1 CHAPTER 1
INTRODUCTION
1.1 Introduction
There is no doubt, human activities contribute to pollutions. There are many kinds of human activity that leads to pollution such as agricultural, commercial and industrial sector. Pollution occurrences in our environment exist in three forms which are water, soil and air pollution. Generally, out of the Earth surface, terrestrial part covers 30 % and the remaining 70 % over is covered by water surface (Chang et al., 2012). As water dominates the largest portion on Earth, the unsafe and serious water pollution should be given more attention.
Water pollution has a severe impact on all living organisms, and can harmfully affect the use of water for drinking, household needs, recreation, fishing and transportation. There are many causes of water pollution. One of it is the fertilizers that are discharged from agricultural sector, which contains heavy metal toxic from industrial sector and sewage from domestic sector (Yang et al., 2012). High chemical content in fertilizers such as phosphate and nitrogen are able to increase the nutrient level thus
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stimulate the growth of Oscillatoria sp. that is a type of microalgae. Uncontrolled growth of Oscillatoria sp. will lead to eutrophication occurrence (Cloern et al., 2001).
Eutrophication leads to algae blooms that can bring major problem in freshwater and marine habitat. This is because the algae may use up all the oxygen in the water thus resulting in death of many aquatic organisms such as fish that required oxygen to live (Backer, 2002). Additionally, the bloom of algae could block the sunlight from photosynthetic aquatic plants under the water surface. Worse come to worst, Oscillatoria sp. produces toxin that is known as microcystin that lethal to pests, livestock and human (Huynh et al., 2006)
For this study, several alkoxyl substituted thiourea derivatives that consist of four difference molecule structure that are compounds 1-4 were used to inhibit the growth of Oscillatoria sp. For this study, the aim was to investigate that alkoxyl substituted thiourea derivatives can inhibit the growth of cyanobacteria (Oscillatoria sp.).
1.2 Significance of Study
In condition of warm water with high level of nutrients especially phosphorus, Oscillatoria sp. produce Harmful Algae Blooms (HAB). This bloom creates surface scum and has been associated with low levels of dissolved oxygen (<0.5 ppm) (Backer, 2002). This condition will produce toxic known as microcystin that can be lethal to fish and invertebrate species. Thus the significance of this study will show the ability of alkoxyl substituted thiourea derivatives in inhibiting the growth of Oscillatoria sp. since alkoxyl substituted thiourea derivatives are known as good anti-microbial effect and inhibitor.
3 1.2 Objectives of Study
1) To determine the inhibition effect of several molecules of alkoxyl substituted thiourea to the growth of cyanobacteria (Oscillatoria sp.)
2) To investigate the inhibition effect of several concentrations of alkoxyl substituted thiourea to the growth of cyanobacteria (Oscillatoria sp.)
4 CHAPTER 2
LITERATURE REVIEW
2.1 Water Pollution
One of the most essential and important resources for human beings is water. On the contrary, when water pollution take place, it can cause harm toward human particularly and other living things. Kemp (1998) emphasized that pollution is the introduction of contaminants to the environment that involved physical and biological component of earth system. Meanwhile, Wang et. al., (2009) stated that contamination can sources from various ways such as fertilizer factories, urban runoff, automobile emission and mining operations. These sources release heavy metal, and fertilizer pollutants which affect water, soil and air. As aquatic ecosystem contains a wide variety of life forms such as fish, plant and microorganisms that interrelate with each other, water pollution can caused imbalance and disturbed the ecological system.
5 2.3 Cyanobacteria Bloom
Cyanobacteria also formally known as blue-green algae are prokaryotes of huge importance in many ecological living things and effect water quality and function a great part in global biogeochemical cycles as mentioned by Roderick et al., (2000). Skulberg et al., 1993 reported that cyanobacteria form colonies of photosynthetic cells, either in cluster or connected into filaments and are naturally a problem only when the cell concentrations become high that produce harmful algal bloom (HAB). This HAB that is caused by eutrophication that have been reported almost every industrialized nation (Hans et al., 2001; Joan & Wang., 2008).
