Sreekanth B. Jonnalagadda

Elemental composition and chemical characteristics of five edible nuts (almond, Brazil, pecan, macadamia and walnut) consumed in Southern Africa

The total elemental concentrations and proximate chemical composition of five different tree nuts, almond (Prunus dulcus), Brazil (Bertholletia excelsa), pecan (Carya pecan), macadamia (Macadamia integrifolia) and walnut (Juglans nigra) that are consumed in South African households were investigated. In addition, six physicochemical properties of the extracted nut oils, namely acid value, iodine value, saponification value, refractive index, density and specific gravity were evaluated. A high concentration of Se (36.1 ± 0.4 μ g g− 1) was found in the Brazil nuts only. With maximum and minimum limits being set by the almond and pecan nut samples, Cr ranging from 0.94 ± 0.14–2.02 ± 0.07 μ g g− 1 was detected in the nut samples. Generally, the order of the concentrations of the elements in all the nut samples is found to be Mg > Ca > Fe > Cu > Cr > As > Se. The concentrations of Mn and Zn showed greater variation amongst the different types of nuts. The extracted oils showed low acid values and high saponification values with the macadamia nut sample having the highest oil content (76.0 ± 0.5 g per 100 g of sample), the lowest acid value (0.42 ± 0.01 mg KOH per g of oil) and highest saponification value (193.7 ± 2.4 mg KOH per g of oil). The present findings are useful in calculating the Dietary Reference Intakes of these nutrients.

Ozone-initiated disinfection kinetics of Escherichia coli in water

The effect of ozonation on the rate of disinfection of Escherichia coli was investigated as a function of ozone concentration, ozonation duration and flow rates. Ozone was generated in situ using Corona discharge method using compressed oxygen stream and depending on the oxygen flux the ozone concentrations ranged from 0.91–4.72 mg/L. The rate of disinfection of all the three microbes followed pseudo–first-order kinetics with respect to the microbe count and first order with respect to ozone concentration. The influence of pH and temperature the aqueous systems on the rate of ozone initiated disinfection of the microbe was investigated. The inactivation was faster at lower pH than at basic pH. Molecular ozone is found more effective in disinfection than hydroxyl radicals. Two reported mechanisms for antimicrobial activity of ozone in water systems from the literature are discussed. Based on the experimental findings a probable rate law and mechanism are proposed. Ozonation of natural waters significantly decreased the BOD levels of the control and microbe contaminated waters.

Elemental composition and fatty acid profile of the edible fruits of Amatungula (Carissa macrocarpa) and impact of soil quality on chemical characteristics

The Amatungula fruit, from Carissa macrocarpa, is commonly consumed by the local people of KwaZulu-Natal (KZN), South Africa. Levels of elements in the fruit were determined to assess if they conform to recommended dietary allowances (RDAs) and to assess for potential toxicities. Soils and fruit samples from nine sites in eastern KZN were investigated. Concentrations of elements in the fruit were found to be in the order of Ca>Mg>Fe>Mn≈Cu≈Pb>Se>Cr>Ni>Zn. For the elements in focus, except for Pb, all of the elements found in the fruit contribute significantly towards the RDAs. Lipid profiling was also done to determine the fruits potential as a source of essential fatty acids. The fruit was rich in monounsaturated and essential fatty acids with the linoleic acid to α-linolenic acid ratio conforming to the recommended range for cardiac health. Concentrations of elements in soil had no significant effect on plant concentrations, but competition between elements in soil influenced their availability. Total soil concentrations of most metals studied have significantly correlated Pb availability, indicating the impact of these metals on Pb availability. The Amatungula fruit showed tendency to accumulate Pb, with Pb levels in fruit at all sites being toxic to human health. Site location had a major effect on plant concentrations however uptake and distribution was primarily dependent on the plants inherent controls, as evidenced by the accumulation and exclusion of elements, to meet its physiological requirements.

