The aim of the study is to examine in vitro antioxidant and antimicrobial activities of the methanol extract of the green microalga Trentepohlia umbrina. Antioxidant activity was evaluated by five different methods: free radical scavenging, superoxide anion radical scavenging, reducing power, determination of total phenolic compounds and determination of total flavonoid content. As a result of the study methanol extract of Trentepohlia umbrina had moderate free radical scavenging activity with IC50 values 665.28 ?g/ml. Moreover, the tested extract had effective reducing power and superoxide anion radical scavenging. Total content of phenol and flavonoid in extract were determined as pyrocatechol equivalent, and as rutin equivalent, respectively. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method against five species of bacteria and five species of fungi, including agents of human, animal and plant diseases, mycotoxin producers, and food spoilage agents. Generally, the tested extract had relatively strong antimicrobial activity against the tested microorganisms with minimum inhibitory concentration values ranging from 1.25 to 5 mg/ml. The present study shows that tested methanol extract demonstrated relatively strong antioxidant and antimicrobial activities. It suggests that this microalga may be used as good sources of natural antioxidant and antimicrobial agents.
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