Abstract
Subcritical water extraction (SWE) of Inonotus Obliquus polysaccharides (IOP) was investigated using response surface methodology (RSM) with a design by Box–Behnken design (BBD). Results showed that the optimum SWE conditions for IOP production were as follows: extraction temperature 194°C, residence time 5.36 min and liquid-solid ratio 53 mL/g, yielding 168.80 ± 0.59 mg/g of IOP, which was in close agreement with the values predicted by the mathematical model. FT-IR spectra of the polysaccharides extracted by SWE and hot water extraction (HWE) were compared as well. Moreover, in vitro antioxidant assays revealed that SWE-IOP exhibited stronger scavenging activity that HWE-IOP. This investigation suggests that polysaccharides of Inonotus Obliquus extracted by SWE could be further developed as a potential antioxidant resource for dietary supplements of functional food.
Highlights
Nowadays, the interest in natural antioxidants considered as functional ingredients for pharmaceuticals, functional foods, dietary supplements, animal feed, cosmetics and other products, is getting momentum due to the generalizability of their action in various redox systems and broad spectra of possible applications (Augustyniak et al, 2010)
Targets compounds tied on the sample matrices by means of physical adsorption and chemical interactions were released into extraction solvents (Qi et al, 2015) and even modify the characteristics of solvent like decreasing the viscosity and increasing the diffusion, which all make great contributions to the mass transportation of targeted ingredients
The polysaccharide yield decreased sharply, indicating that excessive temperature may lead to degradation and decomposition of polysaccharides induced by browning reaction, whose chemical products are not detected in a phenol–sulphuric assay and, decrease the concentration of Inonotus Obliquus polysaccharides (IOP) yield (Xu et al, 2016)
Summary
The interest in natural antioxidants considered as functional ingredients for pharmaceuticals, functional foods, dietary supplements, animal feed, cosmetics and other products, is getting momentum due to the generalizability of their action in various redox systems and broad spectra of possible applications (Augustyniak et al, 2010). Subcritical water extraction (SWE, called hot-compressed water or hydrothermal extraction) has been applied in the isolation of valuable components, especially polysaccharides from plants. The water polarity affected by dielectric constant decreases as the temperature increase, which makes it possible to selectively extract polar, bipolar, and nonpolar substances (Anekpankul, Goto, Sasaki, Pavasant, & Shotipruk, 2007). Ionization constant of the subcritical water substantially increases with temperature, catalyzing chemical reactions such as hydrolysis and degradation without any additional catalyst (Öztürk, Irmak, Hesenov, & Erbatur, 2010). SWE has been attracted considerable attention due to its temperature-dependent selectivity, environmentally friendly nature, highefficiency, and low-cost, compared with the conventional methods (Chao et al, 2013)
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