Elemental composition and nutritional value of the edible fruits of Harpephyllum caffrum and impact of soil quality on their chemical characteristics

Harpephyllum caffrum is a medicinal plant and common street tree distributed throughout the eastern part of South Africa. The elemental concentration in the edible fruit of H. caffrum was determined to assess for nutritional value and health impact. Concentrations of metals in the fruit and growth soil were determined from samples acquired from eight different sites in eastern KwaZulu-Natal, South Africa, to evaluate the impact of soil parameters on elemental distribution in the fruit. Typical elemental concentrations (μg g−1, dry mass) in soil (Exchangeable/Total) and fruit samples, at Umhlanga, north of Durban, were Ca (1221/696 and 3333), Co (2.5/2.1 and 0.16), Cr (35/0.8 and 5.8), Cu (14/9 and 21), Fe (9424/394 and 116), Mg (199/139 and 915), Mn (268/187 and 13), Ni (2.8/0.51 and 3.4), Pb (36/32 and 1.2), and Zn (26/21 and 15). The analytical results showed that metal interactions in soil influenced their availability, but uptake was to a greater extent controlled by the plant. The concentrations of elements in the fruits were found to be in the order of Ca > Mg > Fe > Cu > Zn > Mn > Cr > Ni > Pb > Co. The concentrations of toxic metals, arsenic and lead were low. The fruits can contribute to the health and nutritional needs of individuals for most elements. It has potential to improve the Fe status and contribute towards a balanced diet.

EFFICIENT ONE-POT SYNTHESIS OF BENZOXAZOLE DERIVATIVES CATALYZED BY NICKEL SUPPORTED SILICA

A simple and efficient method has been developed for the synthesis of benzoxazoles from 2-aminophenol and substituted aldehydes in the presence of a catalytic amount of nickel supported silica at room temperature. . Two protocols for the synthesis of benzoxazoles have been developed. One is the copper-catalyzed intramolecular o-arylations or intermolecular domino annulations of o-arylhalides 2-4 and the other is the direct condensation of 2-aminophenol with carboxylic acid or aldehyde under harsh conditions, such as in the presence of strong acid, high temperature 5 or strong oxidants 6-9 . Catalytic aerobic oxidation using oxygen as terminal oxidant has received much attention 10,11 and been used in the synthesis of benzoxazoles 12,13 . Nickel supported silica as an environmental friendly and economical catalyst has been attracting increasing research interest from chemists 14 . Although kinds of Ni supported SiO2 catalyzed organic transformations have been developed, the Ni-SiO2 to form carbon-carbon and carbon-heteroatom bond has remained largely undeveloped 15 . Herein, we report an efficient and environmentally friendly method for the synthesis of benzoxazoles catalyzed by nickel supported silica at room temperature (Scheme 1). We studied the possibility to synthesis of benzoxazoles by the reaction of 2-aminophenol and substituted aldehyde using Ni-SiO2 as the catalyst (Scheme 1). Here, an efficient and simple method for the synthesis of target compounds is described and the synthesis of some compounds has been reported in our previous studies.

Solvent-free Knoevenagel condensation over iridium and platinum hydroxyapatites

The Knoevenagel condensation between various aldehydes (benzaldehyde, p-methoxybenzaldehyde and 1-naphthaldehyde) and esters (ethylcyanoacetate, ethylacetoacetate and diethylmalonoester) was carried out under solvent-free condition in the presence of iridium or platinum hydroxyapatites as a catalyst.

Kinetics of ozone-initiated oxidation of textile dye, Amaranth in aqueous systems

The ozone facilitated oxidation mechanism of water soluble azo anionic dye, amaranth (Am) was investigated monitoring the depletion kinetics of the dye spectrometrically at 521 nm. The oxidation kinetics of the dye by ozone was studied under semi-batch conditions, by bubbling ozone enriched oxygen through the aqueous reaction mixture of dye, as function of flow rate, ionic strength, [O3] and pH variations. With excess concentration of ozone and other reagents and low [amaranth], reaction followed pseudo–first-order kinetics with respect to the dye. Added neutral salts had marginal effect on the reaction rate and the variation of pH from 7 to 2 and 7 to 12 exerted only small increases in the reaction rate suggesting molecular ozone possibly is the principle reactive species in oxidation of dye. The reaction order with respect ozone was near unity and it varied slightly with pH and flow rate variations. The overall second-order rate constant for the reaction was (105 ± 4) M−1 min−1. The main oxidation products immediately after amaranth decolorization were identified. The reaction mechanism and overall rate law were proposed. After spiking the seawater, river water and wastewaters with Amaranth dye, the reaction rates and trends in BOD and COD under control and natural conditions were investigated. The rate of depletion of the dye in natural waters was relatively lower, but the ozonation process significantly decreased both the BOD and COD levels.

