Eleutherol

Application of MEKC and monolithic CEC for the analysis of bioactive naphthoquinones in Eleutherine americana.[Pubmed:19862752]

Electrophoresis. 2009 Nov;30(21):3757-63.

Two microscale separation techniques for the analysis of bioactive naphthoquinones in Eleutherine americana were developed and validated. By MEKC four compounds (eleuthoside B, isoeleutherin, Eleutherol and eleutherinoside A) could be determined in plant extracts using an aqueous electrolyte solution composed of 25 mM sodium tetraborate, 50 mM sodium cholate and 20% THF. CEC on a polymeric methacrylate-based monolith with strong cationic properties showed promising results, as it additionally enabled the separation of two enantiomers, eleutherin and isoeleutherin. The mobile phase for CEC experiments comprised 3 mM ammonium formate in a mixture of ACN and water. At an applied voltage of -25 kV, all five markers were baseline separated in less than 12 min. Both methods were successfully validated for linearity (MEKC: R(2) > or = 0.999; CEC: R(2) > or = 0.997), sensitivity (MEKC: LOD = 4-5 microg/mL; CEC: LOD=2-8 microg/mL), accuracy (MEKC: 96.5-102.7% recovery; CEC: 97.1-103.5% recovery) and precision (MEKC: sigma(rel) < or = 2.43%; CEC: sigma(rel) < or = 2.21%). The quantitative analysis of naphthoquinone derivatives in several E. americana samples showed that both methods are suitable for practical applications, because the results were well comparable to those obtained by established techniques such as HPLC.

Antifungal Activity of Pyranonaphthoquinones Obtained from Cipura paludosa Bulbs.[Pubmed:26594766]

Nat Prod Commun. 2015 Sep;10(9):1589-92.

Previous studies with the bulbs of Cipura paludosa (Iridaceae) showed the presence of pyranonaphthoquinones, including eleutherine, isoeleutherine and Eleutherol. The aim of this study was to evaluate the antifungal properties of these compounds. The activity was tested against the clinically relevant yeasts Candida albicans, C. tropicalis, Saccharomyces cerevisiae and Cryptococcus neoformans with the microbroth dilution method, following the guidelines of CLSI. Eleutherine, isoeleutherine and Eleutherol all presented significant antifungal activity, especially the first two, the major components, with MIC values between 7.8 and 250 microg/mL. In conclusion, these results demonstrate that C. paludosa bulbs produce active principles with relevant antifungal potential, contributing, at least in part, to the antimicrobial effect evidenced for this plant and justifying its popular use against infections.

Polyketides from Eleutherine bulbosa.[Pubmed:20835959]

Nat Prod Res. 2010 Oct;24(16):1578-86.

Four new polyketides, (R)-4-hydroxyeleutherin, eleuthone, eleutherinol-8-O-beta-D-glucoside and isoeleuthoside C (dihydroisoeleutherin-5-O-beta-D-gentiobioside) were isolated from the bulbs of Eleutherine bulbosa, to join eleutherin, isoeleutherin, eleutherinol, Eleutherol, eleuthoside B (Eleutherol-4-O-beta-D-gentiobioside), eleuthoside C (dihydroeleutherin-5-O-beta-D-gentiobioside), hongconin (4-oxodihydroisoeleutherin) and elecanacin, which have already been isolated from the same plant. The structures of the new polyketides, based on oxydated cyclic systems, have been elucidated by chemical and spectroscopic methods.

Eleutherinone, a novel fungitoxic naphthoquinone from Eleutherine bulbosa (Iridaceae).[Pubmed:12973542]

Mem Inst Oswaldo Cruz. 2003 Jul;98(5):709-12. Epub 2003 Sep 8.

The dichloromethane extract prepared from the underground parts of Eleutherine bulbosa (Miller) Urban (Iridaceae) showed strong activity in the direct bioautography assay with the phytopathogenic fungus Cladosporium sphaerospermum. This assay was used to guide the fractionation of this extract and allowed the isolation of four compounds: the new naphthoquinone eleutherinone[8-methoxy-1-methyl-1,3-dihydro-naphtho(2,3-c)furan-4,9 -dione] and the known compounds, previously isolated from this species, eleutherin [9-methoxy-1(R),3(S)-dimethyl-3,4-dihydro-1H-benzo(g)isochromene-5,10-dione], isoeleutherin [9-methoxy-1(R),3(R)-dimethyl-3,4-dihydro-1H-benzo(g)isochromene-5,10-dione], and Eleutherol [4-hydroxy-5-methoxy-3(R)-methyl-3H-naphtho(2,3-c)furan-1 -one]. All quinonoid compounds showed strong antifungal activity in the bioautography assay at 100 g/spot, while Eleutherol was inactive.

alpha-Glucosidase inhibitors from the bulb of Eleutherine americana.[Pubmed:25212136]

Food Chem. 2011 Sep 15;128(2):308-11.

