Обучение по природни науки и върхови технологии

2018/1, стр. 109 - 119

SYNTHESIS OF NEW 3-[(CHROMEN-3-YL) ETHYLIDENEAMINO] -PHENYL] -THIAZOLIDIN-4ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti
Naser Troni
E-mail: naser_troni@yahoo.com
Department of Chemistry
University of Prishtina
Mother Teresa Street
10000 Prishtina Kosovo
Hamit Ismaili
University of Prishtina
Prishtina Kosovo
Malesore Pllana
University of Prishtina
Prishtina Kosovo
Musaj Pacarizi
University of Prishtina
Prishtina Kosovo
Veprim Thaçi
University of Prishtina
Prishtina Kosovo
Gjyle Mulliqi-Osmani
Institute of Public Health of Kosovo
Kosovo

Резюме: A series of novel substituted thiazolidyn-4-ones were synthesized by cyclization of various Schiff bases of chromen-3-one with thioacetic acid. 3-(1-4-Amino-phenylamino)-ethyl-4-hydroxybenzopyran-2-one 3 is synthesized in high yield by condensation reaction of 4-hydroxy-3-acetylcoumarin 2 and 1,4-benzenediamine. The catalytic condensation of product 3 with benzaldehyde and their analogues (salicylaldehyde and 3-nitrobenzaldehyde) yielded corresponding 3-[1-(4-benzylidene-amino)-phenylamino]-ethyl-4-hydroxybenzopyran-2ones 4(a-c). The cyclization reaction of compounds 4(a-c) with thioacetic acid yielded corresponding substituted thiazolidin-4-ones 5(a-c) . The structures of the synthesised compounds were established by FT-IR and NMR spectrometric data and their elemental analysis. Compounds of series 4(a-c) and 5(a-c) were screened for their antibacterial activity against S. aureus, E. coli and Klebsiella by Diffusion Disc Method. Antibacterial activity of the compounds 4(a-c) and 5(a-c) against S. aureus, E. coli and Klebsiella was examined by measuring the zones of inhibition around the disks impregnated with the corresponding solutions in N,N-DMF concentration 2 mg/mL , 4 mg/mL and 6 mg/mL. Compounds of series 4 exhibited significant antibacterial activity, whereas compounds of series 5 displayed moderate activity against these microorganisms. The impact of substitutions in antimicrobial activity was also explored.

Ключови думи: t hiazolidin-4-one; benzopyran-2-on; condensiation; cyclization; zones of inhibition

Introduction

Benzopyran-2-one derivatives are important class of heterocyclic compounds that have been found as ingredient of the plant world. Many such compounds are well known for their biological activities (Mohamed et al., 2012; Rajasekaran et al., 2011) sush as antimicrobial (Desai et al., 2013; Reihman et al., 2013; Mayekar&Mulwad, 2008), antifungal (De Araújo et al., 2013) and antimalarial (Sashidhara et al., 2012). Novobiocin, chartesium and coumaromycin are potent antibiotics with benzopyrone moiety. Many of coumarins exhibited antioxidant (Tyagi et al., 2005; Osman et al., 2012; Vazquez-Rodriguez et al., 2013), and antitumor activity (Nawrot-Modranka et al., 2006). It was reported that a significant number of substituted benzopyran-2-ones showed anticoagulant, anti-HIV (Rao et al., 2002; Yu et al., 2003), sedative, analgesic and hepatoprotective activity (Ahmed et al., 2003; Okamota et al., 2007; Atmaca et al., 2011). It is indicative that many of naturally and synthetic coumarins have found widespread usage in pharmacies (Rajasekaran et al., 2011). On the other hand, thiazolidynone derivatives also have great importance and demonstrate a wide range of pharmacological activities, including those anti-convulsant (Siddiqui et al., 2007), antibacterial (Mayekar & Mulwad, 2008) and anti-fungal (Mazzei et al., 2008) activity. The biological activity is conditioned by their structure and the presence of different substituents on the benzopyrone ring indicates their impact on the type and potency of biological activity. Despite continuous efforts, the relationship between structure and biological activity of these derivatives, so far has not yet been sufficiently clarified. Extraordinary biologically importance of compounds with thiazolidine-4-one moiety has generated a constant interest for their synthesis and research. In view of the considerable importance of these derivatives and in continuation of our previous studies (Hoti et al., 2014; 2017a; 2017b), the present work is aimed at the design and synthesis of new Schiff bases and related thiazolidyne-4-ones with benzopyran-2-one moiety which could serve as pharmaceutical products. Moreover, the study includes testing of target compounds for their antibacterial activity against S. Aureus, E. Coli and Klebsiella.

Material and methods

Synthesis reactions were conducted by refluxing under catalytic conditions. All the chemicals used in the synthesis were of analytical grade as commercial reagents of Aldrich company. Reactions were monitored by TLC using Merck Kieselgel-60 (F-254) as the stationary phase and a mixture of benzene, toluene, glacial acetic acid (v/v/v, 75:10:15) as the mobile phase. The synthesized products were purified by crystallization from methanol and ethanol. Melting points were determined in paraffin oil bath with open capillary tube. FT-IR spectra were recorded in KBr discs on Shimadzu 8400xFTIR spectrometer with 4 cm1 resolution. 1H-NMR and 13C-NMR spectra were recorded in DMSO on UNITYplus-300“NMR 1” spectrometer and chemical shifts were reported in ppm downfield from TMS as an internal standard (δ0.00).

Screening of the antibacterial activity of the synthesized compounds was done on the basis of Standard Disc Method using standard discs ( d=5.0 mm, maximum capacity 10 pg). The experiments were carried out at three different concentrations and standard discs were previously impregnated with 2 mg/mL, 4 mg/mL and 6 mg/ mL solutions of compounds in N,N-DMF.

