Abstract
The strawberry tree (Arbutus unedo L., Ericaceae family) is an evergreen Mediterranean shrub whose leaves and fruits are used in traditional medicine due to their antioxidant, antimicrobial, antidiabetic, diuretic, and antiproliferative properties. The health benefits are mainly attributed to the presence of phenolic compounds. The aim of this study was to compare the phenolic profiles, total phenolic content (TPC), and radical scavenging activity (RSA) of A. unedo leaves and fruits collected at two locations in Croatia. Phenolic profiles were identified using an ultra-high-performance liquid chromatograph (UHPLC) coupled with a hybrid mass spectrometer (LTQ Orbitrap MS). TPC was determined by Folin–Ciocalteu’s assay, while RSA was investigated using DPPH reagent. A total of 64 phenolics (60 and 42 compounds in leaves and fruits, respectively) were identified. Hyperoside and flavan-3-ols were predominant compounds in leaves, while gallocatechin and catechin were the major compounds found in fruits. To the authors’ knowledge, 16 and 5 phenolics in leaves and fruits, respectively, were reported for the first time. Principal component analysis (PCA) showed that UHPLC-LTQ Orbitrap MS could be used to identify which phenolics were able to discriminate samples regarding plant tissue and geographical origin. TPC in leaves and fruits were in the ranges of 67.07–104.74 and 16.78–25.86 mg gallic acid equivalents (GAE)/g dried weight (dw), respectively. RSA for leaves and fruits were in the ranges of 408.92–430.98 and 74.30–104.04 μmol Trolox equivalents (TE)/g dw, respectively. The number of identified phenolics was lower in fruits compared to leaves. Such a large number of bioactive phenolics identified and the strong antioxidant activity pointed to A. unedo as a promising health-promoting plant and natural food preservative.
Highlights
Secondary metabolites are bioactive compounds generally involved in plant defence against ultraviolet radiation, diminished water supply, or aggression by pathogens [1]
In studies by Mosele et al [18] and El Cadi et al [19], 40 and 42 phenolics in total were identified, respectively, which was in accordance with our study, in which 42 phenolics were identified in fruits (Table 1), 5 of which were identified for the first time
This study reported the investigation of the main phytochemicals found in strawberry tree (A. unedo L., Ericaceae) leaves and fruits originating from Croatia
Summary
Secondary metabolites are bioactive compounds generally involved in plant defence against ultraviolet radiation, diminished water supply, or aggression by pathogens [1] These substances, in addition to nutritional value, have a protective effect in reducing the risk of various diseases: they are helpful in the cellular defence and activation of enzyme systems for detoxification, have antioxidant activity, reduce inflammation, and exhibit antimutagenic and antitumor activity [2]. Due to their strong antioxidant properties, there is increased interest in the identification of phytochemicals in Mediterranean wild plants such as evergreen shrub strawberry tree (Arbutus unedo L., Ericaceae family) [3]. The increased interest in replacing synthetic antioxidants from food with natural ones has supported research on plants with a high content of bioactive compounds as a source of new antioxidants
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