Non-targeted metabolite profiling highlights the potential of strawberry leaves as a resource for specific bioactive compounds.

The non-edible parts of horticultural crops, such as leaves, contain substantial amounts of valuable bioactive compounds which are currently only little exploited. For example, strawberry (Fragaria × ananassa) leaves may be a promising bioresource for diverse health-related applications. However, product standardization sets a real challenge, especially when the leaf material comes from varying cultivars. The first step towards better quality control of berry fruit leaf-based ingredients and supplements is to understand metabolites present and their stability in different plant cultivars, so this study surveyed the distribution of potentially bioactive strawberry leaf metabolites in six different strawberry cultivars. Non-targeted metabolite profiling analysis using LC/qTOF-ESI-MS with data processing via principal component analysis and k-means clustering analysis was utilized to examine differences and commonalities between the leaf metabolite profiles. Quercetin and kaempferol derivatives were the dominant flavonol groups in strawberry leaves. Previously described and novel caffeic and chlorogenic acid derivatives were among the major phenolic acids. In addition, ellagitannins were one of the distinguishing compound classes in strawberry leaves. In general, strawberry leaves also contained high levels of octadecatrienoic acid derivatives, precursors of valuable odour compounds. The specific bioactive compounds found in the leaves of different strawberry cultivars offer the potential for the selection of optimized leaf materials for added-value food and non-food applications. © 2016 Society of Chemical Industry.

Kårlund A ，Hanhineva K ，Lehtonen M ，McDougall GJ ，Stewart D ，Karjalainen RO ... -  《-》

NMR and UPLC-qTOF-MS/MS characterisation of novel phenylethanol derivatives of phenylpropanoid glucosides from the leaves of strawberry (Fragaria x ananassa cv. Jonsok).

Strawberry (Fragaria x ananassa) is rich in polyphenols, particularly anthocyanins, flavonols, condensed tannins and ellagic tannins. In addition to the fruits, the leaves of strawberry also contain a wide range of phenolic compound classes, but have not been investigated to the same extent as the fruit. To characterise a metabolite group present in the leaves of strawberry, that was not amenable for identification based on earlier information available in the literature. Methanolic extracts of strawberry leaves were analysed by UPLC-qTOF-MS/MS and iterative quantum mechanical NMR spectral analysis. The structures of phenylethanol derivatives of phenylpropanoid glucosides Eutigoside A ( F4) and its two isomeric forms 2-(4-hydroxyphenyl)ethyl-[6-O-(Z)-coumaroyl]-beta-D-glucopyranoside (F6) and 4-(2-hydroxyethyl)phenyl-[6-O-(E)-coumaroyl]-beta-D-glucopyranoside (F1) were resolved by NMR and UPLC-qTOF-MS/MS. In addition, two other derivatives of phenylpropanoid glucosides similar to Eutigoside A but possessing different phenolic acid moieties, namely Grayanoside A ( F5) and 2-(4-hydroxyphenyl)ethyl-[6-O-(E)-caffeoyl]-beta-D-glucopyranoside (F14), were similarly identified. Also, accurate characteristic coupling constants for the subunits are reported and their usefulness in structural analysis is highlighted. Chemical analysis of the leaves of strawberry (Fragaria x ananassa cv. Jonsok) resulted in the identification of a compound class, phenylethanol derivatives of phenylpropanoid glycosides, not previously found in strawberry.

Hanhineva K ，Soininen P ，Anttonen MJ ，Kokko H ，Rogachev I ，Aharoni A ，Laatikainen R ，Kärenlampi S ... -  《-》

Polyphenols in strawberry (Fragaria × ananassa) leaves induced by plant activators.

