatly between samples. Two compounds usually not described in olive fruit were identified, namely morine dihydrate and coumarin. The amounts of total phenolics varied widely in the investigated extracts and ranged from 495 to 2325 mg GAE/100 g for black olives and from 865 to 2387 mg GAE/100 g for green olives, whereas the flavonoids content expressed as rutin equivalent per 100 gram of defatted dry matter was ranged between 155 and 354 mg/100 g for green olives and between 214 and 260 mg/100 g for black olives. The antioxidant activity of black and green olives ranged from 5.86 and 4.88 to 59.44 and 50.50 mM Trolox equivalents respectively, while ferric reducing antioxidant power (FRAP) was within the range of 0.36 and 0.31 to 4. 41 and 3.04 mM Fe(II) respectively. Majority of extracts exhibited a beneficial antihemolytic effect. CONCLUSIONS: Results showed that the level of maturation influences the chemical composition, antioxidant and bioactive properties. Consequently, this allows us to estimate the best and optimal harvest time.