- Research Article
- Open Access
Microwave synthesis, crystal structure, antioxidant, and antimicrobial study of new 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline compound
© The Author(s) 2018
- Received: 30 April 2018
- Accepted: 3 December 2018
- Published: 20 December 2018
Although the development of antibiotic and antioxidant manufacturing, the problem of bacterial resistance and food and/or cosmetics oxidation still needs more efforts to design new derivatives which can help to minimize these troubles. Benzimidazo[1,2-c]quinazolines are nitrogen-rich heterocyclic compounds that possess many pharmaceutical properties such as antimicrobial, anticonvulsant, immunoenhancer, and anticancer.
A comparative study between two methods, (microwave-assisted and conventional heating approaches), was performed to synthesise a new quinazoline derivative from 2-(2-aminophenyl)-1H-benzimidazole and octanal to produce 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline (OCT). The compound was characterised using FTIR, 1H and 13C NMR, DIMS, as well as X-ray crystallography. The most significant peak in the 13C NMR spectrum is C-7 at 65.5 ppm which confirms the cyclisation process. Crystal structure analysis revealed that the molecule grows in the monoclinic crystal system P21/n space group and stabilised by an intermolecular hydrogen bond between the N1–H1A…N3 atoms. The crystal packing analysis showed that the molecule adopts zig-zag one dimensional chains. Fluorescence study of OCT revealed that it produces blue light when expose to UV-light and its’ quantum yield equal to 26%. Antioxidant activity, which included DPPH· and ABTS·+ assays was also performed and statistical analysis was achieved via a paired T-test using Minitab 16 software with P < 0.05. Also, the antimicrobial assay against two Gram-positive, two Gram-negative, and one fungus was screened for these derivatives.
Using microwave to synthesise OCT have drastically reduced reaction time, and increased yield. OCT show good antioxidant activity in one of the tests and moderate antimicrobial activity.
- Single crystal
Free radicals and various reactive oxygen or nitrogen species are produced either exogenously from pollution, radiation and food, or endogenously inside the human body from metabolic pathways, leading to oxidative stress. Oxidative stress is the primary cause of many disorders including atherosclerosis, cancer, diabetes, and ageing . Compounds which can scavenge free radicals can, therefore, contribute towards the protection and prevention of these illnesses . Hence, the need for new antioxidants is increasing to solve these problems.
Furthermore, bacterial infections have become a serious threat after many decades of treating the first patient with antibiotic. That is because of the fast increasing in bacterial resistance which become prevalent all over the world. Bacterial resistance to antibiotic is a result of overuse and misuse of these drugs . Therefore, there is continuous need for exploration new medication.
Attempting to solve the said problems, chemists and pharmacists have tried for years to synthesis new nitrogen-comprising compounds which are known for their biological activities. Nevertheless, the problem of using organic solvent in chemical routes presents a significant threat to the environment as it can cause pollution during processing handling, and storage. As a result, many researchers have focused on developing alternative methods and procedures that not only facilitates organic synthesis but also reduces the amounts of solvents. One of these methods uses microwave irradiation to perform organic reactions .
Microwave technique to heat organic reactions have been widely discussed and debated within the organic and medicinal chemist community since the publication of the first scientific article in 1986 . In recent years, this fast-moving protocol has been used in many laboratories to synthesise organic materials within a very brief time, resulting in considerable yield, and enhancing pure products. This technique includes direct interaction between the microwave radiation and molecules in the reaction system which dramatically reduces any undesired side-products and increases the yield of the target product .
Since 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline (OCT) is combining skeleton of bioactive quinazoline and benzimidazole nucleolus, it is expected to have some pharmaceutical activities. Also, the literature survey resulted to only one study that have focused on antioxidant activities of benzimidazoquinazoline compounds . Therefore, we report herein the crystal structure, spectroscopic characterisation, antioxidant, and antimicrobial activities of new 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline resulting from two different synthetic methods.
Materials and experimental conditions
The analytical grade chemicals used for this project were commercially available from several suppliers and applied without any additional purification. The glacial acetic acid was supplied from J. T. Baker/USA. The analytical grade methanol and Mueller–Hinton agar were procured from Merck/Germany. The DMSO-d6 for nuclear magnetic resonance was obtained from Merck/Switzerland. The 2-(2-aminophenyl)-1H-benzimidazole, octanal, potassium persulfate, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS), (±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were all supplied from Sigma-Aldrich. Three-angstrom molecular sieves were supplied by Acros Organics/USA and used to dry the solvents.
