HPTLC and FTIR Fingerprinting of Olive Leaves Extracts and ATR-FTIR Characterisation of Major Flavonoids and Polyphenolics.

Snezana Agatonovic-Kustrin,Kobakhidze Tamara Ilinichna,Dementyev Sergey Petrovich,Vladimir Gegechkori,David William Morton

doi:10.3390/molecules26226892

Snezana Agatonovic-Kustrin, Kobakhidze Tamara Ilinichna + Show 3 more

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https://doi.org/10.3390/molecules26226892

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Abstract

The aim of this study was to analyse the effect of spontaneous microbial maceration on the release and extraction of the flavonoids and phenolics from olive leaves. Bioprofiling based on thin-layer chromatography effect-directed detection followed by ATR-FTIR spectroscopy proved to be a reliable and convenient method for simultaneous comparison of the extracts. Results show that fermentation significantly enhances the extraction of phenolic compounds and flavonoids. The polyphenolic content was increased from 6.7 µg GAE (gallic acid equivalents) to 25.5 µg GAE, antioxidants from 10.3 µg GAE to 25.3 µg GAE, and flavonoid content from 42 µg RE (rutin equivalents) to 238 µg RE per 20 µL of extract. Increased antioxidant activity of fermented ethyl acetate extracts was attributed to the higher concentration of extracted flavonoids and phenolic terpenoids, while increased antioxidant activity in fermented ethanol extract was due to increased extraction of flavonoids as extraction of phenolic compounds was not improved. Lactic acid that is released during fermentation and glycine present in the olive leaves form a natural deep eutectic solvent (NADES) with significantly increased solubility for flavonoids.

Highlights

Olive (Olea europaea L.), or European olive, is one of the oldest known agricultural fruit trees cultivated to produce olives, olive oil, and olive oil derivatives
The effect of spontaneous fermentation and microbial maceration on the extraction of phenolics and terpenoids from olive leaves was compared with classic maceration with different solvents and Soxhlet extraction via high-performance thin-layer chromatography (HPTLC) chromatographic and ATR-Fourier transform infrared spectra (FTIR) spectral fingerprinting
Despite the weaknesses of conventional methods, Soxhlet extraction is considered as a reference method that is generally used for comparison with new extraction methodologies

Summary

Introduction

Olive (Olea europaea L.), or European olive, is one of the oldest known agricultural fruit trees cultivated to produce olives, olive oil, and olive oil derivatives. The olive tree is one of the species with the highest antioxidant activity in its oil, fruits, and leaves [4]. Olive oil contains high amounts of phenolic compounds with antioxidant capacity to prevent oxidative damage [5,6]. The utilisation of agricultural waste products is gaining more and more attention Due to their high polyphenolic content, olive leaves present an abundant source of phenolic compounds, an important raw material that can be used as a natural antioxidant [9]. Olive tree leaves are known as a traditional antidiabetic and antihypertensive herbal drug [15]. Olive leaf infusions have been used in traditional herbal medicine to treat malaria, reduce fevers [16], and as an anti-inflammatory tonic [17]

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