Benzoyloxy-ethyl-carbamic acid: A novel anticancerous secondary metabolite produced by Streptomyces globosus VITLGK011
Lokesh Ravi & Kannabiran Krishnan*
School of Biosciences and Technology, Department of Biomedical Sciences, VIT University, Vellore, Tamil Nadu, India.
Received 27 January 2017; revised 26 March 2017
Marine actinomycetes are known to possess novel anticancer compounds. In this study, we screened marine actinomycetes for isolation and identification of possible cytotoxic anticancer secondary metabolites, if there any. Screening of antagonistic actinomycetes isolates from Rameswaram and Dhanushkodi marine soil samples resulted in the selection of VITLGK011. Molecular taxonomic characterization identified the isolate as Streptomyces globosus VITLGK011. Silica gel column chromatographic separation, purification and characterization by spectroscopic studies lead to the identification of a novel secondary metabolite benzoyloxy-ethyl-carbamic acid (BECA) with a molecular weight 209.2 g/mol and molecular formula C10H11NO4. BECA demonstrated selective cytotoxicity towards cancer cell lines, in particular against MCF-7. The results of in vivo studies in zebrafish model showed that the compound BECA is non-toxic and capable of reducing tumor progression. In silico studies revealed that BECA by inhibiting PARP1 in MCF-7 cells demonstrated its cytotoxic activity, and hence this molecule can be probed further for its usefulness as a cytotoxic agent.
Keywords: Actinomycetes, BECA, MCF-7, VERO, Zebrafish
Actinomycetes are group of Gram’s positive, filamentous bacteria present in the soil with high GC content in their genome, considered as biofactories for production of novel chemical compounds1,2. Due to the increased stress conditions in the marine ecosystem, microorganisms produce several complex chemical compounds to adapt and survive in the much competitive marine environment. Extraction and identification of novel anticancer compounds and the secondary metabolites with multiple medical/
biological applications from marine actinomycetes are not uncommon2-5. Nearly, 80% of all natural product based medicines available in the market are derived from the genus Streptomyces and known for its antibiotic production1.
For humans, cancer is one of the most life threatening diseases with more than 27 major types and a fatality rate of 8.2 million deaths/year6,7. Caused by various factors, such as work place, food habit, life style and chemical exposure apart from mutagenic, cancer registers about 14.1 million fresh incidences every year7. Developing and less developed countries account for about 57% of cases and 65% of mortality7. Breast cancer is the most commonly diagnosed and highly prevalent malignancies among
women and the leading cause of cancer death in less developed countries7 and second leading in developed countries next to lung cancer8. Globally, breast cancer constitutes to 23% of all cancers in women of age group of 45-559. In India, breast cancer is the most prevalent type in 19 registry areas with the highest rates observed in the Northeast and in major metropolitan cities like Mumbai and Delhi10,11. Though common among women, cases of breast cancer have also been reported from men12. Increased incidences and limited success of clinical therapies including radiation, chemotherapy, immunomodulation and surgery have urged researchers to look for more effective drug molecules, particularly from natural resources13-18.
Discovery of drugs is a lengthy process, that takes several laboratory screenings, and clinical trials before a potential molecule could be used as marketable drug19. Generally, it used to take 10-15 years of experimental proof for a molecule to be approved as a drug. Due to the Development of combinatorial chemistry and computational biology, has not only reduced the time frame for drug discovery considerably but also lead to saving cost. Predicting a mechanism of action by a drug is highly important, to understand how it could affect the host and nearby cells13,20,21.
Here, we screened marine actinomycetes isolates for bioactivity and also studied anticancer cytotoxic
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*Correspondence:
Phone: +91 416 2202024 E-mail: kkb@vit.ac.in
activity of the bioactive secondary metabolite extracted from the potential isolate. Further, we tried to predict the protein target of the cancer cells inhibited by the extracted compound as well.
Materials and Methods
Isolation of actinomycetes from soil sample
One gram of marine soil sample was diluted in sterile distilled water up to 10-4 concentration. One hundred microliters of each dilution were plated onto freshly prepared starch casein agar medium in Petri plates. Starch casein agar (SCA) was purchased from Hi-Media, Mumbai, India. The plates were incubated at 37ºC for 7 days, with periodic observation.
Actinomycetes like colonies were sub-cultured onto freshly prepared SCA medium. Sub-culturing was repeated till pure colonies were obtained. Obtained colonies were subjected to Gram’s staining, to identify actinomycetes isolates22,23.
