Species of green macroalgae (Chlorophyta) of the genus Ulva are edible seaweeds with a range of health promoting bioactive components. Ulva is high in dietary fibre which promotes gastrointestinal health and is linked to a reduction in the incidence of chronic diseases. The fundamental active constituent of Ulva is the soluble fibre ulvan, a gelling sulfated polysaccharide with biological activities including immunomodulating, antiviral, antioxidant, antihyperlipidemic and anticancer. Ulvan also has the capacity to modulate cellular signalling processes in both plant and animal systems leading to beneficial effects on productivity and health. Consequently, ulvan is of significant interest as a constituent in human health, agricultural, and biomaterial products. This comprehensive systematic review investigates and recommends acid extraction, ultrafiltration, sugar constituent and molecular weight analysis for the extraction, purification, and characterisation of ulvan, respectively. The biological activities of ulvans are then critically reviewed.

Description of the data

A meta-analysis of publications related to ulvan (a sulfated polysaccharide from green algae). Publications included were collected from Web of Science Core Collection and Scopus on 13/12/2017 using the search string: “(Ulvan* OR ((sulfate* OR sulphate*) AND polysaccharide* AND (Ulva OR Enteromorpha)))” Inclusion of a paper and data in a meta-table was subject to meeting the criteria stipulated by the search string. The paper must use algae from Ulva or Enteromorpha, and involve the extraction of sulfated polysaccharides. The paper must also contribute original quantitative data to the extraction procedure, characterisation and/or application of the sulfated polysaccharide. Each of the 154 publications included in the meta-analysis were read and data collected on: (1) the year, first author, first 40 characters of the title, journal of publication; (2) genera and species used along with country and a description of the biomass source; (3) The extractant applied, and concentration (if applicable), any enzymes applied, along with the temperature and duration of the extraction, and the precipitate if one was used; (4) the yield of polysaccharide (% DW), total carbohydrate, protein, ash, sulfate, uronic acid and neutral sugar content (in % w/w); (5) the average molecular weight; (6) the monosaccharide composition of rhamnose, uronic acids, glucuronic acid, xylose, iduronic acid, glucose and galactose (in % Mol, % DW, or Molar ratio); and (7) the tests applied to assess the biomedical application of the extracted polysaccharide. Data were recorded in the form and units that it was presented in unless the conversion was simply adjusting the magnitude of the value so that the data were comparable to other values in the table. If a conversion was performed, the cell is outlined in a dotted line and reading the formula will provide detail on the exact conversion applied. Some data were also estimated from figures, these values are also outlined in a dotted line. Where data were provided not in the units used in the table, these points were entered as text values with the corresponding units so as to avoid being included in the meta-analysis.