International conference on Frontiers in Chemical Technology 2020 (FCT 2020)
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Item Synthesis of DPA based NNN donor ligands having piperidinyl groups and their platinum complexes towards potent anti-cancer applications(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Peiris, P. A. L.; Perera, N. T.Dipicolylamine (dpa) moiety has received much attention due to its coordination versatility. Our objective is to incorporate piperidinyl groups into the dpa system due to possibility of the piperidinyl group to target sigma receptors as it shows high affinity to sigma receptors, which are expressed in high densities in breast cancer cells. In this study, two novel ligands; N((CH2)2piperidine)dpa (L1) and N((CH2)3piperidine)dpa (L2) (Figure 1) were synthesized by utilizing pendant piperidinyl groups having different chain lengths. The platinum complexes of novel ligands; [PtClN((CH2)2piperidine) dpa]Cl (C1) and [PtClN((CH2)3piperidine)dpa]Cl (C2) were also synthesized during the study. Structural data obtained from single crystal X ray diffraction for C1 confirms that L1 serves as a tridentate donor ligand. UV visible spectra of both ligands and complexes were recorded in methanol. Absorption peaks in 200-300 nm range in UV visible spectra of ligands are due to intra ligand π→π* transitions and peaks above 300 nm range are due to n→π* transitions in the ligands. As expected, no absorption peaks corresponding to n→π* transitions were observed in UV visible spectra of complexes due to lack of lone pairs in the coordination complexes. Methylene protons observed as a singlet (3.87 ppm) in 1H NMR spectrum of L1. The N-H bond of secondary amine group present in dpa gives an IR band in 3310-3350 cm-1 region. However, IR spectra of both ligands and complexes gave no transmittance peaks in region 3310-3350 cm-1 confirming the absence of the N-H group which also confirms the formation of ligands and complexes. Both ligands displayed intense fluorescence in methanol. However, fluorescence spectra of platinum complexes showed lower intensities than the respective ligands, possibly indicating static quenching of fluorescence upon coordination to metal. These ligands and complexes can be explored towards treatment of breast cancer due to incorporation of piperidinyl group.Item Synthesis of platinum complexes with N^N- sulphonamide ligands towards fluorescence imaging applications(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Hettige, I. L.; Perera, N.T.Ethylenediamine has been used as the backbone to synthesize the novel Pt-N^N complexes. The outstanding binding ability of ethylenediamine allows it to be used in the synthesis of hydrophilic ligand systems, by substituting the terminal amine group with bulky aromatic sulphonamide fragments which would also incorporate lipophilicity as well as enhanced fluorescence. Employing such amphipathic ligand systems would be an optimal approach of synthesizing platinum coordination complexes for biological applications with improved uptake by targeted cells. In this study, two ligands (L1=N(SO2biphenyl)ethylenediamine, L2=N(SO2azobenzene)ethylenediamine) (Figure 1) and their corresponding novel platinum complexes(C1=PtCl2(N(SO2biphenyl)ethylenediamine), C2=PtCl2(N(SO2azobenzene)ethylenediamine)) were synthesized. UV-Visible spectra of the ligands indicate clear changes from starting material along with the presence of intra-ligand π→π* and n→π* transitions, giving rise to absorption peaks around 200-400 nm. Shifts of these peaks can be observed in the UV-Visible spectra of the complexes related to MLCT transitions. The strong S-N band detected in the FTIR spectra of the ligands is found at 820 cm-1 in L1 and 842 cm-1 in L2 and shifts to lower wavenumbers in ethylenediamine complexes (801 in C1 and 836 cm-1 in C2) due to direct donation of nitrogen lone pair to platinum. Disappearance of the -NH and -NH2 stretching vibration frequency in the FTIR spectra of the complexes, found around 3300 cm-1 in the ligands, indicates the deprotonation of the amine groups on coordination in the complex. Methylene protons of the amine moiety of the ligands can be seen to be magnetically inequivalent in L1 and L2, appearing as triplets within the 2.00 - 3.00 ppm range in 1H NMR spectra. Complexes display slightly higher fluorescence intensity compared to the ligands, possibly due to rigidification of the ligand systems