Solvent-Free Knoevenagel Condensation over Cobalt Hydroxyapatite

The Knoevenagel condensation between various aldehydes (benzaldehyde, 1-naphthaldehyde, p-bromobenzaldehyde and p-methoxybenzaldehyde) and esters (ethylcyanoacetate, ethylacetoacetate and diethylmalonoester) was carried out under solvent free condition in the presence of cobalt hydroxyapatite (CoHAp), as a catalyst. Good to excellent yields (35–96%) were obtained. The catalyst is found to be superior over fluorapatite and several other heterogeneous catalysts. The catalyst can be recycled at least 3 times.

Synthesis and antimicrobial activity of new 1,3,4-thiadiazoles containing oxadiazole, thiadiazole and triazole nuclei

A new series of 1,3,4-thiadiazole derivatives containing oxadiazole (3a – 3e), thiadiazole (4a – 4e), and triazole (5a – 5e) moieties have been prepared using 2-(5-phenyl-1,3,4-thiadiazol-2-ylamino)acetic acid (2) as intermediate. The structures of newly synthesized compounds are confirmed by 1H NMR, 13C NMR, and FT-IR spectroscopy, LC/MS mass spectrometry, and elemental analysis data. Furthermore, all the newly synthesized compounds were also tested for their in vitro antibacterial activity against selected human pathogens viz. Escherichia coli, Salmonella typhimurium, Legionella monocytogenes, Klebsiella pneumonia, Salmonella typhi, Staphylococcus aureus and Bacillus subtilis and antifungal activity against Candida albicans, Streptococcus pyogenes and Fusarium solani strains. The preliminary results revealed that certain compounds exhibited promising antimicrobial activities against the test microorganisms. Nine of the total of 15 compounds exhibited excellent antibacterial activity and antifungal activity.

Chemical composition of edible Macadamia nuts (Macadamia integrifolia) and impact of soil quality

The distribution of eight selected elements (As, Ca, Cr, Cu, Fe, Mg, Mn and Zn) in edible Macadamia (Macadamia integrifolia) nuts from eight sampling sites in the south east coast region of South Africa is investigated. The levels of the elements in all the Macadamia nuts are found to be in the decreasing order of Mg > Ca > Fe > Zn > Cu > Cr > As. The exception is Mn, which exhibited large variability with concentrations in nuts ranging from 10.21 ± 0.47μg g−1 to 216.4 ± 0.4 μg g−1. The impact of soil quality parameters: soil pH, cation exchange capacity, soil organic matter and elemental concentrations, as well as interactions in the soil on the elemental composition in the nuts are also studied. At the Ifafa site, south of Durban, typical elemental concentrations (in μg g−1 dry weight) in the (nuts and soil) are Mg (4920 and 4656), Ca (2169 and 6173), Fe (92 and 20200), Zn (52 and 30), Cu (20 and 49), Cr (2.0 and 69.0) and As (0.024 and 0.104). The maximum concentration of Mg in the nuts is observed to be 4956.1 ± 92.8 μg g−1, while that of As is below 0.058 ± 0.003 μg g−1. Ca and Mg levels in nuts are antagonistic. Further, when bioavailable levels of Fe, Cu and Zn in soil are low, the bioaccumulation factor for Fe in nuts is high. Although, the soil quality parameters have an influence on the elemental uptake by the Macadamia nut, the results show that uptake and distribution of metals in the nuts are primarily dependent on the plants inherent controls that ensure the physiological well-being of the plant. Macadamia nuts prove to have good control on elemental uptake and are low in the toxic metals investigated.