Browsing by Author "Appiah, Amponsah Preko"
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- Evaluation of the antioxidant and anti-inflammatory activity in macroalgae asparagopsis armata and asparagopsis taxiformisPublication . Appiah, Amponsah Preko; Barreira, LuísaIn recent times, natural compounds have become widely employed in the treatment of human illnesses and health conditions such as cancer, neurological disorders, multiple sclerosis, diabetes, atherosclerosis, arthritis, and cardiovascular diseases all around the world. Plants have been the principal source of numerous pharmaceutical agents throughout history. However, in this modern era, much emphasis has been placed on the amazing biodiversity of life in the marine environment, which has proven to be an extraordinary repository of novel bioactive compounds with diverse structural and chemical properties, as well as a source of inspiration for new drug discovery. In the never-ending quest for novel safe and effective anti-inflammatory and antioxidant compounds beneficial to human health, this research focused on evaluating the ability of two distinct species of the macroalgae Asparagopsis spp (Asparagopsis taxiformis, as a gametophyte and as a sporophyte, and Asparagopsis armata as a gametophyte) to contribute for the treatment of anti-inflammatory diseases by assessing their antioxidant and anti-inflammatory activities. Ethanol, ethyl acetate and hexane were employed as solvents for the extraction of bioactive compounds from Asparagopsis spp. These solvents cover a wide range of polarity indices with polarity ranging from 0.1 for hexane, 4.4 for ethyl acetate, and 5.2 for ethanol to maximize the spectrum of extracted compounds. In this study, the best extraction yields were obtained with ethanol across all species of Asparagopsis with yields of 12.4% in A. armata, 9.0% in A. taxiformis as a gametophyte and 6.8% in the same as a sporophyte. Hexane yielded the least amount of extracts across all the species with yields of 0.4% in A. armata, 1.1% and 1.0% in A. taxiformis as a gametophyte and sporophyte respectively. Ethyl acetate showed yields of 2.4% in A. armata and 2.5% and 1.8% in A. taxiformis gametophyte and sporophyte respectively. Antioxidant properties were evaluated using tests such as ABTS, DPPH, iron & copper chelating activity, total phenolic content, and iron reducing activity while anti-inflammatory analysis was conducted specifically analysing for COX-2 inhibition. Results obtained suggests that Asparagopsis spp contain several bioactive compounds that exhibit good antioxidant abilities especially with metal chelating activities. Activity results in the DPPH assays were rather low (below 50% activity) across all species. For the ABTS assay, only the ethanolic extract of A. armata showed activity above 50% with an IC50 value of 0.24 mg/mL. The best results for copper chelating activity were observed in the hexane extracts of A. taxiformis sporophyte with an IC50 of 0.12 mg/mL. This was followed by the hexane extract of A. armata with an IC50 of 0.28 mg/mL. The best iron chelating activity was seen in the hexane extract of A. taxiformis sporophyte once again with an IC50 of 0.09 mg/mL. The ethyl acetate extracts of A. armata and A. taxiformis sporophyte also showed IC50 values of 0.25 and 0.24 mg/mL respectively. The iron reducing antioxidant assay showed good results for ethyl acetate extracts across all species with IC50 values of 0.07 mg/mL recorded of A. taxiformis sporophyte, 0.16 mg/mL for A. armata and 0.34 mg/mL for the gametophyte life stage of A. taxiformis. These extracts were observed to show activities higher than the gallic acid positive control. The macroalgae also demonstrated tremendous potential for COX-2 inhibition activity at an extract concentration of 1 mg/mL for all species (especially the hexane extracts showing over 50% activity across species) with the highest activity of 98.9 ± 0.4% observed in A. taxiformis gametophyte hexane extracts. Ethanol extract from A. taxiformis gametophyte also showed an activity of 79.1 ± 1.8% to take the second place whereas the hexane extract from A. taxiformis as a sporophyte showed inhibitory activity of 72.3 ± 5.1% taking the third spot. These activities compared to the ibuprofen positive control that was used at a concentration of 5 μg/mL and showed an activity of 55.0 ± 13.2% demonstrates that even as crude extracts Asparagopsis spp have great anti-inflammatory potentials and therefore in their highly refined states, extracts from Asparagopsis spp may be very competitive against other commercially known anti-inflammatory compounds on the market. Total phenolic content analysis (TPC) conducted on the extracts confirmed the presence of phenolic compounds in all the species of Asparagopsis evaluated. The highest levels of TPC were observed in the ethyl acetate extracts of all the species. Levels in the ethyl acetate extracts ranged from 1.50 ± 0.12 mg-GAE/g for A. armata, 1.19 ± 0.03 mg-GAE/g for A. taxiformis gametophyte to 0.61 ± 0.07 mg-GAE/g for A. taxiformis sporophyte. The relatively higher phenolic content observed in the ethyl acetate extracts suggests that most of the phenolic compounds present in Asparagopsis spp may be phenolic compounds of lower polarity such as tocopherols and tocotrienol which have been demonstrated to be well extracted by ethyl acetate. In general, the levels of total phenolic compounds present in Asparagopsis spp were determined to be relatively low compared to other macroalgae in literature. Despite the relatively low phenolic contents demonstrated in Asparagopsis spp it still showed good antioxidant and anti-inflammatory activities thus the antioxidant activity observed in the crude extracts were not solely dependent on the phenolic compounds but rather to a greater extent other bioactive compound(s) that may be present in the crude extracts of Asparagopsis spp. Statistical analysis in the form of ANOVA at a 95% Confidence Interval (alpha = 0.05) and Tukey multiple comparison test (P<0.05) were performed on the results obtained for all the antioxidant and anti-inflammatory tests conducted. The analysis revealed significant differences between the Asparagopsis species (A. taxiformis and A. armata) considered in this study and most importantly between the life stages of A. taxiformis as a gametophyte and a sporophyte. Multivariate data analyses in the form of principal component analysis (PCA) and cluster analysis (CA) were carried out between the antioxidant assay, metal chelating assays, COX-2 anti-inflammatory assay, and total phenolic content assay. Results of the analysis revealed that the solvent type used for extraction had a great influence on the antioxidant performance of the extracts. The analysis also explored the similarities between the tests and identified a good positive correlation between copper chelating activity test and COX-2 anti-inflammatory test. This observation is of great importance because COX-2 inhibition test is noted to be time consuming, complex, and very expensive to carry out. Hence in the event of a study where a large number of samples are to be tested it becomes challenging and puts a great strain on not only human resources, but financial resources and time as well. However, copper chelating activity (CCA) is comparatively simple and economical with time and funds hence could be a great way of pre-screening samples to determine which samples are likely to show good results with COX-2 analysis and hence reduce sample size which will eventually save time and other resources. Overall, findings presented from this research work suggests that the macroalgae Asparagopsis spp demonstrates high anti-inflammatory and antioxidant potentials for use in the pharmaceutical and nutraceutical industries.