Chemical characterization, antioxidant activity and toxicity of sugars present in Annona cornifolia (Annonaceae) seeds

Annona cornifolia, popularly known as “araticum das caatingas” and “araticum mirim,” is native to the Brazilian Cerrado and used to treat chronic ulcers. Seeds of this species were investigated by our group, yielding annonaceous acetogenins that displayed several biological activities, such as larvicidal, cytotoxic, and antioxidant properties. This work aimed to characterize two mixtures of sugars obtained from seeds using ¹H and ¹³C NMR and evaluate their antioxidant and Artemia salina larvicidal activities. The hydromethanolic fraction from the ethanolic extract after solvent partition was fractionated on a silica gel preparative plate and on a Sephadex LH-20 column, yielding a brown solid. Another part of this fraction was acetylated with pyridine and acetic anhydride, and the resultant material was fractionated on a silica gel column, yielding other solids. Two solids were characterized as mixtures of sugars, identified as β-d-fructopyranose, β-d-fructofuranose, 1,2,3,4,6-O-acetyl-α-d-glucopyranose, 1,2,3,4,6-O-acetyl-β-d-glucopyranose, 1,2,3,4,6-O-acetyl-α-d-fructofuranose, and 1,2,3,4,6-O-acetyl-β-d-fructofuranose. The samples showed antioxidant potential in DPPH and FRAP assays. The mixture of acetylated sugars exhibited high toxicity on A. salina at all concentrations tested, with an LC₅₀ value of 0.311 µg/mL. This is the first report of the characterization of these sugars with these biological activities for this species.