Repeated Silica Gel Chromatography Research Articles

Antimicrobial actions of α-mangostin against oral streptococci

The increasing prevalence of dental caries is making it more of a major world health problem. Caries is the direct result of acid production by cariogenic oral bacteria, especially Streptococcus mutans. New and better antimicrobial agents active against cariogenic bacteria are badly needed, especially natural agents derived directly from plants. We have evaluated the inhibitory actions of α-mangostin, a xanthone purified from ethanolic extracts of the tropical plant Garcinia mangostana L., by repeated silica gel chromatography. α-Mangostin was found to be a potent inhibitor of acid production by S. mutans UA159, active against membrane enzymes, including the F(H+)-ATPase and the phosphoenolpyruvate - sugar phosphotransferase system. α-Mangostin also inhibited the glycolytic enzymes aldolase, glyceraldehyde-3-phosphate dehydrogenase, and lactic dehydrogenase. Glycolysis by intact cells in suspensions or biofilms was inhibited by α-mangostin at concentrations of 12 and 120 µmol·L⁻¹, respectively, in a pH-dependent manner, with greater potency at lower pH values. Other targets for inhibition by α-mangostin included (i) malolactic fermentation, involved in alkali production from malate, and (ii) NADH oxidase, the major respiratory enzyme for S. mutans. The overall conclusion is that α-mangostin is a multitarget inhibitor of mutans streptococci and may be useful as an anticaries agent.

Triglycerides constituted of short and medium chain fatty acids and dicarboxylic acids in Momordica charantia, as well as capric acid, inhibit PGE2 production in RAW264.7 macrophages

This study was aimed to identify compounds in bitter gourd (Momordica charantia) ethyl acetate extract (EAE), which inhibit lipopolysaccharide-induced prostaglandin E2 (PGE2) production in RAW264.7 cells. Bitter gourd EAE was partitioned between n-hexane and methanol/H2O (90/10). The hexane fraction was further separated by repeated silica gel chromatographies, and a reverse phase (RP) C18 chromatography. Fraction RP-10 showed the highest inhibition effect on PGE2 production (Max inhibition = 96%, IC50 = 2.3 μg/ml) and was identified to be triglycerides constituted of short and medium chain fatty acids by 1H NMR, IR and H–HCOSY, and dicarboxylic acids by GC/MS. Fatty acids with 3–20 carbons were tested for the inhibitory activity, and capric acid exhibited the highest effect (Max inhibition = 99%, IC50 = 6.5 μM). In conclusion, triglycerides composed of short and medium chain fatty acids and dicarboxylic acids in bitter gourd inhibit PGE2 production, and capric acid is the most potent inhibitor among the fatty acids.

Composition of a Pyrolytic oil from Cupressus funebris Endl. of Vietnamese origin

AbstractA sample of pyrolytic oil of Vietnamese origin, extracted from Cupressus funbris Endl. was investigated by GC‐RI, GC‐MS and 13C‐NMR spectroscopy. In the pyrolytic oil, dominated by sesquiterpenes (76% of the total composition), 46 components were identified after repeated silica gel chromatography. The main components were: α‐cedrene (26.7%), cedrol (12.3%) and β‐cedrene (6.6%). The pyrolytic oil differed from the commercial Chinese cedarwood oil (C. funebris wood oil), on the one hand by the absence of thujopsene and conversely the presence of several bicyclo[4.4.0]decane hydrocarbons and alcohols (selinane and cadinane derivatives), and on the other hand by the presence, as minor components, of phenol derivatives. The composition of the pyrolytic oil was compared with that of a commercial sample of cerdarwood oil [53 components identified, thujopsene (25.9%), α‐cedrene (24.1%), cedrol (11.3%) and β‐cedrene (7.4%)]. Copyright © 2006 John Wiley & Sons, Ltd.

