Abstract
PAP80-2a, purified from Pholiota adiposa mycelia, is a polysaccharide exhibiting prominent antitumor effects. However, the yield of PAP80-2a was low and its structure has not been characterized, impeding the exploration of its structure-function relationship, thus influencing the development of oral drugs for antitumor therapy and immunomodulation. In order to improve the yield of PAP80-2a, response surface methodology along with Box-Behnken design was applied to optimize the ultrasonic-assisted extraction conditions for polysaccharides. Then, the structure of PAP80-2a exhibiting antitumor activity was determined from different angles. The results showed that the extraction yield of P. adiposa polysaccharides increased by 11.5% under optimized ultrasonic extraction conditions. Structural analysis showed that PAP80-2a was mainly composed of glucose, rhamnose, xylose, and galactose in a ratio of 10.00: 2.09: 4.09: 1.13. The total amino acid content in the sugar chain was 69.92 μg/mL. The sugar chain structure was [α-Rha (1 → 3)-]n, and rhamnose was located at the non-reducing end of the sugar chain, while glucose was located at the non-reducing end or in the sugar chain in 1,2,6- and 1,3,6-linked forms. Our study clearly illuminates the primary structure of PAP80-2a, but 3D structure of PAP80-2a and its structure–function relationship is a future challenge.
Highlights
Pholiota adiposa, a fungus that grows from August to October on the dead timber pile of poplars and willows or dead birches, is an edible and medicinal mushroom distributed in China, Korea, Japan, Europe, and North America
The structural characterizations of PAP80-2a were elucidated by high-performance anion-exchange chromatography with pulsed-amperometric detection (HPAEC-PAD), fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometer (GC-MS), which could lay the foundation for the development of oral drugs containing this ingredient
A temperature range from 85 to 95 °C was used in the response surface methodology (RSM) experiment to optimize extraction conditions (Supplementary Fig. 1S-A)
Summary
A fungus that grows from August to October on the dead timber pile of poplars and willows or dead birches, is an edible and medicinal mushroom distributed in China, Korea, Japan, Europe, and North America. The medicinally beneficial functions of P. adiposa are well known worldwide, including antitumor, antimicrobial, antifatigue, antihypertensive, free radical scavenging, and antihyperlipidemic activities. These medicinal functions are attributing to bioactive polysaccharides, amino acids, and ergosterol in the fruiting bodies or mycelia[2,3,4]. RSM is widely used for optimizing extraction process variables of bioactive compounds, such as polysaccharides[11], gelatins[12], and polyphenols[13] This technique can identify the interaction between different variables by establishing the appropriate mathematical model. For the first time, an attempt was made to investigate and optimize the ultrasonic-assisted conditions of polysaccharide from P. adiposa mycelia in order to enhance the extraction yield of PAP80-2a. The structural characterizations of PAP80-2a were elucidated by high-performance anion-exchange chromatography with pulsed-amperometric detection (HPAEC-PAD), fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometer (GC-MS), which could lay the foundation for the development of oral drugs containing this ingredient
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