3-[1-4-Amino-phenylimino)-ethyl]-4-hydroxy-benzopyran-2-one, 3

4-Hydroxy-3-acetyl-benzopyran-2-one (6.1g, 0.05 mol) was dissolved in 30 mL of methanol, then the mixture containing benzene-1,4-diamine (6.5 g, 0.06 mmol) in 10 mL of methanol was added in small portions and then 2-3 drops of triethylamine were added into the mixture. The reaction mixture was stirred for 15 minutes at room temperature, then refluxed for about 6 hours. After cooling, the mixture was concentrated in the rotary evaporator and the crystalline product was filtered off under vacuum and washed with 2 × 1 mL of methanol. The crystalline product was dried and crystallized from methanol, giving 3-[1-4-Amino-phenylimino)-ethyl]-4-hydroxybenzopyran-2-one, yield = 35.83%. mp = 214-215 °C. FT-IR (KBr disc, cm-1): 3415.08 3288.59, 2205.54, 1711.36, 1675.78, 1058.96, 754.50. 3423.67, 3400-3300, 3055.16, 2930.6, 2847.26, 1696.25, 1610.25, 1645.05, 1196.14, 750.71.

3-(1-(4-benzylidene-amino)-phenylamino]-ethyl-4-hydroxybenzopyran-2-ones, 4(a-c)

Compound 3 (0.6 g (0.002 mol) was dissolved in 20 mL of absolute ethanol and then 0.003 mol of corresponding aromatic aldehyde (benzaldehyde, salicylaldehyde or 3-nitrobenzaldehyde) dissolved in 15 mL of absolute ethanol was added in small portions to this mixture. Then two drops of piperidine as a catalyst were added and the mixture was stirred for 15 min at room temperature and then refluxed for 8 to 9 hours. After cooling, the mixture is concentrated and the residue was filtered off under reduced pressure, then washed with 2 × 1 mL of ethanol and dried in the air. Crystallization of the products 4(a-c) was conducted using ethanol or methanol.

4a; Mp=161-162 oC, yield=12.82 %, FT-IR (KBr disc, cm-1): 3400-3300, 3059.28, 2919.9, 1662.45, 1610.25, 1610.9, 1533.19, 1196.14, 757.67. 1 H-NMR; (δ, ppm)8.4 (s, 1H, N=C-H), 7.5-7.6 (m, 3H, Ar), 7.2-7.4 (m, 8H, Ar), 5.1 (1H, OH), 0.9 (s, 3H, CH3). 13C-NMR; (δ, ppm) 173.2 (C-OH), 164.1, 163.4 (C=N), 161.7(C=O), 152,3, 151.2, 147,2, 131,3, 130.4, 129.3, 128.2, 127,4, 126,9, 126.6, 125.9 , 125.2, 123.2, 121.0 (C-ar), 82.2, 9,6 (CH3).

4b; Mp=166-167 oC, yield=98.46 %, FT-IR (KBr disc, cm-1): 3450-3300, 3055.6, 2931.1, 1690.29, 1655.49, 1510.25, 1192.66, 750.71. 1H-NMR; (δ, ppm) 8.3 (s, 1H, N=C-H), 7.2-7.5 (m, 7H, Ar), 6.8-7.0 (m, 3H, Ar), 5.0, 5.1, (2H, OH), 0.9 (s, 3H, CH3). 13C-NMR;(δ, ppm) 173.1 (C-OH), 164.3, 163.7 (C=N), 161.9 (C=O), 157.2 (C-OH ar), 151.4, 150.5, 148.8, 147,2, 132.3, 131,5, 130.4, 128.5, 128.3, 127,3, 126,7, 125.6 , 123.4, 121.4, 115.9, (C-ar), 82.2, 15,1 (CH3).

4c; Mp=208-210 oC, yield=58.29 %, FT-IR (KBr disc, cm-1): 3430-3300, 3076.44, 2923.65, 1620.69, 1618.25, 1519.77, 1352.74, 1196.14, 740.27. 1H-NMR; (δ, ppm) 8.4 (s, 1H, N=C-H), 8.0-8.3 (m, 3H, Ar), 7.2-7.5 (m, 7H, Ar), 5.2, (1H, OH), 0.9 (s, 3H, CH3). 13C-NMR; (δ, ppm) 173.4 (C-OH), 164.1, 163.2 (C=N), 162.2 (C=O), 151.9, 150.8, 150.5, 148.1, 147,2, 135.4, 131,9, 129.2, 128.0, 127.2, 126,4, 125.7 , 124.4, 123.2, 121.6, 115.9, (C-ar), 82.9, 15,8 (CH3).

(2H-Benzopyron -4-ylamino)-2-phenyl-thiazolidyne-4-ones 5(a-c)

The corresponding product 4(a-c) (0.1 mmol) was dissolved in 10 mL of benzene and then 0.12 g (0.25 mmol) of thioacetic acid was added. The reaction mixture was stirred for 10 min at room temperature and then refluxed for 12-14 hours. After cooling the product was concentrated and the remaining solid was dissolved in 5 mL of ethanol, then heated to the boiling point and the excess of acetic acid was neutralized by adding 0.06 mmol sodium bicarbonate (controlled with litmus paper until the solution takes a blue color). The mixture was cooled in an ice bath and filtered off under vacuum, then washed with 2×1 mL of ether and dried in air. The products were crystallized using methanol.

5a; Mp=239-240 oC, yield=54.20 %, FT-IR (KBr disc, cm -1): 3450-3350, 3076.44, 2930.65, 1662.45, 1519.77, 1515.2, 1352.74, 1196.14, 740.27. 1H-NMR; (δ, ppm) 7.4-7.6 (m, 3H, Ar), 7.1-7.3 (m, 7H, Ar), 5.8 (s, 1H, N-C-H), 3.5 (q, 3H, CH3) 1,6 (d, 3H, CH3) 0.9 (s, 3H, CH 3). 13C-NMR; (δ, ppm) 174.5 (C-OH), 172.3, 164.1, 161.7(C=O), 150.6, 150.1, 145,6, 138.2, 138.6, 129.0, 128.5, 126,7, 126,1, 125.5, 123.8, 122.4, 121.7, 121.4, (C-ar), 82.4, 56.2 (C-N), 45.6, 18.8 (CH3), 9.5 (CH3).

5b; Mp=227-229oC, yield=40.26 %, FT-IR (KBr disc, cm-1): 3500-3350, 3050, 2926.87, 1695, 1617.21, 1561.53, 1116.1, 621.95. 1H-NMR; (δ, ppm)7.2-7.6 (m, 2H, Ar), 6.7-7.1(m, 8H, Ar), 5.9 (s, 1H, N-C-H), 3.7 (q, 3H, CH3) 1,5 (d, 3H, CH3) 0.9 (s, 3H, CH3). 13 C-NMR; (δ, ppm) 173.4 (C-OH), 171.9, 165.3, 162.5 (C=O), 157.0, 151.1, 150.5, 144,8, 139.9, 139.3, 138.5, 127.9, 126,7, 126,1, 125.5, 123.8, 123.2, 122.4, 121.7, 121.4, (C-ar), 82.4, 46.3 (C-N), 45.2, 17.3(CH3), 9.9 (CH3).