One effective way to treat diabetes is by suppressing carbohydrate digestion due to the utilisation of alpha-glucosidase inhibitors (AGIs). The determination of prospective herbs, done in vitro by using enzyme assay, resulted in the finding of Eleutherine americana, which showed a potent inhibitory activity. A 50% aqueous methanol-soluble extract of bulbs of E. americana was chromatographed successively and the active fractions were further purified with preparative high performance liquid chromatography (HPLC) to isolate active compounds against alpha-glucosidase. Structure determination by mass and NMR analysis revealed that these isolated compounds were Eleutherol (1), eleutherinoside A (2), and eleuthoside B (3) based on comparisons with the reference data. Considering the amount and the inhibitory activity of each naphthalene in the whole extracts, the bulb of E. americana inhibitory activity against alpha-glucosidase might be a result of compound 2 (IC50=0.5mM, yield=5mg/50g plant sample, with a characteristic structure which has never been found in other AGIs. AGIs play an important role for the treatment of diabetes, therefore these results may suggest novel alternatives for diabetes treatment management.

Analysis of naphthoquinone derivatives in the Asian medicinal plant Eleutherine americana by RP-HPLC and LC-MS.[Pubmed:18486396]

J Pharm Biomed Anal. 2008 Aug 5;47(4-5):990-3.

The first analytical procedure for the determination of a new naphthopyrone, eleutherinoside A, together with the known bioactive compounds eleuthoside B, isoeleutherin, eleutherin and Eleutherol in Eleutherine americana was established. Optimum HPLC separation of these naphthoquinone derivatives was possible on RP-12 column material, using water and acetonitrile as mobile phase. Flow-rate, detection wavelength and temperature were adjusted to 1.0 mL/min, 254 nm and 40 degrees C, respectively. Validation results indicated that the HPLC method is well suited for the determination of naphthoquinone derivatives in the bulbs of E. americana with a good linearity (r2>0.9996), precision (intra-day R.S.D. <4.70%, inter-day R.S.D. <5.68%) and recovery rates from 96.26 to 103.48%. Limit of detection (LOD) was found to be below 0.84 microg/mL for all five compounds. LC-MS analyses performed in positive and negative electrospray ionization mode assured peak purity and identity. The analysis of different E. americana samples from Thailand revealed that Eleutherol (0.10-0.20%) was dominant in all specimens, followed by isoeleutherin and eleutherin. The new natural product 2,5-dimethyl-10-hydroxynaphthopyrone 8-O-beta-d-glucopyranoside occurred in percentages of less than 0.05%.

Assessment of antistaphylococcal activity of partially purified fractions and pure compounds from Eleutherine americana.[Pubmed:19350980]

J Food Prot. 2009 Feb;72(2):354-9.

Ready-to-eat foods were investigated for contamination with methicillin-resistant Staphylococcus aureus (MRSA), and the partially purified fractions from the bulb of Eleutherine americana were evaluated for their anti-MRSA activity. Partially purified fractions Ea6.3 and Ea9 demonstrated good antibacterial activity with a MIC of 125 to 500 microg/ml and MBC of 250 to > or =1000 microg/ml against all the food isolates. Fraction Ea6.3 produced a MIC and MBC of 250 and 500 microg/ml, respectively, whereas fraction Ea9 yielded MIC and MBC of 125 and > or =1000 microg/ml, respectively, against the enterotoxin-producing reference strains. Growth curves in the presence of fraction Ea6.3 at 4 x MIC resulted in total elimination of all the test strains between 20 and 24 h, while fraction Ea9 reduced bacterial population by at least 6 log relative to the control. The partially purified fractions were further purified to obtain pure compounds identified as Eleutherol, eleutherin, isoeleutherin, hongconin, two anthraquinones, and elecanacin. The antibacterial activities of these compounds were also investigated; they produced MICs ranging from 31.25 to > or =1000 microg/ml. This study suggests that E. americana crude extract or its partially purified fractions have potentials for application as natural food preservatives.