Abstract
Enzyme-assisted extraction (EAE) and ultrasound-assisted extraction (UAE) were popular methods used to extract bioactive compounds from citrus peels, by-products of fruit processing industry. In this study, the total phenolic content (TPC), total flavonoid content (TFC), naringin and hesperidin contents, and antioxidant and antimicrobial activities of the extracts from pomelo peels using the combined enzyme and ultrasound-assisted extraction (E-UAE) or ultrasound and enzyme-assisted extraction (U-EAE) technique were investigated and compared with those extracted using the EAE and UAE. The optimal EAE conditions were as follows: enzyme concentration of 2%, water-solid ratio of 40 ml/g, incubation temperature of 50°C, and extraction time of 60 min, whereas the optimal UAE conditions were ultrasonic energy of 40 kHz, water-solid ratio of 40 ml/g at room temperature, and extraction time of 60 min. The results indicate that the total phenolics, total flavonoids, naringin, and hesperidin contents of the extracts significantly increased in the following order of the extraction techniques: UAE < EAE < U-EAE < E-UAE (p<0.05). The combined E-UAE technique was the most effective technique for bioactive compound extraction with the highest antioxidant and antimicrobial activities. The results also indicate that chemical composition and antioxidant and antimicrobial activities of the extracts were different depending on the pomelo species.
Highlights
Flavonoids, a group of pigments including flavones, flavanones, flavonols, isoflavones, anthocyanidins, and flavanols, are present in dietary fruits and vegetables and responsible for flower and fruit coloration [1]
The ultrasound-assisted and enzyme-assisted extraction methods have been widely used for extracting bioactive compounds because they are considered as the innovation Journal of Chemistry green extraction technology without using toxic solvents [10]. e enzyme-assisted extraction (EAE) techniques have been shown to improve the extraction efficiencies of antioxidant compounds including phenolics, flavonoids, anthocyanins, and carotenoids and preserve their functional properties because plant cell walls are degraded and broken down by enzymes to release bioactive compounds [11]
Effect of Enzyme Concentration on Recovery of Flavonoid Content of Extract. e yields of total flavonoids extracted from pomelo peels under enzymatic treatment at different enzyme concentrations (0, 1, 2, 3, and 4%, v/w) are given in Figure 1. e total flavonoid content (TFC) increased with increasing enzyme concentration from 1 to 2% (v/w), and the TFC of the extracts with enzymatic treatments was significantly higher than that of the control without any treatment
Summary
Flavonoids, a group of pigments including flavones, flavanones, flavonols, isoflavones, anthocyanidins, and flavanols (or catechins), are present in dietary fruits and vegetables and responsible for flower and fruit coloration [1]. Flavonoids are well known for their health benefits such as antioxidative, anti-inflammatory, antimutagenic, and anticarcinogenic properties [1, 2]. Pomelo (Citrus maxima), a member of the citrus family, is a native plant in tropical and semitropical countries including Vietnam. A by-product of fruit processing, is a rich source of flavonoids [4, 5], which have anti-inflammatory and anticancer characteristics and play important roles in the prevention of cardiovascular disease, diabetes, and other diseases [6]. Erefore, pomelo peels could be inexpensively and readily available resources of bioactive compounds for application in the food and pharmaceutical industries [7]. E flavonoids found in pomelo almost are flavanones [4, 5]. The ultrasound-assisted and enzyme-assisted extraction methods have been widely used for extracting bioactive compounds because they are considered as the innovation
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