5c; Mp=194-195 oC, yield=33.21 %, FT-IR (KBr disc, cm-1): 3450-3350, 3076.44, 2930.65, 1662.45, 1660.0, 1605.5, 1519, 1349.26, 1025.62 765.5.

Results and discussion

By condensation reaction of 4-hydroxy-3-acetylcoumarin 2 with ethane-1,2-diamine, 3-(1-4-amino-phenylamino)-ethyl-4-hydroxybenzopyran-2-one 3 was synthesized in good yield. Corresponding Schiff bases are synthesized by condensation reaction of compound 3 with benzaldehyde, salicylaldehyde and/or 3-nitrobenzaldehyde. Novel 3-(1-(4-benzylidene-amino)-phenylamino]-ethyl-4-hydroxybenzopiran-2-ones, 4(ac) as condensation products are synthesized in good yield. In the last step, by cyclization of compounds 4(a-c) with thioacetic acid, corresponding thiazolidinones 5(a-c) are synthesized. Synthesis of Schiff bases and related azetidine-2-ones are summarized in Scheme 1.

Structural characterization of the synthesized products is based on spectrometric data. The IR spectrum of compound 3 showed an absorption signal absorption at 3423.67 cm-1 confirming the presence of -NH2 group. The absorption signal at 3400-3300 cm-1 appears due to ν(OH) stretching vibrations while the absorption at 3055.16 cm-1 due to aromatic ν(CH) stretching vibrations. The absorption signals at 2930.6 cm-1 and 2847.26 cm-1 are responsible for asymmetric and symmetric ν(CH) stretching vibrations of methyl group. A sharp peak appeared at 1696.25 cm-1 is responsible for ν(C=O) stretching vibrations, whereas the absorption peak at 1610.25 cm-1results from aromatic ν(C=C) stretching vibrations. The presence of the C=N double bond of the aromatic system was indicated from their stretching absorption at 1645.05 cm-1. On the other hand, the peak at 1196.14 cm-1 results due to lactonic ν(C-O-C) stretching vibrations, while the sharp peak at 750.71 cm-1 correspond to characteristic aromatic δ(C-H) oop bending vibrations.

OOOHOOOHCNCH3NCHOOOHCNCH3NCHOOOHCNCH3NH2OOOHCNCH3NCHOOOHCNCH3NHOHCSCOCH3OOOHCNCH3NHCSCOCH3OOOHCNCH3NHCSCOCHHOOOOHCCH3O+H3CCClOPyridinePiperidine1234a4b4c5a5b5cNH2H2NHOHONO2HOOHH3CCOHSH3CCOHSH3CCOHSNO2NO2

Scheme 1. Synthesis of some Schiff bases and related azetidine-2-ones

The IR spectrum of compound 4a showed a signal at 3400-3300 cm-1 responsible for ν(OH) stretching vibrations, a peak at 3059.28 cm-1 for aromatic ν(CH) stretching, while the absorption peak at 2919.9 cm-1 due to methyl ν(CH) asymmetric stretching vibrations. The sharp peak at 1662.45 cm-1 correspond to ν(C=O) stretching vibrations, whereas the peak at 1610.25 cm-1 resulted from aromatic ν(C=C) stretching vibrations. A signal at 1196.14 cm-1 is characteristic for lactonic (C-O-C) stretching vibrations and the sharp peak at 757.67 cm-1 results from aromatic δ(C-H) bending oop vibrations. In the1H-NMR spectrum, besides multiplets of aromatic protons, a proton singlet resulting from N=C-H is appeared at 8.4 ppm. In the 13C-NMR spectrum two signals at 161.1 and 163.8 ppm for C=N carbons are appeared.

For compound 4b, the IR spectrum showed an absorption signal at 3450-3300 cm-1 which is responsible for ν(OH) stretching vibrations, while a signal at 3055.6 cm-1 corresponds to aromatic ν(CH) stretching vibrations. The peak at 2931.1 cm-1 results from methyl ν(CH) stretching vibrations. At 1690.3 cm-1 appears the absorption signal which responds to ν(C=O) stretching vibrations, the peak at 1192.6 cm-1 correspond due to lactonic (C-O-C) stretching vibrations, whereas the sharp peak at 750.7 cm-1is characteristic for aromatic bending δ(C-H) oop vibrations. On the other hand, the 1H-NMR spectrum correspond to the absorption of respective protons. At 8.3 ppm a proton singlet resulting from N=C-H is displayed. Also in the 13C-NMR spectrum signals at 164.3 and 163.7 ppm that corresponds to the C=N carbon are displayed.

The IR spectra of compound 4c show a broad absorption peak at 3400-3300 cm-1 which is responsible for ν(OH) stretching vibrations, while the signals at 3076.44 and 2923.65 cm-1 appear due to aromatic and methyl ν(CH) stretching vibrations. The peak at 1620.69 cm-1 is responsible for absorbing the ν(C=O) stretching vibrations while signals at 1618.25 and 1519.77 cm-1 result from aromatic ν(C=N) and ν(C=C) stretching vibrations. The sharp peak at 1515.2 cm-1 results from ν(NO2) asymmetric stretching vibrations, while absorption signal at 1352.74 cm-1 reflects ν(NO2) symmetric stretching vibrations. A signal at 1196.14 cm-1 is characteristic for lactonic (C-O-C) stretching vibrations, while the sharp peak at 740.27 cm-1 appears from aromatic δ(C-H) bending oop vibrations. The 1H-NMR spectra show the multiplet signals of aromatic protons at 8.1-8.3 ppm and 7.7-7.4 ppm. A proton singlet resulting from N=C-H at 8.4 ppm appears as well. In the 13C-NMR spectra two signals at 164.1 and 163.2 ppm, that correspond to C=N and a signal at 173.4 ppm resulting from C-OH are apeared.