on developing the coordination complex. Structural data was obtained from single crystal X-ray diffraction of L2 and C1 which validated the formation of the ligand and complex.Item Novel fluorescence sensors for determination of Fe3+ in biological systems using sulfonamide derivatives of dipicolylamine ligands(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Vitharana, K. V. N. N.; Perera, N. T.; Cooray, A.; Deraniyagala, S. P.Since fluorescence techniques are highly demanded area in biological species detection, the main objective of this research was to develop real-time, ratiometric fluorescence sensors which can be used for iron cation detection in physiological systems with high sensitivity and selectivity. Previously synthesized and characterized two new ligand systems were developed into ratiometric fluorescence probes for biological Fe3+ ion detection. Both ligands were sulfonamide derivatives of dipicolylamine with two different R groups, biphenyl (L1=N(SO2biphenyldpa) and azobenzene (L2=N(SO2azobenzdpa). The ligands were soluble at 0.2%(v/v) methanol solutions. Both L1 and L2 displayed ratiometric change with Fe3+ ions at 319 and 458 nm respectively. L2 had a relatively high photostability, fluorescence increasing mechanism and a lower detection limit of 18.22 nM which is a suitable concentration for biological iron detection with high sensitivity and high selectivity. L1 had a lower detection limit of 0.674 μM and fluorescence increasing and decreasing mechanisms. Since both ligands had minimum interferences from other common metal cations such as K+, Na+, Ca2+, Mg2+, Ba2+, Fe2+, Cu2+ and Zn2+, the selectivity was considered to be very high. The pH sensitivity of the both ligands were also considerably low. L2-Fe3+ complex was blue green in color with a possible applicability for common fluorescence microscopes. Both ligands metal complexes had higher UV-Visible absorbance than their respective free ligands. The ligands could be recovered from the metal complexes with the addition of ethylenediaminetetraacetic acid (EDTA). All the experimental procedures were carried out at physiological pH, 7.4 using HEPES buffer system. Beside the biological systems the probes are applicable for other environmental and industrial samples to ferric iron detection.Item Determination of total phenolic content (TPC) of Nymphaea nouchali and Nymphaea pubescens by Folin Ciocalteu method(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Sundaram, T. M.; Napagoda, M. T.; Wijesekera, K. D.; Wijayaratne, Gaya BandaraNymphaea nouchali (Nil Manel) and Nymphaea pubescens (Olu) are aquatic plants, and have a long history of use as food and folk medicine in many countries. Many phenolic compounds isolated from these two plant species have exhibited antioxidants properties and some simple phenolic compounds have shown to possess various pharmacological activities, including anti-inflammatory, antiproliferative, antioxidant and pro-apoptotic potential. The aim of the present study was to determine the content of total phenol in an extract from N. nouchali and N. pubescens flowers collected from Galle, Sri Lanka, by a UV/Vis spectrophotometric method. Aqueous methanol (80%) was used as the solvent to extract flowers including petals, stamens and pistil and all extracts were analyzed for TPC by Folin Ciocalteu method. Results were expressed in terms of gallic acid equivalence in (GAE)/g dry weight (DW) of flower part. N. pubescens petals contained 49.780 ± 0.626, stamens 37.581 ± 0.477 and pistil 31.889 ± 0.711, while N. nouchali petals showed 22.536 ± 0.383, stamens 38.702 ± 1.112 and pistil 30.119 ±1.116 GAEg-1. N. pubescens showed higher TPC in every plant part tested compared to N. nouchali and petal extract of N. pubescens showed highest TPC. Hence, N. pubescens flowers are a good source of antioxidants. Results emphasized that N. nouchali and N. pubescens extracts have high phenolic content and the importance of the use of natural products to treat pathological conditions.Item Phenolic and flavonoid contents and antioxidant activity of methanolic extract of Durio zibethinus Murr. Peels(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Perera, M. P. J.; Rajapakse, C. S. K.Durio zibethinus (durian), known as the King of fruits is one of the most important seasonal fruits in tropical Asia. Even though the edible parts of durian are known to be rich in bioactive compounds, less research