Optimization of Three Extraction Methods and Their Effect on the Structure and Antioxidant Activity of Polysaccharides in Dendrobium huoshanense

Abstract

Dendrobium huoshanense is a famous edible and medicinal herb, and polysaccharides are the main bioactive component in it. In this study, response surface methodology (RSM) combined with a Box–Behnken design (BBD) was used to optimize the enzyme-assisted extraction (EAE), ultrasound–microwave–assisted extraction (UMAE), and hot water extraction (HWE) conditions and obtain the polysaccharides named DHP-E, DHP-UM, and DHP-H. The effects of different extraction methods on the physicochemical properties, structure characteristics, and bioactivity of polysaccharides were compared. The differential thermogravimetric curves indicated that DHP-E showed a broader temperature range during thermal degradation compared with DHP-UM and DHP-H. The SEM results showed that DHP-E displayed an irregular granular structure, but DHP-UM and DHP-H were sponge-like. The results of absolute molecular weight indicated that polysaccharides with higher molecular weight detected in DHP-H and DHP-UM did not appear in DHP-E due to enzymatic degradation. The monosaccharide composition showed that DHPs were all composed of Man, Glc, and Gal but with different proportions. Finally, the glycosidic bond types, which have a significant effect on bioactivity, were decoded with methylation analysis. The results showed that DHPs contained four glycosidic bond types, including Glcp-(1→, →4)-Manp-(1→, →4)-Glcp-(1→, and →4,6)-Manp-(1→ with different ratios. Furthermore, DHP-E exhibited better DPPH and ABTS radical scavenging activities. These findings could provide scientific foundations for selecting appropriate extraction methods to obtain desired bioactivities for applications in the pharmaceutical and functional food industries.

Isolation and Identification of Indole Alkaloids from Aspergillus amstelodami BSX001 and Optimization of Ultrasound-Assisted Extraction of Neoechinulin A

“…Especially at high solid-liquid ratios, the increasing trend of extraction yield became more pronounced with the increase in methanol volume fraction. The large inclination angle and steep slope of the response surface indicate a significant interaction between methanol volume fraction and solid-liquid ratio [31]. Similarly, the interaction of methanol volume fraction and soaking temperature had a significant effect on the extraction yield of neoechinulin A as can be seen in Figure 5b,e.…”

“…The values of R 2 and R 2 Adj were both close to 1, which suggested that the data had a high fit to the regression model [30]. The coefficient of variation (C.V.) was 2.38%, which was below the threshold of 10%, indicating that the model had strong experimental stability [31]. Therefore, the model can effectively analyze and predict the experimental results.…”