Characterization of actinomycetes isolate
Actinomycetes isolates were subjected to standard biochemical characterization and molecular characterization, to identify the genus and species. To study the biochemical properties of the isolate, Gram’s staining, motility test, triple sugar ion test, Vogues Proskauer test, methyl red test, indole test, oxidase test, catalyse test and melanin test were performed, using the respective test kits purchased from Hi-Media. To optimize the culturing conditions of the isolate, it was grown in 7 different International Streptomyces Project (ISP) agar culture media. For molecular characterization, genomic DNA of the isolate was extracted using phenol: chloroform method and was amplified by PCR for its 16S rDNA region, using 27F and 1492R primers in standard PCR conditions. The PCR product was sequenced using 518F/800R primers, ABI PRISM® BigDyeTM Terminator Cycle Sequencing Kits with AmpliTaq®
DNApolymerase (FS enzyme) (Applied Biosystems).
The sequence was electrophoresed in ABI 3730xl sequencer. The obtained sequence was processed, and BLAST searched through the NCBI database to find the closest match and phylogenetic tree was constructed using MEGA-5 software24,25.
Antibacterial testing by Cross-streak method
Actinomycetes colonies were streaked vertically in the middle of a freshly prepared Muller-Hinton Agar (MHA) media and incubated at 37ºC for 5-7 days.
After incubation, pathogenic bacterial strains were
streaked perpendicular to the actinomycetes colonies in such a way that the bacterial colonies touch the edges of the actinomycetes colonies. The plate was incubated at 37ºC overnight and observed for growth of the bacterial pathogens. The absence of growth of the bacterial pathogen, surrounding the actinomycetes, illustrates that the actinomycetes possess antibacterial activity4,26.
Antibacterial testing by Well diffusion method
Pathogenic bacteria were prepared as a lawn culture on an MHA agar media. Wells of 8 mm size were punched in this media using a sterile well borer.
To each of this well, 100 µL of negative control (water), positive control (standard drug dissolved in water) and test (test compound dissolved in water) were added. The Petri plate was incubated overnight at 37ºC and observed for zone-of-inhibition. The diameter of the zone of inhibition was measured and expressed in mm27.
Cell viability assay
VERO, MCF-7, HCT-116, PA-1, and LN-18 cell lines were bought from NCCS, Pune, India and maintained in DMEM media with 10% fetal bovine serum (FBS). Penicillin (10000 I.U/mL) and streptomycin (10 mg/mL) stock solution was used as stock antibiotic. About 100 µL of stock antibiotic was added to 100 mL of DMEM (with FBS). The cells were maintained at 37ºC with 5% CO2 in a CO2
Incubator. At 80% confluence, the cells were used for MTT assay. Cells were trypsinized using 1X trypsin and were seeded into 96-well plate. The plates were incubated again at 37ºC in a CO2 incubator. Once the cells were confluent and healthy within the the plate, it was supplied with DMEM media, containing test drug. Fresh DMEM media without FBS was used to dilute the test drug. The crude extract of VITLGK011 was diluted into 8 dilutions viz., 1000, 500, 250, 125, 62.5, 31.2, 15.6, and 7.8 µg. Similarly, the pure compound was diluted to 7 dilutions viz., 100, 50, 25, 12.5, 6.25, 3.12, and 1.56 µg). These serum-free DMEM media, with the dissolved test drug, was then added to the respective wells in the 96-well plate. The plates were again incubated for 24 h. After incubation, the cells were washed with sterile phosphate buffer saline (PBS), and 20 µL of MTT [3- (4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] was added (concentration of MTT solution was 5 mg/mL dissolved in PBS). After 4 h of incubation, 100 µL of DMSO was added to each well to dissolve the formazan crystals. The intensity of
colour developed was measured in ELISA plate reader at 570 nm. The percentages of viable cells were calculated by comparing the test wells to the negative control wells (100% viability)28,29.
In vivo anticancer cytotoxicity assay
Healthy zebra fishes were divided into five groups of six fishes each (Gr. I, normal control; Gr. II, cancer induced control; Gr. III-V, treated with BECA @ 3, 15 and 30 µg/day. All the fishes were housed at the light/dark cycle of 14/10 h at 28ºC in a 3L water tank, with continuous aeration and bio-filtration. The good animal practice according to Institutional Animal Ethics Committee and by the Committee for the Purpose of Control and Supervision of Experiments (CPCSEA), India was followed. Except for the normal control group fishes, the remaining fishes (four groups) were injected with 3 µL of MCF-7 cells (1×105 cells/mL) intramuscularly using 33-guage Hamilton syringe. The test compound was administered to the fishes by mixing with the fish feed, and three pellets were fed to the fishes daily.