has been conducted to investigate the potential bioactivity of durian peels and seeds which are of less commercial value and being disposed leading to environmental pollution. Therefore, this research was mainly focused on exploration of bioactive properties in methanolic extract of durian peels. Firstly, the dried durian peels were soxhlet extracted using methanol and then the crude extract was sequentially partitioned in hexane, dichloromethane and methanol (30%). The antioxidant activity, total phenolic content (TPC) and total flavonoid content (TFC) of each fraction were evaluated using DPPH (α, α-diphenyl- β- picrylhydrazyl) assay, Folin-Ciocalteu assay and aluminium chloride spectrophotometric assay respectively. Antioxidant activity (IC50) and its correlation to TPC and TFC were analyzed by the Pearson’s method. The dichloromethane fraction showed the highest antioxidant activity (IC50 179.9 ± 6.6 μg/ml) with high TPC and TFC (85.82 ± 12.11 mg gallic acid equivalent/g dried weight and 12.66 ± 1.94 mg of quercetin equivalent/g of dried weight, respectively). According to the Pearson’s correlation, a strong positive correlation was observed between the antioxidant activity and the TPC of fractions of methanol extracts of durian peels with a Pearson coefficient of 0.9904 and a moderate positive correlation was noticed between the antioxidant activity and TFC of the fractions with a Pearson coefficient of 0.6553 indicating that phenolic compounds in durian peels may contribute to their strong antioxidant activities with somewhat contribution from the flavonoid compounds. As the dichloromethane fraction had constituents with the highest antioxidant activity, it was further separated by column chromatography and analyzed by GC-MS to identify its volatile compounds. The results revealed that the dichloromethane fraction of durian peels was rich in [1,2-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester], [2,3-Diphenylquinoxaline], [2-Coumaranone], [4-((1E)-3-Hydroxy-1- propenyl)-2-methoxyphenol], [7,9-Di-tert-butyl-1-oxaspiro (4,5) deca-6,9-diene-2,8-dione] and [Phenol, 2,4-bis(1,1-dimethylethyl)] which are known to exhibit antioxidant activity.Item Detailed evaluation of methylated and acetylated products of cinnamon leaf oil against Aedes aegypti(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Medagedara, H. K.; Paranagama, P. A.; Gunaratna, Medha J.Aedes aegypti is a known vector of several viruses including Yellow fever, Dengue, Chikungunya and Zika virus. Two potential Aedes aegypti mosquito repellents; methyl eugenol and acetyl eugenol were semi-synthesized using eugenol extracted from cinnamon leaf, which is the main constituent in cinnamon leaf as well as in other plant leaf extracts like maduruthala and clove oil. Methyl eugenol was semi-synthesized using methyl iodide as a methylation precursor and acetyl eugenol was semi-synthesized using acetic anhydride, triethylamine base and catalytic amount of DMAP. Synthesis reactions were monitored using TLC and products were purified using flash silica columns. Formations of desired products were confirmed using GC-MS analysis. A diluted series (0.6-8 mg/ mL) was prepared for these semi-synthesized compounds and for the cinnamon leaf extract using ethanol and tested separately for their mosquito repellency using arm-in-cage tests followed by standard WHO methods. Experiments were performed on twenty volunteers in triplicates. Effective dose (ED99) for each repellent was calculated using beta regression analysis. Current study suggests that all compounds tested were effective mosquito repellents. Their ED99 varied as; cinnamon leaf extract (5.80) > methyl eugenol (5.41) > acetyl eugenol (5.13). Acetyl eugenol could be a potential safe repellent as its ED99 was achieved at a lower concentration and due to the absence of any side effects on skin when applied. Both maduruthala and clove oil contained significant contents of eugenol and clove oil had slight amounts of acetyl eugenol which could be extracted to synthesize repellent compounds or use directly in future.Item Isolation of cysteine-rich peptides from the deep-sea marine sponge Stryphnus fortis and determination of its antimicrobial effect(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Kosgahakumbura, K. N. M. L. N; Hettiarachchi, C. M; Jayasinghe, R. P. P. K.; Cárdenas, P.; Gunasekera, S.Cysteine-rich peptides are a promising resource for a wide range of