Anticariogenic activity of macelignan isolated from Myristica fragrans (nutmeg) against Streptococcus mutans

The occurrence of dental caries is mainly associated with oral pathogens, especially cariogenic Streptococcus mutans. Preliminary antibacterial screening revealed that the extract of Myristica fragrans, widely cultivated for the spice and flavor of foods, possessed strong inhibitory activity against S. mutans. The anticariogenic compound was successfully isolated from the methanol extract of M. fragrans by repeated silica gel chromatography, and its structure was identified as macelignan by instrumental analysis using 1D-NMR, 2D-NMR and EI-MS. The minimum inhibitory concentration (MIC) of macelignan against S. mutans was 3.9 microg/ml, which was much lower than those of other natural anticariogenic agents such as 15.6 microg/ml of sanguinarine, 250 microg/ml of eucalyptol, 500 microg/ml of menthol and thymol, and 1000 microg/ml of methyl salicylate. Macelignan also possessed preferential activity against other oral microorganisms such as Streptococcus sobrinus, Streptococcus salivarius, Streptococcus sanguis, Lactobacillus acidophilus and Lactobacillus casei in the MIC range of 2-31.3 microg/ml. In particular, the bactericidal test showed that macelignan, at a concentration of 20 microg/ml, completely inactivated S. mutans in 1 min. The specific activity and fast-effectiveness of macelignan against oral bacteria strongly suggest that it could be employed as a natural antibacterial agent in functional foods or oral care products.

Anti-MRSA Compounds from Hericium erinaceus (Bull.:Fr.) Pers.

Methicillin-resistant Staphylococcus aureus (MRSA) is currently one of the most prevalent pathogens in nosocomial infections. Because hospital-acquired MRSA strains exhibit resistance to many antibiotics and are transmitted from patient to patient via transiently colonized hands of hospital personnel, MRSA infections pose a serious problem for hospitalized patients. We found that extracts of the fruiting bodies and the mycelia of Hericium erinaceus (Bull.:Fr.) Pers. exhibited anti-MRSA activity. Therefore, we tried to isolate the anti-MRSA compounds from the fungus. Isolation of the active compounds was guided by anti-MRSA activity. The fungus was cultivated by shaking at 30 °C for 4 weeks. The culture was centrifuged, and the resulting residue was extracted with 85% ethanol, and the extract, after evaporating the solvent, was partitioned between chloroform and water and then ethyl acetate and water. Repeated silica gel chromatography and HPLC of the chloroform-soluble and ethyl-acetate–soluble parts gave five active compounds. The fruiting bodies of the fungus were also extracted with 85% ethanol, and the extract was concentrated and fractionated by solvent partitions between chloroform and water, and then ethyl acetate and water. Repeated silica gel chromatography and HPLC of the chloroform-soluble part gave an anti-MRSA compound.

Anti-MRSA Compounds from Hericium erinaceus (Bull.:Fr.) Pers.

350 International Journal of Medicinal Mushrooms Methicillin-resistant Staphylococcus aureus (MRSA) is currently one of the most prevalent pathogens in nosocomial infections. Because hospital-acquired MRSA strains exhibit resistance to many antibiotics and are transmitted from patient to patient via transiently colonized hands of hospital personnel, MRSA infections pose a serious problem for hospitalized patients. We found that extracts of the fruiting bodies and the mycelia of Hericium erinaceus (Bull.:Fr.) Pers. exhibited anti-MRSA activity. Th erefore, we tried to isolate the anti-MRSA compounds from the fungus. Isolation of the active compounds was guided by anti-MRSA activity. Th e fungus was cultivated by shaking at 30 °C for 4 weeks. Th e culture was centrifuged, and the resulting residue was extracted with 85% ethanol, and the extract, after evaporating the solvent, was partitioned between chloroform and water and then ethyl acetate and water. Repeated silica gel chromatography and HPLC of the chloroform-soluble and ethyl-acetate–soluble parts gave fi ve active compounds. Th e fruiting bodies of the fungus were also extracted with 85% ethanol, and the extract was concentrated and fractionated by solvent partitions between chloroform and water, and then ethyl acetate and water. Repeated silica gel chromatography and HPLC of the chloroformsoluble part gave an anti-MRSA compound. As a result, erinacines A (1) and B (2) were isolated as anti-MRSA compounds from the mycelia (Figure 1). Th ese compounds have already been isolated as nerve growth factor (NGF) stimulators (Kawagishi et al., 1994, 1996). Determination of the structures and estimation of detailed biological activity of the other active compounds are now in progress. In addition, a clinical test of this mushroom was done in a hospital in Japan, and MRSA in some patients disappeared when they were given this mushroom to eat.

