Abstract
Quality characteristics of olive products significantly depend on cultivar (cv), among other factors. In this study, seven traditional, noncommercial Greek cultivars, along with the commercial Spanish Arbequina cv., were examined for the phenolic antioxidant dynamic of their leaves. Polar extracts (aqueous, methanol, and ethanol) were analyzed for Total Phenol (TP), Flavonoid (TFL), Hydroxycinnamic Acid Derivatives (THAD), Flavonol (TFLVN) contents, DPPH radical scavenging ability, and Ferric Reducing Capacity (FRAP). Selective characteristics of olive leaf methanol extracts for all cultivars were re-examined on a second sampling period. Olive leaf is considered a rich source of phenolic antioxidants total phenol content reaching 29.3 ± 1.3, 30.6 ± 0.4, and 27.0 ± 1.1 mg caffeic acid/g dry leaf for aqueous, methanol, and ethanol extracts, respectively) and all cultivars were considered of equal bioactive dynamic. TP data derived from Folin–Ciocalteu and another spectrophotometric assay employed presented a high correlation for all examined cases (R2 = 71.5–86.9%). High correlation (R2 = 0.92) was also found between TP and FRAP findings of aqueous extracts. Olive leaf is considered a promising source of phenolic antioxidants irrelevant to cultivar and therefore even cultivars less effective for oil or table olive production could be efficiently exploited for the bioactive dynamic of their leaves.
Highlights
IntroductionThe culture and significance of the olive tree in Mediterranean, and in Greece, is manifested in many ways (documentary and Linear B tablets evidence, iconographic representations, archaeological evidence, paleobotanical remains, molecular analysis evidence, mythology, ethnobotanical information, literature, and customs) and dates back to prehistoric times
The culture and significance of the olive tree in Mediterranean, and in Greece, is manifested in many ways and dates back to prehistoric times
Total phenol content was determined by two protocols; the widely employed Folin–Ciocalteu phenol content was determined by two the widelyand employed
Summary
The culture and significance of the olive tree in Mediterranean, and in Greece, is manifested in many ways (documentary and Linear B tablets evidence, iconographic representations, archaeological evidence, paleobotanical remains, molecular analysis evidence, mythology, ethnobotanical information, literature, and customs) and dates back to prehistoric times. The olive tree is one of the earliest horticultural fruit trees whose products were and still are a part of religious rituals and ceremonial activities, symbols of peace, prosperity, and victory, used for aromatic oils and ointment preparation, as pharmaceuticals, cosmetics, food consumption, and other daily needs (lighting and heating) [1,2]. The well documented health related benefits of olive products, mainly due to their polyphenolic constituents, have launched the interest of consumers, industries (food, medicinal, and cosmetic) and scientists. Foods 2018, 7, 197 lipids from oxidative stress and the related disorders from olive oil polyphenols intake (at least 5 mg of hydroxytyrosol and its derivatives per day) initiated the marketing of relevant products.
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