Abstract
The large number of marine organisms present in the ocean, together with the diverse marine environments to which they have adapted, provides an enormous and mostly unexploited source of structurally novel and biologically active secondary metabolites . Some of these organisms have provided compounds that have served as important leads in the discovery of new drugs , as probes in molecular pharmacology , and use as pest control agents . In particular, they are a rich source of antioxidants but there has been limited work in screening organisms containing this rich source of structurally unique natural products for antioxidant activity. For instance, there are a large number of active components in macroalgae with antioxidant properties, including pigments such as polyphloroglucinols and fucoxanthin , bioactive carbohydrates such as fucoidan and laminarin, minerals, and UV absorbing mycosporine like amino acids . Glutathione, an important antioxidant in plants, animals, fungi and some bacteria, is found in all macroalgae with some species containing as much as 3082 mg/100 g
Highlights
The large number of marine organisms present in the ocean, together with the diverse marine environments to which they have adapted, provides an enormous and mostly unexploited source of structurally novel and biologically active secondary metabolites [1]. Some of these organisms have provided compounds that have served as important leads in the discovery of new drugs [2], as probes in molecular pharmacology [3], and use as pest control agents [4]. They are a rich source of antioxidants but there has been limited work in screening organisms containing this rich source of structurally unique natural products for antioxidant activity
One way to screen crude marine extracts for antioxidant activity or radical-scavenging effects is to use either: (i) a solution based or (ii) a high performance thin layer chromatography (HPTLC) based 2,2diphenyl-1-picrylhydrazyl (DPPH) free radical bioassay[9,10,11,12]. This method is based on the use of stable DPPH free radical species which when added to a sample, react and neutralize antioxidants present in the sample [13,14]
If a known amount of DPPH is added to a sample, the decrease in absorbance at 517 nm due to the disappearance of DPPH free radical is directly proportional to the amount of antioxidants present
Summary
The large number of marine organisms present in the ocean, together with the diverse marine environments to which they have adapted, provides an enormous and mostly unexploited source of structurally novel and biologically active secondary metabolites [1]. In order to isolate and identify which are the most potent free radical scavengers present in a sample, the DPPH assay can be combined with either high performance liquid chromatography (HPLC) or high performance thin layer chromatography (HPTLC). HPTLC combined with DPPH radical detection of antioxidants in situ has been reported and successfully used to screen for antioxidants produced by marine bacteria and antioxidants present in plant extracts [18].
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