A comparative study of the antioxidant profiles of olive fruit and leaf extracts against five reactive oxygen species as measured with a multiple free‐radical scavenging method

Abstract

Olive fruits and leaves are recognized to have great potential as natural sources of antioxidants. The major phenolic antioxidant component in these plant tissues is oleuropein. The antioxidant activity of olive fruits and leaves was evaluated in this study using multiple free‐radical scavenging (MULTIS) methods, wherein we determined the scavenging abilities of different extracts against five reactive oxygen species (ROS; HO·, O2−·, RO·, t‐BuOO·, and 1O2). Raw olive fruits taste bitter and are inedible without undergoing a debittering treatment. Following the NaOH‐debittering process, the radical scavenging activity of olives decreased by 90%. The MULTIS measurements indicated that oleuropein and hydroxytyrosol are responsible for the radical scavenging activity of olive fruits. Furthermore, we evaluated the radical scavenging profiles of olive leaf extracts against five ROS and found significant seasonal variations in their antioxidant activities. Leaves picked in August possessed greater radical scavenging abilities (180% to 410% for different ROS) than those picked in the cold season (December and February). In roasted olive leaves, we found marked increases (230% to 300% and 180% to 220%) in the antioxidant activities of Maillard reaction products against RO· and t‐BuOO·, respectively. This study presented a useful comparative analysis of the antioxidant capacities of food against various types of ROS. Practical Application In this study, we evaluated the natural antioxidant activity of olive fruits and leaves against five reactive oxygen species (ROS). We found characteristic differences in the antioxidant profiles of different olive tissues, which varied after different treatments (debittering [fruit], drying [leaf], and roasting [leaf]). Comparative studies of the antioxidant capacities of foods against various ROS are useful to improve the functionality of food products.

Behavioral and Metabolic Effects of a Calorie-Restricted Cafeteria Diet and Oleuropein Supplementation in Obese Male Rats

“…OLE has also been shown to protect against oxidative stress in anesthetic-treated rats and to improve cognitive function [61]. Its antioxidant effect could account for a neuroprotective effect, which would promote the survival of DA neurons in the ventral tegmental area and therefore increase the availability of DA in the NAcc, improving sensitivity of the reward system [62].…”

Phytochemistry and Diverse Pharmacology of Genus Mimosa: A Review

“…There is a constant need to counteract the effect of reactive oxidative species to delay the progression on these diseases. Reactive oxygen species and free radicals are scavenged by antioxidants through the termination of a chain reaction, which otherwise can cause damage to cells [ 147 ]. Plants are a source of antioxidants and can help to lessen the diseases caused by reactive oxidative species.…”

Olive leaf powder prevents nonalcoholic steatohepatitis in Sprague–Dawley rats fed a high-fat and high-cholesterol diet

“…Our products of OLP contain only a low concentration of oleuropein to mitigate its bitter taste. The polyphenols found in olive leaf extract vary depending on the extraction process, state of the leaf (fresh, refrigerated, dried, or frozen), climate, harvesting season, and geographic olive-growing area [5,10,19,34]. Further studies are needed to investigate the optimal dose and concentration of olive leaf products to obtain the maximum preventive effects against NASH.…”