Preparative isolation and purification of macrolactin antibiotics from marine bacterium Bacillus amyloliquefaciens using high-speed counter-current chromatography in stepwise elution mode

Hyalangiumruber sp. nov, characterization of a novel myxobacterium strain s54d21 and their secondary metabolites

Myxobacteria are special bacteria with wide adaptability, which are rich sources of structurally diverse natural products with intriguing biological properties. Here, a gram-negative myxobacterium strain s54d21T was isolated from the sediment of a wetland park in China using the Escherichia coli baiting method. Based on 16S rRNA gene sequence and genomic data, the strain was demonstrated to be a novel species of a rare genus Hyalangium, designated Hyalangium ruber sp. nov (type strain s54d21T = GDMCC 1.1945T = JCM 39263T). The subsequent chemical investigation of the strain s54d21T led to the isolation of three rare 3,5,6-trisubstituted 2(1H)-pyrazinones, namely, hyalanones A-C (1-3), together with a known macrolactin A (4). Those new structures and their absolute configurations were unambiguously assigned by extensive analyses of spectroscopic data and density functional theory (DFT) calculations. In biological assays, compound 4 exhibited moderate cytotoxic activities against human cell lines RKO, A549, and NCM460 with IC50 values ranging from 27.21 to 32.14 μM.

The antifungal metabolites isolated from maize endophytic fungus Fusarium sp. induced by OSMAC strategy

Six new sesquiterpenes, fusarchlamols A-F (1, 2, 4-7); one new natural product of sesquiterpenoid, methyltricinonoate (3); and ten known compounds were found from Fusarium sp. cultured in two different media by the one strain many compounds strategy. The compounds (1, 2, and 4-11) were isolated from Fusarium sp. in PDB medium, and compounds (3-5, 8, and 10-17) were discovered from Fusarium sp. in coffee medium. Additionally, the configuration of 8 was first reported in the research by Mosher's method. The structures were established by 1D, 2D NMR, mass spectrometry, calculated ECD spectra, and Mosher's method. Compounds 1, 2, 6/7, 12, and 16 indicated significant antifungal activities against the phytopathogen Alternaria alternata isolated from Coffea arabica with MICs of 1 μg/mL. The investigation on the anti-phytopathogen activity of metabolites can provide lead compounds for agrochemicals.

Citriquinolinones A and B: Rare Isoquinolinone-Embedded Citrinin Analogues and Related Metabolites from the Deep-Sea-Derived Aspergillus versicolor 170217

A systematic chemical investigation of the deep-sea-derived fungus Aspergillus versicolor 170217 resulted in the isolation of six new (1-6) and 45 known (7-51) compounds. The structures of the new compounds were established on the basis of exhaustive analysis of their spectroscopic data and theoretical-statistical approaches including GIAO-NMR, TDDFT-ECD/ORD calculations, DP4+ probability analysis, and biogenetic consideration. Citriquinolinones A (1) and B (2) feature a unique isoquinolinone-embedded citrinin scaffold, representing the first exemplars of a citrinin-isoquinolinone hybrid. Dicitrinones K-L (3-4) are two new dimeric citrinin analogues with a rare CH-CH3 bridge. Biologically, frangula-emodin (32) and diorcinol (17) displayed remarkable anti-food allergic activity with IC50 values of 7.9 ± 3.0 μM and 13.4 ± 1.2 μM, respectively, while diorcinol (17) and penicitrinol A (20) exhibited weak inhibitory activity against Vibrio parahemolyticus, with MIC values ranging from 128 to 256 μM.