In the IR spectra of the compound 5a a broad absorption signal appears at 34503350 cm-1 which is responsible for ν(OH) stretching vibrations whereas the absorption peak at 3076.44 cm-1 results from aromatic ν(CH) vibrations. A medium band at 2930.65 cm-1 resulted from aliphatic ν(CH) stretching vibrations, whereas a sharp peak at 1662.45 cm-1 correspond to ν(C=O) stretching vibrations. The absorption signals at 1618.25 and 1519.77cm-1 result from aromatic ν(C=N) and ν(C=C) stretching vibrations. The absorption peak at 1196.14 cm-1results from lactonic ν(C-O-C) stretching vibrations, whereas at 740.27 cm-1 due to aromatic δ(CH) oop vibrations. The 1H-NMR spectra, a proton singlet at 5.8 ppm results from N-C-H, while a doublet at 1.6 ppm and a singlet 0.9 ppm appear due to methyl protons. The 13C-NMR spectra exhibits a signal at 56.2 ppm results due to C-N carbon, while signals at 18.8 and 9.5 ppm appear due to methyl carbons.

Table 1. Physical properties of compounds 4(a-c) and 5(a-c) and their elemental analysis

NrMolecularformulasMolecularMassElemental analysis (%), calc / foundmp/ oCYield(%) 4aC24H18N2O3382.40(C-75.376; H-4.744; N-7.327; O-12.552) (C-75.380; H-4.742; N-7.330) 161-16212.824bC24H18N2O4398.40(C-72.349; H-4.553; N-7.033; O-16.064) (C-72.352; H-4.549; N-7.065) 166-16798.464cC24H17N3O5427.41(C-67.439; H-4.001; N-9.834; O-18.717) (C-67.443; H-3.997; N-9.831) 208-21058.295aC27H22N2O4S470.54(C-68.914; H-4.714; N-5.955; O-13.601;S-6.816) (C-68.917; H-4.710; N-5.960; S-6.811) 239-24054.205bC27H22N2O5S486.54(C-66.648; H-4.559; N-5.759; O-16.443;S-6.591) (C-66.65; H-4.554; N-5.761; S- 6.586) 227-22940.265cC27H21N3O6S515.54(C-62.899; H-4.106; N-8.153; O-18.621;S-6.221) (C-62.914; H-4.102; N-8.147; S-6.218) 194-19533.21

In the IR spectra of compound 5b, a broad absorption signal appears at 35003350 cm-1 which is responsible for ν(OH) stretching vibrations and the signal at 3050 cm-1 for aromatic ν(CH) stretching vibrations. The peak at 2926.87 cm-1 results from methyl ν(CH) stretching vibrations, while the peak at 1695 cm-1 correspond to ν(C=O) stretching vibrations. The characteristic peaks at 1617.21 and 1561,53 cm-1 result from ν(C=N) and ν(C=C) stretching vibrations of aromatic moiety. A signal at 1116.1 cm-1 results from lactonic ν(C-O-C) vibrations, while the sharp peak at 621.95 cm-1 is characteristic for δ(C-S) bending vibrations. In the 1H-NMR spectra are shown a singlet at 5.9 ppm, a quartet at 3.7 ppm and a doublet at 1.5 ppm due to thiazole proton N-C-H, CH and CH3 protons. The 13C-NMR spectrum also show corresponding signals for thiazole carbons.

IR spectrum of compound 5c exhibit the absorption signal at 3450-3350 cm-1 responsible for ν(OH) stretching vibrations and a signal at 3076.44 cm-1 which resulted from aromatic ν(CH) stretching vibrations. The peak at 2930.65 cm-1 results from the absorptions of methyl stretching vibrations, while the signal at 1662.45 cm-1 reflects the ν(C=O) stretching vibrations. The peak at 1660.0 cm-1 results from ν(C=N) stretching mode, while aromatic ν(C=C) stretching vibrations show a signal at 1605.5 cm-1. A signal at 1025.62 cm-1 is characteristic for lactonic (C-O-C) stretching vibrations, whereas the sharp peak at 765.5 cm-1 is characteristic for aromatic δ(C-H) oop bending vibrations.

Antibacterial activity of the compounds 4(a-c) and 5(a-c)

Following this study, compounds 4 (a-c) and 5(a-c) are screened for their antibacterial activity. Our research is oriented to test the activity against bacteria S. aureus, E. coli and Klebsiella, on the basis of Standard Disc Method (Bayer et al., 1966), by measuring the zones of inhibition. The discs have previously been impregnated with solutions of the compounds in N,N-DMF with concentrations of 2 mg mL-1, 4 mg mL-1 and 6 mg mL-1. Results are expressed in mm and were summarized in Figs. 1 – 3.

Figure 1. Graphical presentation of zones of inhibition (mm) against S. aureus

Compounds of series 4 showed significant antimicrobial activity against these microorganisms, while those of series 5 exhibited moderate activity. Compounds 4a and 4c were most active against S. aureus, compounds 4c and 5c showed the most activity against E. Coli whereas 4b was more active against Klebsiella.

Antibacterial activity against E. Coli and Klebsiella shown as bactericide activity is displayed in a moderate range. Furthermore, these compounds express both bacteriostatic and bactericide activity against S. Aureus. Bacteriostatic activity is exhibited in large range (+2.0 mm), whereas bactericide activity showed smaller zones of inhibition. Thiazolidin-4-one moiety showed small impact on antimicrobial activity. Likewise, the impact of polar groups was distinctive. It is particularly noted the impact of the nitro group, which affected the increasing of antibacterial activity. The impact of the hydroxy group of 5b, which has affected the increase of antibacterial activity, has been particularly noted. Moreover, nitro group of 4b has shown significant impact on the range of inhibition of E. coli. It has been assumed that antibacterial activity may result as a consequence of the involvement of these compounds in enzymatic reactions. They may cause enzymatic inhibition cell wall construction of the microorganisms. However, the mechanism of enzymatic inhibition has not been fully studied yet. In general, by increasing the concentration of solvents, their antimicrobial activity increases.

Figure 2. Graphical presentation of zones of inhibition (mm) against E. coli

Conclusions

Novel derivatives of 3(1-(4-benzylidene-amino)-phenylamino]-ethyl-4-hydroxybenzopyran-2-one 4(a-c) and respective thiazolidin-4-ones 5(a-c) are synthesized in the moderate and high yield. It has been concluded that compounds 4a and 4c show significant activity against S. aureus, compounds 4c and 5c display more activity against E. Coli, whereas 4b was more active against Klebsiella bacteria. The impact of polar groups in antibacterial activity was significant. Antibacterial activity is shown to be proportional to the concentration of these compounds.

