3.1.4. Other Bioactivities Attribute to Seaweed Lipids

Complex lipids from seaweeds have showed a broad spectrum of bioactivates (Table 4), including antioxidant activity associated with GL and PL groups from the red seaweed *Solieria chordalis* and the brown seaweed *Sargassum muticum*, and evidenced through in vitro free radical scavenging activity [86]. However, the study did not characterize the compounds in the isolated fractions, which raises doubts about their purity and possible interference of other compounds.

Fractionated lipid classes, such as MGDG, were suggested to play an important role in the design of optimized nanoparticulate tubular immune-stimulating complexes. Sanina et al. (2021) found different degrees of effectiveness on anti-porin response, porin conformation, and cytokine profile of MGDG from different phyla with different FA composition [87].

A study that bio-prospected and isolated bioactive molecular species from the green seaweed *Capsosiphon fulvescens* highlighted two GL species: (2S)-l-*O*-(6Z,9Z,12Z,15Zoctadecatetraenoyl)-2-*O*-(4Z,10Z,13Z-hexadecatetraenoyl)-3-O-*β-*D-galactopyranosylglycerol and (2S)-l-*O*-(9Z,12Z,15Z-octadecatrienoyl)-2-*O*-(10Z,13Z-hexadecadienoyl)-3-*O*-*β-*D-galactopyranosylglycerol (designated by capsofulvesin A and B, respectively) (Figure 11A) that showed capacity to inhibit rat lens aldose reductase (RLAR), thus showing potential for application as anti-diabetic agents [88]. The inhibitory effect on lipid accumulation of (2S)- 1-*O*-myristoyl-2-*O*-linoleyl-3-*O*-*β*-D-galactopyranosyl-*sn*-glycerol MGDG (14:0/18:2) and (2S)-1-*O*-palmitoyl-2-*O*-linoleyl-3-*O*-*β*-D-galactopyranosyl-*sn*-glycerol MGDG (16:0/18:2) glycolipids species (Figure 11B) from the brown seaweed *Sargassum horneri* was also reported in 3T3-L1 adipocytes [89]. These two MGDG species have in common the presence of linoleic acid (LA) (18:2 *n*-6) on *sn*-2 FA chain position, and when compared to other isolated MGDG species they were the most effective. Thus, this study suggested that LA on the *sn-2* position of MGDG species played an important role on the inhibition of triglyceride accumulation in this biological model.

**Figure 11.** Chemical structures of bioactive complex lipids reported with anti-diabetic and anti-obesity activities. (**A**) (2S)-l-*O*-(6Z,9Z,12Z,15Z-octadecatetraenoyl)-2-*O*-(4Z,10Z,13Z-hexadecatetraenoyl)-3-*O*-β-D-galactopyranosylglycerol and (2S)-l-*O*-(9Z,12Z,15Z-octadecatrienoyl)-2-*O*-(10Z,13Z-hexadecadienoyl)- 3-*O*-β-D-galactopyranosylglycerol capsofulvesin A and B (green seaweed *Capsosiphon fulvescens*); (**B**) (2S)- 1-*O*-myristoyl-2-*O*-linoleyl-3-*O*-β-D-galactopyranosyl-*sn*-glycerol MGDG(14:0/18:2) (1) and (2S)-1-*O*palmitoyl-2-*O*-linoleyl-3-*O*-β-D-galactopyranosyl-*sn*-glycerol MGDG(16:0/18:2) (2) (brown seaweed *Sargassum horneri*).

A human sperm motility stimulating activity was achieved by an isolated sulfonoglycolipid (named by S-ACT-1) from the red seaweed *Gelidiella acerosa*, whose molecular structure was not evidenced [90]