Antibacterial activity of isoflavonoids isolated from Erythrina variegata against methicillin-resistant Staphylococcus aureus.

To screen 16 isoflavonoids isolated from Erythrina variegata (Leguminosae) for their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The roots of E. variegata were macerated with acetone. The chloroform-soluble fraction of the residue was subjected to repeated silica gel column chromatography followed by elution with various solvents. Structures of the isolated compounds were determined by extensive spectroscopic studies. Each compound was dissolved in dimethyl sulphoxide and added to agar plates (final concentration 1.56-100 microg ml(-1) and suspensions of MRSA spotted onto the agar plates to determine the minimum inhibitory concentration (MIC). Repeated silica gel chromatography yielded 16 compounds and spectroscopic studies revealed that all were isoflavonoids. Whilst 14 compounds showed antibacterial activity in this concentration range, the MIC values varied significantly among them. Of the active compounds, 3,9-dihydroxy-2,10-di(gamma,gamma-dimethylallyl)-6a,11a-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-gamma,gamma-dimethylallylpterocarpan (orientanol B) exhibited the highest activity with MIC values of 3.13-6.25 microg ml(-1). Erycristagallin and orientanol B showed the highest anti-MRSA activity (3.13-6.25 microg ml(-1). Erycristagallin and orientanol B could be leading compounds for phytotherapeutic agents against MRSA infections.

Characterization of a New Decahydropyridoquinoline from Indigofera longeracemosa Boiv. Ex Baill. (Fabaceae)

Repeated silica gel chromatography of the dichloromethane extract of air-dried stems of Indigofera longeracemosa followed by reverse-phase HPLC separation yielded a new decahydropyridoquinoline, rel-(3S, 5R, 6S, SR, 8aR, 12aR)-8-acetoxy-6-butyl-3-isothiocyanatodecahydropyrido (2,1) quinoline.

Protective effects of the fractions extracted from the callus of Acer nikoense Maxim. on alpha-naphthylisothiocyanate induced liver injury

It has been reported that the methanol extract from the bark of Acer nikoense MAXIM. (AN) and the fractions separated from this extract showed the protection for liver injuries induced by carbontetrachloride (CCl4) in rat. On the other hand, the evidence manifested that the fractions of the callus of young branches from AN were recognized to have protective effects on the CCl4-induced liver injuries in rat. In this study, the protective activities of the fractions extracted from the callus of AN were investigated on the alpha-naphthylisothiocyanate (ANIT)-induced liver injuries in rat. The protectively active principles on the ANIT-induced liver injuries were found in the ether soluble fraction. The components of the protective effect were purified by repeated silica gel chromatographies. One of the protective substances in this fraction was identified to be beta-sitosterol. The protective fractions on the ANIT-induced liver injuries showed the protective effects on ANIT-induced cholestasis, but did not show cholagogic effects.

Some aspects of (-)-citramalic acid accumulation by respiration-deficient mutants of yeasts.

A comparative study of the organic acid productivities of respiration-competent (normal) and respiration-deficient (RD) strains of brewers' yeasts (Saccharomyces carlsbergensis) was made using a chemically defined medium containing 5% glucose. After growing for 6 days, lactic and an unknown acids were mainly accumulated by RD-mutants, while acetic, succinic and lactic acids were the major acids accumulated by the normal strains.The unknown acid was then isolated in a pure form by repeated silica gel chromatography and was identified as (-)-citramalic acid by elemental analysis, IR and NMR spectra, and rotation measurement. (-)-Citramalic acid was also accumulated by RD-mutants in other media, and the ratio of (-)-citramalic acid to the total amount of organic acids produced was almost constant (32-39%), even when the amount of citramalic acid increased by increasing glucose concentration or by the addition of calcium carbonate to the media.