# Pharmacological and Cosmeceutical Potential of Seaweed Beach-Casts of Macaronesia
## 3 Results and Discussion
### Antigaging Activity
#### 3.4.3 Inhibition of ECM and Skin-Degrading Enzymes  
The tested samples presented little to no inhibition against hyaluronidase (percentage of inhibition between 19.00 \(\pm\) 1.08 and 25.06 \(\pm\) 2.65 at 250 \(\upmu\)g/mL), therefore this enzyme is not a good target for the ethanol and methanol extracts analyzed. There are several examples of macroalgal extracts which inhibit hyaluronidase, namely the work of [PERSON] et al. [68] with Phaeophyceae _Padina pavonica_, although these authors used supercritical fluid extraction (SFE) and also pressurized liquid extraction (PLE), obtaining IC\({}_{50}\) value of 35.1 \(\upmu\)g/mL. SFE maximizes the extraction yield, and the use of water greatly increases the extraction of sulfated polysaccharides, which are known for their hyaluronidase inhibition capability [69]. Seaweed compounds presented also hyaluronidase inhibition, such as the phlorotannin 8,8\({}^{\prime}\)-bieckol from _Eisenia bicyclis_ brown alga, (IC\({}_{50}\) of 30 \(\upmu\)g/mL)[70]. Tyrosinase Inhibition  
Of the 30 extracts assayed, 14 samples inhibited the tyrosinase enzyme by 50% or more at the highest concentration tested (250 \(\upmu\)g/mL), including eight (\(\sim\)1/4 of the extracts tested), which inhibited tyrosinase by at least 90% at same concentration. The IC\({}_{50}\) values were calculated for these 14 active extracts (Figure 7 and Table S4, Supplementary Material). The IC\({}_{50}\) values obtained range from 15.18 \(\upmu\)g/mL to 239.31 \(\upmu\)g/mL, the three most active extracts being 11.E, 11.M, and 12.E (IC\({}_{50}\) values between 15.18 \(\upmu\)g/mL to 32.85 \(\upmu\)g/mL). None of the extracts were as active as control inhibitor kojic acid (IC\({}_{50}\) = 1.82 \(\pm\) 0.13 \(\upmu\)g/mL). The most active extracts were fractionated, and 12 fractions exhibited significant activity (IC\({}_{50}\) values from 9.01 \(\upmu\)g/mL to 95.21 \(\upmu\)g/mL) 50% of which presented no loss of activity in relation to the original extracts. On the contrary, each extract produced at least two fractions 1.2- to 3.6-fold more active than the original extract. The best fraction (12.E.1) presented an IC\({}_{50}\) that was only about five times higher than the IC\({}_{50}\) of kojic acid (Figure 7), which is quite impressive considering that fractions still contain an array of different compounds. Comparing the tyrosinase inhibitory activity of extracts and fractions with the activity reported in the literature, it is concluded that the extracts and fractions of beach-casts seaweeds biomass exhibit excellent antityrosinase activity. In fact, [PERSON] et al. [71] reported IC\({}_{50}\) values of 295.21 \(\upmu\)g/mL and 436.89 \(\upmu\)g/mL for _Turbinaria decurens_ brown alga extracts and fucoxanthin-enriched extracts, respectively, although these results should be analyzed with caution, since the IC\({}_{50}\) value reported for kojic acid standard by those authors was 479.95 \(\upmu\)g/mL, compared with 1.82 \(\upmu\)g/mL in the present work. It appears too high to be credible (see also, e.g., [PERSON] et al., [72]). [PERSON] et al. [73] reported  
Figure 7: Tyrosine inhibition activity (IC\({}_{50}\) values) by the extracts (light bars) and fractions thereof (dark bars). Reference: Kojic acid. IC\({}_{50}\) values on the order of 3.5-4.5 mg/mL for methanolic extracts of _Halimeda_ spp., _Valoniorysis pachynema_ (Chlorophyta), _Gracilaria debilis_ (formerly _Gracilaria regrosonii)__Spyridia hyproides_ and _Amphiroa anceps_ (Rhodophyta) while the ethanol extract of _Turbinaria conoides_ (Ochrophyta, Phaeophyceae) exhibits IC\({}_{50}\) value of 188.85 ug/mL [74]. All these activities are much lower than the ones presented here. The compounds responsible for this activity can be very diverse, since several metabolites isolated from seaweed have been reported [75].