Abstract
There is an ancient and prodigious history of olive trees because of their nutritional, medicinal, and traditional uses. Intensive studies have been conducted on olive leaves because they have many positive and beneficial effects for human health. In this study, different solvents were used to examine the olive leaves for their antioxidant and antimicrobial activities and their possible food applications. The obtained results showed that the amounts of phenolic compounds of the olive leaf were 190.44 ± 0.50, 173 ± 1.72, 147.78 ± 0.69, and 147.50 ± 0.05 mg gallic acid/g extracts using methanol, ethanol, diethyl ether, and hexanol, respectively. The statistical analysis revealed that there was a significant difference in the phenolic contents in terms of the used solvents. The stability of the olive leaves extraction was also studied and the results indicated that increasing the storage temperature could negatively affect and encourage the degradation of the phenolic compounds. Furthermore, the olive leaf extraction was applied to raw sheep meat slides at 0.5%, 1.5%, and 2.5% (w/v) in order to test its antioxidant and antimicrobial effects. The results obviously showed that the sample treated with 2.5% olive leaf extract had the significantly (p < 0.05) lowest Thiobarbituric Acid (TBA) values of 1.92 ± 0.12 (mg Malonaldehyde MDA/kg) throughout 12 days of cold storage. Moreover, the results showed that the sample, which was treated with 2.5% olive leaf extract, had low total bacterial count and total coliform bacteria (6.23 ± 0.05, 5.2 ± 0.35 log colony forming unit (CFU)/g, respectively) among the control, 0.5%, and 1.5% olive leaf treated samples throughout 12 days of storage. The phenolic extracts from the olive leaf extract had significant antioxidant and antimicrobial activities, which could be used as a source of potential antioxidant and antimicrobial agents.
Highlights
Olive trees are known as trees of the subtropical region, which can survive and live for a few decades
The results showed that the sample, which was treated with 2.5% olive leaf extract, had low total bacterial count and total coliform bacteria (6.23 ± 0.05, 5.2 ± 0.35 log colony forming unit (CFU)/g, respectively) among the control, 0.5%, and 1.5% olive leaf treated samples throughout 12 days of storage
The phenolic extracts from the olive leaf extract had significant antioxidant and antimicrobial activities, which could be used as a source of potential antioxidant and antimicrobial agents
Summary
Olive trees are known as trees of the subtropical region, which can survive and live for a few decades. The original homeland of olive trees is the Mediterranean region, including Iraq [1]. The estimated area of planted olive trees is approximately eight million hectares. Many studies pointed out that the cultivation of olive trees began around 3500 years ago [2]. The olive leaf is one of the tree byproducts, which are obtained through either the pruning and harvesting process or fall due to different climatic factors. There is an ancient and prodigious history of olive trees because of their nutritional, medicinal, and traditional uses [3]. An essential part of the Mediterranean diet is olive products because of their ability to modulate and control the oxidative balance in vivo; they can monitor and inhibit pathogenic bacteria [4,5]
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