The concentration of compound was controlled by the number of pellets containing the compound and the quantity of compound per pellet. Feed pellets without drug but with vehicle were used as placebo. After the incubation period, the fishes were anesthetized with 15ºC water and sacrificed by a cut between the brain and the spinal cord. Liver, intestine and muscle was dissected and were removed with a pin and knife. The tissue is smeared on a glass slide and stained with haematoxylin& eosin for 2 min each followed by water washes. Slides were viewed at 45X magnification, and the numbers of normal cells were counted for three fields per smear. Lysed cells were characterized by the loss of cell structure, either swollen or constricted cells, irregularly shaped cell membrane, stain relatively lighter with a high rate of cell lysis during smear preparation30,31.
Purification and identification of the lead compound
The crude extract was separated by thin layer chromatographic (TLC) using the solvent system of carbinol: ammonium hydroxide at a ratio of 99:1 and the separated bands were tested for the presence of nitrogenous compounds by Dragondorff’s reagent.
The crude extract was analysed using GC-MS, and the gas chromatogram obtained from the GC-MS was analysed for the presence of peaks. Further, 2 g of the crude extract was separated by a silica gel column chromatography, pencil column (1.1 cm width and 10 cm length) was used for separation of the lead
compound with carbinol: ammonium hydroxide at a ratio of 99:1 was used as a solvent system. The active fraction was collected and pooled and condensed to obtain the pure crystals of the nitrogenous compound.
The active fraction was subjected to TLC separation.
The pure compound was subjected to spectroscopic analyses such as FTIR, mass spectrum, and 1H NMR analysis. The active fraction was subjected to GC-MS analysis using Perkin Elmer workstation Clarus 600 GC coupled to a mass spectrometer. Elite-5MS (30 m
× 0.25 mm) width film depth of 250 μm capillary tube was used under the following condition. The instrument has an initial oven temperature of 55°C for 3 min and a ramp program which elevates from 6°C/min up to 310°C, and further 3 min isothermal hold. The helium (He) carrier gas was used, with a flow rate split ratio of 10:1. The 2 µL volume of sample was injected, and temperature of the injector was maintained to 250°C. The mass spectrum obtained was compared with spectra available in the National Institute of Standards and Technology (NIST-LIB 0.5) library for matching using the in-built software of the GCMS system (Wiley GC-MS-2007) as per the literature data available32.
FTIR was used to determine the functional groups present in the pure compound by using Perkin Elmer Spectrum1 FTIR spectrometer at a resolution of 1 cm-1 at a scan range of 450-4000 cm-1. 1H NMR and 13C NMR spectra were recorded using AV500 FT NMR spectrometer to determine the positions of hydrogen and carbon in the pure compound24.
In silico docking analysis
A total of 11 drug target proteins were chosen and the 3D structure was downloaded from PDB website (www.rcsb.org) with the following PDB-ID: 5JSN, 5FMJ, 5J9Y, 2YJA, 3G73, 5FWL, 5I3E, 5JSB, 3S4E, 5HA9, and 5HHD. Downloaded protein structures were prepared for docking, by removing all non-amino acid moieties in the structure, using PyMOL software. The 3D structure of the ligand was drawn using ChemSketch-11. The interaction between the ligand and protein was studied using AutoDock-4.2 MGLTools.
Result obtained from AutoDock was viewed in PyMOL13,33.
Results
Isolation and identification of marine actinomycetes
A total of 100 actinomycetes were isolated from marine soil samples of Rameswaram and Dhanushkodi.
Among the isolates, isolate designated as VITLGK011
was identified as a most potent bioactive isolate, based on its antibacterial activity. Morphological appearance of VITLGK011 is shown in Fig. 1A. The image shows the isolate to be pale white in colour, with the production of pigment (diffused in the agar media, surrounding the colony). The isolate was confirmed as actinomycetes, based on the results of Gram’s staining (Fig. 1B). The colonies were Gram’s positive, filamentous with spore formation characteristics of actinomycetes. The isolate demonstrated significant antibacterial activity at preliminary cross-streak method against four common bacterial pathogens, i.e., Escherichia coli, Staphylococcus aureus, Bacillus cereus and Proteus vulgaris (Fig. 1C). The isolate was mass cultured in ISP.No.1 broth media, and its secondary metabolites were extracted using chloroform as a solvent in liquid: liquid separation. The crude secondary metabolite extracted from VITLGK011 demonstrated significant antibacterial activity against the tested bacterial pathogens (Fig. 1D), and the results are shown in Table 1.
