Abstract
BackgroundFlavonoids have shown to exert multiple beneficial effects on human health, being also appreciated by both food and pharmaceutical industries. Citrus fruits are a key source of flavonoids, thus promoting studies to obtain them. Characteristics of these studies are the discrepancies among sample pretreatments and among extraction methods, and also the scant number of comparative studies developed so far.ObjectiveEvaluate the effect of both the sample pretreatment and the extraction method on the profile of flavonoids isolated from lemon.ResultsExtracts from fresh, lyophilized and air-dried samples obtained by shaking extraction (SE), ultrasound-assisted extraction (USAE), microwave-assisted extraction (MAE) and superheated liquid extraction (SHLE) were analyzed by LC–QTOF MS/MS, and 32 flavonoids were tentatively identified using MS/MS information. ANOVA applied to the data from fresh and dehydrated samples and from extraction by the different methods revealed that 26 and 32 flavonoids, respectively, were significant (p≤0.01). The pairwise comparison (Tukey HSD; p≤0.01) showed that lyophilized samples are more different from fresh samples than from air-dried samples; also, principal component analysis (PCA) showed a clear discrimination among sample pretreatment strategies and suggested that such differences are mainly created by the abundance of major flavonoids. On the other hand, pairwise comparison of extraction methods revealed that USAE and MAE provided quite similar extracts, being SHLE extracts different from the other two. In this case, PCA showed a clear discrimination among extraction methods, and their position in the scores plot suggests a lower abundance of flavonoids in the extracts from SHLE. In the two PCA the loadings plots revealed a trend to forming groups according to flavonoid aglycones.ConclusionsThe present study shows clear discrimination caused by both sample pretreatments and extraction methods. Under the studied conditions, liophilization provides extracts with higher amounts of flavonoids, and USAE is the best method for isolation of these compounds, followed by MAE and SE. On the contrary, the SHLE method was the less favorable to extract flavonoids from citrus owing to degradation.
Highlights
Flavonoids are compounds widely distributed in plants, giving place to beverages obtained from them rich in these compounds
Extracts from fresh, lyophilized and air-dried samples obtained by shaking extraction (SE), ultrasound-assisted extraction (USAE), microwave-assisted extraction (MAE) and superheated liquid extraction (SHLE) were analyzed by liquid chromatography (LC)–quadrupole–time of flight detector (QTOF) mass spectrometry (MS)/MS, and 32 flavonoids were tentatively identified using MS/MS information
The pairwise comparison (Tukey HSD; p0.01) showed that lyophilized samples are more different from fresh samples than from air-dried samples; principal component analysis (PCA) showed a clear discrimination among sample pretreatment strategies and suggested that such differences are mainly created by the abundance of major flavonoids
Summary
Flavonoids have shown to exert multiple beneficial effects on human health, being appreciated by both food and pharmaceutical industries. Citrus fruits are a key source of flavonoids, promoting studies to obtain them. Characteristics of these studies are the discrepancies among sample pretreatments and among extraction methods, and the scant number of comparative studies developed so far
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