As mentioned by Hendrik (1996), heavy metal for example nickel, cobalt, manganese and iron are vital trace nutrients and frequently added to fertilizers to enhance plant growth. Unregulated industrial water effluent also released these heavy metals. Furthermore, numerous of these heavy metals have been designated by the US Environmental Protection Agency (EPA) as potential threats. The examples of heavy metal that are targeted by EPA are nickel, cobalt, iron, zinc and manganese. The HAB not only caused by eutrophication but also the presence of several EPA target metals as reported by Stephane et al., (2004). However, Thajuddin et al., (2005) stated that heavy metal such as copper that often used as inhibition agent for the HAB had been resistant and cause the cyanobacteria to flourish and potentially bloom. Alternative treatment that utiliza heavy metal to control the growth of HAB must be carried out.
6 2.4 Thiourea Derivatives As Antimicrobial Effect
Thiourea derivatives can inhibit the growth of microbial (Saeed et al., 2009). Thiourea is the molecular structure that substituted oxygen atom in urea by sulfur atom. Koch et al., (2002) mentioned that thiourea compounds is classify as one of the precious ligand in organic chemistry which contains the elements of carbon, sulfur, nitrogen and hydrogen atoms.
Meanwhile ligand can be distinct as atom, ion, or molecules which have the ability to donate electrons to the empty vacant metal center as stated by Misseler et al. (2004). In addition, according to (Ibrahim Baba & Abdul Hamid, 1989) cited in Adibah Izzati (2012), there are 3 types of ligand such as monodentate, polydentate and ambidentate. Ligands that have only one donor atoms with only one site of attachment towards metals is a definition of monodentate ligand. Meanwhile polydentate ligands is a ligands that have more donor atoms with more site of attachments towards metal. For ligands that have more than one donor atoms that shows different properties when the metals do attach to either one of the potential donor atoms are known as ambidentate ligands.
Lange et al. (1996) stated that thiourea able to function as a ligand because the presence of thiocyanate ion (SCN-), that a type of functional groups in a molecule of thiourea. This result thiourea to develop into the potential and versatile ligand. This potential and versatile ligand can be synchronized towards variety of transition metals as bidentate and monodentate ligand (Tadjarodi et al., 2007).
This brings a lot of research have been reported that thiourea derivatives have worldwide benefits in many distinct areas such as ability to inhibit the growth of both gram negative and gram positive of bacteria species (Saeed et al., 2009) and antiviral activity (Karakus
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et al., 2009). Faidallah et al. (2011) mentioned that preliminary biological test of thiourea compounds show significant response as antimicrobial effect. Besides that, Saeed et al. (2009) mentioned that thiophene and morpholine from thiourea derivatives contain nitro group electron withdrawing group on benzothiazole nucleus showed good antimicrobial activity.
8 CHAPTER 3
METHODOLOGY
3.1 Chemicals and Materials
For preparation and inhibitory test of alkoxyl thiourea derivatives to the growth of cyanobacteria (Oscillatoria sp.), part of chemicals, materials and solvents such as Blue Green Medium and gauze that were used were commercially purchased from ordinary supplier. Besides that, the other part of chemicals, materials and solvents such as acetone and dimethylsulfoxide (DMSO) that were used in this research were obtained from Department of Biological Sciences and Department of Chemical Sciences, Faculty of Science and Technology, Universiti Malaysia Terengganu.
Blue Green Medium or also known as BG11 was function in this study as a universal medium for the culture and maintenance of the cyanobacteria. The composition of this medium were sodium nitrate, dipotassium hydrogen phosphate, magnesium sulphate, calcium chloride dihydrate, sodium carbonate, disodium magnesium EDTA, citric acid and ferric ammonium citrate. This all inclusive medium was purchased from Sigma Aldrich. This medium was stored below 8ºC and protected from direct light.