A 10-mL vial capacity single-mode CEM microwave (USA) along with Synergy software were used to achieve the condensation reaction. An IR Tracer-100 (Shimadzu/Japan) was activated to determine the functional groups applying FTIR analysis and GCMS QP5050A (Shimadzu/Japan) recorded the mass spectrum (DI-MS). JEOL JNM ECA 400 was executed at ambient room temperature to analyse the 1H-NMR (400 MHz) and 13C-NMR (100 MHz) spectra. A Barnstead Electrothermal/UK instrument was used to measure the melting point, and a Thermo Scientific ELISA reader/UK was used to measure the absorbance of the radical-OCT mixture. A UV–Visible spectrophotometer (UV-1700, Shimadzu/Japan) was operated at ambient room temperature to measure ABTS·+ absorbance. An Autopol VI, Automatic Polarimeter manufactured by Rudolph Research Analytical/Hackettstown, NJ, USA was used to measure the optical rotation, and a CHNS instrument (LECO TruSpec Micro CHNS/US) was used to analyse the carbon, hydrogen, and nitrogen percentage contents in the compound. UV-1650 PC (UV–Visible spectrophotometer, SHIMADZU/Japan) was run to measure the UV–Vis absorbance spectra of the studied compounds. Perkin Elmer LS 55 Fluorescence Spectrometer/UK was used to measure emission spectra. Lastly, thin layer chromatography was carried out using silica gel aluminium plates 60 F254 (Merck/Germany).
The microwave-assisted synthesis was conducted according to Negi et al.  with some modifications. In a 10-mL volume microwave vial, octanaldehyde (1.2 mmol, 186 µL) was dissolved in methanol (1 mL) and added dropwise to 2-(2-aminophenyl)-1H-benzimidazole (1 mmol, 0.21 g) which was dissolved in 5 mL methanol, followed by addition of two drops of glacial acetic acid. The solution was irradiated in a single-mode benchtop microwave for 5 min at 102 °C, and the reaction was monitored using Synergy software. The TLC was performed to check the progress of the reaction and completion. After 5 min, the vial was cooled to room temperature, dried in a vacuum oven, and washed with hexane to provide the final pure product. The crystals were obtained by slow evaporation of toluene to produce off-white crystalline solid with a premium yield of 91% (0.29 g).
Conventional heating synthesis
The conventional reflux method was performed according to Kapoor et al.  with slight modifications. In a 50-mL round bottom flask, octanaldehyde (1.2 mmol, 186 µL) dissolved in methanol (1 mL) was added dropwise to 2-(2-aminophenyl)-1H-benzimidazole (1 mmol, 0.21) which was dissolved in 15 mL hot methanol, followed by addition of two drops of glacial acetic acid. The prepared mixture was refluxed at 95 °C for around 80 min over an oil bath. The reaction progress was monitored every 15 min to check the reaction progression. Next, it was cooled to room temperature after completion as evident by TLC. The target crystals were obtained after vacuum drying, and vigorously washing the crude product with hexane to produce the precipitate which was recrystallised from toluene to furnish off-white, shiny crystals of 77% yield (0.24 g).
Characterization of 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline (OCT)
Structure determination by X-ray crystallography analysis
Single crystal X-ray determinations were conducted at Center for Research and Instrumentation (CRIM), Universiti Kebangsaan Malaysia (UKM). A suitable crystal with appropriate size was mounted on a gonio head. Reflection data was collected at 25 °C using (graphite-monochromated Mo Kα radiation, λ = 0.71073 Å) with a photon detector distance of 4 cm and a swing angle of − 30° maximum. The data collected were reduced using the program SAINT  and an empirical absorption correction was carried out using SADABS . The structure was solved by direct methods and refined by using the full- matrix least-squares method using the SHELXTL  software package. All non-H atoms were anisotropically refined. The hydrogen atoms were located by difference syntheses and refined isotropically. The molecular graphics were created using SHELXTL and MERCURY softwares. PLATON program was used for molecular structure calculation . Atomic scattering factors and anomalous dispersion corrections were taken from the international table for X-ray crystallography.
Carbon, hydrogen, and nitrogen percentage analyses were performed to determine the actual ratios of these elements in the OCT sample, comparing them with the calculated ratios.