A novel and high-efficient method for the preparation of heat-stable antifungal factor from Lysobacter enzymogenes by high-speed counter-current chromatography

Heat-stable antifungal factor (HSAF) produced by the biocontrol bacterium Lysobacter enzymogenes shows considerable antifungal activity and has broad application potential in the agricultural and medical fields. There is a great demand for pure HSAF compounds in academic or industrial studies. However, an efficient preparation method that produces a high yield and high purity of HSAF is lacking, limiting the development of HSAF as a new drug. In the present study, high-speed counter-current chromatography (HSCCC) combined with column chromatography was successfully developed for the separation and preparation of HSAF from the crude extract of L. enzymogenes OH11. The crude extract was obtained by macroporous resin adsorption and desorption, and the main impurities were partly removed by ultraviolet light (254 nm) and gel filtration (Sephadex LH-20). In the HSCCC procedure, the selected suitable two-phase solvent system (n-hexane/ethyl acetate/methanol/water = 3:5:4:5, v/v, the lower phase added with 0.1% TFA) with a flow rate of 2.0 mL/min and a sample loading size of 100 mg was optimized for the separation. As a result, a total of 42 mg HSAF with a purity of 97.6% and recovery of 91.7% was yielded in one separation. The structure elucidation based on HR-TOF-MS, 1H and 13C NMR, and antifungal activities revealed that the isolated compound was unambiguously identified as HSAF. These results are helpful for separating and producing HSAF at an industrial scale, and they further demonstrate that HSCCC is a useful tool for isolating bioactive constituents from beneficial microorganisms.

Macrolactin R from Bacillus siamensis and its antifungal activity against Botrytis cinerea

Botrytis cinerea is listed among the most important fungal pathogens infecting strawberries. The use of biological control agents, such as Bacillus species, offers an alternative and effective way to reduce airborne pathogens. The aim of this research was to select the macrolactin R produced by Bacillus siamensis with potential for using as biological agents against the pathogenetic fungi (Botrytis cinerea) of strawberries, and to assess the mechanisms involved. Macrolactin R had significant inhibitory effects on spore germination, germ tube elongation, and mycelial growth of Botrytis cinerea. The MICs of macrolactin R inhibitions in vitro was 12.5 mg/L and The EC₅₀ value of NJ08-3 to Botrytis cinerea spores and mycelial was 1.93 and 2.88 mg/L, respectively. Macrolactin R impacted the membrane structure of Botrytis cinerea, resulting in changes in membrane permeability and leakage of proteins and nucleic acids, then cell death. The application of the macrolactin R of Bacillus siamensis reduced the disease severity index of gray mold on strawberries. This study demonstrated that the production of macrolactin R produced by Bacillus siamensis are involved in the antifungal activity against Botrytis cinerea.

Shallow Hydrothermal Vent Bacteria and Their Secondary Metabolites with a Particular Focus on Bacillus

Extreme environments are hostile for most organisms, but such habitats represent suitable settings to be inhabited by specialized microorganisms. A marine shallow-water hydrothermal vent field is located offshore in northeast Taiwan, near the shallow shore of the southeast of Kueishantao Island (121°55' E, 24°50' N). Research on extremophilic microorganisms makes use of the biotechnological potential associated with such microorganisms and their cellular products. With the notion that extremophiles are capable of surviving in extreme environments, it is assumed that their metabolites are adapted to function optimally under such conditions. As extremophiles, they need specific culture conditions, and only a fraction of species from the original samples are recovered in culture. We used different non-selective and selective media to isolate bacterial species associated with the hydrothermal vent crab Xenograpsus testudinatus and the sediments of its habitat. The highest number of colonies was obtained from Zobell marine agar plates with an overall number of 29 genetically distinct isolates. 16sRNA gene sequencing using the Sanger sequencing method revealed that most of the bacterial species belonged to the phylum Firmicutes and the class Bacilli. The present study indicates that hydrothermal vent bacteria and their secondary metabolites may play an important role for the reconstruction of the evolutionary history of the phylum Procaryota.

Inducing secondary metabolite production of Aspergillus sydowii through microbial co-culture with Bacillus subtilis

Background

The co-culture strategy which mimics natural ecology by constructing an artificial microbial community is a useful tool to activate the biosynthetic gene clusters to generate new metabolites. However, the conventional method to study the co-culture is to isolate and purify compounds separated by HPLC, which is inefficient and time-consuming. Furthermore, the overall changes in the metabolite profile cannot be well characterized.