Hence, VITLGK011 was further characterised to identify its genus and species. The morphology of the isolate was studied using Scanning Electron Microscopy (SEM), (Fig. 1E). The isolate had concave cells and had a crippled cell surface.
Filamentous growth of the isolate was clearly visible.
Biochemical characterization identified the isolate as a Gram positive, nonmotile bacteria, with melanin production. In the triple-sugar-ion test, the isolate the isolate showed positive for gas production, and also produced alkaline slant and alkaline butt. The isolate
was positive for methyl red test. The isolate showed negative for Voges-Proskauer test, indole test, oxidase test and catalase test. The isolate was cultured on different ISP media to observe the morphological characters and to study the nutritional preference. The results of various morphological observations on different ISP media are given in Table 2. The genomic DNA (16S rDNA) of the isolate was extracted and was amplified using PCR The amplified product was sequenced and found to contain1468 nucleotides. The 16S rDNA sequence showed 98%
similarity through NCBI nBLAST search to Streptomyces globosus. The gene sequence was processed and submitted to GenBank as Streptomyces globosus VITLGK011 under the accession ID KR150758. A phylogenetic tree was constructed to identify the closest partner of the isolate (Fig. 1F).
Based on molecular taxonomy and phylogeny the actinomycetes isolate was identified as Streptomyces and designated as Streptomyces globosus VITLGK011, with potential antibacterial activity.
Antiproliferative and antioxidant activity of crude extract
Crude chloroform extract prepared from VITLGK011 was assayed for antiproliferative cytotoxic activity by MTT assay. The crude extract
Fig. 1—Characterization and identification of VITLGK011. (A) morphology; (B) Gram’s staining; (C & D) antibacterial activity; (E) SEM image; (F) phylogenetic tree; (G) cytotoxicity; and (H) antioxidant activity
Table 1—Antibacterial activity of the isolate VITLGK011
Bacterial Pathogens Zone of
Inhibition (mm) MIC (μg) Escherichia coli [MTCC: 1886] 18 6.25 Staphylococcus aureus [MTCC: 7405] 17 6.25 Proteus vulgaris [MTCC: 7299] 21 3.12 Bacillus cereus [MTCC: 1168] 17 6.25
demonstrated an IC50 value at 250 µg/mL on MCF-7 cells after 24 h of incubation (Fig. 1G). The results of DPPH antioxidant assay is shown in Fig. 1H. The moderate antioxidant potential was observed, with a maximum of 40% antioxidant activity at a concentration of 4 mg/mL.
Purification and characterization of active fraction
Thin layer chromatographic (TLC) separation of crude extract using the solvent system of carbinol:ammonium hydroxide at a ratio of 99:1 resulted in the separation of 2 bands at 0.92 Rt and the other band appeared as a smear at the lower end of the TLC plate (Fig. 2B). The distinct band at 0.92 Rt was tested for the nitrogenous compound, by Dragondorff’s reagent. The crude extract was analysed in GC-MS and the gas chromatogram (Fig. 2A) obtained from the GC-MS showed the presence of three peaks at the retention time of 8.18, 23.03 and 26 min. Further, 2 g of the crude extract was separated in a pencil column chromatography, with a packed silica gel column (1.1 cm width and 10 cm length) with the same solvent system. The pure compound eluted was collected and pooled and condensed to obtain the pure
crystals of the nitrogenous compound. The purity was observed in TLC as shown in Fig. 2B.
FTIR spectrum showed the presence of the following functional groups: O-H (2357), C-H (2943, 2831), C=O (1658), aromatic C-C (1408, 1444), N-O (1381), C-O (1112) and C-N (1020) as represented in the Fig. 2C. Mass spectrum analysis demonstrated that the compound had a molecular weight of 209.1 g/mol as represented in Fig. 2D. The 1H-NMR analysis showed that there is only 4 phase shifts in the compound (4 distinct positions of hydrogen in the molecule) (Fig. 2E) Based on these three results, the structure of the pure nitrogenous compound isolated from VITLGK011 crude extract was identified as benzoyloxy-ethyl-carbamic acid (BECA). The chemical structure of the lead compound BECA is shown in Fig. 2F. BECA has the molecular formula of C10H11NO4. The purity of the BECA was assessed using HPLC. The HPLC chromatogram revealed a distinct single peak at Rt 0.922min (Fig. 2G).
