Estudo fitoquímico das partes aéreas da Melochia tomentosa L.

Abstract

Ancient reports reveal the use of natural products for the most diverse purposes, such as therapeutic, agricultural, defense mechanisms against pests and in the search for relief or cure of illnesses. Currently, the culture of using medicinal plants to treat diseases remains alive. The Malvaceae family represents a group of plants widely spread throughout Brazil, especially in the Southeast and Northeast regions. The species Melochia tomentosa L., popularly known as ‘Malva-roxa’ or ‘Candieiro’, is a herb native from the caatinga of Brazilian Northeastern usually used to treat flu, colds, bronchitis and lung inflammation. The literature reports the isolation and identification of twenty-four chemical constituents in few studies, which makes this species the target of this research. Considering that, the present work aims to carry out a phytochemical study on the aerial parts of the species M. tomentosa and investigate the antioxidant potential in order to contribute to the taxonomic and biological knowledge of the Malvaceae family. The aerial parts of the species were collected in August 2022, in the rural area of Jataúba City, Pernambuco. Using the collected botanical material, an exsicata was prepared and deposited in the Jaime Coelho de Moraes Herbarium, at the Agricultural Sciences Center, at the Federal University of Paraíba (CCA/UFPB). After being dried and crushed, the plant material was submitted to Soxhlet and maceration extraction, producing n-hexane, chloroform, methanolic and ethanolic extracts, which were submitted to phytochemical study, quantification of Total Flavonoids, and compound identification by LC-MS, as well as biological assays to investigate its antioxidant activity as described in the literature. The results obtained indicated that alkaloids, steroids, tannins, flavonoids and coumarins are present in the aerial parts of M. tomentosa. Through phytochemical screening with hexane, chloroform and methanolic extracts from the aerial parts of M. tomentosa, it was possible to characterize the presence of alkaloids, steroids, tannins, flavonoids and coumarins. The total flavonoid content for these extracts was quantified at 2.04 mg, 2.38 mg and 2.33 mg EQ/g, respectively, indicating promising chemical and biological potential. The chromatographic fractionation of the methanolic extract allowed the obtaining of fractions that, after analysis by LC-MS, led to the identification of 20 compounds (identified for the first time in the species), of which 12 are flavonoids, with emphasis on the peak majority characterized as the glycosylated flavonoid tiliroside, widely isolated from Malvaceae species and known for a wide range of biological activities. The evaluation of the antioxidant potential of EEB by the DPPH assay showed an EC50 value = 121.81 μg/mL, demonstrating a good profile in the elimination of these free radicals, corroborating data described in the literature. The results obtained contributed to the chemical and biological profile of the Malvaceae s.l. family and encourage the continuation of studies, with the aim of isolating the identified compounds and characterizing them structurally, as well as exploring the antioxidant potential of these substances.