Results

A new approach which integrates computational programs, MS-DIAL, MS-FINDER and web-based tools including GNPS and MetaboAnalyst, was developed to analyze and identify the metabolites of the co-culture of Aspergillus sydowii and Bacillus subtilis. A total of 25 newly biosynthesized metabolites were detected only in co-culture. The structures of the newly synthesized metabolites were elucidated, four of which were identified as novel compounds by the new approach. The accuracy of the new approach was confirmed by purification and NMR data analysis of 7 newly biosynthesized metabolites. The bioassay of newly synthesized metabolites showed that four of the compounds exhibited different degrees of PTP1b inhibitory activity, and compound N2 had the strongest inhibition activity with an IC₅₀ value of 7.967 μM.

Conclusions

Co-culture led to global changes of the metabolite profile and is an effective way to induce the biosynthesis of novel natural products. The new approach in this study is one of the effective and relatively accurate methods to characterize the changes of metabolite profiles and to identify novel compounds in co-culture systems.

Efficient Preparation of Bafilomycin A1 from Marine Streptomyces lohii Fermentation Using Three-Phase Extraction and High-Speed Counter-Current Chromatography

An efficient strategy was developed for the rapid separation and enrichment of bafilomycin A1 (baf A1) from a crude extract of the marine microorganism Streptomyces lohii fermentation. This strategy comprises liquid−liquid extraction (LLE) with a three-phase solvent system (n-hexane–ethyl acetate–acetonitrile–water = 7:3:5:5, v/v/v/v) followed by separation using high-speed counter-current chromatography (HSCCC). The results showed that a 480.2-mg fraction of baf A1-enriched extract in the middle phase of the three-phase solvent system was prepared from 4.9 g of crude extract after two consecutive one-step operations. Over 99% of soybean oil, the main hydrophobic waste in the crude extract, and the majority of hydrophilic impurities were distributed in the upper and lower phase, respectively. HSCCC was used with a two-phase solvent system composed of n-hexane–acetonitrile–water (15:8:12, v/v/v) to isolate and purify baf A1 from the middle phase fraction, which yielded 77.4 mg of baf A1 with > 95% purity within 90 min. The overall recovery of baf A1 in the process was determined to be 95.7%. The use of a three-phase solvent system represents a novel strategy for the simultaneous removal of hydrophobic oil and hydrophilic impurities from a microbial fermentation extract.

Quality Control of Psoralea corylifolia L. Based on High-Speed Countercurrent Chromatographic Fingerprinting

Traditional Chinese medicine (TCM)has played an important role in promoting the health of Chinese people. The TCM Psoralea corylifolia L. has been used in the treatment of various kinds of diseases including enuresis, vitiligo, and calvities. However, therapeutic effects of P. corylifolia L. have often influenced by the quality of plants. So, it is very important to control the quality of P. corylifolia L. In this study, analytical high-speed countercurrent chromatography (HSCCC) was successfully used to fingerprint P. corylifolia L. Samples of P. corylifolia L. were extracted by ultrasonic extraction. n-hexane-ethyl acetate–methanol–water at a ratio of 5:5.5:6.5:5 (v/v) was selected as a two-phase solvent system and the condition of HSCCC were optimized in order to good separation. And the method of HSCCC was verified (reproducibility, precision, and stability). HSCCC chromatograms exhibited six common peaks, which were selected as indicator compounds for the quality control of P. corylifolia L. Within 20 types of medicinal materials, chemical components are similar, but the levels of components are quite different in HSCCC fingerprint. The present results demonstrate that the HSCCC method provides a reliable basis for the quality control of P. corylifolia L. and can also be applied to confirm the authenticity of plant materials.

Separation of α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn using solvent and flow-rate gradient high-speed counter-current chromatography target-guided by ultrafiltration HPLC-MS screening

INTRODUCTION

Potentilla kleiniana Wight et Arn is widely used as a herbal medicine to treat type 2 diabetes. However, detailed information about its active compounds is lacking.

