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ARTICLE

Potential antioxidant and toxicological activity of the essential oil of Rhaphiodon echinus (Nees & Mart) Schauer (Lamiaceae): morphoanatomy and polyphenolic composition of its extracts

Rodrigues Costa A^1,2, PS Pereira³, MK Alves de Sousa^1,2, FC Rodrigues⁵, VR Duarte Mendes¹, KR Rodrigues Lima¹, L Marivando Barros^1,4, CM Rocha Sousa¹, MS Alcântara¹, AB Leite Cavalcante⁴, R Cruz Macedo⁵, JP Kamdem³, AE Duarte^1,2

1 Center of Biological and Health Sciences (CCBS), Department of Biological Sciences, Regional University of Cariri (URCA), Crato 63105-000, CE, Brazil
2 Biology and Toxicology Laboratory (BIOTOX)., Regional University of Cariri (URCA), Crato, CE, Brazil;
3 Department of Biological Sciences, Microscopy Laboratory (LABOMIC), Regional University of Cariri (URCA), CEP: 63105-000, Crato, CE, Brazil.
4 Laboratory of Plant Ecophysiology (LECOV), Regional University of Cariri (URCA), Crato, CE, Brazil.
5 Secretariat of Education of the State of Ceará. Juazeiro do Norte, CE, Brazil.

Address correspondence to: Antonia Eliene Duarte, e-mail:

Phyton-International Journal of Experimental Botany 2018, 87(all), 79-86. https://doi.org/10.32604/phyton.2018.87.079

Abstract

The species Rhaphiodon echinus, known as betonica or creeping mint, is considered an infesting plant species, typical of the caatinga biome. Morphoanatomy is a very important tool to study the structure of plants, both its external and internal morphology, opening the knowledge about the production of secondary metabolites. These compounds are of great importance for scientific research, which may present themselves as the best antioxidants. Taking into account a lack of data in the literature on the essential oil of R. echinus, this study aimed to demonstrate its antioxidant activity and toxicity. In order to test this hypothesis, tests were carried out by the DPPH method, its toxicological activity on Artemia salina microcrustacean, as well as studies involving cuts of plant anatomy of leaf structures of the species. The vegetal material was collected at URCA and the essential oil was obtained by hydrodistillation, in a type of Clevenger. The HPLC profile of the extract revealed caffeic acid (62.45 mg/g), gallic acid (15.36 mg/g), Quercetin (9.02 mg/g) as the major compounds in the morning, while quercetin (4.15 mg/g) and caffeic acid (2.03 mg/g) were the major compounds in afternoon. DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical was used to assess the radical scavenging ability of the oil. The results demonstrated that the oil exhibited IC₅₀ of 297.7 μg/mL in emulsions with ascorbic acid 73.07 μg/mL. The A. salina lethality assay showed that the oil was toxic at concentrations above 50 μg/mL, with an LC₅₀ of 2.4 μg/mL compared to the positive control, LC₅₀ was 11.50 μg/mL. Regarding the results of the research in Plant Anatomy, some peculiarities for R. echinus are described. Up to date, studies on the toxicity of this plant have not been published.

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