In vitro anticancer cytotoxicity activity of benzoyloxy-ethyl- carbamic acid (BECA)
The anticancer cytotoxic activity of BECA on cancer cell lines demonstrated the lowest IC50 value of 3.12 µg/mL against MCF-7. It showed the IC50 value of 6.25 µg/mL against LN-18, PA-1, and HCT-116. In the case of VERO cells, BECA showed the IC50 value of 12.5 µg/mL. The anticancer cytotoxic activity of BECA on normal VERO cells is shown in Fig. 3 A-EA (A on MCF-7,B on HCT-116,C on LN-18, D and E on PA-1. The morphological changes observed in MCF-7 cells treated with BECA (3.12 µg/mL) are shown in Fig. 3F.
In vivo anticancer activity of BECA
The anticancer effect of BECA on zebra fishes injected with MCF-7 cancer cells showed at 3 µg/day dosage, the tumor progression was reduced by 20%
when compared to cancer control; swelling of the liver was reduced; dead tumor cells were observed (Table 3). At 15 µg/day dosage, tumor progression was reduced by 25%; recovery of cells was observed in the liver; swelling of the liver was also reduced considerably; dead tumor cells were observed. At 30 µg/day dosage, tumor progression was reduced by 30%; swelling of the liver was greatly reduced;
recovery of cells from necrotic changes was observed in the liver; dead cells were present in the tumor.
Tumor pathogenesis of control and BECA treated groups are shown in Fig. 4A.
Table 2—Growth of VITLGK011 on different ISP culture media Culture
Media Description
ISP 1
Mycelium Aerial: Light Brown Substrate: Dark Brown
Morphology Rough, Concave, Big, Translucent, Melanin
Aerial: Light Brown with White colonies
ISP 2 Mycelium Substrate: Creamy White Morphology Rough, Concave, Small, Translucent
Aerial: Light Brown with White colonies
ISP 3 Mycelium Substrate: Light Brown Morphology Rough, Concave, Translucent
Aerial: Light Brown
ISP 4 Mycelium Substrate: Creamy White Morphology Rough, Concave, Translucent
Aerial: Light Brown ISP 5
Mycelium Substrate: Creamy White Morphology Rough, Concave, Translucent,
Powdery
ISP 6 Mycelium Aerial: Dark Grey Substrate: Brown
Morphology Concave, Small, Translucent, Melanin
Aerial: Light Brown ISP 7 Mycelium Substrate: Dirty White
Morphology Raised, Medium, Translucent
Fig. 2—Spectroscopic characterization and identification of BECA. (A) gas chromatogram; (B) TLC analysis; (C) FTIR; (D) mass spectrum; (E) NMR; (F) chemical structure of BECA; and (G) purity in HPLC
In silico anticancer activity of BECA
Interactions of BECA with 11 of the common cancer drug targets were studied by in silico molecular docking. Among the 11 protein targets, BECA demonstrated the highest affinity towards Poly-ADP-Ribose-Polymerase-1 (PARP1) protein with a free binding energy of −6.71 Kcal/mol and Ki
value of 12.11 µM and formed 4 hydrogen bonds (Lys-272, Ser-278, and Lys-279) (Table 4). Graphical representation of the interaction of BECA with PARP1 is shown in Fig. 4B.
Discussion
Reports are available for isolation of S. globosus from other environments such as high mountain soil and industrial effluent samples34,35. S. globosus has been reported to possess antibacterial activity against
methicillin-resistant Staphylococcus aureus36. Ours is the first report on the extraction and identification of benzoyloxy-ethyl-carbamic acid (BECA) from the
Fig. 3—Cytotoxic activity of BECA. (A) VERO cells; (B) MCF7 cells; (C) HCT116 cells; (D) LN18 cells; (E) PA1 cells; and (F) morphology of MCF7 cells
Table 3—In vivo anticancer activity of BECA
Clinical Parameters Control Tumor model BECA (3µg/day) BECA (15µg/day) BECA (30µg/day)
Liver anatomy Normal Swollen Pale Pale Pale
Liver pathology Normal Irregularly
shaped cells Presence of lysed
cells Recovery of few cells
was observed Mild Necrosis and recovery of few cells were observed
Anatomyof intestine Normal Normal Normal Normal Normal
Pathologyof intestine Normal Normal Normal Normal Normal
Tumour pathology Normal Irregularly shaped
cells Presence of
lysed cells Presence of
lysed cells Presence of lysed cells
Pathology of skeletal muscle Normal Normal Normal Normal Normal
Percentage of tumour cells 0 80 60 55 50
Percentage of normal cells 100 20 40 45 50
Table 4—In Silico docking of BECA with cancer drug target proteins Protein
Name PDB
ID Binding
Energy Inhibition
Constant Hydrogen Bonds
BCL2 5JSN 6.35 22.17 µM 3
BCLxl 5FMJ 5.47 98.64 µM 2
EGFR 5J9Y 5.54 87.14 µM 1
ER alpha 2YJA 5.92 45.59 µM 2
FoxM1 3G73 4.79 309 µM 1
HSP90 5FWL 5.86 50.55 µM 2
LSD1 5I3E 6.32 23.23 µM 2
MCL1 5JSB 6.28 24.81 µM 3
MKP1 3S4E 5.38 114 µM 3
PARP1 5HA9 6.71 12.11 µM 4
VEGF 5HHD 4.92 249 µM 1
marine Streptomyces globosus VITLGK011. The anticancer cytotoxic potential of extracted compound was demonstrated by in vitro, in vivo and in silico studies.