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Four types chemicals of alkoxyl substituted thiourea derivatives such as compounds 1-4 were obtained from Chemical Science Department, Faculty of Science and Technology, Universiti Malaysia Terengganu. Meanwhile, solvent such as dimethylsulfoxide (DMSO) and acetone were obtained from Department of Biological Sciences and Department of Chemical Sciences, Faculty of Science and Technology, Universiti Malaysia Terengganu. All related chemicals and solvent were carried out in very intensive care in laminar flow.
3.2 Apparatus
The apparatus and glassware that were used in this study were phytoplankton net, inoculum loop, plastic bottle, conical flask with different sizes (100 ml, 150 ml, 500 ml and 3000 ml), petri dishes, filter funnel, spectrophotometer, parafilm, microscope, freezer, incubator, air-pump, centrifuge, filter paper, parafilm, gauze, micropipette with different sizes (10 mL, 20 mL, 100 mL, 1000 mL and 5000 mL), vials, dropper, cotton swap, beaker with different sizes (50 mL, 100 mL, 250 mL and 500 mL) and centrifuge tube.
3.3 General Procedure
Cyanobacteria from Oscillatoria sp. was sampled in a pond at Universiti Malaysia Terengganu. Then, the cyanobacteria was further isolated and identified under the microscope. Then, the cyanobacteria was cultured in petri dish to grow. Subsequently, the cyanobacteria was mass culture in the flask to prepared enough numbers for inhibition treatment.
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Then, four several molecule structure of compounds 1-4 were diluted from the powder to become liquid. Next, the cyanobacteria was treated by the compounds. Afterward, the process extraction chlorophyll-A was done and the percentage of inhibition was counted by using formula.
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Figure 3.1: Flow chart of general procedure approach
Sampling of cyanobacteria (Oscillatoria sp.) Cultured of cyanobacteria (Oscillatoria sp.) Inhibitory test of alkoxyl substituted thiourea derivatives to the growth of cyanobacteria (Oscillatoria sp.) Extraction of chlorophyll a and inhibition percentage was calculated by using formula.
12 3.4 Study Sites
Sampling was conducted in a channel Malaysia Terengganu (UMT). UMT located in the Kuala Terengganu, Terengganu and strategically located on the shoreline of Terengganu facing South China Sea (Figure 3.1) UMT originally founded as Centre for Fisheries and Marine Science. Later, in 1999, it was renamed as Universiti Putra Malaysia Terengganu (UPMT) before turned into College of Science and Technology Malaysia (KUSTEM) in June 2001. Subsequently it was approved by Malaysian goverment to rename KUSTEM to UMT in 2007.
Figure 3.2 Satelite image showing study site in Universiti Malaysia Terengganu note that the yellow star indicate the sampling site
13 3.5 Field Sampling
Cyanobacteria (Oscillatoria sp.) was collected from channel as in the area of Universiti Malaysia Terengganu beside the building of Research Management Inovation Centre (RMIC) in early October 2012 (Figure 3.2). Oscillatoria sp. was determined by the characteristics that tend to float underwater and appear green in colour. Oscillatoria sp. was collected by using 25 µm phytoplankton net (Saeed et al., 2009). Then the sample was placed inside labeled plastic bottle. The labeled plastic bottle with the sample was brought back to the laboratory for further identifying and isolation procedure.
Figure 3.3: Photo of the channel where the samples of Cyanobacteria (Oscillatoria sp.) was collected
14 3.6 Identification and Isolation of Oscillatoria sp.
The identification of Oscillatoria sp. was made based on the identification key of freshwater algae (Presscott et al., 1999). Oscillatoria sp. was identified under compound microscope as shown in the Figure 3.3. Then, the identified colony of Oscillatoria sp. was transferred and isolate onto sterile BG-11 media by using inoculum loop. The media was remained up to 10 days in order to obtain pure culture of Oscillatoria sp.
Figure 3.3: Process of identification and isolation of Oscillatoria sp. by using compound microscope
15 3.7 Mass Culture of Oscillatoria sp.
The pure cultured Oscillatoria sp. colony was cultured by using BG-11 liquid media in 3000 ml conical flask. The flask was sterilized by being autoclaved it at 126 ºC for 20 minute and with pressure 1 atm. Then the cultures as shown in Figure 3.5 was incubated and maintained at 25 ºC under continuous illumination of cool fluorescent light (Zhang et al., 2011). It was left in 10 days for optimum growth to provide optimum rate for inhibition test.