Electronic spectral analysis
Fluorescence emission study
DPPH· scavenging activity of OCT
The DPPH· scavenging activity of OCT and AMINE was conducted according to Chan et al. . In a 96 well microplate, 50 µL of the diluted OCT sample in DMSO was reacted with 195 μL of 0.2 mM DPPH· (methanolic solution) and kept in a dark ambient room where the mixture was kept for 1 h at 25 °C. Next, using the microplate ELISA reader and at 540 nm, the absorbance was read. The analysis was conducted in triplicate, and the antioxidant activity of both compounds was expressed in mg Trolox equivalent/g sample.
ABTS·+ scavenging activity of OCT
The ABTS·+ scavenging activity of both samples was conducted according to the previous study performed by Chan et al.  with some additional modifications. Briefly, ABTS·+ was generated by adding 10 mL of 7 mM ABTS to 10 mL of 2.45 mM potassium persulfate and kept in a dark place at room temperature for 24 h. Then, the ABTS·+ solution was diluted to the absorbance of 1.40 ± 0.05 at 734 nm with the UV–vis spectrophotometer. Subsequently, 180 μL of ABTS·+ solution was added to 20 μL of the OCT sample in a ninety-six well microplate. After 1 h of incubation at room temperature, the absorbance was recorded at 734 nm using a microplate ELISA reader. The analysis was conducted in triplicate, and the scavenging activity of the OCT compound was expressed in mg Trolox equivalent/g sample.
Antioxidant values were expressed as mean ± SD of three replicates for both samples. Statistical analysis was performed by paired T-test using Minitab 16 software with P < 0.05.
All the microorganisms used in this study were human clinical strains, provided by the Microbial Culture Collection Unit (UNiCC), Institute of Bioscience, University Putra Malaysia. The microbes strain includes two Gram-positive: Staphylococcus aureus ATCC 43300, Bacillus sublitis UPMC 1175; two Gram-negative: Pseudomonas aeruginosa ATCC 15542, Salmonella choleraesuis ATCC 10708; and one fungus: Aspergillus brasilliensis ATCC 16404.
The antimicrobial activities of the studied compounds were evaluated using an agar-well diffusion assay  with some modifications. Into each of the sterile Petri dishes (Ø 90 mm), 20 mL of molten agar at 45 °C was poured. After the plates were aseptically dried, the agar surface of each plate was streaked using a sterilised cotton swab with the specified microbial strain. Then, with a 5 mm Cork borer diameter, the wells were punctured into the agar. The synthesised compounds were then dissolved in DMSO to produce 100 mg/mL final concentration. Next, 20 μL of the studied samples were loaded into each well, and the plates were incubated invertedly between 30 and 37 °C for 18 and 24 h. or until proper growth had occurred. Once the incubation was completed, the circular inhibition zones were measured using callipers, including the well diameter. The DMSO was used as a negative control while the tetracycline or nystatin was used as a positive control. The experiments were performed in triplicate.
Reaction time and % yield of OCT under conventional reflux and microwave irradiation, respectively
Reaction time, min.
Seemingly, Schiff base could initially be forming but reacts to create benzimidazoquinazoline, which is applicable for all aldehydes. In the future, the R group in amine can be changed to decrease its’ reactivity to obtain isolate Schiff base compounds.
The structure of the OCT crystal was confirmed via FTIR, 1H and 13C NMR, and DIMS and it immediately became apparent by observing the 1H, and 13C NMR spectra (Figs. 2 and 3) that there was no Schiff base formed, but, a new diazine ring had been formed. Furthermore, there is a new aliphatic multiplet at 6.03–6.09 ppm which belongs to H-7 of the newly formed ring, and the N1–H proton appears as a singlet at 7.15 ppm. This, therefore, proved that the cyclisation process rather than Schiff base formation occurred. Moreover, there is no singlet peak around 8.5 to 9 ppm which would belong to the imine proton (–N=C–H). The 1H NMR also displayed four different peaks in the aliphatic area belonging to protons CH3, H-17, 18, 19 and 20. The other characteristic peaks are diastereotopic protons HA and HB which rose up at different chemical shifts as a multiplet at 1.61–1.72 and doublet of the triplet at 1.80 ppm for HA and HB respectively. In the 13 C NMR spectrum, the most important peak is C-7 at 65.5 at the aliphatic area which confirms the cyclisation process and the formation of OCT. Otherwise, there will be a peak around 165 to 170 ppm belonging to carbon (C=N) of the Schiff base. Figure 3 illustrates the remaining peaks.
