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

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 x 105 and 9.59 x 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)-alpha-d-GalpA-(1 ->, -> 4)-beta-d-Xylf-(1 ->, -> 4,6)-beta-d-Glcp-(1 ->, -> 5)-alpha-L-Araf-(1 ->, -> 4,6)-alpha-d-Galp-(1 -> residues and 4)-alpha-d-GalpA-(1 ->, -> 4)-beta-d-Xylf-(1 ->, -> 6)-beta-d-Glcp-(1 ->, -> 5)-alpha-l-Araf-(1 -> 4,6)-alpha-d-Galp-(4,6 ->, -> 2)-alpha-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 alpha-glucosidase and alpha-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.