Seasonal Variation of Phenolic Antioxidant-mediated α-glucosidase Inhibition of Ascophyllum nodosum

Abstract

Ascophyllum nodosum is a brown seaweed that grows abundantly in the US Northeast coastal region. This study examined the seasonal variation of A. nodosum in phenolic contents and subsequent antioxidant, α-glucosidase and α-amylase inhibitory activities. A. nodosum was harvested monthly and extracted in hot water and the resulting extracts were spray-dried. The results indicate a clear seasonal variation in terms of phenolic content, with June and July being the highest (36.4 and 37 mg/g, respectively) and May the lowest (21.8 mg/g). The antioxidant activities, in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, correlated with the phenolic contents observed (r = 0.81), with the month of July being the highest (58%) and April the lowest (26%). Similarly in terms of Trolox equivalent, July had the highest activity (15.53 μM) and April and May the lowest (8.40 and 8.27 μM, respectively). α-glucosidase inhibitory activity exhibited a pattern similar to the phenolic contents observed with July having the highest inhibitory activity (IC(70) 2.23 μg) and April the lowest (IC(70) 26.13 μg), resulting in an inverse correlation between IC(70) values and total phenolic content (r = -0.89). Such seasonal variation is believed to be caused by temperature-related stress considering that A. nodosum is a cold water species.

Stimulation of Phenolics, Antioxidant and α-Glucosidase Inhibitory Activities During Barley (Hordeum vulgare L.) Seed Germination

“…1, Table 2) correlate with observed phenolic contents ( Table 1) (PCC r = 0.973). This is in agreement with previous reports suggesting that phenolic phytochemicals have carbohydrate hydrolyzing enzyme inhibitory activity [5,9,10]. Also, our findings suggest that to ensure the highest rat α-glucosidase inihibitory activity it is important to identify the appropriate point that the lignification process is initiated.…”

“…Recent studies showed that phenolic phytochemicals from botanical sources are natural inhibitors of α-amylase and α-glucosidase and thus can be used to manage postprandial hyperglycemia with minimal side effects [5,9,10]. More specifically, plants belonging in the Lamiaceae family as well as corn, bean, and pumpkin extracts have shown a good inhibitory profile against carbohydrate degrading enzyme such as α-glucosidase [5,9].…”

“…More specifically, plants belonging in the Lamiaceae family as well as corn, bean, and pumpkin extracts have shown a good inhibitory profile against carbohydrate degrading enzyme such as α-glucosidase [5,9]. Additionally, research with the brown seaweed Ascophyllum nodosum confirmed the correlation between phenolic content, antioxidant activities and α-glucosidase inhibitory potential relevant to type 2 diabetes management [10].…”

Seasonal influence on phenolic-mediated antihyperglycemic properties of Canadian sugar and red maple leaves using in vitro assay models

“…Therefore, inhibition of these enzymes can significantly decrease the postprandial hyperglycemia after a mixed carbohydrate diet and can be a key strategy in the control of diabetes mellitus (5). Recent research findings have shown that plant-derived phenolics play a role in mediating α-glucosidase and α-amylase inhibition and thus have potential to contribute to the management of type-2 diabetes (6)(7)(8)(9)(10).…”

Manipulating antioxidant content in macroalgae in intensive land-based cultivation systems for functional food applications

“…Asparagopsis armata cultured in fishpond effluents at higher nitrogen fluxes had an increased content of mycosporinelike amino acids (MAAs) which have a UV-protective and antioxidant function [9], and the reducing capacity of extracts from the red macroalga Palmaria palmata (dulse) harvested from a high UV-exposure environment was 86% higher than extracts from dulse harvested from a low UV-exposure environment [8]. In addition, there is substantial data on how the antioxidant content of marine macroalgae in natural habitats is influenced by abiotic stresses such as light, temperature, and desiccation stress [10,11]. On-land culture manipulations therefore provide the potential to exploit or enhance the antioxidant capacity of the biomass.…”