OBJECTIVE

To develop an efficient method for the rapid screening and separation of α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn.

METHODOLOGY

Potential α-glucosidase inhibitors from Potentilla kleiniana Wight et Arn were rapidly screened out through ultrafiltration high-performance liquid chromatography mass spectrometry (HPLC-MS), and then followed by a target-guided high-speed counter-current chromatography (HSCCC) separation using two-phase solvent systems composed of n-hexane/ethyl acetate/methanol/water (1:10:1:10, v/v/v/v and 1:10:5:6, v/v/v/v), and adopting increasing flow-rate from 1.5 to 3.0 mL/min after 200 min. Their structures were identified by ultraviolet (UV), MS, proton nuclear magnetic resonance (¹ H-NMR) and carbon-13 (¹³ C)-NMR, and their α-glucosidase inhibitory activities were assessed by in vitro assay.

RESULTS

Five α-glucosidase inhibitors including gallic acid (25.7 mg, 98.2%, 1), brevifolincarboxylic acid (9.86 mg, 95.3%, 2), ethyl evifolincarboxylate (13.26 mg, 97.6%, 3), 3,3'-di-O-methylellagic acid-4'-O-β-d-glucopyranoside (16.26 mg, 95.1%, 4), and 3,3'-di-O-methylellagic acid (10.54 mg, 96.8%, 5) were successfully purified from 250 mg n-butanol extract in a single run. Compounds 1, 2, 4 and 5 exhibited stronger α-glucosidase inhibitory activities[half maximal inhibition concentration (IC₅₀ ) values at 173.41 ± 6.35, 323.46 ± 8.08, 44.63 ± 2.50, and 20.73 ± 2.56 μM, respectively] than acarbose (IC₅₀ value at 332.12 ± 5.52 μM, reference compound).

CONCLUSIONS

Notably, compounds 2-5 were reported in the Potentilla kleiniana Wight et Arn for the first time. The results indicated that the proposed method could be applied for the rapid screening and preparative separation of α-glucosidase inhibitors from a complex matrix.

Purified Phlorizin from DocynIa Indica (Wall.) Decne by HSCCC, Compared with Whole Extract, Phlorizin and Non-Phlorizin Fragment Ameliorate Obesity, Insulin Resistance, and Improves Intestinal Barrier Function in High-Fat-Diet-Fed Mice

Natural products generally contain complex and multiple bioactive compounds that are responsible for the effects on health through complicated synergistic and/or suppressive actions. As an important raw material of local ethnic minority tea, ethnomedicines and food supplements in southwestern areas of China, Docynia indica (Wall.) Decne (DID) mainly consists of phlorizin (PHZ), which is the main active component. In this study, the holistic activities and the interactions of components of PHZ, non-phlorizin (NP) in the DID extract (DIDE) were evaluated. A rapid and effective high-speed counter-current chromatography (HSCCC) was performed to knock out PHZ from DIDE and the purity of PHZ was 96.01% determined by HPLC, with a recovery rate of 96.76%. After 13 weeks of treatment course in a high-fat diet (HFD)-induced obese mice model, the results revealed that the DIDE and PHZ significantly decreased weight gain, blood lipid levels, hyperplasia of adipocytes and alleviated inflammation (p < 0.05). Both DIDE and PHZ improves insulin resistance (p < 0.001). Meanwhile, the intestinal barrier function was improved compared to HFD group, through the determination of serum lipopolysaccharides (LPS), glucagon-likepeptide-2 (GLP-2) and hematoxylin-eosin staining of jejunum. Interestingly, after NP treatment, the metabolic syndrome of the HFD-induced obesity appeared to have a similar improvement. All the experiments showed that there is a synergistic weakening phenomenon when PHZ and NP interact with each other in the mixed state. In conclusion, for the PHZ and NP showing a good effect on anti-obesity, anti-inflammation, and intestinal barrier function, DIDE could be a good source of functional food to prevent obesity.

