Antioxidant activity and flavonoid content in Lippia origanoides Kunth

Luciana Mendes Souza, Francine Fonseca, Júlio Silva, Amanda Silva, Julian Silva, Ernane Martins

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Introduction: Lippia origanoides Kunth. (Verbenaceae) is an aromatic shrub used as a spice and for medicinal purposes. Its medicinal use is generally associated to the essential oil obtained from its leaves. However, studies have shown the presence of flavonoids capable of sweeping off antioxidant free radicals.
Objectives: Determine the antioxidant capacity and content of total flavonoids in extracts from the leaves of eight specimens of L. origanoides obtained from the germplasm bank at the Institute of Agricultural Sciences of the Federal University of Minas Gerais.
Method: Antioxidant activity of the L. origanoides leaf extracts was evaluated with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical method. Estimations were made of the effective concentration (EC 50) and the antioxidant activity index (AAI). Total flavonoid content was determined by the aluminium chloride method. Analysis of variance was used to analyze the results. Means were verified with Tukey's test considering a 5% probability. Assessment of the relationship between flavonoids and antioxidant activity was performed with the Pearson correlation coefficient.
Results: Mean effective concentration (EC50) values were 27.09 µg ml -1 in the leaf specimen obtained from the Institute of Agricultural Sciences 1 (IAS 1, municipality of Salinas) and 44,38 µg ml-1 in the specimen obtained from IAS 6 (municipality of Cristália). Antioxidant activity was more effective in the IAS 1 specimen, since its EC50 was the lowest. The ethanolic L. origanoides leaf extracts displayed moderate antioxidant activity. Average flavonoid content in the IAS 6 specimen was significantly higher than in the remaining specimens (417.04 mg RE g-1), whereas the lowest flavonoid content was found in the IAS 2 specimen (from the municipality of Turmalina) (114.69 mg RE g-1). A significant positive relationship (r = 0.83) was found between total flavonoid content in the extracts and antioxidant activity.
Conclusions: The extracts studied display different antioxidant activities and flavonoid contents, and classify for their use as natural antioxidants.

Keywords: carvacrol, thymol, DPPH, flavonoids, germplasm bank.