Figure 3. Graphical presentation of zones of inhibition (mm)) against Klebsiella

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Георги Върбанов, Радостин Михайлов, Деница Симеонова, Йорданка Енева

NATURAL RADIONUCLIDES IN DRINKING WATER

Natasha Ivanova, Bistra Manusheva

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АДАПТИРАНЕ НА ОБРАЗОВАНИЕТО ДНЕС ЗА УТРЕШНИЯ ДЕН

И. Панчева, М. Недялкова, П. Петков, Х. Александров, В. Симеонов

INTEGRATED ENGINEERING EDUCATION: THE ROLE OF ANALYSIS OF STUDENTS’ NEEDS

Veselina Kolarski, Dancho Danalev, Senia Terzieva

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ZAGREB CONNECTION INDICES OF \(\mathrm{TiO}_{2}\) NANOTUBES

Sohaib Khalid, Johan Kok, Akbar Ali, Mohsin Bashir

SYNTHESIS OF NEW 3-[(CHROMEN-3-YL) ETHYLIDENEAMINO] -PHENYL] -THIAZOLIDIN-4ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Malesore Pllana, Musaj Pacarizi, Veprim Thaçi, Gjyle Mulliqi-Osmani

2017 година
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GEOECOLOGICAL ANALYSIS OF INDUSTRIAL CITIES: ON THE EXAMPLE OF AKTOBE AGGLOMERATION

Zharas Berdenov, Erbolat Mendibaev, Talgat Salihov, Kazhmurat Akhmedenov, Gulshat Ataeva

TECHNOGENESIS OF GEOECOLOGICAL SYSTEMS OF NORTHEN KAZAKHSTAN: PROGRESS, DEVELOPMENT AND EVOLUTION

Kulchichan Dzhanaleyeva, Gulnur Mazhitova, Altyn Zhanguzhina, Zharas Berdenov, Tursynkul Bazarbayeva, Emin Atasoy

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47-А НАЦИОНАЛНА КОНФЕРЕНЦИЯ НА УЧИТЕЛИТЕ ПО ХИМИЯ

В последните години тези традиционни за българското учителство конфе- ренции се организират от Българското дружество по химическо образование и история и философия на химията. То е асоцииран член на Съюза на химици- те в България, който пък е член на Европейската асоциация на химическите и

SYNTHESIS OF TiO 2-M (Cd, Co, Mn) AS A PHOTOCATALYST DEGRADATION OF METHYLENE BLUE DYE

Candra Purnawan, Sayekti Wahyuningsih, Dwita Nur Aisyah

EFFECT OF DIFFERENT CADMIUM CONCENTRATION ON SOME BIOCHEMICAL PARAMETERS IN ‘ISA BROWN’ HYBRID CHICKEN

Imer Haziri, Adem Rama, Fatgzim Latifi, Dorjana Beqiraj-Kalamishi, Ibrahim Mehmeti, Arben Haziri

PHYTOCHEMICAL AND <i>IN VITRO</i> ANTIOXIDANT STUDIES OF <i>PRIMULA VERIS</i> (L.) GROWING WILD IN KOSOVO

Ibrahim Rudhani, Florentina Raci, Hamide Ibrahimi, Arben Mehmeti, Ariana Kameri, Fatmir Faiku, Majlinda Daci, Sevdije Govori, Arben Haziri

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„СИМВОЛНИЯТ КАПИТАЛ“ НА БЪЛГАРСКОТО УЧИЛИЩЕ

Николай Цанков, Веска Гювийска

KINETICS OF PHOTO-ELECTRO-ASSISTED DEGRADATION OF REMAZOL RED 5B

Fitria Rahmawati, Tri Martini, Nina Iswati

ALLELOPATHIC AND IN VITRO ANTICANCER ACTIVITY OF STEVIA AND CHIA

Asya Dragoeva, Vanya Koleva, Zheni Stoyanova, Eli Zayova, Selime Ali

NOVEL HETEROARYLAMINO-CHROMEN-2-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Gjyle Mulliqi-Osmani, Veprim Thaçi

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OPTIMIZATION OF ENGINE OIL FORMULATION USING RESPONSE SURFACE METHODOLOGY AND GENETIC ALGORITHM: A COMPARATIVE STUDY

Behnaz Azmoon, Abolfazl Semnani, Ramin Jaberzadeh Ansari, Hamid Shakoori Langeroodi, Mahboube Shirani, Shima Ghanavati Nasab

CHEMOMETRICASSISTEDSPECTROPHOTOMETRIC ESTIMATION OF LANSOPRAZOLE AND DOMEPERIDONE IN BULK AND COMMERCIAL DOSAGE FORM

Farheen Sami, Shahnaz Majeed, Tengku Azlan Shah Tengku Mohammed, Noor Fatin Amalina Kamaruddin, Mohammad Zulhimi Atan, Syed Amir Javid Bukhari, Namra, Bushra Hasan, Mohammed Tahir Ansari

EVALUATION OF ANTIBACTERIAL ACTIVITY OF DIFFERENT SOLVENT EXTRACTS OF <i>TEUCRIUM CHAMAEDRYS</i> (L. ) GROWING WILD IN KOSOVO

Arben Haziri, Fatmir Faiku, Roze Berisha, Ibrahim Mehmeti, Sevdije Govori, Imer Haziri

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ПРИРОДОНАУЧНАТА ГРАМОТНОСТ НА УЧЕНИЦИТЕ В НАЧАЛОТО НА XXI ВЕК – В ТЪРСЕНЕ НА КОНЦЕПТУАЛНО ЕДИНСТВО

Теодора Коларова, Иса Хаджиали, Мимия Докова, Веселин Александров

COMPUTER SIMULATORS: APPLICATION FOR GRADUATES’ADAPTATION AT OIL AND GAS REFINERIES

Irena O. Dolganova, Igor M. Dolganov, Kseniya A. Vasyuchka

SYNTHESIS OF NEW [(3-NITRO-2-OXO-2H-CHROMEN4-YLAMINO) -PHENYL] -PHENYL-TRIAZOLIDIN-4-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Hamit Ismaili, Idriz Vehapi, Naser Troni, Gjyle Mulliqi-Osmani, Veprim Thaçi