Acaricidal Activity of Cyclodipeptides from Bacillus amyloliquefaciens W1 against Tetranychus urticae

Bioassay-guided fractionation of the supernatant of the biocontrol strain Bacillus amyloliquefaciens W1 led to the isolation of eight acaricidal cyclodipeptides from the active fractions by column chromatography separation and HPLC purification. The chemical structures of these compounds were identified as cyclo-(Gly-l-Phe), 2, cyclo-(l-Phe- trans-4-OH-l-Pro), 3, cyclo-(Gly-l-Tyr), 4, cyclo-(l-Ala-l-Pro), 5, cyclo-(l-Pro- trans-4-OH-l-Pro), 6, cyclo-(Gly-l-Pro), 7, cyclo-(l-Pro-l-Pro), 8, and cyclo-(l-Tyr- trans-4-OH-l-Pro), 9. Those cyclodipeptides displayed significant acaricidal activities with LC₅₀ values of 13.85-98.24 μM. Cyclo-(l-Tyr- trans-4-OH-l-Pro) (LC₅₀ 13.85 μM) was five times more effective than the positive control abamectin (LC₅₀ 72.06 μM). The results indicated that the hydroxyl group is an important component. This is the first report on the acaricidal capabilities of cyclodipeptides against Tetranychus urticae. The results revealed that the acaricidal activity of the biocontrol strain B. amyloliquefaciens W1 was dependent on its constituent cyclodipeptides, which have the potential to be safe and environmentally friendly acaricides.

Comprehensive optimization of precursor-directed production of BC194 by Streptomyces rochei MB037 derived from the marine sponge Dysidea arenaria

BC194, a derivative of borrelidin (BN) that features a lower cytotoxicity than that of BN due to an altered starter unit, trans-1,2-cyclobutanedicarboxylic acid (trans-1,2-CBDA), is a potent inhibitor of angiogenesis. However, BC194 production has only been reported to occur via mutasynthesis, which requires tedious, multistep genetic manipulation. In this study, we surveyed several factors contributing to the precursor-directed biosynthesis of BC194 and provided an alternative method for the production of BC194 that is directly applicable to other BN-producing strains. First, the precursor-directed biosynthesis of BC194 by a BN-producing strain, Streptomyces rochei MB037 derived from sponge Dysidea arenaria, was carried out in modified Radix astragali (RA) medium with 5 mM trans-1,2-CBDA. Next, possible inhibitors of BN starter unit trans-1,2-cyclopentanedicarboxylic acid (trans-1,2-CPDA) biosynthesis were investigated. It was found that potassium ferricyanide was a possible inhibitor of 3,4-dihydroxyphenylacetate 2,3-dioxygenase (DHPAO) and capable of suppressing the yield of BN and increasing the BC194 yield by 112.5% (from 5.2 ± 0.76 to 11.9 ± 0.59 mg/L). BC194 yield was further enhanced in the presence of 50 mM trans-1,2-CBDA, reaching 20.2 ± 0.62 mg/L. Furthermore, 3% macroporous adsorbent DA-201 resin was added to the fermentation broth, enabling a further 36.6% increase in BC194 production and reaching 27.59 ± 1.15 mg/L. Moreover, an efficient separation of BC194 with approximately 95% purity was developed by employing high-speed counter-current chromatography (HSCCC), achieving an improved recovery (approximately 93%).

Preparative Separation and Purification of Trichothecene Mycotoxins from the Marine Fungus Fusarium sp. LS68 by High-Speed Countercurrent Chromatography in Stepwise Elution Mode

