Triglycerides Isolated from Streptomyces sp . ZZ 035 and Their Nuclear Magnetic Resonance Spectroscopic Characters

Streptomyces sp. ZZ035 isolated from a folk medicinal soil sample in China showed remarkable antimicrobial activities. During the isolation of secondary metabolites, a white crystal powder (1) was isolated from the broth of this strain. Its nuclear magnetic resonance (NMR) and infrared (IR) spectra indicated that it was a complex composed of triglycerides. Next, six C15-17 longchain fatty acids derived from these triglycerides were respectively identified as n-pentadecanoyl, 12-methyltetradecanoyl, 14-methyl pentadecanoyl, palmitoyl, 15-methyl hexadecanoyl and 14-methyl hexadecanoyl using the gas chromatography-mass spectroscopy (GC-MS) technology. Finally, the C and H assignments of 1 were achieved through the analyses of NMR data. Based on above, their detailed NMR spectroscopic elucidation and meticulous C, H assignments, especially the split peaks and coupling correlation of protons attached on the glycerol carbons, were performed for distinguishing triglycerides from other glycerides and for the identification of the long-chain fatty acids, and which would be helpful to the qualitative and quantitative analyses of tri-, diand mono-glycerides.


Introduction
Around the reservoir for domestic water in Chinese rural areas, a folk medicinal soil in a dark and moist environment is used to prevent infection and accelerating cure by being spread around the wound after dog bite.To reveal the anti-infection reasons of this soil, a sample was collected in Xianjing Countryside in Zhuzhou County, China, and sixty-one actinomycete strains ZZ01 to ZZ061 were selectively isolated from this sample [1].After chemical analysis were performed for discovering strains producing a series of secondary metabolites, the bioactive evaluation showed that thirteen strains had antimicrobial activities against Staphylococcus aureus, Escherichia coli and/or Candida albicans, and then the classification and identification of targeted seven strains indicated that they belonged to the genus Streptomyces [2].Among them, Streptomyces sp.ZZ035 with remarkable antimicrobial activities against S. aureus, E. coli and C. albicans was targeted for discovering antimicrobial metabolites.During the iso- lation of components from the broth of this strain, a white crystal powder was isolated and identified as triglycerides, and many nuclear magnetic resonance (NMR) data including 1 H, 13 C, distortionless enhancement by polarization transfer (Dept), heteronuclear single-quantum correlation (HSQC), 1 H-1 H correlation spectroscopy ( 1 H-1 H COSY) and heteronuclear multiple-bond correlation (HMBC) were obtained for the structural analyses of these triglycerides.
Main 13 C, 1 H signals of tri-, di-and mono-glycerides were fully assigned in previous works [3]- [8], while seldom of them presented the detailed elucidation of those signals in 13 C, 1   [5], the assignments of those protons easily confused when some of them were showed in the same 1 H NMR spectrum.Moreover, the protons attached on C-1' and C-3' of triglycerides Figure 1.Key hydrogen-hydrogen correlations and heteronuclear multiple-bond correlations of 1. R', the ester acyl linked the carbon-1' of glycerol; R'', the ester acyl linked the carbon-2' of glycerol; R''', the ester acyl linked the carbon-3' of glycerol; R', R'' or R''' was one of six acyl groups identified by gas chromatography-mass spectroscopy technology.
were indistinctly assigned to a doublet of double doublets centered at 4.22 ppm, and the split peaks and meticulous assignments of these protons were not clarified [3] [4] [5] [6] [7].As many glycerides were widely used in foods, cosmetics and drugs, a variety of analyses in vivo and in vitro usually need to be performed.The detailed NMR spectroscopic elucidation and meticulous 13 C, 1 H assignments of these triglycerides would provide a foundation for NMR technology applying for the qualitative and quantitative analyses of tri-, di-and mono-glycerides.Used triglycerides isolated by us as an example, detailed elucidation of NMR data and meticulous 13 C, 1 H assignments were performed with one dimension (1D) and two dimensions (2D) NMR technology presented in this paper.Some new NMR data for identifying triglycerides were updated, and provided some references for the identification of fatty acids and glycerides.

Strain
Streptomyces sp.ZZ035 was isolated from a soil sample collected in Xianjing Countryside in Zhuzhou County, China (Geographic coordinates: 27˚30'N, 113˚17'E) [1], and was store at 4˚C in College Bioscience and Bioengineering, Jiangxi Agricultural University, China.Polyphasic taxonomy procedure indicated that this strain belonged to the genus Streptomyces and was closest to S. cinnamonensis [2].Its 16S deoxyribonucleic acid (16S rDNA) sequence was de- posited at NCBI GenBank with accession numbers KJ995739.

