Abstract
Dried litchi pulp has been used in traditional remedies in China for many years to treat various diseases, and the therapeutic activity has been, at least partly, attributed to the presence of bioactive polysaccharides. Polysaccharide-protein complexes from vacuum freeze-(VF), vacuum microwave-(VM) and heat pump (HP) dried litchi pulp, which were coded as LP-VF, LP-VM and LP-HP, were comparatively studied on the physicochemical and immunomodulatory properties. LP-HP had a predominance of galactose, while glucose was the major sugar component in LP-VF and LP-VM. Compared with LP-VF and LP-VM, LP-HP contained more aspartate and glutamic in binding protein. LP-HP also exhibited a stronger stimulatory effect on splenocyte proliferation at 200 μg/mL and triggered higher NO, TNF-α and IL-6 secretion from RAW264.7 macrophages. Different drying methods caused the difference in physicochemical properties of polysaccharide-protein complexes from dried litchi pulp, which resulted in significantly different immunomodulatory activity. HP drying appears to be the best method for preparing litchi pulp to improve its immunomodulatory properties.
Highlights
Litchi (Litchi chinensis Sonn.), a fruit originating from China, is planted widely in subtropical areas worldwide
The final yields of litchi polysaccharides from vacuum freeze, vacuum microwave and heat pump dried litchi pulp, which were coded as LP-VF, LP-VM and LP-HP, were 3.51%, 3.28% and 3.43%, respectively
Our results showed that the three drying methods used in this study—vacuum freeze, vacuum microwave and heat pump dying—resulted in polysaccharides with similar molecular weight distribution in the dried litchi pulp
Summary
Litchi (Litchi chinensis Sonn.), a fruit originating from China, is planted widely in subtropical areas worldwide. It is well known that different drying processes have different effects on the physico-chemical properties of materials, as well as the functional properties of their active ingredients because of the distinction of temperature, drying time and other conditions These parameters have been reported to affect the structure and biological activity of the polysaccharides [14]. Fan et al [16] reported that the VF drying process led to higher scavenging radical activity and stronger reducing power in Ganoderma lucidum polysaccharides than hot air drying Together, these studies showed that the methods used for extracted polysaccharide drying affected the properties of polysaccharides, but little is known about how drying raw materials affects the structure and biological activity of the polysaccharides. (2) compare the in vitro immunomodulatory activity of the samples to probe the relationship between structure and immunomodulatory activity of the polysaccharides
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