The contamination of foods and animal feeds with trichothecene mycotoxins is a growing concern for human and animal health. As such, large quantities of pure trichothecene mycotoxins are necessary for food safety monitoring and toxicological research. A new and effective method for the purification of trichothecene mycotoxins from a marine fungus, Fusarium sp. LS68, is described herein. Preparative high-speed countercurrent chromatography (HSCCC) was utilized for the scalable isolation and purification of four trichothecene mycotoxins for the first time in stepwise elution mode, with a biphasic solvent system composed of hexanes-EtOAc-CH₃OH-H₂O (6:4:5:5, v/v/v/v) and (8.5:1.5:5:5,v/v/v/v). This preparative HSCCC separation was performed on 200 mg of crude sample to yield four trichothecene mycotoxins, roridin E (1), roridin E acetate (2), verrucarin L acetate (3), and verrucarin J (4) in a single run, with each of >98% purity. These compounds were identified by MS, ¹H NMR, 13C NMR, and polarimetry. The results demonstrate an efficient HSCCC method for the separation of trichothecene mycotoxins, which can be utilized to produce pure commercial and research standards.

Anti-Allergic Compounds from the Deep-Sea-Derived Actinomycete Nesterenkonia flava MCCC 1K00610

A novel cyclic ether, nesterenkoniane (1), was isolated from the deep-sea-derived actinomycete Nesterenkonia flava MCCC 1K00610, together with 12 known compounds, including two macrolides (2, 3), two diketopiperazines (4, 5), two nucleosides (6, 7), two indoles (8, 9), three phenolics (10–12), and one butanol derivate (13). Their structures were established mainly on detailed analysis of the NMR and MS spectroscopic data. All 13 compounds were tested for anti-allergic activities using immunoglobulin E (IgE) mediated rat mast RBL-2H3 cell model. Under the concentration of 20 μg/mL, 1 exhibited moderate anti-allergic activity with inhibition rate of 9.86%, compared to that of 37.41% of the positive control, loratadine. While cyclo(d)-Pro-(d)-Leu (4) and indol-3-carbaldehyde (8) showed the most potent effects with the IC₅₀ values of 69.95 and 57.12 μg/mL, respectively, which was comparable to that of loratadine (IC₅₀ = 35.01 μg/mL). To the best of our knowledge, it is the first report on secondary metabolites from the genus of Nesterenkonia.

Antibacterial Compounds-Macrolactin Alters the Soil Bacterial Community and Abundance of the Gene Encoding PKS

Macrolactin produced by many soil microbes has been shown to be an efficient antibacterial agent against many bacterial pathogens. However, studies examining the effect of macrolactin on both the soil bacterial community and the intrinsic bacterial species that harbor genes responsible for the production of this antibiotic have not been conducted so far. In this study, a mixture of macrolactin was isolated from the liquid culture of Bacillus amyloliquefaciens NJN-6, and applied to the soil once a week for four weeks. 16S rRNA Illumina MiSeq sequencing showed that continuous application of macrolactin reduced the α-diversity of the soil bacterial community and thereby changed the relative abundance of microbes at both the phylum and genus level. The relative abundance of Proteobacteria and Firmicutes was significantly increased along with a significant decrease in the relative abundance of Acidobacteria. However, the application of macrolactins had an insignificant effect on the total numbers of bacteria. Further, the native gene responsible for the production of macrolactin, the gene encoding polyketide synthase was reduced in copy number after the application of macrolactin. The results of this study suggested that a bactericide from a microbial source could decrease the diversity of the soil bacterial community and change the bacterial community structure. Moreover, the populations of the intrinsic bacterial species which harbor genes responsible for macrolactin production were inhibited when the external source antibiotic was applied.

Efficient Preparation of Streptochlorin from Marine Streptomyces sp. SYYLWHS-1-4 by Combination of Response Surface Methodology and High-Speed Counter-Current Chromatography