Fermentation and Isolation
The strain of Streptomyces sp.ZZ035 was cultured in 5000 mL Erlenmeyer flasks that contained 2000 mL of 2A medium consisting of 1.0% glucose, 3.5% soluble starch, 0.2% yeast, 0.4% casein, 4.6% 3-[N-morpholino] propane sulfonic acid, and 1.8% sodium chloride (W/V) at 28˚C for 8 d on a rotary shaker at 190 rpm until 60 L of broth obtained.The broth was centrifuged to obtain mycelium, and which was extracted with methanol (MeOH).The extract was concentrated under decompression, and then freeze-dried to obtain lyophilized powder.The powder successively dissolved in chloroform (CHCl 3 ) to obtained chloroformsoluble fraction, and which was purified using a silica column eluted with chloroform-petroleum ether (10:4).Finally, the fraction contained identical spots on thin layer chromatography (TLC) plates were combined and concentrated to remove solvent, and then the residue was crystallized with CHCl 3 -MeOH (1:1) at 4˚C to give a white crystal powder (1, 547 mg).

Structural Elucidation and Components Analyses
Thin layer chromatography using for the isolation and analysis was carried out with silica GF 254 (Qingdao Haiyang Chemical Co., Ltd, China), and iodine vapor were used as chromogenic agents.All NMR experiments were recorded on a Bruker AV-400 NMR spectrometer equipped with a 5-mm PABBO BB-probe head.The chemical shifts were respectively relative to deuterochloroform (CDCl 3 ) at δ H 7.26 ppm and δ C 77.0 ppm.For the gas chromatography-mass spectroscopy (GC-MS) analyses, the methanolysis of 1 was performed by potassium hydroxide in methanol/hexane, and then the fatty acid methyl esters were determined on a Thermo Trace 1300/ISQ GC-MS spectrometer with an electron ionization (EI) ion source (70 eV).The chromatographic peaks were identified by comparing their mass spectra with those in the NIST 11 MS data library.IR spectrum was determined on a Thermo Nicolet 380 FT-IR spectrometer with potassium bromide pellet.
The template is used to format your paper and style the text.All margins, column widths, line spaces, and text fonts are prescribed; please do not alter them.You may note peculiarities.For example, the head margin in this template measures proportionately more than is customary.This measurement and others are deliberate, using specifications that anticipate your paper as one part of the entire journals, and not as an independent document.Please do not revise any of the current designations.

Structural Elucidation and Components Analyses
1 was obtained as a white crystal powder, and was easily soluble in chloroform.
The 13 C and Dept 135˚ NMR spectra of 1 showed two carbonyl carbons at δ C 173.23 and 172.86, one methine carbon at δ C 68.89 and one methylene carbon signal at 62.10 ppm.From the HSQC spectra of 1, two signals at δ H 4.14 and 4.29 with two double protons observed in its 1 H NMR spectrum were attached on the methylene carbon signal at 62.10 ppm.This deduced that the signal at 62.10 ppm were assigned to two methylene carbons C-1' and C-3' (Figure 1 Many carbon signals at 29.26 -29.95 ppm and their one-bond related proton signals at 1.20 -1.36 ppm in the 13 C, 1 H and HSQC spectra of 1 were assigned to most methylenes of fatty acid chain [3,9].To understand the carbon numbers composed fatty acid, GC-MS technology was used for the analyses of the fatty acid methyl esters (FAME) synthesized from 1, and six FAME were identified as shown in Table 1.Thereby, six C 15-17 long-chain fatty acyl groups composed of 1 were identified as n-pentadecanoyl (1a), 12-methyltetradecanoyl (1b), 14-methyl pentadecanoyl (1c), palmitoyl (1d) and 15-methyl hexadecanoyl (1e) and 14methylhexadecanoyl (1f).

Nuclear Magnetic Resonance Data of Triglycerides
Comparing previous reports [3]- [9] [12], their detailed and meticulous 13 C, 1 H assignments were achieved by the 13 C, 1 H, HSQC, 1 H-1 H COSY and HMBC spectra, and shown in Table 2 and Table 3.

Discussion
These triglycerides were isolated from the broth of Streptomyces sp.ZZ035 derived from a folk medicinal soil sample.Their detailed NMR spectroscopic    C-3' due to an AMX coupling system.Their 13 C and 1 H assignments were up to date in Table 2, and the relative split peaks in the 1 H NMR spectrum were amplified in Figure 2.
Another, an A 2 MX 2 coupling system led H-2' to split triple-triplets centered at 5.26 ppm, among which three middle ones mostly overlapped to form an abnormal peak (Figure 2).These 13 C, 1 H assignments and split analyses of triglycerides were first confirmed by their HMBC and HSQC spectra shown on Figure  technology applying for the qualitative and quantitative analyses of tri-, di-and mono-glycerides.

