Elsevier

Phytochemistry Letters

Volume 38, August 2020, Pages 78-83
Phytochemistry Letters

Montanacin-L and montanacin-K two previously non-described acetogenins from Annona montana twigs and leaves

https://doi.org/10.1016/j.phytol.2020.04.016Get rights and content

Highlights

  • The chemical study of the twigs and leaves of Annona montana led to the isolation of two previously non-described ACGs.

  • The previously no-described compounds were evaluated for their insecticide action against Spodoptera frugiperda.

  • The isolation and structure elucidation of compounds 1 and 2, along with their toxicity are reported.

Abstract

A phytochemical study on Annona montana twigs and leaves led to the isolation of eleven annonaceous acetogenins, including two previously non-described compounds, montanacin-L and montanacin-K. Their structures were elucidated by extensive analyses of spectroscopic data (IR, UV, HRTOFMS, EI-MS and 1H, 13C and 2D NMR). The ACGs montanacin-L, montanacin-K, montanacin-D and montanacin-E were evaluated for their toxicity against Spodoptera frugiperda Smith (Lepidoptera: Noctuidae). Results revealed that montanacin-D and montanacin-K exhibited insecticide action.

Graphical abstract

A phytochemical study on Annona montana twigs and leaves led to the isolation of two previously non-described ACGs as natural products montanacin-L (1) and montanacin-K (2). Given the problems caused by synthetic insecticides there has been an upsurging on research for plant compounds for insect control. Natural annonaceous acetogenins are promising metabolites for insect control.

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Introduction

The Annonaceae family includes about 2400 species within 108 genera, based on nucleotide sequences on multiple plastid DNA loci (Chatrou et al., 2012). This classification is better than previous ones based mostly on morphology. The new classification consists of four major clades which were given the taxonomic rank of subfamily (Chatrou et al., 2012).

Annonaceous acetogenins (ACGs) constitute a series of polyketides found almost exclusively in Annonaceae family plants, and are widely distributed in tropical and sub-tropical regions. They have been isolated from the fruit pulp, seeds, twigs, roots, stems, leaves, and bark of plants (Bermejo et al., 2005).

ACGs have attracted much attention mainly due to their in vitro and probably in vivo anticancer activities, but also because of their antiinflammatory, antitumor, pesticidal, antimalarial, anthelmintic, piscicidal, antiviral, and antimicrobial effects. (Arthur et al., 2012; C.-H. Hu, 2012; Chen et al., 2012c, 2012b, 2012a; Dai et al., 2012; Foong and Hamid, 2012; González-Esquinca et al., 2012; Grzybowski et al., 2012; Hamizah et al., 2012; Liaw et al., 2010; Chakrapani and A.R.R.J.B.A.K.V. (2011); Pomper et al., 2009)

In addition, they are potential inhibitors of plasma membrane NADH oxidase of cancer cells (Chakrapani and A.R.R.J.B.A.K.V. (2011)2011), inhibition resulting in a depletion of ATP levels which causes arrest in the cell cycle at the G1 phase, and subsequently apoptosis being induced (Dai et al., 2012). So, ACGs are regarded to be a probable source for potential drug development.

However, recent studies have reported the relationship existing between this type of compound and sporadic neurodegenerative tau pathologies in humans who have ingested annonaceous plants containing ACGs. (Höllerhage et al., 2009).

From a chemical viewpoint, ACGs are derivatives of long chain (C35 or C37) fatty acids. They are usually characterized by a long aliphatic chain bearing a terminal methyl substituted α,β-unsaturated γ-lactone ring with one, two, three tetrahydrofuran (THF) or tetrahydropyran (THP) rings.

A great advance in experimental techniques has led to many worldwide efforts focusing on the isolation and structural identification of new bioactive ACGs.

Previous results from our laboratory suggested that acetogenins from Annona cherimolia Mill. and A. montana Macfad. have larvicidal effects on Spodoptera frugiperda Smith (Lepidoptera) corn pest, (Alvarez Colom et al., 2007; Di Toto Blessing et al., 2015, 2012, 2010; Ruiz Hidalgo et al., 2018, 2016; Tolosa et al., 2014, 2012) nymphal and adult mortality on Oncopeltus fasciatus Dallas (Hemiptera) cotton pest, (Alvarez Colom et al., 2008) and insecticidal activity against Ceratitis capitata Wiedemann (Diptera) (Alvarez Colom et al., 2010).

Therefore, we investigated the chemical constituents of A. montana Macfad twigs and leaves, which resulted in the isolation of two previously non-described ACGs with THF and THP rings, as well as nine known ACGs. The two previously non-described compounds, montanacin-L and montanacin-K and the two known montanacin-D and montanacin-E were evaluated for their toxicity against Spodoptera frugiperda Smith (Lepidotera, Noctuidae). In this paper, the isolation and structure elucidation of compounds 1 and 2, along with their toxicity are reported.

Section snippets

Phytochemical investigation

The chemical study of A. montana Macfad twigs and leaves led to the isolation of two previously non-described ACGs as natural products: montanacin-L (1) and montanacin-K (2) (Fig. 1) and nine ACGs previously reported in the literature, montanacin-B (3) (Wang et al., 2000), montanacin-D (4) (Wang et al., 2000), montanacin-E (5) (Wang et al., 2000), annonacin-10-one (6) (Xu et al., 1989), cis-annonacin-10-one (7) (Lieb et al., 1990), annonacin-A (8) (Lieb et al., 1990), cis-annonacin (9) (Rieser

General experimental procedures

UV spectra were obtained by using a Shimadzu UV-Vis160A spectrophotometer. Optical rotations were measured with a Perkin-Elmer 241 polarimeter. IR spectra were obtained by a Shimadzu IR-408 spectrometer with KBr pellets. Spectrometer 1D (1H, 13C, and DEPT) and 2D (1H-1H COSY, HSQC, HMBC, and NOESY) spectra were recorded on an Bruker 200 MHz spectrometer by using the solvent signal as reference (CDCl3 at δ 7.26 and 77.0 ppm).

EIMS and HRQ-TOFMS 5600 LC/MS/MS were performed on a Thermo Polaris Q

Declaration of Competing Interest

The authors have declared no conflict of interest.

Acknowledgments

This work was financed by the Investigation Board of the National University of Tucuman (CIUNT) and The National Council of Scientific and Technical Research (CONICET).

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