STABILITY OF RJ-5 FUEL

Lemi Türker, Serhat Variş

A STUDY OF BEGLIKTASH MEGALITHIC COMPLEX

Diana Kjurkchieva, Evgeni Stoykov, Sabin Ivanov, Borislav Borisov, Hristo Hristov, Pencho Kyurkchiev, Dimitar Vladev, Irina Ivanova

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2016 година
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THE EFFECT OF KOH AND KCL ADDITION TO THE DESTILATION OF ETHANOL-WATER MIXTURE

Khoirina Dwi Nugrahaningtyas, Fitria Rahmawati, Avrina Kumalasari

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VOLTAMMERIC SENSOR FOR NITROPHENOLS BASED ON SCREEN-PRINTED ELECTRODE MODIFIED WITH REDUCED GRAPHENE OXIDE

Arsim Maloku, Liridon S. Berisha, Granit Jashari, Eduard Andoni, Tahir Arbneshi

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ИЗСЛЕДВАНЕ НА ПРОФЕСИОНАЛНО-ПЕДАГОГИЧЕСКАТА РЕФЛЕКСИЯ НА УЧИТЕЛЯ ПО БИОЛОГИЯ (ЧАСТ ВТОРА)

Надежда Райчева, Иса Хаджиали, Наташа Цанова, Виктория Нечева

EXISTING NATURE OF SCIENCE TEACHING OF A THAI IN-SERVICE BIOLOGY TEACHER

Wimol Sumranwanich, Sitthipon Art-in, Panee Maneechom, Chokchai Yuenyong

NUTRIENT COMPOSITION OF CUCURBITA MELO GROWING IN KOSOVO

Fatmir Faiku, Arben Haziri, Fatbardh Gashi, Naser Troni

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CONTEXT-BASED CHEMISTRY LAB WORK WITH THE USE OF COMPUTER-ASSISTED LEARNING SYSTEM

N. Y. Stozhko, A. V. Tchernysheva, E.M. Podshivalova, B.I. Bortnik

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ПО ПЪТЯ ON THE ROAD

Б. В. Тошев

INTERDISCIPLINARY PROJECT FOR ENHANCING STUDENTS’ INTEREST IN CHEMISTRY

Stela Georgieva, Petar Todorov, Zlatina Genova, Petia Peneva

2015 година
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COMPLEX SYSTEMS FOR DRUG TRANSPORT ACROSS CELL MEMBRANES

Nikoleta Ivanova, Yana Tsoneva, Nina Ilkova, Anela Ivanova

SURFACE FUNCTIONALIZATION OF SILICA SOL-GEL MICROPARTICLES WITH EUROPIUM COMPLEXES

Nina Danchova, Gulay Ahmed, Michael Bredol, Stoyan Gutzov

INTERFACIAL REORGANIZATION OF MOLECULAR ASSEMBLIES USED AS DRUG DELIVERY SYSTEMS

I. Panaiotov, Tz. Ivanova, K. Balashev, N. Grozev, I. Minkov, K. Mircheva

KINETICS OF THE OSMOTIC PROCESS AND THE POLARIZATION EFFECT

Boryan P. Radoev, Ivan L. Minkov, Emil D. Manev

WETTING BEHAVIOR OF A NATURAL AND A SYNTHETIC THERAPEUTIC PULMONARY SURFACTANTS

Lidia Alexandrova, Michail Nedyalkov, Dimo Platikanov

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TEACHER’S ACCEPTANCE OF STUDENTS WITH DISABILITY

Daniela Dimitrova-Radojchikj, Natasha Chichevska-Jovanova

APPLICATION OF LASER INDUCED BREAKDOWN SPECTROSCOPY AS NONDESDUCTRIVE AND SAFE ANALYSIS METHOD FOR COMPOSITE SOLID PROPELLANTS

Amir Hossein Farhadian, Masoud Kavosh Tehrani, Mohammad Hossein Keshavarz, Seyyed Mohamad Reza Darbany, Mehran Karimi, Amir Hossein Rezayi

THE EFFECT OF DIOCTYLPHTHALATE ON INITIAL PROPERTIES AND FIELD PERFORMANCE OF SOME SEMISYNTHETIC ENGINE OILS

Azadeh Ghasemizadeh, Abolfazl Semnani, Hamid Shakoori Langeroodi, Alireza Nezamzade Ejhieh

QUALITY ASSESSMENT OF RIVER’S WATER OF LUMBARDHI PEJA (KOSOVO)

Fatmir Faiku, Arben Haziri, Fatbardh Gashi, Naser Troni

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БЛАГОДАРЯ ВИ!

Александър Панайотов

ТЕМАТА ВЪГЛЕХИДРАТИ В ПРОГРАМИТЕ ПО ХИМИЯ И БИОЛОГИЯ

Радка Томова, Елена Бояджиева, Миглена Славова, Мариан Николов

BILINGUAL COURSE IN BIOTECHNOLOGY: INTERDISCIPLINARY MODEL1)

V. Kolarski, D. Marinkova, R. Raykova, D. Danalev, S. Terzieva

ХИМИЧНИЯТ ОПИТ – НАУКА И ЗАБАВА

Елица Чорбаджийска, Величка Димитрова, Магдалена Шекерлийска, Галина Бальова, Методийка Ангелова

ЕКОЛОГИЯТА В БЪЛГАРИЯ

Здравка Костова

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SYNTHESIS OF FLUORINATED HYDROXYCINNAMOYL DERIVATIVES OF ANTI-INFLUENZA DRUGS AND THEIR BIOLOGICAL ACTIVITY

Boyka Stoykova, Maya Chochkova, Galya Ivanova, Luchia Mukova, Nadya Nikolova, Lubomira Nikolaeva-Glomb, Pavel Vojtíšek, Tsenka Milkova, Martin Štícha, David Havlíček

SYNTHESIS AND ANTIVIRAL ACTIVITY OF SOME AMINO ACIDS DERIVATIVES OF INFLUENZA VIRUS DRUGS

Radoslav Chayrov, Vesela Veselinova, Vasilka Markova, Luchia Mukova, Angel Galabov, Ivanka Stankova

