α-Glucan rich polysaccharide fraction obtained from rhizomes of Kaempferia parviflora (black ginger) exhibits immunostimulatory activity in RAW264.7 cells

Abstract

This study investigated the structural characteristics and immunostimulatory activities of polysaccharides, primarily composed of α-glucan, isolated from the rhizomes of Kaempferia parviflora (black ginger), with a focus on F2 using RAW264.7 cells. The extracted and purified polysaccharides yielded two fractions, F1 and F2. The primary components of these fractions included carbohydrates (84.47 ± 4.33 and 45.69 ± 2.26%), protein (2.72 ± 0.21% and 29.14 ± 0.60%), and sulfates (8.89 ± 0.23 and 23.47 ± 1.72%), with glucose being the dominant monosaccharide (98.7 ± 0.38 and 77.5 ± 0.28%), followed by arabinose (0.5 ± 0.02 and 9.8 ± 0.44%) and galactose (0.2 ± 0.01 and 7.6 ± 0.25%), along with minor amounts of rhamnose, xylose, and mannose. F2 is rich in α-glucans with a predominant →4)-Glc-(1 → linkage, typical of unbranched glucan chains. It has a highly branched structure with (1 →)-, (1 → 4), (1 → 2), (1 → 6), (1 → 2,3), and (1 → 3)-linked glucopyranose residues, arabinose, galactose, and rhamnose linkages. The F2 fraction significantly increased NO production and upregulated macrophage surface receptor expression, thereby activating the NF-κB and MAPK signaling pathways. The study confirms that the immunostimulatory activity observed in K. parviflora rhizomes is primarily due to the polysaccharide component, suggesting its potential as a natural immunotherapeutic agent.