Since first isolated from the lipophilic extract of Streptomyces sp. SF2583, streptochlorin, has attracted a lot of attention because of its various pharmacological properties, such as antibiotic, antiallergic, antitumor, and anti-inflammatory activities. For the efficient preparation of streptochlorin from a producing strain Streptomyces sp. SYYLWHS-1-4, we developed a combinative method by using response surface methodology (RSM) and high-speed counter-current chromatography (HSCCC). In the fermentation process, we used RSM to optimize the condition for the efficient accumulation of streptochlorin, and the optimal parameters were: yeast extract 1.889 g/L, soluble starch 8.636 g/L, K₂HPO₄ 0.359 g/L, CaCl₂ 2.5 g/L, MgSO₄ 0.625 g/L, marine salt 25 g/L, medium volume 50%, initial pH value 7.0, temperature 27.5 °C, which enhanced streptochlorin yield by 17.7-fold. During the purification process, the preparative HSCCC separation was performed using a petroleum ether–ethyl acetate–methanol–water (9:0.8:5:5, v/v/v/v) biphasic solvent system, where 300 mg of crude sample yielded 16.5 mg streptochlorin with over 95% purity as determined by UPLC. Consequently, the combination method provided a feasible strategy for highly effective preparation of streptochlorin, which ensured the supply of large amounts of streptochlorin for in vivo pharmacological assessments or other requirements.

Preparative isolation, quantification and antioxidant activity of dihydrochalcones from Sweet Tea (Lithocarpus polystachyus Rehd.)

Dihydrochalcones are the main active components of Lithocarpus polystachyus Rehd. (Sweet Tea), they are directly related to the sweet tonic beverage and traditional herb. In this work, two runs of preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane/ethyl acetate/ethanol/water (1:4:3:4, v/v) were employed to separate three dihydrochalcones (phloridzin, trilobatin and phloretin) from Sweet Tea. About 6.4mg of phloridzin, 48.4mg of trilobatin, and 4.7mg of phloretin with purities of 96.7%, 98.4% and 98.1% were obtained from 130mg of the crude Sweet Tea extract. Phloridzin, trilobatin, and phloretin had effective radical scavenging activities, with IC50 values of 866.80, 20.16 and 179.47μg/mL, respectively, in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method. The contents of phloridzin, trilobatin and phloretin in dried old leaves and tender leaves of tea were in the range of 10.1-18.0, 113.7-128.8, 3.6-4.3mg/g and 9.3-9.8, 82.9-103.1, 1.9-2.5mg/g, respectively. The results indicated that the HPLC had good precision, accuracy and repeatability for the determination of three dihydrochalcones in samples.

Countercurrent Separation of Natural Products: An Update

This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod. 2008, 71, 1489-1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources.

Preparative isolation and purification of lignans from Justicia procumbens using high-speed counter-current chromatography in stepwise elution mode

Lignans, which are recognized as main constituents in Justicia procumbens, have attracted considerable attention due to their pharmacological activities, including antitumor, anti-hepatitic, cytotoxic, anti-microbial, and anti-virus properties. Preparative high-speed counter-current chromatography (HSCCC) was successfully applied to the isolation and purification of four lignans (justicidin B (1), justicidin A (2), 6'-hydroxyjusticidin C (3) and lignan J1 (4)) from J. procumbens using stepwise elution with a pair of two-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water at (1.3:1:1.3:1, v/v) and (2.5:1:2.5:1, v/v). The preparative HSCCC separation was performed on 300 mg of crude sample yielding compounds 1 (19.7 mg), 2 (9.86 mg), 3 (11.26 mg), and 4 (2.54 mg) in a one-step separation, with purities over 95% as determined by HPLC. The structures of these compounds were identified by MS, 1H-NMR and 13C-NMR. This is the first report on the application of HSCCC to the efficient separation of lignans from J. procumbens.

Preparative separation of sulfur-containing diketopiperazines from marine fungus Cladosporium sp. using high-speed counter-current chromatography in stepwise elution mode

High-speed counter-current chromatography (HSCCC) was successively applied to the separation of three sulfur-containing diketopiperazines (DKPs) (including two new compounds cladosporin A (1) and cladosporin B (3), and a known compound haematocin (2)) from a marine fungus Cladosporium sp. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at (1:1:1:1, v/v) and (2:1:2:1, v/v), in stepwise elution mode, was used for HSCCC. The preparative HSCCC separation was performed on 300 mg of crude sample yielding 26.7 mg of compound 3 at a purity of over 95%, 53.6 mg of a mixture of compounds 1 and 2, which was further separated by preparative-HPLC yielding 14.3 mg of compound 1 and 25.4 mg of compound 2 each at a purity of over 95%. Their structures were established by spectroscopic methods. The sulfur-containing DKPs suppressed the proliferation of hepatocellular carcinoma cell line HepG2. The present work represents the first application of HSCCC in the efficient preparation of marine fungal natural products.

