Abstract
Stems are the important residues of Trapa quadrispinosa Roxb., which are abundant in phenolic compounds. Ultrasonic-assisted enzymatic extraction (UAEE) is confirmed as a novel extraction technology with main advantages of enhancing extraction yield and physiological activities of the extracts from various plants. In this study, UAEE was applied to obtain the highest yield of phenolic content, strongest antioxidant, and antitumor activities and to optimize the extraction conditions using response surface methodology (RSM). The extracts from the stems of T. quadrispinosa were characterized by determination of their antioxidant activities through 2,2-azinobis(3-ethylbenzthiazoline)-6-sulfonic acid (ABTS), 1,1-Diphenyl-2-picrylhydrazxyl (DPPH) radical scavenging, total antioxidant capacity (TAC), ferric reducing antioxidant capacity (FRAC) methods and of their antitumor activity by MTT method. The selected key independent variables were cellulase concentration (X1: 1.5%–2.5%), extraction time (X2: 20–30 min) and extraction temperature (X3: 40–60 °C). The optimal extraction conditions for total phenolic content (TPC) value of the extracts were determined as 1.74% cellulase concentration, 25.5 min ultrasonic extraction time and 49.0 °C ultrasonic temperature. Under these conditions, the highest TPC value of 53.6 ± 2.2 mg Gallic acid equivalent (GAE)/g dry weight (DW) was obtained, which agreed well with the predicted value (52.596 mg GAE/g·DW. Furthermore, the extracts obtained from UAEE presented highest antioxidant activities through ABTS, DPPH, TAC and FRAC methods were of 1.54 ± 0.09 mmol Trolox equivalent (TE)/g·DW; 1.45 ± 0.07 mmol·TE/g·DW; 45.2 ± 2.2 mg·GAE/g·DW; 50.4 ± 2.6 μmol FeSO4 equivalent/g·DW and lowest IC50 values of 160.4 ± 11.6 μg/mL, 126.1 ± 10.8 μg/mL, and 178.3 ± 13.1 μg/mL against Hela, HepG-2 and U251 tumor cells, respectively. The results indicated that the UAEE was an efficient alternative to improve extraction yield and enhance the antioxidant and antitumor activities of the extracts. The phenolic extracts from the stems of T. quadrispinosa had significant antioxidant and antitumor activities, which could be used as a source of potential antioxidant and antitumor agents.
Highlights
Phenolic compounds, one of the most important secondary metabolites, are greatly distributed in all parts of higher plants [1]
The results indicated that the ultrasonic-assisted enzymatic extraction (UAEE) was an efficient alternative to improve extraction yield and enhance the antioxidant and antitumor activities of the extracts
With UAEE, the enzyme andrelease destruction of the cell-wall matrix have been considered considered as a primary stepdegradation to enhance the of phenolic compounds, keep their stability and as a primary step to enhance the release of phenolic compounds, keep their stability and antioxidant antioxidant activities [29]
Summary
One of the most important secondary metabolites, are greatly distributed in all parts of higher plants [1]. Natural antioxidant phenolic compounds obtained from edible byproducts or residual sources have become interesting because they could be recycled and developed into new medicinal resources [7,8,9,10]. The main drawback of these methods are the loss of phenolic compounds and their bioactivities due to oxidation, ionization and hydrolysis caused by long extraction time and high extraction temperature during extraction process [11,12] In this context, other innovative extraction techniques, including ultrasonic assisted extraction (UAE), microwave assisted extraction (MAE), enzymatic assisted extraction (EAE) and pressurized assisted extraction (PAE), have been developed [13,14,15,16]. EAE coupled with ultrasound irradiation may be an effective method for target compounds extraction and many positive results for ultrasonic-assisted enzymatic extraction of target compounds have been reported [20,21,22]
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