Fucoidans from South African brown seaweeds: establishing the link between their structure and biological properties (anti-diabetic and anti-cancer activities)
- Authors: Mabate, Blessing
- Date: 2022-10-14
- Subjects: Fucoidan , Diabetes Treatment , Cancer Treatment , Brown algae
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365677 , vital:65775 , DOI https://doi.org/10.21504/10962/365677
- Description: Type 2 diabetes mellitus (T2DM) and cancer are major non-communicable diseases causing a heavy morbidity-mortality and economic burden globally. The therapeutic efforts in managing these diseases are primarily chemotherapeutic and are associated with demerits, including side effects and toxicity, limiting the prescribed amounts. These dosage limits may cause drug resistance, another major challenge in maintaining quality global health. The pursuit of novel natural bioproducts is a reasonable strategy to add to the arsenal against T2DM and cancer. Fucoidans, sulphated fucose polysaccharides abundant in brown seaweeds, have recently become popular for their biological activities, including anti-diabetic and anti-cancer properties. However, endemic South African brown seaweeds have not been adequately explored. Therefore, this study sought to characterise fucoidans extracted from South African brown seaweeds and elucidate their structure to their biological activities. Also, this study highlighted carbohydrate and glucose metabolism as major target processes in the control efforts of T2DM and cancer using fucoidans. Harvested brown seaweeds were identified as Ecklonia radiata and Sargassum elegans. E. maxima was kindly donated by KelpX. The fucoidans were then extracted using hot water, EDTA assisted, and acid extraction protocols. The integrity of the extracted fucoidan was confirmed through structural analysis using FTIR, NMR and TGA. The fucoidan extracts were then chemically characterised to determine their carbohydrate and monosaccharide composition and sulphate content. The characterised fucoidans were profiled for inhibiting the major amylolytic enzymes, namely α-amylase and α-glucosidase. The mode of inhibition by fucoidans and synergy experiments with the commercial anti-diabetic drug acarbose were also investigated. Furthermore, the fucoidans were screened for potential anti-cancer activities on the human colorectal HCT116 cancer cell line. The cytotoxicity of fucoidans was quantified using the resazurin assay. The effect of fucoidan on HCT116 cell adhesion on the tissue culture plastic was also investigated using the crystal violet-based cell adhesion assay. In addition, cancer antimigration properties of fucoidans were also investigated using 2D wound healing and 3D spheroid-based assays. Furthermore, the long-term survival of HCT116 cells was investigated through the clonogenic assay after treatment with fucoidans. Lastly, glucose uptake and lactate export assays revealed the influence of fucoidan on glucose uptake and the glycolytic flux of HCT116 cells. Fucoidans were successfully extracted with a yield between 2.2% and 14.2% on a dry weight basis. EDTA extracts produced the highest yields than the water and the acid extracts. Ecklonia spp. fucoidans displayed the highest total carbohydrate content, with glucose and galactose being the major monosaccharides. S. elegans and commercial Fucus vesiculosus had lower carbohydrate contents but contained more sulphates than the Ecklonia spp. fucoidans. Furthermore, the extracted fucoidan contained little to no contaminants, including proteins, phenolics and uronic acids. In addition, the extracted fucoidans were determined to be >100 kDa through ultracentrifugation. Mass spectrometry also detected the most abundant peak for all fucoidans to be around 700 Da (m/z). Extracted fucoidans inhibited the activity of α-glucosidase more strongly than the commercial anti-diabetic agent acarbose but were inactive on α-amylase. Fucoidans were also shown to be mixed inhibitors of α-glucosidase. Compellingly, fucoidans synergistically inhibited α-glucosidase in combination with the anti-diabetic agent acarbose, highlighting prospects for combination therapy. Finally, fucoidans demonstrated some anti-proliferative characteristics on HCT116 cancer cells by inhibiting their ability to adhere to the tissue culture plate matrix. Furthermore, some fucoidan extracts inhibited the migration of HCT116 cancer cells from 3D spheroids. Some of our fucoidan extracts also inhibited HCT116 colony formation, demonstrating inhibition of long-term cell survival. The E. maxima water extract also inhibited glucose uptake by HCT116 cells, thereby influencing the glycolytic flux. In conclusion, biologically active fucoidans were successfully extracted from South African brown seaweeds. These fucoidans demonstrated anti-diabetic and anti-cancer properties, revealing their relevance as potential drugs for these diseases. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Mabate, Blessing
