Drying is commonly used for preservation and processing of litchi. However, its polysaccharide structure may be altered by the drying process, resulting in biological activity changes. Polysaccharides from fresh and dried litchi pulp (denoted as LPF and LPD, respectively) were isolated, investigated by GC-MS, GPC and UV/IR spectrum analysis and their antitumor and immunomodulatory activities were evaluated in vitro. LPD, the molecular weight of which was lower than that of LPF, contained more protein, uronic acid, arabinose, galactose and xylose. Compared with LPF, LPD exhibited a higher inhibitory effect on the proliferation of HepG2, Hela and A549 cells from 50–750 μg/mL. LPD was also a better stimulator of spleen lymphocyte proliferation, NK cells cytotoxicity and macrophage phagocytosis from 50–400 μg/mL. In summary, drying could change the physicochemical properties and enhance the bioactivity of polysaccharides from litchi pulp. This finding is supported by the fact that dried litchi pulps are used in Traditional Chinese Medicine.

Three polysaccharide-protein complexes of longan pulp (LP1-3) were isolated in this work. Their physicochemical characteristics and immunomodulatory effects on splenocytes, natural killer (NK) cells and macrophages in vitro were investigated. The carbohydrate portions of LP1-3 were principally composed of glucose, arabinose and mannose. LP3 displayed the maximal moisture absorption, and the thermal stability of LP2 was obviously higher than that of LP1 and LP3. All of them showed the characteristic polysaccharide and protein bands in the Fourier Transform Infrared (FTIR) spectrum. For a certain dose, all the fractions could significantly stimulate splenocyte proliferation, macrophage phagocytosis against neutral red, and NK cell cytotoxicity against YAC-1 lymphoma cell (P < 0.05). The results demonstrated that the polysaccharide-protein complexes of longan pulp have medical potential as immunotherapeutic adjuvants due to their immunomodulatory activities.

Momordica charantia Linn. is used as an edible and medicinal vegetable in sub-tropical areas. Until now, studies on its composition and related activities have been confined to compounds of low molecular mass, and no data have been reported concerning the plant’s polysaccharides. In this work, a crude polysaccharide of M. charantia (MCP) fruit was isolated by hot water extraction and then purified using DEAE-52 cellulose anion-exchange chromatography to produce two main fractions MCP1 and MCP2. The immunomodulatory effects and physicochemical characteristics of these fractions were investigated in vitro and in vivo. The results showed that intragastric administration of 150 or 300 mg·kg⁻·d⁻¹ of MCP significantly increased the carbolic particle clearance index, serum haemolysin production, spleen index, thymus index and NK cell cytotoxicity to normal control levels in cyclophosphamide (Cy)-induced immunosuppressed mice. Both MCP1 and MCP2 effectively stimulated normal and concanavalin A-induced splenic lymphocyte proliferation in vitro at various doses. The average molecular weights of MCP1 and MCP2, which were measured using high-performance gel permeation chromatography, were 8.55 × 10⁴ Da and 4.41 × 10⁵ Da, respectively. Both fractions exhibited characteristic polysaccharide bands in their Fourier transform infrared spectrum. MCP1 is mainly composed of glucose and galactose, and MCP2 is mainly composed of glucose, mannose and galactose. The results indicate that MCP and its fractions have good potential as immunotherapeutic adjuvants.

The solution properties of four fractions (LPI–IV) from crude longan pulp polysaccharides (LP3) were analyzed by size-exclusion chromatography combined with laser light scattering, viscometry, complex formation with Congo red, and atomic force microscopy. Their radii of gyration (_z^1/2) were 43.3, 62.6, 43.2 and 77.3 nm, exponents of _z^1/2 = k M_w^v were 0.04, 0.50, 0.52 and 0.02, and intrinsic viscosities ([η]) were 9.945, 25.38, 308.2 and 452.1 mL/g, respectively. Moreover, the dependence of [η] on M_w was established to be [η] = 5.3 × 10⁻²M_w^0.61 (mL/g). LPI had both a sphere-like conformation and a triple-helix structure, and LPII–IV existed as flexible chains. LP3, LPI, LPII and LPIII all exhibited direct inhibitory effects on A549, HeLa and HepG2 cells in a positive dose-dependent manner in the range of 50–400 µg/mL. The activities of LPIII, especially the inhibition of HepG2 cell proliferation, were stronger than those of others, which may be partly related to its flexible conformation. The present results support the cancer therapeutic potential of longan polysaccharides.

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.