A Substance Inhibiting the Growth of Lactic Acid Bacteria in Duhat (Sizygium Cumini Skeels) Bark
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Biocontrol Science, 2000, Vol.5, No.1, 33-38 Original A Substance Inhibiting the Growth of Lactic Acid Bacteria in Duhat (Sizygium cumini Skeels) Bark KIYOSHI MURA*, HIDEAKI SHIRAMATSU, AND WAHACHIRO TANIMURA Faculty of Applied Bioscience, Tokyo University of Agriculture , 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan Received 2 April 1999/Accepted 8 September 1999 We isolated a substance inhibiting the growth of lactic acid bacteria from duhat bark, which is added to "basi" , a sugar cane wine in the Philippines, and investigated its structure . By adding gelatin to the aqueous extract of duhat bark (AEDB), 63.2% of the polyphenol compo- nents in AEDB were precipitated, and the resulting supernatant lost its inhibitory activity on the growth of lactic acid bacteria. This result indicates that the inhibitory substance was the polyphenol component combining to protein. In addition, we fractionated AEDB into two frac- tions by ultrafiltration and investigated their inhibitory activities on the growth of lactic acid bacteria. A strong inhibitory activity was found in the fraction having molecular weight (MW) above 1•~104 containing about 53% of the polyphenol components in AEDB, indicating that the main inhibitory substance is a polyphenol component with high MW. We then separated the polyphenol components with MW above 1•~104 by ion-exclusion chromatography using CM- Sepharose CL-6B, and obtained a polyphenol component with inhibitory activity on the growth of lactic acid bacteria. The polyphenol component produced gallic acid, anthocyanidins of delphinidin and cyanidin, and glucose by hydrolysis with HCl, and was assumed to be con- densed tannin comprised of gallic acid and leucoanthocyanin. Key words : Duhat/Basi/Lactic acid bacteria/Polyphenol/Condensed tannin. INTRODUCTION other materials used in "basi" production on the growth of lactic acid bacteria, acetic acid bacteria and In the northwestern Luzon Island in the Philippines yeasts. We found that many of these materials there is a sugar cane wine called "basi" (Tanimura strongly inhibited the growth of lactic acid bacteria et al., 1977). Among liquors made from sugar cane, and acetic acid bacteria, which cause deterioration rum, which is well-known throughout the world, is a during fermentation, and identified that the addition of spirituous liquor, while "basi" is non-spirituous. The barks and other materials is indispensable to the fer- characteristic of "basi" production is the addition of mentation of "basi" in the Philippines, a tropical re- barks and the likes to sugar cane juice before fermen- gion with high air temperatures. Moreover, we tation. Those materials usually used in "basi" prod- investigated the substances inhibiting the growth of uction include samac (Macharanga grandifolia Linn.) lactic acid bacteria in samac bark and fruit and identi- bark, fruit and leaves, and duhat (Sizygium cumini fied that, the main inhibitory substance was con- Skeels) bark. densed tannin comprised of catechin and leuco- In previous studies (Mura and Tanimura, 1986; anthocyanin in samac bark, and was gallotannin Mura et al., 1986, 1987 and 1996) , we investigated combining glucose or xylose with multiple galloyl radi- the impact of aqueous extracts from some barks and cals in samac fruit. In this study, we report the investigation results on *Corresponding author . Tel : +81-3-5477-2459, Fax : +81- the substance inhibiting the growth of lactic acid bac- 3-5477-2626. teria in duhat bark used in "basi" production. 34 K.MURA ET AL. MATERIALS AND METHODS detected by the blue color using the spray of potas- sium ferricyanide-ferric chloride reagent (Nakagawa Preparation of AEDB and Torii, 1964). The polyphenol compounds sepa- Dry duhat bark, used in "basi" production in the rated by TLC were individually determined by a TLC Philippines, was used as the material in this study. scanner (CS-920; Shimadzu Co., Ltd., Kyoto) at a The bark was crushed and extracted with water of 50- wavelength of 630 nm. fold volume in boiling water for 30 min, and the extrac- tion was performed three times. All extracts were TLC and absorption spectrum measurement for filtered, concentrated under reduced pressure, and anthocyanidins what was used in this study was an aqueous extract Anthocyanidins were separated by cellulose-TLC of duhat bark (AEDB). using a HPTLC cellulose plate. Three kinds of devel- opment solvents, acetic acid-concentrated HCl-water Fractionation by ultrafiltration (30:3:10 in volume ratio), n-butanol-acetic acid-water Ultrafilter of UK-10 (MW cutoff: 1•~104) from (4:1:5 in volume ratio, upper layer) and n-butanol-2 N Advantec Toyo Co., Ltd. (Tokyo) was used and filtra- HCI (1:1 in volume ratio, upper layer) were