Efficient preparation of pseudoalteromone A from marine Pseudoalteromonas rubra QD1-2 by combination of response surface methodology and high-speed counter-current chromatography: a comparison with high-performance liquid chromatography

Pseudoalteromone A (PA) is a cytotoxic and anti-inflammatory ubiquinone discovered recently from a marine bacterium Pseudoalteromonas sp. CGH2XX. In order to meet its sample supply for further in vivo pharmacological investigation, an efficient method was developed for the preparation of PA by combination of response surface methodology (RSM) and high-speed counter-current chromatography (HSCCC) from marine bacterium P. rubra QD1-2. First, optimization of culture conditions was studied by the RSM to enhance PA production. The results indicated that the optimal cultivation condition was peptone (2.21 g/l), yeast extract (3.125 g/l), glucose (0.125 g/l), KBr (0.02 g/l), inoculum size (6.5 %), medium volume (595 ml), initial pH value (7.0), temperature (28 °C). Under the optimized fermentation condition, PA production was 1.04 mg/l with 14.8-fold increase comparing to 0.07 mg/l under original standard fermentation condition. The PA production was further investigated using a 14-l jar fermenter. Compared to the flask culture, P. rubra QD1-2 offered 45 % increase of PA production at 1.51 mg/l. Then, a rapid and efficient method for the separation and purification of PA from crude culture extract was developed using HSCCC. The two-phase solvent system used for HSCCC separation was composed of n-hexane-ethyl acetate-methanol-water (5:5:9:5, v/v/v/v). The isolation was accomplished within 100 min, and the purity of PA was over 95 %. The recovery of the process was 93 %.

Use of O-carboxymethyl chitosan in high-speed counter-current chromatography: a novel additive for a biphasic solvent system

A novel additive,O-carboxymethyl chitosan, for high-speed counter-current chromatography was found and evaluated for the separation and purification of active constituents from natural plants.

Liquid–liquid/solid three-phase high-speed counter-current chromatography based on O-carboxymethyl chitosan-functionalized multi-walled carbon nanotubes as solvent additive

A new liquid–liquid/solid three phase HSCCC system was established based on O-carboxymethyl chitosan-functionalized multi-walled carbon nano tubes as additive of biphasic solvent system.

Response surface methodology optimization of fermentation conditions for rapid and efficient accumulation of macrolactin A by marine Bacillus amyloliquefaciens ESB-2

In the present work, an antibiotic-producing marine bacterium was isolated from a seawater sample collected from Yuhuan, Zhejiang, China, identified and named as Bacillus amyloliquefaciens ESB-2 on the basis of phenotypic characteristics and 16S rRNA gene sequencing. Response surface methodology was applied to optimize the fermentation conditions for rapid and efficient accumulation of macrolactin A, a pharmacologically important marine antibiotic. Eight fermentation conditions were examined for their significance on macrolactin A production using Plackett–Burman factorial design, where peptone, medium volume and temperature significantly improved production rate. Further optimization was carried out using Box-Behnken design of experiments to study the influence of process variables. The optimized fermentation condition for maximum production was peptone 14.8 mg/mL, yeast extract 1 mg/mL, FePO₄ 0.01 mg/mL, temperature 26.3 °C, initial pH value 6.0, medium volume 72.4%, rotation speed 150 r/min, inoculation 5% and fermented for 2 days. Under the optimized conditions, the concentration of macrolactin A reached 21.63 mg/L, representing a 2.4-fold increase compared to the original standard condition, which was also 17% higher than previous highest report of 18.5 mg/L and three times higher in terms of daily productivity.