Antioxidant and immune modulatory activities of polysaccharides fractions isolated from Khaya grandifoliola stem bark and Cryptolepis sanguinolenta leaves were analyzed. Water-soluble total polysaccharides (TP) were extracted and precipitated in alcohol. Pectic (PF) and hemicellulosic fractions (HF) of cell walls were obtained using ammonium oxalate and potassium hydroxide. TP of K. grandifoliola and C. sanguinolenta pectins are mostly linked to proteins (86.39 ± 1.13 and 67.66 ±2.05 μg eqBSA/mg DW). Polysaccharide fractions of C. sanguinolenta are rich in phenolic compounds. Gas chromatography analyses showed that TP of C. sanguinolenta is an arabinoglucan type, consisting mainly of glucose (60.51%) and arabinose (10.36%), while TP of K. grandifoliola is constituted of glucose (30.53%), galactose (28.89%), arabinose (17.57%) and rhamnose (10.74%). Pectic fractions of the two plants would be a rhamnogalacturonan type constituted of galacturonic acid, rhamnose and arabinose; while HF fractions might be xyloglucan as they were mainly constituted of glucose, xylose and arabinose. The polysaccharide fractions (50 to 300 µg/mL) exhibited antioxidant activity on both DPPH and ABTS radicals, with TP showing the highest activities. Polysaccharides were assessed to be non-toxics at 200 µg/mL to Peripheral Blood Mononuclear Cells (PBMCs) and strongly inhibited MSP1 (Malaria antigen)-induced overproduction of IL-1β, IL-6 and TNF-α by PBMCs in the in vitro immunological assays.

Keywords: Khaya grandifoliola, Cryptolepis sanguinolenta, polysaccharides, antioxidants, immunomodulatory activities.