NEW DERIVATIVES OF OSELTAMIVIR WITH BILE ACIDS

Kiril Chuchkov, Silvia Nakova, Lucia Mukova, Angel Galabov, Ivanka Stankova

MONOHYDROXY FLAVONES. PART III: THE MULLIKEN ANALYSIS

Maria Vakarelska-Popovska, Zhivko Velkov

LEU-ARG ANALOGUES: SYNTHESIS, IR CHARACTERIZATION AND DOCKING STUDIES

Tatyana Dzimbova, Atanas Chapkanov, Tamara Pajpanova

LACTOBACILLUS PLANTARUM AC 11S AS A BIOCATALYST IN MICROBIAL ELECYTOLYSIS CELL

Elitsa Chorbadzhiyska, Yolina Hubenova, Sophia Yankova, Dragomir Yankov, Mario Mitov

STUDYING THE PROCESS OF DEPOSITION OF ANTIMONY WITH CALCIUM CARBONATE

K. B. Omarov, Z. B. Absat, S. K. Aldabergenova, A. B. Siyazova, N. J. Rakhimzhanova, Z. B. Sagindykova

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TEACHING CHEMISTRY AT TECHNICAL UNIVERSITY

Lilyana Nacheva-Skopalik, Milena Koleva

ФОРМИРАЩО ОЦЕНЯВАНЕ PEER INSTRUCTION С ПОМОЩТА НА PLICКERS ТЕХНОЛОГИЯТА

Ивелина Коцева, Мая Гайдарова, Галина Ненчева

VAPOR PRESSURES OF 1-BUTANOL OVER WIDE RANGE OF THEMPERATURES

Javid Safarov, Bahruz Ahmadov, Saleh Mirzayev, Astan Shahverdiyev, Egon Hassel

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РУМЕН ЛЮБОМИРОВ ДОЙЧЕВ (1938 – 1999)

Огнян Димитров, Здравка Костова

NAMING OF CHEMICAL ELEMENTS

Maria Atanassova

2014 година
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LUBRICATION PROPERTIES OF DIFFERENT PENTAERYTHRITOL-OLEIC ACID REACTION PRODUCTS

Abolfazl Semnani, Hamid Shakoori Langeroodi, Mahboube Shirani

ALLELOPATHIC AND CYTOTOXIC ACTIVITY OF ORIGANUM VULGARE SSP. VULGARE GROWING WILD IN BULGARIA

Asya Pencheva Dragoeva, Vanya Petrova Koleva, Zheni Dimitrova Nanova, Mariya Zhivkova Kaschieva, Irina Rumenova Yotova

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GENDER ISSUES OF UKRAINIAN HIGHER EDUCATION

Н.H.Petruchenia, M.I.Vorovka

МНОГОВАРИАЦИОННА СТАТИСТИЧЕСКА ОЦЕНКА НА DREEM – БЪЛГАРИЯ: ВЪЗПРИЕМАНЕ НА ОБРАЗОВАТЕЛНАТА СРЕДА ОТ СТУДЕНТИТЕ В МЕДИЦИНСКИЯ УНИВЕРСИТЕТ – СОФИЯ

Радка Томова, Павлина Гатева, Радка Хаджиолова, Зафер Сабит, Миглена Славова, Гергана Чергарова, Васил Симеонов

MUSSEL BIOADHESIVES: A TOP LESSON FROM NATURE

Saâd Moulay Université Saâd Dahlab de Blida, Algeria

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ЕЛЕКТРОННО ПОМАГАЛO „ОТ АТОМА ДО КОСМОСА“ ЗА УЧЕНИЦИ ОТ Х КЛАС

Силвия Боянова Професионална гимназия „Акад. Сергей П. Корольов“ – Дупница

ЕСЕТО КАТО ИНТЕГРАТИВЕН КОНСТРУКТ – НОРМАТИВЕН, ПРОЦЕСУАЛЕН И ОЦЕНЪЧНО-РЕЗУЛТАТИВЕН АСПЕКТ

Надежда Райчева, Иван Капурдов, Наташа Цанова, Иса Хаджиали, Снежана Томова

44<sup>-ТA</sup> МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка Ташева, Пенка Василева

ДОЦ. Д.П.Н. АЛЕКСАНДЪР АТАНАСОВ ПАНАЙОТОВ

Наташа Цанова, Иса Хаджиали, Надежда Райчева

COMPUTER ASSISTED LEARNING SYSTEM FOR STUDYING ANALYTICAL CHEMISTRY

N. Y. Stozhko, A. V. Tchernysheva, L.I. Mironova

С РАКЕТНА ГРАНАТА КЪМ МЕСЕЦА: БОРБА С ЕДНА ЛЕДЕНА ЕПОХА В ГОДИНАТА 3000 СЛЕД ХРИСТА. 3.

С РАКЕТНА ГРАНАТА КЪМ МЕСЕЦА:, БОРБА С ЕДНА ЛЕДЕНА ЕПОХА, В ГОДИНАТА 000 СЛЕД ХРИСТА. .

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ВИСША МАТЕМАТИКА ЗА УЧИТЕЛИ, УЧЕНИЦИ И СТУДЕНТИ: ДИФЕРЕНЦИАЛНО СМЯТАНЕ

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ВАСИЛ ХРИСТОВ БОЗАРОВ

Пенка Бозарова, Здравка Костова

ЖИВАТА ПРИРОДА

Б. В. Тошев

БИБЛИОГРАФИЯ НА СТАТИИ ЗА МИСКОНЦЕПЦИИТЕ В ОБУЧЕНИЕТО ПО ПРИРОДНИ НАУКИ ВЪВ ВСИЧКИ ОБРАЗОВАТЕЛНИ НИВА

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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BOTYU ATANASSOV BOTEV

Zdravka Kostova, Margarita Topashka-Ancheva

CHRONOLOGY OF CHEMICAL ELEMENTS DISCOVERIES

Maria Atanassova, Radoslav Angelov

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КАК ДА МОТИВИРАМЕ УЧЕНИЦИТЕ OT VII КЛАС ДА УЧАТ

Маргарита Бозова, Петко Бозов

ОБРАЗОВАНИЕ ЗА ПРИРОДОНАУЧНА ГРАМОТНОСТ

Адриана Тафрова-Григорова

2013 година
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DIFFERENTIAL TEACHING IN SCHOOL SCIENCE EDUCATION: CONCEPTUAL PRINCIPLES

