Chemical Characterization Analysis, Antioxidants, and Anti-Diabetic Activity of Two Novel Acidic Water-Soluble Polysaccharides Isolated from Baobab Fruits

Abstract

This study explores the isolation and characterization of two acidic polysaccharides from baobab (Adansonia digitata) fruits, named ADPs40-F3 and ADPs60-F3; the two types of acidic polysaccharides exhibited high sugar content and chemical structural features characterized by O–H, C–H, carbonyl C=O, and COOH carboxyl functional groups. The two fractions showed molecular weights of 1.66 × 105 and 9.59 × 104 Da. ADPs40-F3 residues consist of arabinose (2.80%), galactose (0.91%), glucose (3.60%), xylose (34.70%), and galacturonic acid (58.10%). On the other hand, ADPs60-F3 is composed of rhamnose (1.50%), arabinose (5.50%), galactose (2.50%), glucose (3.10%), xylose (26.00%), and galacturonic acid (61.40%). Furthermore, NMR analysis showed that the main acidic structures of ADPs40-F3 and ADPs60-F3 are formed by 4,6)-α-d-GalpA-(1→, →4)-β-d-Xylf-(1→, →4,6)-β-d-Glcp-(1→, →5)-α-L-Araf-(1→, →4,6)-α-d-Galp-(1→ residues and 4)-α-d-GalpA-(1→, →4)-β-d-Xylf-(1→, →6)-β-d-Glcp-(1→, →5)-α-l-Araf-(1→ 4,6)-α-d-Galp-(4,6→, →2)-α-Rhap- residues, respectively, based on the observed signals. Antioxidant assays against DPPH, ABTS+, and FRAP revealed significant antioxidant activities for ADPs40-F3 and ADPs60-F3, comparable to ascorbic acid (VC). Additionally, both polysaccharides exhibited a dose-dependent inhibition of α-glucosidase and α-amylase activities, suggesting potential anti-diabetic properties. In vivo evaluation demonstrated that ADPs60-F3 significantly reduced blood glucose levels, indicating promising therapeutic effects. These findings underscore the potential utility of baobab fruit polysaccharides as natural antioxidants and anti-diabetic agents.