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3.8 Inhibition test of alkoxyl substituted thiourea on the Oscillatoria sp.
In the exponential growth of 10 days, 27 ml of Oscillatoria sp. cultivation was harvested and transferred into 100 ml conical flask. 3 ml each of four different types of alkoxyl substituted thiourea which has concentration 10 µg/mL, 12 µg/mL, 14 µg/mL, 16 µg/mL, 18 µg/mL and 20 µg/mL was added into each of the conical flask. The controlled system without treatment of alkoxyl substituted thiourea derivatives also were set up. Each treatment was conducted in triplicate.
Figure 3.5: Inhibition test of alkoxyl thiourea derivatives to the growth of cyanobacteria (Oscillatoria sp.)
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3.9 Chlorophyll a extraction and the calculation of inhibition test.
The treatment and controlled of the inhibition test were filtered with 0.45 µm whatman filter paper. Then, the filter paper washed in 5 to 10 mL of 100% acetone in a centrifuge tube with glass rod. Next, there were sealed with aluminium foil and left 24 hour in the dark conditions in 4 ºC. Later, the blank filter paper also washed with 100% acetone. On the following days, the centrifuge tube was centrifuged at 3000 rpm for 10 minutes. The absorbance of supernatant was measured at 665 nm, 645 nm and 630 nm. Next, the chlorophyll a content was calculated by using the formula as shown as below. Then, the inhibition percentage of alkoxyl thiourea substituted derivatives to the growth of cyanobacteria (Oscillatoria sp.) was calculated by using formula that shown in Figure 3.7.
Chlorophyll a, Chl-a (mg/m) = (Ca x Va) / Vc
Where Ca = 11.6 x OD665 - 1.31 x OD645 - 0.14 x OD630
Va= Volume of acetone (mL) used for extraction Vc= Volume of culture (L)
The formula to calculate the chlorophyll-a content
Inhibition Percentage = [(Control - Treatment) / Control] x 100%
The formula to calculate the inhibition percentage of alkoxyl thiourea substituted derivatives to the growth of cyanobacteria (Oscillatoria sp.)
18 CHAPTER 4
RESULTS
4.1 Sampling of Oscillatoria sp.
Oscillatoria sp. was sampling as shown in Figure 4.1. The physical appearance of Oscillatoria sp. that was green scum expose in the water surroundings help the process of sampling. The specimen was further identified under the microscope in the laboratory. Under observation of microscope, it was easily to determine by the similarities of its shape that is filamentous and non-differentiated as shown in Figure 4.2.
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Figure 4.2: Successfull identification of Oscillatoria sp. under the microscope
4.2 Culture of Oscillatoria sp.
The process of cultured of Oscillatoria sp. was continued after the process of identification and isolation done. It was successfully cultured in agar plate that containing BG-11 agar medium to obtain pure cultured of Oscillatoria sp. as shown in Figure 4.3. After that, it was successfully propagate in 10 day by mass cultured it using BG-11 liquid medium.
4.3 Inhibition Effect of Six Different Concentration of Compound 1 to the growth of Cyanobacteria (Oscillatoria sp.)
Figure 4.4 showed the inhibition effects of six different concentration of compound 1 on the growth of cyanobacteria (Oscillatoria sp.) Based on this result, there was an increasing of inhibition percentage along together with the increasing of the treatment concentrations from 10 µg/mL until the optimum treatment concentrations that was at
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18µg/mL. However, the 20 µg/mL treatment showed decreasing in the inhibition percentage towards the growth of cyanobacteria (Oscillatoria sp.). Treatment concentration of 18 µg/mL showed highest inhibition percentage that was 69.43 % while the lowest inhibition percentage was 27.7 % with at 20 µg/mL treatment concentration.
Figure 4.4: Inhibition effect of six different concentration of compound 1 to the growth of cyanobacteria (Oscillatoria sp.)
