Antidiabetic properties of polysaccharide- and polyphenolic-enriched fractions from the brown seaweedAscophyllum nodosumThis article is one of a selection of papers published in this special issue (part 2 of 2) on the Safety and Efficacy of Natural Health Products.

Abstract

Abstract:We screened seaweed species from Atlantic Canada for antidiabetic activity by testing extracts for a-glucosidase inhibitory effect and glucose uptake stimulatory activity. An aqueous ethanolic extract of Ascophyllum nodosum was found to be active in both assays, inhibiting rat intestinal a-glucosidase (IC 50 =7 7mg/mL) and stimulating basal glucose uptake into 3T3-L1 adipocytes during a 20-minute incubation by about 3-fold (at 400 mg/mL extract). Bioassay-guided fractionation of the A. nodosum extract showed that a-glucosidase inhibition was associated with polyphenolic components in the extract. These polyphenolics, along with other constituents appeared to be responsible for the stimulatory activity on glucose uptake. However, attempts to further concentrate this activity through fractionation techniques were unsuccessful. A crude polyphenol extract (PPE), an enriched polyphenolic fraction (PPE-F1) and a polysaccharide extract (PSE) were prepared from commercial A. nodosum powder and administered to streptozotocin-diabetic mice for up to 4-weeks by daily gavage at 200 mg/kg body mass. PPE and PPE-F1 improved fasting serum glucose level in diabetic mice; however, the effect was only statistically significant at day 14. In addition, PPE-F1 was shown to blunt the rise in blood glucose after an oral sucrose tolerance test in diabetic mice. Mice treated with PPE and PPE-F1 had decreased blood total cholesterol and glycated serum protein levels compared with untreated diabetic mice, whereas PPE also normalized the reduction in liver glycogen level that occurred in diabetic animals. All 3 A. nodosum preparations improved blood antioxidant capacity.Key words: seaweed, Ascophyllum nodosum, a-glucosidase, diabetes.Résumé : On a établit une recherche d'un produit anti-diabétique, parmi les algues locales de la région Atlantique du Canada, en examinant la capacité d'un effet inhibiteur de l'enzyme a-glucosidase et une stimulation de l'incorporation cellulaire du glucose. Un extrait éthanol-aqueux de Ascophyllum nodosum nous a donné une activité positive chez les deux essais, une inhibition de l'a-glucosidase provenant de l'intestin du rat (IC50 =7 7mg/mL) et puis une stimulation triple, à une concentration de 400 mg/mL, de l'incorporation du glucose dans les adipocytes 3T3-L1 durant une période de 20 minutes. L'extrait de A. nodosum aété divisé, guidé par les résultats biologiques, et a ainsi démontré la présence d'éléments polyphénoliques associé à l'inhibition de l'a-glucosidase. Ces éléments polyphénoliques ainsi que d'autres semblent être responsables de l'incorporation stimulée du glucose. Il a été impossible de raffiner cette activité lors d'une division des composants. Un extrait brut polyphénolique (PPE), un extrait enrichi polyphénolique (PPE-F1) et puis un extrait polysaccharide (PSE) furent préparés d'une poudre commerciale de A. nodosum et utilisés dans une étude utilisant des souris, rendues diabétiques par injections de streptozotocin, traitées par un gavage journalier de l'extrait 200 mg/kg du poid...

The Phytocomplex from Fucus vesiculosus and Ascophyllum nodosum Controls Postprandial Plasma Glucose Levels: An In Vitro and In Vivo Study in a Mouse Model of NASH

“…The ability of a phytocomplex obtained from these algae to inhibit both enzymes has already been demonstrated by Roy et al [32], and was confirmed in this research. In particular, the IC 50 value of this extract for α-amylase inhibition was 10 to 1000-fold lower than that reported for algae extracts prepared with solvents [17], fruit extracts [38], or polyphenols obtained from other plants [39,40]. Moreover, the Ki value (6.0 × 10 −8 M) indicated a strong affinity of binding the algae inhibitory component to α-amylase.…”

“…Algae extracts are considered a good source of digestive enzyme inhibitors. In particular, they contain polyphenolic compounds, such as bromophenols [15,16] and phlorotannins (PHTs) [5,17], which are well known α-glucosidase inhibitors. The enzyme α-glucosidase, together with α-amylase, is a key enzyme in starch breakdown and absorption.…”

Fucaceae: A Source of Bioactive Phlorotannins

“…and particularly from A. nodosum have demonstrated promising effects against these enzymes (Table 2). Per Zhang et al [45], the inhibitory effects of different fractions from A. nodosum ethanol 50% extracts towards α-glucosidase activity was highly correlated with their phlorotannin content, as the lowest IC 50 value (24.0 μg/mL) was observed for the C18 purified ethyl acetate fraction (TPC = 70.2% PE), followed by non-purified ethyl acetate fraction (IC 50 = 38.0 μg/mL; TPC = 39.8% PE) and crude ethanol extract (IC 50 = 77.0 μg/mL; TPC = 22.5% PE). When comparing the α-glucosidase inhibitory activities of ethanol 96% and acetone 70% extracts from A. nodosum and F. vesiculosus , both rich in phlorotannins, to that of acarbose (i.e., a well-known inhibitor of α-glucosidase and α-amylase currently used as an antidiabetic drug), IC 50 values of 8.9 and 0.72 μg/mL, respectively, for the former, and 4.4 and 0.34 μg/mL, respectively, for the latter were obtained, corresponding to an inhibitory activity 160–2000-times stronger than that of acarbose (IC 50 = 720 μg/mL) [111].…”

“…F. vesiculosus has also been commonly used for the treatment of rheumatoid arthritis, asthma, atherosclerosis, psoriasis and skin diseases, as well as several other complications [35,36,37]. Likewise, Ascophyllum and Pelvetia are endowed with several medicinal properties including antioxidant [38,39], anticoagulant [40,41], anti-inflammatory [41,42], antitumor [43,44] and antidiabetic [45,46,47], among others. In addition, these Fucaceae can be currently found in the ingredient labels of a dozen cosmetic products used as antiaging, anti-wrinkle, anti-photoaging, slimming, moisturizing and skin-whitening agents [48,49].…”

Effects of Dietary Fermented Seaweed and Seaweed Fusiforme on Growth Performance, Carcass Parameters and Immunoglobulin Concentration in Broiler Chicks

“…Bioactive components in seaweeds include polyphenols, peptides, and polysaccharides (Zhang et al, 2007; Jimenez-Escrig et al, 2011). Many of these active compounds were useful functional ingredients with numerous health benefits (Yuan and Walsh, 2006; Kim and Joo, 2008).…”