Four new cycloartane-type triterpenoids from the leaves of Combretum mellifluum Eichler: assessment of their antioxidant and antileishmanial activities

ABSTRACT

The beneficial pharmacological actions including antioxidant effects as an antileishmanial, antibacterial, antifungal, antidiabetic, anti-inflammatory, antitumor, antiviral, and analgesic of compounds isolated from Combretum mellifluum Eichler (Combretaceae) are well established. The aim of the present study was to determine the phytochemistry as well as assess the antioxidant and antileishmanial activities of the leaves from Combretum mellifluum Eichler (Combretaceae). Analysis of ethanolic extract resulted in isolation and identification of two epimeric mixtures of four previously unknown cycloartane-type triterpenoids, methyl quadrangularate M and methyl 24-epiquadrangularate M, and 2α,3β,24β-trihydroxy-cycloart-25-ene and 2α, 3β, 24α-trihydroxy-cycloart-25-ene, and eight known compounds. Their structures were using one-dimensional nuclear magnetic resonance (1D NMR), 2D NMR and high-resolution electrospray ionization mass spectroscopy (HRESIMS) analysis. Further, the extract and fractions were tested for antioxidant potential. The ethyl acetate and aqueous fractions demonstrated the highest antioxidant activity against 2,2-dipheny-1-picrylhydrazl (DPPH) free radicals, which correlated directly with total flavonoid content. All extracts and fractions from C. mellifluum Eichler were assessed for antileishmanial activity. The supernatant fraction exhibited highest potential, inhibiting the growth of Leishmania amazonensis with IC₅₀ value 31.29 μg/ml. Our findings provide information on the chemical composition of C. mellifluum and the potential beneficial therapeutic usefulness as an antioxidant agent in various diseases.

KEYWORDS:

• Combretum mellifluum
• Combretaceae
• triterpenoids
• antileishmanial activity
• antioxidant activity

Acknowledgments

The authors wish to acknowledge the Brazilian research funding agencies National Council for Scientific and Technological Development (CNPq, 302470/2018-2 and 406126/2018-6) and Instituto Nacional de Ciência e Tecnologia em Biodiversidade e Produtos Naturais (INCT BioNat, 465637/2014-0) for financial support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data supporting of this study are available within the supplementary materials.

Author contributions

J. S. Silva and A. M. Lima contributed to isolation and antioxidant activity. R. R. S. de Farias contributed to species collection and identification. R. R. L. Santos and J. A. A. Carvalho performed the anti-leishmanial study. J. Q Junior discussed antioxidant and antileishmanial evaluation. B. Q. Araújo analyzed the samples by GC-MS. G. M. Vieira Júnior and M. H. Chaves identified the molecules. M. Rai, É L F Ferreira, and M H Chaves conceived and wrote the manuscript. All other authors discussed and commented on the manuscript preparation.

Additional information

Funding

This work was supported by the CNPq [302470/2018 and 406126/2018-6] and Instituto Nacional de Ciência e Tecnologia em Biodiversidade e Produtos Naturais [465637/2014-0].