Ulvan is a complex, water soluble sulfated anionic polysaccharide obtained from cell wall complex of green algae, members of Ulvales (Chlorophyta) (Toskas et al., 2011). The name ulvan is derived from the original terms ulvin and ulvacin and usually extracted by the process of hydrolysis at around 80-90 °C using divalent cation chelator such as ammonium oxalate (Lahaye and Robic, 2007).
Generally, ulvan extracted from following species such as Ulva pertusa, Ulva lactuca, Ulva clathrata, Ulva compressa, Ulva conglobata, and Enteromorpha prolifera (Majee et al., 2018). Ulvan is typically composed of ?- and ?-(1?4)-linked sugar residues, namely of ?-1,4- and ?-1,2,4-linked L-rhamnose 3-sulphate, with branching at O-2 of rhamnose, ?-1,4- and terminally connected D-glucuronic acid and ?-1,4-linked D-xylose, partially sulphated on O-2. The major structural units found in ulvan include ?-D-glucuronosyluronic acid- (1,4)-L-rhamnose 3-sulphate dimer (?-D-GlcpA-(1?4)-LRhap 3-sulphate) and ?-L-IdopA-(1?4)-?-L-Rhap 3-sulphate, also known as ulvanobiuronic acid A and B, respectively. The main difference between these aldobiuronic acids is the presence of glucuronic acid in A, which is replaced by iduronic acid in B (Lahaye 1998; Quemener et al.
1997; Alves et al., 2013).