Conclusion
A white crystal powder (1) composed of several triglycerides was isolated from the broth of Streptomyces sp.ZZ035, and analysized by GC-MS, IR and NMR technology.The important 13 C and 1 H assignments of these triglycerides were achieved through the analyses of NMR data.Moreover, their detailed NMR spectroscopic elucidation and meticulous 13 C, 1 H assignments, especially the split peaks and coupling correlation of protons attached on the glycerol carbons, were performed for distinguishing triglycerides from other glycerides and for the identification of the long-chain fatty acids, and which would be helpful to the qualitative and quantitative analyses of tri-, di-and mono-glycerides.
for13 C shifts relative to CDCl 3 at δ C 77.0.b Positions were numbered according to Figures1(b)-(d) for acyl terminals Figure1(a), Figure1(c) and Figure1(f).c Figure1(a), n-pentadecanoyl terminal (that same to palmitoyl one); Figure1(c), 14-methyl pentadecanoyl terminal (same to 15-methyl hexadecanoyl one), Figure1(f), 14-methylhexadec-anoyl terminal (same to 12-methyltetradecanoyl one).Dept is the abbreviation of distortionless enhancement by polarization transfer spectrum.elucidation and key13 C, 1 H assignments were performed for distinguishing triglycerides from other glycerides and for the identification of the long-chain fatty acid terminals.More and more glycerides isolated from bacteria and other bioresources, they showed a variety of bioactivities[8] [11][13] [14][15].Some of them showed antimicrobial[8], and some were platelet aggregation inhibitors or antagons of cannabinoid receptor[11] [13] [14].Our antimicrobial experiments indicated that 1 contained C 15-17 fatty acyl groups had no antimicrobial activities against S. aureus and C. albicans.Same to most glycerides [8] [9] [11] [12], triglycerides also present a large peak at 29.26 -29.95 ppm in their 13 C NMR spectra and a large peak at 1.20 -1.36 ppm in their 1 H spectra NMR spectra.The acyl terminals of glycerides were deduced from the chemical shifts of methyl carbons in their 13 C NMR spectra, such as a methyl carbon at δ C 14.09 for a straight chain acyl terminals, two methyl carbons at δ C 22.65 for an iso-fatty acid terminal (Figure 1(c)), and two methyl carbons at δ C 11.38 and 19.21 for an anteiso-fatty acid terminal (Figure 1(d)).For distinguishing triglycerides from other glycerides, peaks due to protons attached on the glycerol carbons are of primary importance.The chemical shifts of protons on C-1' or C-3', and C-2' for triglycerides were respectively 4.22 and 5.27 ppm in CDCl 3 according to previous reports [3] [4] [5], while two nonequivalent protons attached on C-1' or C-3' of these trig1ycerides were deduced from the 1D and 2D NMR data of 1.The chemical shift of one proton was 4.14 ppm, and another was 4.30 ppm.Each proton attached on C-1' or C-3' presented a geminal coupling (J = 11.9Hz) with another and a vicinal coupling (J = 6.0 or 4.2 Hz) with H-2', and which gave a double doublets for each proton on C-1' or

Figure 3 .
Figure 3. Part hydrogen-hydrogen ( 1 H-1 H) correlation spectroscopy (a) and heteronuclear multiple-bond correlation spectrum (b) for the 13 C and 1 H assignments of glyceryl of 1.

Table 1 .
Fatty acid methyl esters synthesized from 1 detected by gas chromatographymass spectroscopy (GC-MS) technology.a a The GC-MS analyses were determined on a Thermo Trace 1300/ISQ GC-MS spectrometer with an electron ionization ion source (70 eV), and the chromatographic peaks were identified by the NIST 11 MS data library.RT, Retention time; SI, Similarity index; RSI, Reversed search index.

Table 2 .
13C and 1 H nuclear magnetic resonance assignments of glyceryl and part long-chain fatty acyl groups (δ, ppm in deuterochloroform).a400MHz for 1 H shifts relative to deuterochloroform (CDCl 3 ) at δ C 7.26; 100 MHz for13C shifts relative to CDCl 3 at δ C 77.0.b R', R'' or R'' was one of six acyl groups 1a-1f identified by gas chromatography-mass spectroscopy technology.c Dept is the abbreviation of distortionless enhancement by polarization transfer spectrum.d n was equal to 9 for acyl 1b, 11 for acyls 1c and 1e, 12 for acyls 1a and 1f, and 13 for acyl 1d. a