Abstract
The present study was designated to evaluate the antioxidant, antibacterial and antischistosomal activities of Grateloupia livida (GL) extracts in vitro. A GL Ethanol extract (EE) was separated into petroleum ether (PE), ethyl acetate (EA), n-butyl alcohol (BuOH) and aqueous (AQ) fractions to fractionate the polar and non-polar compounds in the EE. Extracts antioxidant activities were evaluated in vitro by DPPH radical-scavenging, deoxyribose radical scavenging, and β-carotene bleaching assays, all using butylated hydroxytoluene (BHT) as the reference antioxidant compound. The most effective antioxidant properties were observed in the PE fraction in all three assays. Antimicrobial testing showed that the PE fraction exhibited broad-spectrum antimicrobial activity, with the PE fraction also exhibiting strong activity against the human pathogenic trematode S. japonicum adult worm. In order to investigate the relationships between bioactivity and chemical composition, the chemical composition of the PE fraction was analyzed by gas chromatography-mass spectrometry (GC-MS). In total, 25 components were identified in the PE fraction, most of which have known antioxidant and antimicrobial activities. However, none of the compounds have reported activity against Schistosoma, suggesting that the schistosomicidal activity of the PE fraction may be related to minor constituents present in the extract, or governed by more intricate synergistic or additive relationships. Finally, fractions with the greatest biological activity displayed neither cellular cytotoxicity, at concentrations up to 100 ug/ml, or acute oral toxicity in mice, at doses up to 2000 mg/kg. Based on antioxidant, antimicrobial, antischistosomal activities, and low toxicity, the PE fraction possesses properties useful for food preservation and overall improvement of human health.
Highlights
We applied the same approach to identify active components for Grateloupia livida (Harv) Yamada (GL), initially partitioning ethanol extract constituents into solventpartitioned fractions (Table 1).The percentage of GL weight extracted by ethanol was 14.8%
This yield was higher than yields found previously for the 70% ethanol extracts from the brown seaweed S.pallidum (12.7%), [7] but significantly lower than yields reported for ethanol extracts of seaweeds including Laminaria ochroleuca (21.2%), Saccorhiza polyschides (34.6%) and Fucus vesiculosus (24.1%)
[25] These considerable differences in the yield of ethanol extract from various seaweeds might be due to species-specific differences as well as changes in extraction conditions, such as fluctuations in solvent, temperature, and duration of extraction
Summary
Reactive oxygen species (ROS) such as the hydroxyl radical, superoxide anion and hydrogen peroxide radicals are formed in human cells through endogenous metabolism and result in extensive oxidative damage that in turn leads to geriatric degenerative disorders, cancer, and a wide range of other human diseases. [1] Antioxidants are effective in protecting living organisms against ROS-mediated oxidative damage, and several synthetic antioxidants are commercially available, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG). [2] due to safety issues and consumer demand, there has been considerable interest in replacing synthetic antioxidants with natural plant-based alternatives. [3] Several studies report a positive correlation between increased dietary intake of natural antioxidants and reduced coronary heart disease, reduced cancer mortality and longer life expectancy. [4,5]Marine algae have attracted attention in the search for natural bioactive compounds that may be used for new medicinal and functional food ingredients. 8,000 species of marine algae have been identified and grouped into different classes, including brown, red, and green seaweeds,[6] which have enormous potential to be sources for antioxidant, antimicrobial, antiviral, and antitumor drugs.[7]. Despite extensive research on the bioactive potential of extracts from the Grateloupia family, few studies have characterized the bioactive activities of GL, which is ubiquitous, cultivated and an important natural resources of the locality. In the present study, we demonstrate potent antioxidant, antibacterial and antischistosomal activity of GL extracts, using various in vitro assays, and characterize the chemical composition of active fractions by gas chromatography-mass spectrometry (GC-MS). The toxicity of active fractions was tested with the aim of identifying novel nutraceuticals to be further explored as potential functional foods or nutraceuticals
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