pharmacological applications such as development of drug leads and as scaffolds for potential oral drug delivery due to their stable disulfide framework. A handful of these compounds have been isolated from marine sponges and it is speculated that plenty of them remain unexplored. In the present study, four peptides A, B, C and D containing three disulfides were isolated from the aqueous extract of the deep-sea marine sponge Stryphnus fortis (Demospongiae, Tetractinellida, Ancorinidae) from Norway, and were further purified using RP-HPLC (Reverse Phase High Performance Liquid Chromatography). The mass spectroscopic analysis using MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization- Time Of Flight) revealed monoisotopic masses of 3331.809 Da [M+H]+, 3349.731 Da [M+H]+, 3517.973 Da [M+H]+, 3917.61 Da [M+H]+respectively for the four peptides A, B, C and D. The antimicrobial activity was screened using a peptide adapted Micro dilution assay against E. coli (ATCC 25922), S. aureus (ATCC 29213) and C. albicans (ATCC 90028) up to a concentration of 50 μM. The average concentration derived from triplicates that exhibited a growth inhibition on visual inspection was considered as the Minimum Inhibitory Concentration (MIC). Moderate antimicrobial activity for peptide C was observed against S. aureus (MIC = 36.14 μM) and C. albicans (MIC = 18.07 μM). However, no inhibition was observed against E. coli up to the highest concentration tested. The human antimicrobial peptide LL 37 was used as the control (MIC value around 1-2 μM). The sequence analysis of the four peptides, their structural characterization and investigation of their potential applications are currently underway.Item Nephelium lappaceum L. peels as a source of phytochemicals with antioxidant and α-amylase inhibitory activities(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Binuwangi, A. K. D. M.; Rajapakse, C. S. K.Nephelium lappaceum L. (Rambutan) is a popular seasonal fruit native to Southeast Asia, enriched in varieties of phytochemicals including vitamins and secondary metabolites. This fruit is consumed fresh, canned, or as a processed food, but unfortunately its consumption results in production of vast amounts of waste from its seeds and peels which eventually create mosquito breeding grounds. Therefore, this study was conducted to investigate the potential of utilizing fruit waste (peels) of Sri Lankan variety of rambutan, Malwana special as a source of phytochemicals with antioxidant and α-amylase inhibitory activities. Phytochemicals of dried rambutan peels were first extracted into methanol by Soxhelt extraction. Then the crude extract was sequentially partitioned in hexane, dichloromethane (DCM) and methanol (30%). Total phenolic content (TPC) and total flavonoid content (TFC) of methanol extracts of rambutan peels and its fractions were determined using Folin- Ciocalteu and aluminium chloride method, respectively. Among the fractions, the highest TPC of 141.73 ± 18.66 mg gallic acid equivalents/g dried weight was found to be in aqueous methanol fraction and the DCM and aqueous methanol fractions were rich in flavonoids with TFC of 136.41 ± 32.25, and 110.67 ± 1.43 mg quercetin equivalents/g dried weight, respectively. Further, the radical scavenging properties of all the fractions were investigated using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay and their correlations with phenolics and flavonoids were analyzed using Pearson’s correlation. The methanol extract of peels (IC50 = 9.70 ± 0.50 μg/mL) and its aqueous methanol fraction (IC50 = 12.04 ± 0.80 μg/mL) showed higher DPPH radical scavenging activity than that of the control, butylated hydroxytoluene (IC50 = 13.92 ± 1.19 μg/mL). Strong positive correlations were observed between the antioxidant activity and the TPC and TFC with Pearson’s correlation coefficients of 0.9018 and 0.8493, respectively. Interestingly, it was also found out that the in vitro α-amylase inhibitory activity of the aqueous methanol fraction of the peels (IC50=75.17 ± 3.40 μg/mL) was significantly higher than the standard drug acarbose (IC50=171.5 ± 8.50 μg/mL). Results revealed that the peels of Sri Lankan variety of rambutan, Malwana special is a potential source of phytochemicals with antioxidants and α- amylase inhibitory properties.Item Development of an herbal drink using Sri Lankan varieties of Sesbania grandiflora and Citrofortunella microcarpa and its