- Date: 2022-10-14
- Subjects: Fucoidan , Diabetes Treatment , Cancer Treatment , Brown algae
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365677 , vital:65775 , DOI https://doi.org/10.21504/10962/365677
- Description: Type 2 diabetes mellitus (T2DM) and cancer are major non-communicable diseases causing a heavy morbidity-mortality and economic burden globally. The therapeutic efforts in managing these diseases are primarily chemotherapeutic and are associated with demerits, including side effects and toxicity, limiting the prescribed amounts. These dosage limits may cause drug resistance, another major challenge in maintaining quality global health. The pursuit of novel natural bioproducts is a reasonable strategy to add to the arsenal against T2DM and cancer. Fucoidans, sulphated fucose polysaccharides abundant in brown seaweeds, have recently become popular for their biological activities, including anti-diabetic and anti-cancer properties. However, endemic South African brown seaweeds have not been adequately explored. Therefore, this study sought to characterise fucoidans extracted from South African brown seaweeds and elucidate their structure to their biological activities. Also, this study highlighted carbohydrate and glucose metabolism as major target processes in the control efforts of T2DM and cancer using fucoidans. Harvested brown seaweeds were identified as Ecklonia radiata and Sargassum elegans. E. maxima was kindly donated by KelpX. The fucoidans were then extracted using hot water, EDTA assisted, and acid extraction protocols. The integrity of the extracted fucoidan was confirmed through structural analysis using FTIR, NMR and TGA. The fucoidan extracts were then chemically characterised to determine their carbohydrate and monosaccharide composition and sulphate content. The characterised fucoidans were profiled for inhibiting the major amylolytic enzymes, namely α-amylase and α-glucosidase. The mode of inhibition by fucoidans and synergy experiments with the commercial anti-diabetic drug acarbose were also investigated. Furthermore, the fucoidans were screened for potential anti-cancer activities on the human colorectal HCT116 cancer cell line. The cytotoxicity of fucoidans was quantified using the resazurin assay. The effect of fucoidan on HCT116 cell adhesion on the tissue culture plastic was also investigated using the crystal violet-based cell adhesion assay. In addition, cancer antimigration properties of fucoidans were also investigated using 2D wound healing and 3D spheroid-based assays. Furthermore, the long-term survival of HCT116 cells was investigated through the clonogenic assay after treatment with fucoidans. Lastly, glucose uptake and lactate export assays revealed the influence of fucoidan on glucose uptake and the glycolytic flux of HCT116 cells. Fucoidans were successfully extracted with a yield between 2.2% and 14.2% on a dry weight basis. EDTA extracts produced the highest yields than the water and the acid extracts. Ecklonia spp. fucoidans displayed the highest total carbohydrate content, with glucose and galactose being the major monosaccharides. S. elegans and commercial Fucus vesiculosus had lower carbohydrate contents but contained more sulphates than the Ecklonia spp. fucoidans. Furthermore, the extracted fucoidan contained little to no contaminants, including proteins, phenolics and uronic acids. In addition, the extracted fucoidans were determined to be >100 kDa through ultracentrifugation. Mass spectrometry also detected the most abundant peak for all fucoidans to be around 700 Da (m/z). Extracted fucoidans inhibited the activity of α-glucosidase more strongly than the commercial anti-diabetic agent acarbose but were inactive on α-amylase. Fucoidans were also shown to be mixed inhibitors of α-glucosidase. Compellingly, fucoidans synergistically inhibited α-glucosidase in combination with the anti-diabetic agent acarbose, highlighting prospects for combination therapy. Finally, fucoidans demonstrated some anti-proliferative characteristics on HCT116 cancer cells by inhibiting their ability to adhere to the tissue culture plate matrix. Furthermore, some fucoidan extracts inhibited the migration of HCT116 cancer cells from 3D spheroids. Some of our fucoidan extracts also inhibited HCT116 colony formation, demonstrating inhibition of long-term cell survival. The E. maxima water extract also inhibited glucose uptake by HCT116 cells, thereby influencing the glycolytic flux. In conclusion, biologically active fucoidans were successfully extracted from South African brown seaweeds. These fucoidans demonstrated anti-diabetic and anti-cancer properties, revealing their relevance as potential drugs for these diseases. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-10-14