The FTIR spectrum of OCT exhibited two medium absorption bands at the 3202 and 2928 cm−1 regions corresponding to N–H and –C–H sp2 stretching, respectively. Also, the band at 2859 and the medium sharp band at 1614 cm−1 corresponds to –C–H sp3 and C=N stretching absorptions, respectively. The C=C aromatic absorption peaks resulted in a medium peak at 1520 cm−1, and at 1461 cm −1 the N–H bending band is observed. Also, the C–N stretching band appears at 1261 cm −1 and C–H aromatic out of plane bending at 736 cm −1. Figure 4 summarises all distinctive peaks for the mentioned derivative.
The molecular ion peak was determined for OCT and is equivalent to its molecular weight (C21H25N3 = 319. 44). The peak at 220 m/z with 100% intensity is considered as the base peak belonging to the [C14H10N3]+ fragment. The remainder of the fragments with their molecular weights is illustrated in Fig. 5.
Crystallography study of 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline (OCT)
Refinement of structure and crystal data for 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline
293 (2) K
Unit cell dimensions
a = 9.37 (4) Å α = 90°
b = 17.14 (5) Å β = 101.5 (2)°
c = 11.27 (4) Å ɣ = 90°
1773 (11) Å3
0.500 × 0.430 × 0.270 mm3
Theta range for data collection
3.009 to 25.249°
− 11 ≤ h ≤ 11, − 20 ≤ k ≤ 20, − 13 ≤ l ≤ 13
3186 [R(int) = 0.1192]
Completeness to θ = 25.243°
Full-matrix least-squares on F2
Goodness-of-fit on F2
Final R indices [I > 2 sigma (I)]
R1 = 0.1062, wR2 = 0.2552
R indices (all data)
R1 = 0.1858, wR2 = 0.3193
Largest diff. peak and hole
0.330 and − 0.297 e Å−3
CCDC reference no.
The benzimidazole ring N2/N3/(C8–C14) is planar with a maximum deviation of 0.012 (5) Å and 0.012 (7) Å for C8 and C11, respectively from the least square plane. The benzene ring (C1–C6) is planar with a maximum deviation of 0.007 (5) Å for C1 from the least square plane. The dihedral angle between the benzimidazole plane and the benzene ring is 7.26 (17)°.
The N3-C14 is 1.318 (7) Å indicating a double bond character while the other bond lengths and angles (Table 3) are in normal ranges and are comparable to those in its analogues of 6-butyl-5,6-dihydrobenzo-[4, 5]imidazo[1,2-c]quinazoline .
Selected bond lengths (Å) and angles (°)
lengths (Å) and angles (°)
Hydrogen bonds parameters (Å) of OCT compound
The handling and experimental work with this compound unexpectedly disclosed that this compound fluoresces and emits a bright blue colour when exposed to ultraviolet light either from the sun or a UV-lamp. Therefore, it is meaningful if not necessary, to study the fluorescent properties of this compound as a part of the characterisation process which hopefully will expose new potential applications.
Electronic spectral data
The UV–Vis spectrum of the OCT compound was measured in DMSO solvent at 25 °C and the result exhibited various absorption bands at 267 (ɛ, 0.236 × 104), 293 (ɛ, 0.228 × 104), 304 (ɛ, 0.319 × 104), and 360 (ɛ, 0.191 × 104) nm which are ascribed to π–π* and n–π* intramolecular transitions between electronic energy levels. When the OCT compound is exposed to ultraviolet radiation, the electrons are excited and transfer from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). The molar absorptivity εmax values (molar extinction coefficient) of this derivative have medium intensities for π → π* transitions which are higher than that of n → π* transition which refers to the higher probability of π electron transitions rather than non-bonding electrons transfer (Fig. 6).