MCF-7 cells were highly susceptible to BECA (3.12 µg/mL), and most of the cells were observed to undergo apoptosis after 24 h of incubation, and the control VERO cells were considerably less susceptible to BECA. The observed result proves that BECA has selective anticancer cytotoxic activity on cancer cells. The reduction in tumor progression in zebrafish under in vivo studies further confirmed the anticancer cytotoxic activity of BECA. In vivo zebrafish model study, also suggested that BECA has no toxic side effects. The in silico results show that BECA had the highest affinity towards PARP1, and it could be the possible mode of action for its anticancer cytotoxic potential.
Poly-ADP Ribose Polymerase (PARP1) is one of the key DNA repair proteins, and it is a validated drug
target for cancer therapy14. PARP1 has been identified as a drug target for treatment for breast and ovarian cancers, with mutations in BRCA1 and BRCA2.
Upon inhibition of PARP1, the cell cycle arrest and cell death were observed in breast cancer. A significant interaction of BECA with PARP1 suggested that BECA is a potential PARP1 inhibitor molecule. The anticancer cytotoxic activity demonstrated by BECA could solely be due to inhibition of PARP1.
BECA is a nitrogenous compound that could be classified as an alkaloid. Since BECA has an ester group in its structure, it can also be termed as alkaloid-ester.
Alkaloids are one among the bioactive molecules that have been studied for various antagonistic applications.
Actinomycetes from the marine origin have been reported to produce several alkaloid molecules. Two indolocarbazole alkaloids (K252c and Arcyriaflavin-A) were identified from marine-derived actinomycetes and was proven to have cytotoxic activity by inducing apopotosis37. Streptopyrrolidine is an alkaloid molecule produced by marine actinomycetes Streptomyces sp KORDI-3973 isolate, and has been proven to inhibit angiogenesis, and thereby leading to anticancer effect38. These findings prove that marine actinomycetes are a valuable source for production of anticancer cytotoxic alkaloid molecules. Being an alkaloid molecule, BECA is yet another novel alkaloid compound produced by marine Streptomyces, which has the potential to be developed as the drug. Many researchers have also reported non-alkaloid secondary metabolites produced by Streptomyces sp., with anticancer activity. Furan-2- yl-Acetate produced by Streptomyces sp. VITSDK139. Rhodomycin-B produced by Streptomyces purpurascens was reported to be cytotoxic in nature against HeLa cancer cell line24. Aporphine alkaloid SSV produced by Streptomyces sp. KS1908 was found to be cytotoxic against Hep2, HeLa, HL-60 & MCF7cells40. The 1-(3- bromo-5-methylphenyl)-1H-indole produced by Streptomyces sp. LCJ85 was reported as a cytotoxic compound against HePG2 cell line41. Our results also support that anticancer cytotoxic potential of secondary metabolites extracted from marine Streptomyces species.
Conclusion
BECA extracted from Streptomyces globosus VITLGK011 has demonstrated significant anticancer cytotoxic activity both under in vitro and in vivo conditions towards cancer cells. In silico docking studies showed the interaction of BECA with PARP1
Fig. 4—Antiproliferative activity of BECA on MCF-7 cancer cells injected zebrafish. (A) tumor pathology of zebra fishes in control and test groups; and (B) interactions of BECA and PARP1.
protein. Ours is the first report of antiproliferative activity of BECA derived from Streptomyces globosus VITLGK011.
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