From Ecology to Biotechnology, Study of the Defense Strategies of Algae and Halophytes (from Trapani Saltworks, NW Sicily) with a Focus on Antioxidants and Antimicrobial Properties.

Concetta Messina,Claire Hellio,Andrea Santulli,Rozenn Trepos,Marilyne Fauchon,Vincenzo Laudicella,Giuseppe Renda

doi:10.3390/ijms20040881

Abstract

This study aimed at the characterization of the antioxidant power of polyphenol extracts (PE) obtained from the algae Cystoseira foeniculacea (CYS) (Phaeophyta) and from the halophyte Halocnemum strobilaceum (HAL), growing in the solar saltworks of western Sicily (Italy), and at the evaluation of their anti-microfouling properties, in order to correlate these activities to defense strategies in extreme environmental conditions. The antioxidant properties were assessed in the PE based on the total antioxidant activity test and the reducing power test; the anti-microfouling properties of the two PE were evaluated by measuring the growth inhibition of marine fish and shellfish pathogen bacteria as well as marine surface fouling bacteria and microalgae exposed to the fractions. Similar polyphenol content (CYS 5.88 ± 0.75 and HAL 6.03 ± 0.25 mg gallic acid equivalents (GAE) g−1 dried weight, DW) and similar reducing power percentage (93.91 ± 4.34 and 90.03 ± 6.19) were recorded for both species, even if they exhibited a different total antioxidant power (measured by the percentage of inhibition of the radical 2,2 diphenyl-1-picrylhydrazyl DPPH), with CYS (79.30) more active than HAL (59.90). Both PE showed anti-microfouling properties, being inhibitors of adhesion and growth of marine fish and shellfish pathogen bacteria (V. aestuarianus, V. carchariae, V. harveyi, P. elyakovii, H. aquamarina) and fouling bacteria (V. natriegens, V. proteolyticus, P. iirgensii, R. litoralis) with minimum inhibitory concentrations comparable to the commercial antifouling products used as a positive control (SEA-NINE™ 211N). Only CYS was a significant inhibitor of the microalgae strains tested, being able to reduce E. gayraliae and C. closterium growth (MIC 10 µg·mL−1) and the adhesion of all three strains tested (E. gayraliae, C. closterium and P. purpureum), suggesting its promise for use as an antifouling (AF) product.

Highlights

Natural bioactive compounds have been the most successful source of potential drugs and, historically, are considered to have been the first drugs used by humans, with records dating back to Mesopotamia and Egypt more than 3000 years ago [1]
This study aimed at the characterization of the antioxidant power of polyphenol extracts (PE) obtained from the algae Cystoseira foeniculacea (CYS) (Phaeophyta) and from the halophyte Halocnemum strobilaceum (HAL), growing in the solar saltworks of western Sicily (Italy), and at the evaluation of their anti-microfouling properties, in order to correlate these activities to defense strategies in extreme environmental conditions
The extraction of the total polyphenols was performed with different solvents, in order to evaluate the respective yield of polyphenols

Summary

Introduction

Natural bioactive compounds have been the most successful source of potential drugs and, historically, are considered to have been the first drugs used by humans, with records dating back to Mesopotamia and Egypt more than 3000 years ago [1]. Marine ecosystems are dynamic environments, and host organisms have adapted to live in such challenging habitats. This is especially true for sessile organisms, which employ numerous strategies to survive, ranging from spatial or temporal avoidance (ephemeral vs perennial species), to the production and secretion of physical and chemical barriers [6]. A unique variety of physical factors (salinity, dryness, elevate temperatures and high solar radiations) is found in hypersaline environments. These environments have been employed for human usages since ancient times, while nowadays, their biotechnological potential is being explored [11,12]

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