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Chemical screening, antioxidant properties and total phenolic content of Eunicella cavolini organic extract and semi-purified fractions

Marine organisms have traditionally been used as part of the diet resulting in certain benefits to human health. However, since the discovery of the first natural product in the 1940s, there have been reported more than 25, 000 molecules obtained from the sea. Soft and stony corals represent unique, complex and heterogenous living system, extremely fragile and susceptible to external influences (temperature, anthropogenic effects, predatory species) producing various secondary metabolites to survive [1, 2]. Many of those compounds showed interesting biological activity, both in vitro and in vivo which makes them promising candidates for drug development [3]. With the aim of isolating new biologically active natural products, we studied a yellow gorgonian coral Eunicella cavolini, a widely distributed species in the East Atlantic, particularly the Mediterranean Sea. Eunicella cavolini was extracted with dichloromethane and methanol to afford an organic extract (OE) followed by fractionation with different organic solvents (c- hexane, ethyl acetate and methanol) to obtain four semi-purified fractions (F1-F4). The presence of alkaloids, terpenoids, steroids, saponins, phenols and glycosides was examined by Mayer’s, Salkowski’s, Libermann- Burchard’s, froth, ferric chloride and Keller-Killiani tests, respectively. The antioxidant activity was assayed by ability to inhibit the stable, DPPH radical (1, 1- diphenyl-2- picrylhydrazyl) while the total phenolic content was estimated using Folin- Ciocalteu's phenol reagent and gallic acid as a standard [4]. The fraction F2 exhibited the strongest radical scavenging activity, displaying an IC50 value of 0.76 mg/mL, while the fraction F4 was found to contain the highest phenolic content of 2.93 mg gallic- acid equivalent/g dried sample. Pearson’s correlation coefficient showed moderately strong correlation between scavenging activity and phenolic content indicating that other types of compounds, detected by a series of qualitative chemical screening tests, contribute to antioxidant activity as well. Further studies will be performed in order to isolate and characterize secondary metabolites responsible for observed biological properties.

Eunicella cavolini extract/fractions ; antioxidant activity ; total phenolic content ; qualitative chemical screening

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