used. The tion was carried out under a nitrogen gas pressure of anthocyanidins separated by TLC developed in acetic 4kg/cm2. acid-concentrated HCl-water were scratched up from the plate, eluted in 0.01% (w/v) HCI-methanol and Fractionation by CM-Sepharose CL-6B 0.01% (w/v) HCl-ethanol respectively, and the ab- A column made by connecting two columns of 2.5 sorption spectra of the eluates were measured. In ad- ×90 cm filled with CM-Sepharose CL-6B was used dition, each 4 ml eluate of 0.01% (w/v) HCI-ethanol and elution was performed using 0.05M borate buffer was mixed with 3 drops of 5% (w/v) aluminium (pH 7.8). chloride-ethanol and its absorption spectrum was measured again to calculate the shift of spectral Growth measurement of lactic acid bacteria maxima caused by the addition of aluminium chloride. The lactic acid bacteria, Pediococcus acidilactici ATCC 8042, was used in this study. The synthetic TLC for sugars medium of Tamura et al. (1952) was used as basal Sugars were separated by cellulose-TLC using medium (pH 6.8). Two ml of double strength basal HPTLC cellulose plate. A mixture of n-butanol- medium was mixed with 2 ml of AEDB adjusted to the pyridine-water (6:4:3 in volume ratio) was used as the same pH and sterilized at 120•Ž for 10 min. To this 4 development solvent. After development, the TLC ml medium, a drop of 100 times dilution (number of plate was immersed in silver nitrate-acetone solution, cells: about 1•~108/ml) of the preculture medium of then dried, and immersed in another solution of 0.5 N P. acidilactici, which had been cultured in 10 ml basal NaOH-ethanol. The sugars on the TLC plate were medium at 37°C for 24 h, was inoculated by using a black-brown in color (Smith, 1954; Trevelyan et al., capillary pipet and incubated at 28°C for 72 h. After 1950). To fix the color, the TLC plate was immersed incubation, the acid produced in the 4 ml culture me- in a fixer for photographic film (Fujifix; Fuji Photo Film dium was neutralized with 0.1 N NaOH, and the Co., Ltd., Tokyo). After being dried, the sugars sepa- growth of P. acidilactici was measured by the acidity rated by TLC were individually determined by TLC of the medium. scanner at a wavelength of 550 nm. Determination of total polyphenol compound GLC and GLC-MS for gallic acid The total polyphenol compound was determined us- Gallic acid was converted to trimethylsilyl ether/ ing the method of Folin and Denis (1915) and calcu- methyl ester, and analyzed by gas-liquid chromatog- lated as D-(+) -catechin. raphy (GLC) and GLC-mass spectrometry (GLC-MS) (Horvat and Senter, 1980). The GLC device (GC- TLC for polyphenol compounds 4CM; Shimadzu Co., Ltd., Kyoto) was made with a Polyphenol compounds were separated by two- flame ionization detector and a glass column of 3 mm dimensional cellulose thin-layer chromatography ×4m packed with 3% SE-30 absorbed on Chro- (TLC) using a HPTLC cellulose plate of 10•~10 cm mosorb W of 100-120 mesh. The oven temperature from MERK (Darmstadt, Germany). As development was programmed to increase from 120 to 225•Ž at a solvents, n-butanol-acetic acid-water (4:1:2.2 in vol- speed of 4°C/min, and the nitrogen gas flow was set ume ratio) and 2% (w/w) acetic acid were used. to 30 ml/ min. The GLC-MS device (GCMS-6020; After development, polyphenol compounds were Shimadzu Co., Ltd., Kyoto) was set so that the ion INHIBITORY SUBSTANCE IN DUHAT BARK 35 source temperature was 270•Ž and the electron en- removed. In contrast with AEDB which completely in- ergy was 20 eV. hibits the growth of P. acidilactici, the supernatant showed no inhibitory activity after the precipitate had RESULTS been removed. This result suggests that the sub- stance in AEDB inhibiting the growth of lactic acid Growth inhibition of AEDB after removal of the bacteria is the polyphenol component which binds to precipitate caused by gelatin protein, since about 63% of the polyphenol compo- As duhat bark contains 4.8% polyphenol com- nents in AEDB formed precipitate with gelatin and the pounds in its dry weight (Mura and Tanimua, 1986) , inhibitory activity on the growth of lactic acid bacteria the substance inhibiting the growth of lactic acid bac- disappeared after the removal of the precipitate. teria in duhat bark was expected to be the polyphenol compound, as in samac bark and fruit (Mura et al., Fractionation of AEDB by ultrafitration 1986, 1987 and 1996). Since some polyphenol com- AEDB was fractionated into two fractions, the high pounds can bind to protein and form precipitate MW fraction and the low MW fraction by ultrafiltration (Oshima, 1958), we removed the precipitate in AEDB using an ultrafilter with a MW cutoff of 1•~104. The after adding gelatin and investigated the inhibitory ac- two fractions were then measured for polyphenol con- tivity of the remaining solution on the growth of lactic tent and inhibitory activity on the growth of P.