Antioxidant, antiproliferative, and immunostimulatory effects of cell wall α-d-mannan fractions from Kluyveromyces marxianus

This study evaluated the antioxidant, antiproliferative, and immunostimulatory properties of cell wall α-d-mannan fractions from yeast Kluyveromyces marxianus CCT7735. Filter centrifugation was used to obtain four fractions (KMM-1, KMM-2, KMM-3, and KMM-4) with molecular weight ranging from 7.6 to 75.1 kDa. KMM-1 and KMM-2 comprised D-mannose with traces of D-glucose, whereas other fractions contained only D-mannose. Total sugar found in samples ranged from 85.9% to 96.1%, while protein and phenolic contents were 1.21% and 0.41%, respectively. Although only KMM-1 was able to scavenge superoxide radicals, all fractions presented total antioxidant capacity as well as reducing power, hydroxyl-radical scavenging, and copper- and iron-chelating activities. No fraction was cytotoxic to HeLa cells. However, all samples inhibited the proliferation of the tumor cell Hep-G2 and presented minor cytotoxicity against normal 3T3 cells. All fractions showed mitogenic activity in macrophages and all, except KMM-4, induced nitric oxide production in macrophages, suggestive of their immunostimulatory effects.