We extracted ulvan from the green seaweed Ulva reticulata collected from the Nha-Trang bay, central coast of Vietnam. The ulvan is composed of rhamnose, galactose, xylose, mannose, and glucose with molar ratio Rha:Gal:Xyl:Man:Glu = 1:0.1:0.11:0.01:0.21, uronic acid content of 19.3 wt %, and sulfate content of 14.3 wt %. Chemical structure determination using NMR and ESI-MS techniques showed that ulvan is composed of mainly two disaccharides β-d-GlcAp(1→2)-α-l-Rhap and α-l-IdoAp(1→4)-α-l-Rhap. Branching point is at O-2 of uronic acid. Sulfate groups were attached at C-2, C-3, and C-4 of the rhamnose residues.

Ulvans are sulfated polysaccharides derived from the cell wall of green seaweeds. The chemical structure of ulvan extracted from Ulva reticulata is reported, focusing on investigation of the sulfated modification of the ulvan and the changes in structure and anticoagulant activity. The results showed that sulfated modification was able to change the ulvan conformational structure and markedly enhance its anticoagulant activity.

In this paper, the extraction conditions of ulvan from green seaweed Ulva lactuca by using Ultrasound-assisted extraction method were optimised. Experience was designed using Box-behnken model with experient areas as following: extraction temperature (X1: 50–90 °C), extraction time (X2: 20–40, min) and solvent-to-material ratio (X3: 50/1–70/1, v/w), objective function (Y: extraction yield) was required to get maximum value. The result showed that the optimization conditions for extraction were: extraction temperature 84.28 °C, extraction time 30.59 min with 60.21/1 (v/w) as solvent-to-material ratio, and the expected objective function Y is 22.86% based on dried seaweed weight.

In this study, the structural characteristics of a polysaccharide extracted from the Ulva fasciata green seaweed were determined using the chemical composition analytical methods combined with IR, MS, and NMR spectra. The results showed that the polysaccharide consists of two major repeating disaccharide units designated as ulvanobiuronic acid 3-sulfate type A (A3s) [→4)-β-D-GlcA-(1 → 4)-α-L-Rha 3S-(1→] and type B (B3s) [→4)-α-LIdoA-(1 → 4)-α-L-Rha 3s(1→]. This kind of polysaccharide exhibited a significant in vitro antioxidant activity. This study demonstrated that the Ulva fasciata green algae can be considered as a source of bioactive ulvan.

Pectin is a heterogeneous complex polysaccharide found in the primary cell wall of most cells. In this work, low‐methoxyl pectin was extracted from pumpkin (Cucurbita moschata). The obtained pectin was characterized by GPC FTIR and NMR spectra. The obtain results showed that structural feature of the pectin is a main chain of poly‐α(1→4)‐D‐galacturonic acid and occasionally interrupted by α(1→2)‐linked α‐L‐rhamnopyranose residues and branches Galp is linked to GalpA at C‐2 position.