4.4 Inhibition Effect of Six Different Concentration of Compound 2 to the growth of Cyanobacteria (Oscillatoria sp.)
Figure 4.5 shows that the inhibition percentage increased proportionally towards the treatment concentration of 16 µg/mL. However, for the treatment of compound 2, at 18 µg/mL and 20 µg/mL of concentration, the inhibition percentage decreased. The highest inhibition percentage was 58.4 % at 16 µg/mL of treatment concentration. In contrast, the
0 10 20 30 40 50 60 70 80 10 12 14 16 18 20 In h ib ition Pe rc e n tage (% ) Concentration (µg/mL) Compounds 1
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lowest inhibition percentage was recorded at 20 µg/mL treatment concentration which was 33.43 %.
Figure 4.5: Inhibition effect of six different concentration of compound 2 to the growth of cyanobacteria (Oscillatoria sp.)
4.5 Inhibition Effect of Six Different Concentration of Compound 3 to the growth of Cyanobacteria (Oscillatoria sp.)
Figure 4.6 shows the inhibition effects of six different concentration of compounds 3 on the growth of cyanobacteria (Oscillatoria sp.). Based on this result, there was an increasing of inhibition percentage along together with the increasing of the treatment concentrations from 10 µg/mL until the optimum treatment concentrations that was at 14µg/mL. However at the 16 µg/mL, 18 µg/mL and 20 µg/mL treatment concentration showed decreasing in the inhibition percentage towards the growth of cyanobacteria (Oscillatoria sp.). Treatment concentration of 14 µg/mL showed highest inhibition
0 10 20 30 40 50 60 70 10 12 14 16 18 20 In h ib ition Pe rc e n tage (% ) Concentration (µg/mL) Compounds 2
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percentage that was 50.53 %. Meanwhile the lowest inhibition percentage recorded at 20 µg/mL treatment concentration which was 37.73 %.
Figure 4.6: Inhibition effect of six different concentration of compound 3 to the growth of cyanobacteria (Oscillatoria sp.)
4.6 Inhibition Effect of Six Different Concentration of Compound 4 to the growth of Cyanobacteria (Oscillatoria sp.)
Figure 4.7 shows that the inhibition percentage increased proportionally towards the treatment concentration of 14 µg/mL. However, for the treatment of compound 4, at 16 µg/mL, 18 µg/mL and 20 µg/mL of concentration, the inhibition percentage decreased. The highest inhibition percentage was 63.17 % at 14 µg/mL of treatment concentration. In contrast, the lowest inhibition percentage was recorded at 20 µg/mL treatment concentration which was 35.5 %.
0 10 20 30 40 50 60 10 12 14 16 18 20 In h ib ition Pe rc e n tage(% ) Concentration (µg/mL) Compound 3
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Figure 4.7: Inhibition effect of six different concentration of compound 4 to the growth of cyanobacteria (Oscillatoria sp.)
4.7 Inhibition Effect of Four Different Compounds to the growth of Cyanobacteria (Oscillatoria sp.)
Figure 4.8 shows the inhibition effect of four different compounds to the growth of Cyanobacteria (Oscillatoria sp.). The result showed there were increasing trend of toward treatment concentration of 14 µg/mL, 16 µg/mL and 18 µg/mL in each compounds. However all compound shows decreasing inhibition percentage at 20 µg/mL. At 10 µg/mL, compound 1 shows the highest inhibition percentage that was 38.63 percent while compound 4 shows the lowest inhibition percentage that was 35.5 %.
0 10 20 30 40 50 60 70 10 12 14 16 18 20 Inh ib iti on Per ce n tag e(% ) Concentration (µg/mL) Compounds 4
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Treatment concentrations at 12 µg/mL shows that compound 4 recorded the highest inhibition percentage at the concentration that was 48.57 % while compound 2 record the lowest inhibition percentage that was 38.27 %. The highest inhibition percentage for treatment concentration at 14 µg/mL record by compound 4 which was 63.17 % whereas compound 2 shows the lowest inhibition percentage that was 42.1 %. At 16 µg/mL of treatment concentration, compound 2 recorded the highest inhibition percentage that was 58.4 % while the lowest inhibition percentage recorded by compounds 3 which was 40.27 %.
