Separation and characterization of high- and low-molecular-weight polysaccharides from Caulerpa lentillifera

Caulerpa lentillifera is a rich source of sulfated polysaccharides with potential applications in nutraceuticals, pharmaceuticals, and cosmeceuticals. However, limited information is available on low-molecular-weight polysaccharides (LMWPs) and the secondary metabolites bound to or associated with polysaccharides. This study aimed to separate high-molecular-weight polysaccharides (HMWPs) and LMWPs using 0.2 µm and 10 kDa membranes to yield retentate (R0.2) and R10 extracts, respectively. Furthermore, secondary metabolites in the R10 extract were analyzed using liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS/MS). The R0.2 extract (HMWP) contained high levels of total sugars (69.28 % of extract weight) and sulfates (13.49 %) as the major functional groups, whereas the R10 extract (LMWP) contained high levels of uronic acid (6.04 %) and phenolic compounds (11.52 mg gallic acid equivalent (GAE)/g extract). Fractionation using diethylaminoethyl (DEAE)-Sepharose fast flow and Sepharose 6B gel filtration columns revealed six HMWP fractions in the R0.2 extract, with molecular weights (MWs) of 1770, 2421, 1657, 1293, 1180, and 1187 kDa. In contrast, the five LMWP fractions in the R10 extract exhibited MWs of 8.6, 15.7, 37.9, 44.3, and 16.9 kDa. LC-ESI-QTOF-MS/MS analysis of the R10 extract identified several antioxidant compounds, including quercetagetin (m/z 319.2872 [M+H]⁺) and quercetin (m/z 301.0362 [M–H]^–), which contributed to its potent antioxidant activity. These findings highlight the potential of the R10 extract for health promotion and disease prevention.