In vitro pharmacological screening of thiazolidinedione-derivatives on diabetes and Alzheimer’s potential therapeutic targets
- Authors: Arineitwe, Charles
- Date: 2022-10-14
- Subjects: Diabetes Treatment , Alzheimer's disease Treatment , Antioxidants Therapeutic use , Rosiglitazone , Hypoglycemic agents , In vitro screening , Thiazolidinedione Derivatives
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/232171 , vital:49968
- Description: There is an increased prevalence of diabetes and other non-communicable diseases in Sub-Saharan Africa and globally. In South Africa, the prevalence of type 2 Diabetes mellitus is currently estimated at 9.0% in people aged 30 and older and is expected to increase. Diabetes-related complications result in acute alterations in the mental state due to poor metabolic control as well as greater rates of decline in cognitive functioning with age, higher prevalence of depression and increased risk of Alzheimer’s disease. Alzheimer’s disease is the most common form of dementia in older adults and possibly contributes to 60 - 70% of cases. Alzheimer’s disease remains incurable, its progression inevitable with the currently available symptomatic therapies being palliative while the treatment of diabetes relies on insulin preparations and other glucose-lowering agents. Current treatment options have numerous side effects such as hypoglycaemia, diarrhoea, weight gain and abnormal liver function. This has geared the investigation of new generations of small molecules which exhibit improved efficacy and safety profiles. On this basis, several studies have shown that thiazolidinediones and their corresponding derivatives exhibit a broad spectrum of biological activities including anti-inflammatory, and antioxidant activities. Furthermore, recent evidence from experimental, epidemiological, and clinical studies highlight the utility of antioxidants for treating diabetes and its complications. Interestingly, there is increasing evidence that links diabetes and Alzheimer’s disease due to their pathophysiology and suppressing glycaemia has been shown to be beneficial in Alzheimer’s disease treatment. Accordingly, the aim of this study, was to evaluate the anti-diabetic and anti-Alzheimer’s properties of four novel synthesized thiazolidinedione-derivatives owing to their antioxidant properties. Methods The aim of this study was achieved through performing ferric reducing antioxidant power activity, 2,2’-Diphenyl-1-Picry Hydrazyl radical scavenging activity, α-amylase inhibition, α-glucosidase inhibition, aldose reductase inhibition, protein tyrosine phosphatase-1B inhibition, dipeptidyl peptidase-4 inhibition, acetylcholinesterase inhibition, matrix metalloproteinase-1 inhibition, and β-amyloid aggregation inhibition assays. In addition, peroxisome proliferator-activated receptor-γ activation was performed through docking studies. To establish physicochemical properties of TZD derivatives investigated, further in-silico studies were done using SwissADME tools. Results To this end, in-vitro and in-silico studies were successfully performed. In-silico ADME profiling predicted these derivatives to be drug-like with moderate to good solubility in the GI and not blood-brain barrier permeable. Furthermore, docking of these molecules against PPARγ predicted a similar mode of action to that of thiazolidinediones using Rosiglitazone as the standard drug with TZDD2 and TZDD4 forming equivalent conformations to that of Rosiglitazone in the same binding site and TZDD3 having an equivalent LBE to that of Rosiglitazone (-8.84 and -8.63kcal/mol respectively). In-vitro evaluation predicted a moderate antioxidant activity with TZDD2 and 3 exhibiting the highest FRAP activity and DPPH radical scavenging activity. Furthermore, enzymatic inhibition assays showed a relative inhibition activity with TZDD3 exhibited > 100% inhibition in concentrations ≥ 30 μg/mL and TZDD1, 2 and 4 exhibited ≥ 50% inhibition activity in all the concentrations (10, 20, 30, 40 and 50 μg/mL) in the α-amylase inhibition assay. Similarly, in the α-glucosidase inhibition assay, all the four derivatives exhibited a concentration dependent activity