*Article* **Immunostimulatory E** ff**ect of Sulfated Galactans from the Green Seaweed** *Caulerpa cupressoides* **var.** *flabellata*

**Je** ff**erson da Silva Barbosa 1,2,3, Diego Araújo Sabry 1, Cynthia Haynara Ferreira Silva 1, Dayanne Lopes Gomes 4, Arquimedes Paixão Santana-Filho 5, Guilherme Lanzi Sassaki 5 and Hugo Alexandre Oliveira Rocha 1,2,\***


Received: 15 March 2020; Accepted: 31 March 2020; Published: 29 April 2020

**Abstract:** Sulfated polysaccharides (SPs) obtained from green seaweeds are structurally heterogeneous molecules with multifunctional bioactivities. In this work, two sulfated and pyruvated galactans were purified from *Caulerpa cupressoides* var. *flabellata* (named SP1 and SP2), and their immunostimulatory effect was evaluated using culturedmurinemacrophage cells. Both SPs equallyincreased the production of nitric oxide, reactive oxygen species, and the proinflammatory cytokines TNFα and IL-6. NMR spectroscopy revealed that both galactans were composed primarily of 3)-β-<sup>d</sup>-Galp-(1 →3) units. Pyruvate groups were also found, forming five-membered cyclic ketals as 4,6- *O*-(1'carboxy)-ethylidene-β-<sup>d</sup>-Galp residues. Some galactoses are sulfated at C-2. In addition, only SP2 showed some galactose units sulfated at C-4, indicating that sulfation at this position is not essential for the immunomodulatory activity of these galactans. Overall, the data showed that the galactans of *C. cupressoides* exhibited immunostimulating activity with potential therapeutic applications, which can be used in the development of new biomedical products.

**Keywords:** sulfated polysaccharides; galactans; green seaweed; NMR; immunostimulation; inflammatory mediators
