Three New Steroidal Glycoalkaloids from Solanum pseudoquina A. St.-Hil. (Solanaceae)

Vitor Soares,Rita Lafetá,Antonio Jorge Da Silva,Thaís Bezerra,Ricardo Borges

doi:10.21577/0103-5053.20160229

Abstract

Three new steroidal glycoalkaloids (SGA) were isolated from green berries of Solanum pseudoquina A. St.-Hil. The extract obtained after treatment with 5% acetic acid aqueous solution was subjected to several chromatographic procedures, leading to an enriched alkaloidal fraction. The enriched alkaloidal fraction was subjected to a semi preparative high performance liquid chromatography (HPLC) leading to the isolation of three new SGA from S. pseudoquina: 3-O-(β-D-glucopyranosyl) (20S,25S)-22,26-epimino-16α-acetyl-cholesta-22(N)ene, 3-O-(β-D-glucopyranosyl) (20R,25ξ)-23,26-epimino-16α-acetyl-cholesta-5,23(N)-dien-22one and 3-O-(β-D-glucopyranosyl) (20S,25ξ)-23,26-epimino-16α-acetyl-cholesta-5,23(N)-dien22-one. The structures of the new compounds were elucidated with the help of 1D and 2D nuclear magnetic resonance (NMR) and infrared spectroscopy together with high resolution electrospray ionization and atmospheric pressure chemical ionization mass spectrometry.

Highlights

The aqueous acidic extract of S. pseudoquina berries was subjected to chromatographic purification over a XAD‐2 resin and repeated silica gel column chromatography, followed by semi preparative high performance liquid chromatography (HPLC) purification, to afford three new compounds (1, 2, and 3) (Figure 1)
The edited heteronuclear single quantum coherence (HSQC) spectrum allowed the identification of five methyl groups, twelve methylene and fourteen methine groups
The results found so far led us to propose that compound 1 is a 22(N)-unsaturated 22,26-epimino-5αcholestane type steroidal alkaloid bearing an acetyl group at C-16 and a β-anomeric glucopyranosyl residue at C-3

Summary

Introduction

The aqueous acidic extract of S. pseudoquina berries was subjected to chromatographic purification over a XAD‐2 resin and repeated silica gel column chromatography, followed by semi preparative HPLC purification, to afford three new compounds (1, 2, and 3) (Figure 1). The 1H NMR spectrum of compound 1 (Table 1) displayed two superimposed three proton singlet resonances at d 0.65 (H-18 and H-19) assigned to two steroidal angular methyl groups and two three proton doublet signals at 1.13 (d, 3JHH 6.9 Hz, H-21) and 0.83 (d, 3JHH 6.6 Hz, H-27), Figure 1.

Results

Conclusion