with TZDD3 showing the most activity. All the four derivatives exhibited ≥ 30% inhibition in the aldose reductase inhibition assay except TZDD1 at 10 μg/mL. TZDD4 exhibited a concentration dependent inhibition activity in the protein tyrosine phosphatase-1B inhibition assay. Interestingly, TZDD3 showed a decreasing inhibition activity as its concentration increased from 10 μg/mL through to 50 μg/mL. In the dipeptidyl peptidase–4 inhibition assay, TZDD2 and TZDD4 exhibited ≥ 20% inhibition activity across all the concentrations and in the acetylcholinesterase assay, TZDD1, 3 and 4 exhibited ≥ 25% across all the concentrations. Interestingly, in the matrix metalloproteinase-1 inhibition assay, some of these derivatives exhibited partial activation activity and partial inhibition with TZDD1 showing activation in concentrations 10 and 20 μg/mL and inhibition in concentrations 30, 40 and 50 μg/mL. TZDD4 showed activation in all the concentrations. In the β-amyloid aggregation assay, all the four derivatives showed inhibition activity ≥ 10% except TZDD1 at 50 μg/mL. Conclusions Diabetes mellitus and Alzheimer’s disease are a type of pathology of global concern, and several researchers worldwide have strived to search for novel therapeutic treatments and prevention for diabetes as well as Alzheimer’s disease. Recent studies provide a direct link v between diabetes mellitus and Alzheimer’s disease, and the need to find novel drugs that can mitigate these two is of increasing interest. In our search for antidiabetic and anti-Alzheimer’s activity, TZD derivatives (TZDD1, TZDD2, TZDD3 and TZDD4) exhibited good antioxidant activity, anti-hyperglycaemic activity and a relatively promising anti-Alzheimer’s activity. This was observed from the in vitro evaluation performed which included α – amylase, α – glucosidase, aldose reductase, PTP1B, DPP4, amyloid β aggregation, and AChE inhibition assays. Furthermore, docking of the derivatives against PPARγ predicted a similar molecular interaction to that of thiazolidinediones using Rosiglitazone as the standard drug. Furthermore, in silico ADME profiling predicted the derivatives to have moderate to good solubility in the GI (good GI bioavailability), and also exhibited excellent drug likeness. However, they are predicted not permeate the BBB. Further in silico studies and in vivo should be conducted to establish toxicities, as well as drug delivery to the brain for effective therapeutic effect against Alzheimer’s disease. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacology, 2022
- Full Text: false
- Date Issued: 2022-10-14
- Authors: Arineitwe, Charles
- Date: 2022-10-14
- Subjects: Diabetes Treatment , Alzheimer's disease Treatment , Antioxidants Therapeutic use , Rosiglitazone , Hypoglycemic agents , In vitro screening , Thiazolidinedione Derivatives
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/232171 , vital:49968
- Description: There is an increased prevalence of diabetes and other non-communicable diseases in Sub-Saharan Africa and globally. In South Africa, the prevalence of type 2 Diabetes mellitus is currently estimated at 9.0% in people aged 30 and older and is expected to increase. Diabetes-related complications result in acute alterations in the mental state due to poor metabolic control as well as greater rates of decline in cognitive functioning with age, higher prevalence of depression and increased risk of Alzheimer’s disease. Alzheimer’s disease is the most common form of dementia in older adults and possibly contributes to 60 - 70% of cases. Alzheimer’s disease remains incurable, its progression inevitable with the currently available symptomatic therapies being palliative while the treatment of diabetes relies on insulin preparations and other glucose-lowering agents. Current treatment options have numerous side effects such as hypoglycaemia, diarrhoea, weight gain and abnormal liver function. This has geared the investigation of new generations of small molecules which exhibit improved efficacy and safety profiles. On this basis, several studies have shown that thiazolidinediones and their corresponding derivatives exhibit a broad spectrum of biological activities including anti-inflammatory, and antioxidant activities. Furthermore, recent evidence from experimental, epidemiological, and clinical studies highlight the utility of antioxidants for treating diabetes and its complications. Interestingly, there is increasing evidence that links diabetes and Alzheimer’s disease due to their pathophysiology and suppressing glycaemia has been shown to be beneficial in Alzheimer’s disease treatment. Accordingly, the aim of this