Emission spectral data
Absorption and emission maxima and quantum yields (\(\varPhi\)) for OCT and AMINE compounds
Stock shifts (nm)
Quantum yield (\(\varPhi\))
Quantum yield (%)
Antimicrobial activities of studied compounds
Compounds concentration in 100 (mg/mL)
Inhibition zone diameter in (mm)a
Staphylococcus aureus ATCC 43300
Bacillus subtilis UPMC 1175
Pseudomonas aeruginosa ATCC 15542
Salmonella choleraesuis ATCC 10708
Aspergillus brasiliensis ATCC 16404
DMSO (−ve control)
The 6-heptyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c] quinazoline was successfully synthesised at an excellent yield of 91% using the microwave approach. The FTIR, NMR, and DIMS along with single crystal analysis of titled benzimidazoquinazoline (OCT) confirmed the building structure of this new crystal. The fluorescence study of this compound further disclosed that it fluoresces with double the amount of light compared to the starting AMINE compound. Hence, it could be a potential candidate for further cell imaging applications or single cell level studies for physiological applications. From the antioxidant results, the ABTS·+ test revealed higher scavenging activity as compared to the DPPH· test for the same compound. Furthermore, the antimicrobial study of these derivatives demonstrated that OCT is a more active compound as compared to its parent against each of the Staphylococcus aureus and Bacillus subtilis types of bacteria. Therefore, it could be a good candidate to suppress antibiotic resistant bacteria.
HAH designed the study and performed most experimental works as well as wrote the manuscript draft. EA helped in designing an overall perspective of the study. She provided advice and support as well as she read and corrected the draft. MBAR covered all financial support for this project. BMY did the crystallography part and helped in its’ writing. KWC helped in designing and calculation the antioxidant activity part. KBS helped and supported the overall study. All authors read and approved the final manuscript.
All Authors gratefully acknowledge the financial funding of this work from Ministry of Higher Education, Malaysia under Grant Nanomite 5526306. First Author would like to thank Mustansiriyah University (http://www.uomustansiriyah.edu.iq) Baghdad-Iraq for its supporth in the present work. She is thankful to Ministry of Higher Education and Scientific research, Iraq for Ph.D. scholarship.
The authors declare that they have no competing interests.
Availability of data and materials
All the data and material support this manuscript are available either in the article or attached as additional file.
Ministry of Higher Education/Malaysia under Grant Nanomite 5526306.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Galarce GD, Foncea RE, Edwards AM, Pessoa-Mahana H, Pessoa-Mahana CD, Ebensperger RA (2008) Biological evaluation of novel 6-arylbenzimidazo [1,2-c]quinazoline derivatives as inhibitors of LPS-induced TNF-alpha secretion. Biol Res 41:1–7View ArticleGoogle Scholar
- Bahekar RH, Rao ARR (2000) Bronchodilation and structure-activity relationship studies on new 6-substituted benzimidazo [1,2-c] quinazolines. Arzneim Forsch Drug Res. 50(8):712–716Google Scholar
- Kuarm BS, Reddy YT, Madhav JV, Crooks PA, Rajitha B (2011) 3-[Benzimidazoand 3-[benzothiadiazoleimidazo-(1,2-c)quinazolin-5-yl]-2H-chromene-2-ones as potent antimicrobial agents. Bioorg Med Chem Lett 21:524–527View ArticleGoogle Scholar
- Rohini R, Shanker K, Reddy PM, Ravinder V (2010) Synthesis and antimicrobial activities of a new class of 6-arylbenzimidazo [1, 2-c] quinazolines. J Braz Chem Soc 21(1):49–57View ArticleGoogle Scholar
- Joshi PP, Shirodkar SG (2014) A new approach for the synthesis of 6-aryl-5,6-dihydrobenzimidazo[1,2-c]quinazoline derivatives and its biological study. World J Pharm Pharm Sci. 3(9):950–958Google Scholar
- Sankaran M, Kumarasamy C, Chokkalingam U, Mohan PS (2010) Synthesis, antioxidant and toxicological study of novel pyrimido quinoline derivatives from 4-hydroxy-3-acyl quinolin-2-one. Bioorg Med Chem Lett. 20(23):7147–7151View ArticleGoogle Scholar
