# Pharmacological and Cosmeceutical Potential of Seaweed Beach-Casts of Macaronesia
## 3 Results and Discussion
### Anticolinesterase Activity  
Decreased levels of neuromediators acetylcholine (ACh) and butylcholine (BCh) have been observed in the brains of patients with Alzheimer's disease (AD). For that reason, the inhibition of AChE and BuChE, responsible for the hydrolysis of ACh and BCh has become a treatment option of AD [51].  
The extracts prepared were tested to assay their capacity to inhibit acetylcholinesterase and butylcholinesteraseerase, two enzymes related with the regulation of acetylcholine (ACh) level in the synaptic cleft, a very relevant factor in promoting cognitive function. The results obtained showed that the tested samples cannot be seen as promising sources of anticholinesterase products, since the most active sample at 150 \(\upmu\)g/mL inhibited only 51.3% of AChE activity, although 14 more (1.E, 1.M, 4.E, 5.E, 5.M, 6.M, 7.E, 8.E, 9.E, 10.E, 11.E, 11.M, 12.E, 12.M) inhibited the enzyme by values ranging from 30.8-49.5% at the same maximum tested concentration. These uninteresting results led to the decision that no fraction of these extracts should be tested for this activity.  
It should be noted that in the present work the choice was to test only up to 150 \(\upmu\)g/mL, whereas some results of anticholinesterase activity reported in the literature correspond to extract concentrations more than 2.8-fold higher than the one reported herein, such as the crude methanol extract of _Ecklonia maxima_ (Ochrophyta, Phaeophyceaeae) which inhibits 50% of acetylcholine esterase activity at 385.50 \(\upmu\)g/mL [52]. Another example, by [PERSON] et al. [53], who tested the hydroethanolic extracts of _Ecklonia maxima, Gelidium pristoides, Gracilaria gracilis_ (Rhodophyta) and _Uliva lactuca_ (Chlorophyta), obtained 50% of anticholinesterase effects with concentration ranging from 1.66-2.42 mg/mL. The review by [PERSON] et al. [54] also presents some of these high IC\({}_{50}\) values, going up to 10 mg/mL for AChE and BuChE. These values are too high to be of interest, and that is why 150 \(\upmu\)g/mL was established in the present work as the highest sample concentration to test for anticholinesterase effect.  
To the most active sample, ethanol extract of the beach-cast 6 (6.E), the IC\({}_{50}\) value was determined, exhibiting an AChE inhibition of 137 \(\pm\) 1.06 \(\upmu\)g/mL and 138 \(\pm\) 4.41 \(\upmu\)g/mL to BuChE, with roughly 45% _Asparagopsis armata_ (Rhodophyta) and the rest Phaeophyceaeae (25% _Lobophora variegata_). Although being a dual AChE/BuChE inhibitor, which is interesting when considering applications related with Alzheimer's disease therapy, this sample showed IC\({}_{50}\) value more than 13,000-fold higher the value for the standard (donepezil) in the case of AChE (IC\({}_{50}\) = 0.010 \(\pm\) 0.003 \(\upmu\)g/mL), being more favorable in the case of BuChE (IC\({}_{50}\) = 28.94 \(\pm\) 1.76 \(\upmu\)g/mL), where it is only 4.75-fold higher. These results reinforce the low expectation about these beach-cast extracts as a source of compounds for the treatment of Alzheimer's disease, although several macroalgae and their constituents are described in the literature as promising pharmacological principles for this pathology [55; 56].