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

АНАЛИЗ НА ПОСТИЖЕНИЯТА НА УЧЕНИЦИТЕ ОТ ШЕСТИ КЛАС ВЪРХУ РАЗДЕЛ „ВЕЩЕСТВА И ТЕХНИТЕ СВОЙСТВА“ ПО „ЧОВЕКЪТ И ПРИРОДАТА“

Иваничка Буровска, Стефан Цаковски Регионален инспекторат по образованието – Ловеч

HISTORY AND PHILOSOPHY OF SCIENCE: SOME RECENT PERIODICALS (2013)

Chemistry: Bulgarian Journal of Science Education

45. НАЦИОНАЛНА КОНФЕРЕНЦИЯ НА УЧИТЕЛИТЕ ПО ХИМИЯ

„Образователни стандарти и природонаучна грамотност“ – това е темата на състоялата се от 25 до 27 октомври 2013 г. в Габрово 45. Национална конфе- ренция на учителите по химия с международно участие, която по традиция се проведе комбинирано с Годишната конференция на Българското дружество за химическо образование и история и философия на химията. Изборът на темата е предизвикан от факта, че развиването на природонаучна грамотност е обща тенденция на реформите на учебните програми и главна

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ЗА ХИМИЯТА НА БИРАТА

Ивелин Кулев

МЕТЕОРИТЪТ ОТ БЕЛОГРАДЧИК

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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RECASTING THE DERIVATION OF THE CLAPEYRON EQUATION INTO A CONCEPTUALLY SIMPLER FORM

Srihari Murthy Meenakshi Sundararajan Engineering College, India

CHEMICAL REACTIONS DO NOT ALWAYS MODERATE CHANGES IN CONCENTRATION OF AN ACTIVE COMPONENT

Joan J. Solaz-Portolés, Vicent Sanjosé Universitat de Valènciа, Spain

POLYMETALLIC COMPEXES: CV. SYNTHESIS, SPECTRAL, THERMOGRAVIMETRIC, XRD, MOLECULAR MODELLING AND POTENTIAL ANTIBACTERIAL PROPERTIES OF TETRAMERIC COMPLEXES OF Co(II), Ni(II), Cu(II), Zn(II), Cd(II) AND Hg(II) WITH OCTADENTATE AZODYE LIGANDS

Bipin B. Mahapatra, S. N. Dehury, A. K. Sarangi, S. N. Chaulia G. M. Autonomous College, India Covt. College of Engineering Kalahandi, India DAV Junior College, India

ПРОФЕСОР ЕЛЕНА КИРКОВА НАВЪРШИ 90 ГОДИНИ

CELEBRATING 90TH ANNIVERSARY OF PROFESSOR ELENA KIRKOVA

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SIMULATION OF THE FATTY ACID SYNTHASE COMPLEX MECHANISM OF ACTION

M.E.A. Mohammed, Ali Abeer, Fatima Elsamani, O.M. Elsheikh, Abdulrizak Hodow, O. Khamis Haji

FORMING OF CONTENT OF DIFFERENTIAL TEACHING OF CHEMISTRY IN SCHOOL EDUCATION OF UKRAINE

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

ИЗСЛЕДВАНЕ НА РАДИКАЛ-УЛАВЯЩА СПОСОБНОСТ

Станислав Станимиров, Живко Велков

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COLORFUL EXPERIMENTS FOR STUDENTS: SYNTHESIS OF INDIGO AND DERIVATIVES

Vanessa BIANDA, Jos-Antonio CONSTENLA, Rolf HAUBRICHS, Pierre-Lonard ZAFFALON

OBSERVING CHANGE IN POTASSIUM ABUNDANCE IN A SOIL EROSION EXPERIMENT WITH FIELD INFRARED SPECTROSCOPY

Mila Ivanova Luleva, Harald van der Werff, Freek van der Meer, Victor Jetten

ЦАРСКАТА ПЕЩЕРА

Рафаил ПОПОВ

УЧИЛИЩНИ ЛАБОРАТОРИИ И ОБОРУДВАНЕ SCHOOL LABORATORIES AND EQUIPMENT

Учебни лаборатории Илюстрации от каталог на Franz Hugershoff, Лайциг, притежаван от бъдещия

2012 година
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ADDRESING STUDENTS’ MISCONCEPTIONS CONCERNING CHEMICAL REACTIONS AND SYMBOLIC REPRESENTATIONS

Marina I. Stojanovska, Vladimir M. Petruševski, Bojan T. Šoptrajanov

АНАЛИЗ НА ПОСТИЖЕНИЯТА НА УЧЕНИЦИТЕ ОТ ПЕТИ КЛАС ВЪРХУ РАЗДЕЛ „ВЕЩЕСТВА И ТЕХНИТЕ СВОЙСТВА“ ПО ЧОВЕКЪТ И ПРИРОДАТА

Иваничка Буровска, Стефан Цаковски Регионален инспекторат по образованието – Ловеч

ЕКОТОКСИКОЛОГИЯ

Васил Симеонов

ПРОФ. МЕДОДИЙ ПОПОВ ЗА НАУКАТА И НАУЧНАТА ДЕЙНОСТ (1920 Г.)

Проф. Методий Попов (1881-1954) Госпожици и Господа студенти,

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КОНЦЕПТУАЛНА СХЕМА НА УЧИЛИЩНИЯ КУРС П О ХИМИЯ – МАКР О СКОПСКИ ПОДХОД

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ROLE OF ULTRASONIC WAVES TO STUDY MOLECULAR INTERACTIONS IN AQUEOUS SOLUTION OF DICLOFENAC SODIUM

Sunanda S. Aswale, Shashikant R. Aswale, Aparna B. Dhote Lokmanya Tilak Mahavidyalaya, INDIA Nilkanthrao Shinde College, INDIA

SIMULTANEOUS ESTIMATION OF IBUPROFEN AND RANITIDINE HYDROCHLORIDE USING UV SPECTROPHOT O METRIC METHOD

Jadupati Malakar, Amit Kumar Nayak Bengal College of Pharmaceutical Sciences and Research, INDIA

GAPS AND OPPORTUNITIES IN THE USE OF REMOTE SENSING FOR SOIL EROSION ASSESSMENT

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