antioxidant activity(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Cooray, P. P. D; Wickramasinghe, P. D. S. UA Majority of individuals prefer ready-to-serve (RTS) beverages over preparing herbal drinks due to the busy lifestyle. The current study was focused on the development of a ready-to-serve herbal drink using the pulp of Sesbania grandiflora leaflets and Citrofortunella microcarpa fruit sac juice with sugar, table salt, and distilled water. According to previous studies, the major active compounds of the drink contain high antioxidant activity and nutrients which are considered beneficial for human health. A sensory evaluation was conducted by a trained group of tasters to choose the best sample with significant differences to taste, appearance, and aroma. pH value, titratable acidity, Brix value, reducing sugar activity, antioxidant activity, qualitative analysis of phytochemicals, microbial analysis, and shelf life of the herbal drink were determined. The herbal drink contained a pH value of 2.36 at 298.15 K, titratable acidity of 0.384% when the milliequivalent factor for citric acid is 0.064, and a Brix value of 11 at 293.15 K. The herbal drink contains the phytochemicals such as sterols, terpenoids, flavonoids, phenols, glycosides, and saponins which were identified from qualitative analysis, whereas alkaloids and tannins were absent. Antioxidant activity had a maximum of 71.48% DPPH radical scavenging activity (RSA) at 12.5% (v/v) concentration of drink in methanol and inhibition concentration 50 (IC50) was at 47% (v/v) concentration of the drink in methanol. The total plate count was 840 CFU/ml (colony-forming units per milliliter) and the estimated yeast and mold count was <250 CFU/ml, yet coliform, fecal coliform, and Escherichia coli had no growth for two days under optimum growth conditions. According to the study, the refrigerated sample had the least amount of microbial growth. Therefore, the herbal drink sans preservatives is recommended to be stored in the refrigerator.Item Exploring bioactive compounds in the endolichenic fungus, Xylaria feejeensis, inhabiting the lichen, Graphis librata, collected from Negombo lagoon, Sri Lanka(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Gunawardhana, M. H. A. Y.; Wickramarachchi, P. A. S. R.; Weerasinghe, W. R. H.; Paranagama, P. A.The accelerating pharmaceutical problem of bacteria growing resistant to existing antibiotics forces the scientific community to search for new antibacterial compounds for antibiotic drug development. Literature reveals that Sri Lankan mangrove inhabiting endolichenic fungal (ELF) population is rich in many such bioactive compounds. Previously isolated and cultured ELF, Xylaria feejeensis; from the lichen Graphis librata inhabiting in the mangrove plant Rhizophora mucronata was cultured on 60 large potato dextrose agar medium containing petri dishes and incubated for 14 days at room temperature. After extracting secondary metabolites to ethyl acetate (EA) the resulted crude extract was tested for its antibacterial and antioxidant activity. EA crude extract showed negligible antioxidant activity in DPPH radical scavenging assay hence this assay was not proceeded further. The activity of crude extract (5 mg/ml) against Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923) and Bacillus subtilis (ATCC6051) was tested using agar well diffusion antibacterial assay. An inhibition zone diameter of 1.9 cm, 2.2 cm, and 2.2 cm against three bacterial strains with Azithromycin positive control (5 mg/ml) 2.2 cm, 2.2 cm and 2.3 cm was observed respectively. By partitioning of EA crude extract resulted two antibacterial active hexane and chloroform fractions and one antibacterial inactive 60% methanol in water fraction. Hexane fraction showed the highest antibacterial activity with inhibition diameter zone of 2.6 cm against E.coli with 2.6 cm diameter of inhibition zone for positive control. Further purification of hexane fraction was performed by normal phase column chromatography and 4 fractions were resulted. The highest polar fraction showed 1.4, 2.1 and 1.7 cm diameter inhibition zones of growth of E.coli, S. aureus and B. subtilis comparable with 2.2 cm Azithromycin. The other 3 fractions showed no antibacterial activity against these bacterial strains. Results suggest that further purification of active fraction and structure elucidation might result in new antibiotic lead compounds.