The highest inhibition percentage that recorded at 18 µg/mL of treatment concentration was compound 1 which was 69.43 % while compound 3 shows the lowest inhibition percentage that was 38.1 %. Meanwhile at the treatment concentration of 20 µg/mL, compound 4 shows the highest inhibition percentage that was 39.3 % while compound 1 shows the lowest inhibition percentage that was 27.7 %. In general, compound 1 exhibited the highest inhibition percentage between the compounds and concentrations that was at 18 µg/mL treatment concentration while compound 1 also was the compound with had lowest inhibition percentage between all the compound and concentrations that was at 20 µg/mL.
Besides that, statistical analysis had been done to this result. Two-way analysis of variance (ANOVA) test had been select to analyse this data. This is because in this study two independent variable; structure and concentration had been study. This two way ANOVA is the best analysis used when there are more than one independent variable. The two way ANOVA not only function to determine the main effect of contributions of each independent variable but it is also identified if there significant interaction effect between the independent variable had been choose as shown in Appendix A.
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The analysis using two way ANOVA shows that, there was a significant difference between all concentration treatment (ANOVA, p <0.05) (Appendix A) except for interaction between the concentration 16 µg/mL with 14 µg/mL showed not significant different because the value of p is (ANOVA, p 0.092 <0.05). Meanwile, there was a significant difference between all the molecule structure because the value of p is (ANOVA, p <0.05).
Figure 4.8: Inhibition percentage of four different compounds to the growth of cyanobacteria (Oscillatoria sp.) 0 10 20 30 40 50 60 70 80 10 12 14 16 18 20 In h ib ition p e rc e n tage (% ) Concentration (µg/mL) Compounds 1 Compounds 2 Compounds 3 Compounds 4
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Table 4.1: Highest values inhibition percentage and highest concentration of each compounds
Compounds Highest Inhibition(%) Highest Concentration(µg/mL)
1 69.40 18
2 58.40 16
3 50.53 14
27 CHAPTER 5
DISCUSSION
5.1 Sampling
The sampling site was chosen because it is ideal since it is close to UMT, low cost of transport and has a disturbed environment. Besides that, the output of the study can be used by the future developer to consider any environmental friendly development. In addition, the data collection was carried out in the monsoon season. There are several problems during the sampling in monsoon season such as fast moving water, precipitation of soil that entered the phytoplankton net and difficulties to find Oscillatoria Sp. However all the sampling task was successfully done.
5.2 Inhibition Effect of Alkoxyl Substituted Thiourea Derivatives To The Growth of Cyanobacteria
In this study, compounds 1-4 of alkoxyl substituted thiourea derivatives were proven to inhibit the growth of cyanobacteria (Oscillatoria sp.). As mentioned by Francoise et al., (1998), molecular studies of cyanobacteria much similar to that of other bacteria such as lactose based expression in E. coli and vanillate based expression in Caulobacter crescentus (C. crescentus). The vanillate is the byproduct of the saprotrophic digestion of plant lignin. In addition, cyanobacteria is gram positive prokaryotes. The inhibition result
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was supported by research had been done by Golan et al. (2008) state that the simply coat of murein make a sample easy to penetrate into it.
Furthermore, the result inhibition effect of alkoxyl substituted thiourea also was further supported by a study which had been done by Zhong et al. (2008). This study found that chitosan-thiourea derivatives have inhibition effect towards gram-positive and negative bacteria. Besides that the study found that the presence of potential functional groups C=S, NH and C=O in their derivatives had caused the inhibition effect to the bacteria.
Additionally, Lange et al. (1996) found that molecule of thiourea contains thiocyanate ion (SCN-), a type of functional groups which makes thiourea able to act a ligand. This result of thiourea molecule as potential and versatile ligand as mentioned by Tadjarodi et al. (2007). This ligand makes the compounds 1-4 become suitable to become anti-algae product because the properties of ligand that can be easily degraded compare to other current anti-algae product such copper that types of heavy metal that cannot be degraded and in long times will affect lethal to living things.
