Abstract
Crinum biflorum Rottb. (syn. Crinum distichum) is an Amaryllidaceae plant used in African traditional medicine but very few studies have been performed on this species from a chemical and applicative point of view. Bulbs of C. biflorum, collected in Senegal, were extracted with ethanol by Soxhlet and the corresponding organic extract was purified using chromatographic methods. The pure compounds were chemically characterized by spectroscopic techniques (1D and 2D 1H and 13C NMR, HR MS and ECD) and X-ray analysis. Four homoisoflavonoids (1–4) and one alkylamide (5) were isolated and characterized as 5,6,7-trimethoxy-3-(4-hydroxybenzyl)chroman-4-one (1), as 3-hydroxy-5,6,7-trimethoxy-3-(4-hydroxybenzyl)chroman-4-one (2), as 3-hydroxy-5,6,7-trimethoxy-3-(4-methoxybenzyl)chroman-4-one (3) and as 5,6,7-trimethoxy-3-(4-methoxybenzyl)chroman-4-one (4), and the alkylamide as (E)-N-(4-hydroxyphenethyl)-3-(4-hydroxyphenyl)acrylamide (5), commonly named N-p-coumaroyltyramine. The relative configuration of compound 1 was verified thanks to the X-ray analysis which also allowed us to confirm its racemic nature. The absolute configurations of compounds 2 and 3 were assigned by comparing their ECD spectra with those previously reported for urgineanins A and B. Flavanoids 1, 3 and 4 showed promising anticancer properties being cytotoxic at low micromolar concentrations towards HeLa and A431 human cancer cell lines. The N-p-coumaroyltyramine (5) was selectively toxic to A431 and HeLa cancer cells while it protected immortalized HaCaT cells against oxidative stress induced by hydrogen peroxide. Compounds 1–4 also inhibited acetylcholinesterase activity with compound 3 being the most potent. The anti-amylase and the strong anti-glucosidase activity of compound 5 were confirmed. Our results show that C. biflorum produces compounds of therapeutic interest with anti-diabetic, anti-tumoral and anti-acetylcholinesterase properties.
Highlights
Plants and microorganisms are well-known sources of bioactive metabolites which have only been partly investigated [1]
Correlation spectroscopy with a 45◦ mixing pulse (COSY-45), Nuclear Overhauser effect spectroscopy (NOESY), heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments were performed using Bruker or Varian microprograms
The N-p-coumaroyltyramine alkylamide (5) was selectively cytotoxic against A431 and HeLa cancer cells while it protected immortalized HaCaT cells against oxidative stress induced by hydrogen peroxide
Summary
Plants and microorganisms are well-known sources of bioactive metabolites which have only been partly investigated [1]. Biomolecules 2021, 11, 1298 a plant family extensively studied essentially for its alkaloids and related isocarbostiryls content which show a broad spectrum of biological activities [2,3,4,5]. These plants are principally diffused in tropical and subtropical regions of the world, as Andean South. A. Special Issue of the journal Molecules was edited by Bastida J. and Berkov S. in 2020 on different aspects of Amaryllidaceae alkaloids including biodiversity, chemoecology, pharmacology, in vitro production, structural characterization, mass spectrometry and molecular modeling [8]. Advances on the chemical and biological characterization of the alkaloids and analogs isolated in the last decade from this plant family were reviewed by
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