Investigação fitoquímica das folhas de Metternichia macrocalyx

Abstract

The history of medicinal plant usage combines empirical and scientific knowledge regarding their therapeutic properties. Brazil, home to the world's largest biodiversity, holds significant potential for developing novel drugs from natural products. The Solanaceae family, one of the most relevant among angiosperms, is recognized for producing various bioactive secondary metabolites and includes Metternichia macrocalyx, an endemic species of the Caatinga biome that lacks in- depth phytochemical studies. Given the abundance of characteristic metabolites in this family, this study aims to characterize the chemical composition of M. macrocalyx leaves using classical and modern techniques. Plant material was collected in Boa Vista do Tupim, Bahia, dried in an oven, ground, and macerated with 95% ethanol to obtain the crude ethanolic extract (EEB). The extract was dissolved in an ethanol:water solution (7:3 v/v) and partitioned with hexane, dichloromethane, and ethyl acetate. The ethyl acetate phase was fractionated by column chromatography using silica gel as the stationary phase and hexane, ethyl acetate, and methanol as the mobile phase, yielding 17 fractions. Among these, fraction A13 was analyzed by analytical HPLC, where a method for compound identification was developed and later applied on a preparative scale, resulting in 12 fractions. Structural identification of the chemical constituents was performed through spectroscopic analysis of ¹H and ¹³C NMR data, both one-dimensional and two-dimensional, and comparison with literature data. Based on these analyses, the compound (MMA-2) in fraction A13.12 was identified as Kaempferol-3-O-β- xylopyranosyl-(1→2)-α-rhamnopyranoside. Additionally, an HPLC-ESI-MS/MS methodology was developed, enabling the characterization of 13 glycosylated flavonoids present in the MPF_A13 fraction. Thus, this study significantly advances the phytochemical knowledge of the Metternichia genus and M. macrocalyx, constituting the first scientific report on the identification and characterization of glycosylated flavonoids in this species.