- Roopan SM, Khan FRN (2009) Synthesis, antioxidant, hemolytic and cytotoxicity activity of AB ring core of mappicine. Arkivoc. 13:161–169Google Scholar
- Ventola CL (2015) The antibiotic resistance crisis part 1: causes and threats. P&T 40(4):277–283Google Scholar
- Wardencki W, Curylo JNJ (2005) Green chemistry—current and future issues. Polish J Environ Stud. 14(4):389–395Google Scholar
- Kappe CO, Dallinger D (2009) Controlled microwave heating in modern organic synthesis: highlights from the 2004–2008 literature. Mol Divers. 13:71–193View ArticleGoogle Scholar
- Mahire VN, Patel VE, Mahulikar PP (2016) Facile DES-mediated synthesis and antioxidant potency of benzimidazoquinazolinone motifs. Spectrochim Acta Part A. 44:1–15Google Scholar
- Negi A, Alex JM, Amrutkar SM, Baviskar AT, Joshi G, Singh S, Banerjee UC, Kumar R (2015) Imine/amide–imidazole conjugates derived from 5-amino-4-cyano-N1-substituted benzyl imidazole: microwave-assisted synthesis and anticancer activity via selective topoisomerase-II-a inhibition. Bioorg Med Chem 23:5654–5661View ArticleGoogle Scholar
- Kapoor P, Fahmi N, Singh RV (2011) Microwave assisted synthesis, spectroscopic, electrochemical and DNA cleavage studies of lanthanide(III) complexes with coumarin based imines. Spectrochim Acta Part A. 83:74–81View ArticleGoogle Scholar
- Sheldrick GM (1996) SAINT V4, Software reference manual siemens analytical Xray systems. Brukel AXS Inc., MadisonGoogle Scholar
- Sheldrick GM (1996) SADABS, program for empirical absorption correction of area detector data. University of Gottingen, GermanyGoogle Scholar
- Sheldrick GM (1997) SHELXTL V5.1, software reference manual. Brukel AXS Inc., MadisonGoogle Scholar
- Spek AL (2009) Structure validation in chemical crystallography. Acta crystallogr sect D. Int Union Crystallogr 65:148–155Google Scholar
- Chan K, Khong NMH, Iqbal S, Mansor SM, Ismail M (2013) Defatted kenaf seed meal (DKSM): prospective edible flour from agricultural waste with high antioxidant activity. LWT Food Sci Technol. 53(1):308–313View ArticleGoogle Scholar
- Chan KW, Khong NMH, Iqbal S, Ismail M (2013) Isolation and antioxidative properties of phenolics-saponins rich fraction from defatted rice bran. J Cereal Sci 57:480–485View ArticleGoogle Scholar
- Hasan HA, Raauf AMR, Razik BMAR, Hassan BA (2012) Chemical compositionand-antimicrobial activity of the crude extracts isolated from zingiber officinale by different solvents. Pharm Anal Acta. 3(9):1–5Google Scholar
- Naveen S, Anandanwar SM, Prasad JS, Gayathri V, Bhattacharjee R (2006) Synthesis and crystal structure of 6-Butyl-5,6-dihydrobenzo- [4,5] imidazo [1,2-c] quinazoline. Anal Sci 22:185–186Google Scholar
- Porres L, Holland A, Palsson L-O, Monkman AP, Kemp C, Beeby A (2006) Absolute measurements of photoluminescence quantum yields of solutions using an integrating sphere. J Fluoresc. 16(2):267–272View ArticleGoogle Scholar
- Foo SC, Yusoff FM, Ismail M, Basri M, Khong NMH, Chan KW, Yau SK (2015) Efficient solvent extraction of antioxidant-rich extract from a tropical diatom, Chaetoceros calcitrans (Paulsen) Takano 1968. Asian Pac J Trop Biomed. 5(10):834–840View ArticleGoogle Scholar
- Foo SC, Yusoff FM, Ismail M, Basri M, Khong NMH, Chan KW et al (2015) Production of fucoxanthin-rich fraction (FxRF) from a diatom, Chaetoceros calcitrans (Paulsen) Takano 1968. Algal Res 12:26–32View ArticleGoogle Scholar
- Boligon AA, Machado MM, Athayde ML (2014) Technical evaluation of antioxidant activity. Med Chem (Los Angeles). 4(7):517–522View ArticleGoogle Scholar
- Rohini R, Shanker K, Reddy PM, Ho Y-P, Ravinder V (2009) Mono and bis-6- arylbenzimidazo[1,2-c]quinazolines: a new class of antimicrobial agents. Eur J Med Chem 44:3330–3339View ArticleGoogle Scholar
- Insuasty BA, Torres H, Quiroga J, Abonia R, Rodriguez R, Nogeras M, Sanchez A, Saitz C, Alvarez SL, Zacchino SA (2006) Synthesis, characterization and in vitro antifungal evaluation of novel benzimidazo[1,2-c]quinazolines. J Chil Chem Soc 51(2):927–932View ArticleGoogle Scholar
- Shri CN, Aruna A, Vetrichelvan T (2015) Synthesis of 6-Aryl Benzimidazo[1,2-c]quinazoline derivatives and their antimicrobial evaluation. Int J Sci Res. 4(8):713–714Google Scholar