Meanwhile inhibition percentage of alkoxyl substituted thiourea derivatives towards the growth of cyanobacteria (Oscillatoria sp.) was measured based on extraction of chlorophyll a. The measurement based on extraction of chlorophyll a because cyanobacteria are photosynthetic can manufacture their own food. In addition, cyanobacteria derived their name from bluish pigment phycocyanin which function to capture light for photosynthesis. Furthermore, chlorophyll a contain in cyanobacteria is the same photosynthetic pigment that plant use. Inhibition of alkoxyl substituted thiourea derivatives towards chlorophyll a of cyanobacteria would disturb photosynthetic process which result in the low efficiency food production for cyanobacteria and as a consequence, it will die.
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As the result of this study show different patterns of inhibition effect for each molecule structure and concentration, it can be explained by the presence of a conjugated cyclic system which is stabilized by resonance is called an aromatic system. Besides that, benzene is one of the examples of conjugated six-membered. This supported by the result of this study that four different compounds of aromatic system produce different patterns of inhibition effect particularly caused by delocalization of electron.
30 CHAPTER 6
CONCLUSION AND RECOMMENDATION
6.1 Conclusion
Cyanobacteria bloom does cause various side effects to the environment such as become lethal to living things. Current method to threat it such as by using copper and silver nanoparticle have many disadvantage such as high cost and not easily decompose. Thus, alternative treatment must be find. In this study, alkoxyl thiourea substituted derivatives are very well-known compounds as versatile ligands that easily decompose was used to treat the cyanobacteria bloom. This types of thiourea have proven to be very functional in numerous application particularly in environmental in order to develop new sources energy from different reaction of thiourea derivatives. This is because thiourea is a very versatile ligand because of its ability to provide huge number bonding potential towards metals metal centers. However, there are four compounds of alkoxyl thiourea derivatives substituted that have fully tested to apply as anti-algae agents through the reaction with the cyanobacteria (Oscillatoria sp.) in this study.
Furthermore all the treatment compounds demonstrate positive result towards inhibit the growth of cyanobacteria (Oscillatoria sp.). Compound 1 has highest inhibition percentage towads the growth of cyanobacteria (Oscillatoria sp.) followed by compound 4, 2 and 3
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respectively. All treatment concentration shows increase pattern of inhibition toward the growth of cyanobacteria (Oscillatoria sp.) until treatment concentration of 14 µg/mL for both compounds 3 and 4, however for compounds 1 and 2, it shows different increasing pattern of inhibition towards the growth of cyanobacteria (Oscillatoria sp.) that are until treatment concentration of 18 µg/mL and 16 µg/mL respectively. In conclusion, compounds 1-4 has high potential to be further developed as anti-algae product but all the compounds need further studying in efficiency dosage, environmental effect and clinical effect before it can be used as antialgae product for treatment of cyanobacteria (Oscillatoria sp.) bloom.
6.2 Recommendation
Alkoxyl substituted thiourea derivatives are very interesting molecules as thus give a many advantages towards various field of applications. For future studies on this thiourea, the side effect of this chemical on the environment should be further investigated. Besides that, further studies on the efficient dosage must be done to know the best dosage of treatment.
Besides that, this thiourea system can be also substituted by other novel thiourea derivatives such as thiourea derivatives of metal complexes with various transition metals such as nickel and copper which prove that have tremendous biological activity. The presence of unpaired electrons at oxygen atoms make it easy to gives good yields of products.
Next, the antialgae properties of 1-4 can also be tested using various types of cyanobacteria such as Nostoc, Microcystis and Anabaena. Besides that, compounds 1-4 can also be tested towards other biological species like viruses and protozoa.
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Alkoxyl thiourea substituted derivatives will be great future system because it have large prospect to be developed such as in renewable energy, catalyst, electricity and electronic devices and biomedical. This prospect comes with the fully packaged of this alkoxyl thiourea substituted derivatives that low cost.
