ABSTRACT
Brown seaweed phlorotannins have shown the potential to promote several health benefits. Durvillaea incurvata and Lessonia spicata-species that are widely distributed in central and southern Chile-were investigated to obtain phlorotannin extracts with antioxidant and antihyperglycemic potential. The use of an environmentally friendly and food-grade glycerol-based pressurized hot liquid extraction (PHLE) process (15% v/v glycerol water) was assessed for the first time to obtain phlorotannins. Multiple effects were analyzed, including the effect of the species, harvesting area (Las Cruces and Niebla), and anatomical part (holdfast, stipe, and frond) on the extracts' polyphenol content (TPC), antioxidant capacity (AC), and carbohydrate-hydrolyzing enzyme-α-glucosidase and α-amylase-inhibitory activity. Contaminants, such as mannitol, heavy metals (As, Cd, Pb, Hg, and Sn), and 5-hydroxymethylfurfural (HMF), were also determined. The anatomical part used demonstrated a significant impact on the extracts' TPC and AC, with holdfasts showing the highest values (TPC: 95 ± 24 mg phloroglucinol equivalents/g dry extract; DPPH: 400 ± 140 µmol Trolox equivalents/g dry extract; ORAC: 560 ± 130 µmol TE/g dry extract). Accordingly, holdfast extracts presented the most potent α-glucosidase inhibition, with D. incurvata from Niebla showing an activity equivalent to fifteen times that of acarbose. Only one frond and stipe extract showed significant α-glucosidase inhibitory capacity. No α-amylase inhibition was found in any extract. Although no HMF was detected, potentially hazardous cadmium levels (over the French limit) and substantial mannitol concentrations-reaching up to 50% of the extract dry weight-were found in most seaweed samples and extracts. Therefore, further purification steps are suggested if food or pharmaceutical applications are intended for the seaweed PHLE extracts obtained in this study.
ABSTRACT
Maize silks have been used in Mexico for centuries as a natural-based treatment for various illnesses, including obesity and diabetes. It has been shown in mice that intake of maize silk extracts reduces the levels of blood glucose. However, it is not clear how or what maize silk compounds are involved in such an effect. A hypothesized mechanism is that some maize silk compounds can inhibit carbohydrate hydrolyzing enzymes like α-glucosidases. This work aimed to assess the capability of both saccharides and phenolic compounds from maize silks to inhibit intestinal α-glucosidases. Results showed that saccharides from maize silks did not produce inhibition on intestinal α-glucosidases, but phenolics did. Maize silk phenolics increased the value of Km significantly and decreased the Vmax slightly, indicating a mixed inhibition of α-glucosidases. According to the molecular docking analysis, the phenolics maysin, methoxymaysin, and apimaysin, which had the highest predicted binding energies, could be responsible for the inhibition of α-glucosidases. PRACTICAL APPLICATIONS: The International Diabetes Federation (IDF) reported in 2017 that diabetes affects over 424 million people worldwide, and caused 4 million deaths. Non-insulin-dependent diabetes or type 2 diabetes mellitus (T2DM) accounts for â¼90% of cases. T2DM is characterized by insulin resistance and pancreatic ß-cell failure. Therapy for T2DM includes the use of sulfonylureas, thiazolidinediones, biguanides, and α-glucosidase inhibitors. Regarding the α-glucosidase inhibitors, only few are commercially available, and these have been associated with severe gastrointestinal side effects. This work aimed to assess the capability of both saccharides and phenolic compounds from maize silks to inhibit intestinal α-glucosidases. Results from this work evidenced that maize silk polyphenols acted as effective inhibitors of intestinal rat α-glucosidases. Computational analysis of maize silk polyphenols indicated that maysin, a particular flavonoid from maize silks, could be responsible for the inhibition of α-glucosidases.