Antifungal Activity of the Extract of a Macroalgae, Gracilariopsis persica, against Four Plant Pathogenic Fungi.

Latifeh Pourakbar,Hesham Ali El Enshasy,R Z Sayyed,Sina Siavash Moghaddam

doi:10.3390/plants10091781

Abstract

Nowadays, the extract of seaweeds has drawn attention as a rich source of bioactive metabolites. Seaweeds are known for their biologically active compounds whose antibacterial and antifungal activities have been documented. This research aimed to study the profile of phenolic compounds using the HPLC method and determine biologically active compounds using the GC-MS method and the antifungal activity of Gracilariopsis persica against plant pathogenic fungi. G. persica was collected from its natural habitat in Suru of Bandar Abbas, Iran, dried, and extracted by methanol. The quantitative results on phenolic compounds using the HPLC method showed that the most abundant compounds in G. persica were rosmarinic acid (20.9 ± 0.41 mg/kg DW) and quercetin (11.21 ± 0.20 mg/kg DW), and the least abundant was cinnamic acid (1.4 ± 0.10 mg/kg DW). The GC-MS chromatography revealed 50 peaks in the methanolic extract of G. persica, implying 50 compounds. The most abundant components included cholest-5-en-3-ol (3 beta) (27.64%), palmitic acid (17.11%), heptadecane (7.71%), and palmitic acid methyl ester (6.66%). The antifungal activity of different concentrations of the extract was determined in vitro. The results as to the effect of the alga extract at the rates of 200, 400, 600, 800, and 1000 μL on the mycelial growth of four important plant pathogenic fungi, including Botrytis cinerea, Aspergillus niger, Penicillium expansum, and Pyricularia oryzae, revealed that the mycelial growth of all four fungi was lower at higher concentrations of the alga extract. However, the extract concentration of 1000 μL completely inhibited their mycelial growth. The antifungal activity of this alga may be related to the phenolic compounds, e.g., rosmarinic acid and quercetin, as well as compounds such as palmitic acid, oleic acid, and other components identified using the GC-MS method whose antifungal effects have already been confirmed.

Highlights

Algae are autotrophic organisms that contain chlorophyll but lack flowering organs or real roots, stems, and leaves and can convert solar energy into chemical energy by photosynthesis [1]
The results of the present study revealed that the extract of G. persica had a high potential to inhibit the mycelial growth of plant pathogenic fungi
Singh and Raadha [63] studied the G. corticata extract. They found that this species, at a rate of 1000 μL, could inhibit the growth of human pathogenic bacteria and fungi, including Salmonella typhimurium, Escherichia coli, Staphylococcus aureus, and Candida albicans, and was a natural source of antibiotics

Summary

Introduction

Algae are autotrophic organisms that contain chlorophyll but lack flowering organs or real roots, stems, and leaves and can convert solar energy into chemical energy by photosynthesis [1]. Growth stage, and environmental conditions, algae can contain different amounts of bioactive compounds, including secondary metabolites, that could exhibit antiviral, antibacterial, and antifungal activities [4,5,6,7] Plant diseases, especially those caused by plant pathogenic fungi, are key factors in the production and quality of crops [8,9,10] and in the postharvest life of fresh fruit and vegetables [11]. Aspergillus niger is one of the most dominant species from the genus Aspergillus, which is responsible for black mold disease in fruits and vegetables [15,16] It is known as the common contaminant of foods, especially in sun-dried foods, grains, and nuts, and is the primary agent of postharvest rot of fruits and vegetables. This species is the most important postharvest pathogen of apples and pears as it damages them extensively during storage but is vital, as it produces the carcinogen toxin patulin in the infected fruits used to make fruit juice [20]

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