study, was to evaluate the anti-diabetic and anti-Alzheimer’s properties of four novel synthesized thiazolidinedione-derivatives owing to their antioxidant properties. Methods The aim of this study was achieved through performing ferric reducing antioxidant power activity, 2,2’-Diphenyl-1-Picry Hydrazyl radical scavenging activity, α-amylase inhibition, α-glucosidase inhibition, aldose reductase inhibition, protein tyrosine phosphatase-1B inhibition, dipeptidyl peptidase-4 inhibition, acetylcholinesterase inhibition, matrix metalloproteinase-1 inhibition, and β-amyloid aggregation inhibition assays. In addition, peroxisome proliferator-activated receptor-γ activation was performed through docking studies. To establish physicochemical properties of TZD derivatives investigated, further in-silico studies were done using SwissADME tools. Results To this end, in-vitro and in-silico studies were successfully performed. In-silico ADME profiling predicted these derivatives to be drug-like with moderate to good solubility in the GI and not blood-brain barrier permeable. Furthermore, docking of these molecules against PPARγ predicted a similar mode of action to that of thiazolidinediones using Rosiglitazone as the standard drug with TZDD2 and TZDD4 forming equivalent conformations to that of Rosiglitazone in the same binding site and TZDD3 having an equivalent LBE to that of Rosiglitazone (-8.84 and -8.63kcal/mol respectively). In-vitro evaluation predicted a moderate antioxidant activity with TZDD2 and 3 exhibiting the highest FRAP activity and DPPH radical scavenging activity. Furthermore, enzymatic inhibition assays showed a relative inhibition activity with TZDD3 exhibited > 100% inhibition in concentrations ≥ 30 μg/mL and TZDD1, 2 and 4 exhibited ≥ 50% inhibition activity in all the concentrations (10, 20, 30, 40 and 50 μg/mL) in the α-amylase inhibition assay. Similarly, in the α-glucosidase inhibition assay, all the four derivatives exhibited a concentration dependent activity with TZDD3 showing the most activity. All the four derivatives exhibited ≥ 30% inhibition in the aldose reductase inhibition assay except TZDD1 at 10 μg/mL. TZDD4 exhibited a concentration dependent inhibition activity in the protein tyrosine phosphatase-1B inhibition assay. Interestingly, TZDD3 showed a decreasing inhibition activity as its concentration increased from 10 μg/mL through to 50 μg/mL. In the dipeptidyl peptidase–4 inhibition assay, TZDD2 and TZDD4 exhibited ≥ 20% inhibition activity across all the concentrations and in the acetylcholinesterase assay, TZDD1, 3 and 4 exhibited ≥ 25% across all the concentrations. Interestingly, in the matrix metalloproteinase-1 inhibition assay, some of these derivatives exhibited partial activation activity and partial inhibition with TZDD1 showing activation in concentrations 10 and 20 μg/mL and inhibition in concentrations 30, 40 and 50 μg/mL. TZDD4 showed activation in all the concentrations. In the β-amyloid aggregation assay, all the four derivatives showed inhibition activity ≥ 10% except TZDD1 at 50 μg/mL. Conclusions Diabetes mellitus and Alzheimer’s disease are a type of pathology of global concern, and several researchers worldwide have strived to search for novel therapeutic treatments and prevention for diabetes as well as Alzheimer’s disease. Recent studies provide a direct link v between diabetes mellitus and Alzheimer’s disease, and the need to find novel drugs that can mitigate these two is of increasing interest. In our search for antidiabetic and anti-Alzheimer’s activity, TZD derivatives (TZDD1, TZDD2, TZDD3 and TZDD4) exhibited good antioxidant activity, anti-hyperglycaemic activity and a relatively promising anti-Alzheimer’s activity. This was observed from the in vitro evaluation performed which included α – amylase, α – glucosidase, aldose reductase, PTP1B, DPP4, amyloid β aggregation, and AChE inhibition assays. Furthermore, docking of the derivatives against PPARγ predicted a similar molecular interaction to that of thiazolidinediones using Rosiglitazone as the standard drug. Furthermore, in silico ADME profiling predicted the derivatives to have moderate to good solubility in the GI (good GI bioavailability), and also exhibited excellent drug likeness. However, they are predicted not permeate the BBB. Further in silico studies and in vivo should be conducted to establish toxicities, as well as drug delivery to the brain for effective therapeutic effect against Alzheimer’s disease. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacology, 2022
- Full Text: false
- Date Issued: 2022-10-14
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