Strawberry leaves contain high amounts of diverse phenolic compounds potentially possessing defensive activities against microbial pathogens and beneficial properties for human health. In this work, young strawberry plants were treated with two plant activators, S-methylbenzo-1,2,3-thaidiazole-7-carbothiate (BTH) and birch wood distillate. Phenolic compounds from activator-treated and control leaves were subjected to quantitative analyses by HPLC-DAD, HPLC-ESI-MS, and microQTOF ESI-MS. Thirty-two different phenolic compounds were detected and characterized, and 21 different ellagitannins constituted the largest group of compounds in the strawberry leaves (37.88-45.82 mg/g dry weight, 47.0-54.3% of total phenolics). Treatment with BTH resulted in higher levels of individual ellagitannins, whereas treatment with birch wood distillate strongly increased the levels of chlorogenic acid in strawberry leaves compared with the control. The results suggest that different plant activators may be useful tools for the activation of different branches in the phenylpropanoid biosynthesis in strawberry.

Kårlund A ，Salminen JP ，Koskinen P ，Ahern JR ，Karonen M ，Tiilikkala K ，Karjalainen RO ... -  《-》

Metabolic Response of Strawberry (Fragaria x ananassa) Leaves Exposed to the Angular Leaf Spot Bacterium (Xanthomonas fragariae).

Plants have evolved various defense mechanisms against biotic stress. The most common mechanism involves the production of metabolites that act as defense compounds. Bacterial angular leaf spot disease (Xanthomonas fragariae) of the strawberry (Fragaria x ananassa) has become increasingly destructive to strawberry leaves and plant production. In this study, we examined metabolic changes associated with the establishment of long-term bacterial disease stress using UPLC-QTOF mass spectrometry. Infected leaves showed decreased levels of gallic acid derivatives and ellagitannins, which are related to the plant defense system. The levels of phenylalanine, tryptophan, and salicylic acid as precursors of aromatic secondary metabolites were increased in inoculated leaves, whereas levels of coumaric acid, quinic acid, and flavonoids were decreased in infected plants, which are involved in the phenylpropanoid pathway. In addition, phenylalanine ammonia-lyase (PAL) activity, a key enzyme in the phenylpropanoid pathway, was decreased following infection. These results suggest that long-term bacterial disease stress may lead to down-regulation of select molecules of the phenylpropanoid metabolic pathway in strawberry leaves. This approach could be applied to explore the metabolic pathway associated with plant protection/breeding in strawberry leaves.

Kim MS ，Jin JS ，Kwak YS ，Hwang GS ... -  《-》

Chemometric Characterization of Strawberries and Blueberries according to Their Phenolic Profile: Combined Effect of Cultivar and Cultivation System.

Chemical characterizations of leaves and fruits that were obtained from organically and integrally produced strawberries ('Favette', 'Alba', and 'Clery') and blueberries ('Bluecrop', 'Duke', and 'Nui') from western Serbia were undertaken in this study. Phenolic analysis was done while using ultra-high performance liquid chromatography coupled to a linear ion trap-Orbitrap hybrid mass analyzer, while total phenolic content (TPC), total anthocyanin content (TAC), and radical-scavenging activity (RSA) by spectrophotometry. In general, leaves and fruits from blueberry showed higher levels of TPC and TAC as compared to strawberry. These chemical traits were larger in organic grown fruits and larger in leaves than fruits. The most abundant phenolics in leaves and fruits of blueberry was 5--caffeoylquinic acid, followed by quercetin 3--galactoside, while catechin, quercetin, and kaempferol 3--glucosid were dominant in the leaves and fruits of strawberry. , -Abscisic acid was detected in all fruit samples, but not in leaves. Blueberries (both fruits and leaves) were separated from strawberries, but only organic blueberry fruits were distinguished from integrated fruits, according to principal component analysis. Quercetin, kaempferol, 5--caffeoylquinic acid, ferulic acid, caffeic acid, catechin, -coumaric acid, and -hydroxybenzoic acid were the most influential phenolic compounds for the separation. Much higher contents of TPC, RSA, TAC, quercetin 3--galactoside, and quercetin were found in fruits and TPC, RSA, catechin, -hydroxybenzoicacid, -coumaricacid, and ferulic acid in leaves in all three blueberry cultivars and the strawberry cultivar 'Clery'. These phenolic compounds are good sources of antioxidant compounds with potentially high beneficial effects on human health.

Fotirić Akšić M ，Dabić Zagorac D ，Sredojević M ，Milivojević J ，Gašić U ，Meland M ，Natić M ... -  《MOLECULES》