Fatty acid profile and elemental content of avocado (Persea americana Mill.) oil –effect of extraction methods

Interest in vegetable oil extracted from idioblast cells of avocado fruit is growing. In this study, five extraction methods to produce avocado oil have been compared: traditional solvent extraction using a Soxhlet or ultrasound, Soxhlet extraction combined with microwave or ultra-turrax treatment and supercritical fluid extraction (SFE). Traditional Soxhlet extraction produced the most reproducible results, 64.76 ± 0.24 g oil/100 g dry weight (DW) and 63.67 ± 0.20 g oil/100 g DW for Hass and Fuerte varieties, respectively. Microwave extraction gave the highest yield of oil (69.94%) from the Hass variety. Oils from microwave extraction had the highest fatty acid content; oils from SFE had wider range of fatty acids. Oils from Fuerte variety had a higher monounsaturated: saturated FA ratio (3.45–3.70). SFE and microwave extraction produced the best quality oil, better than traditional Soxhlet extraction, with the least amount of oxidizing metals present.     

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 microg 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 microg 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.     

Passive monitoring of nitrogen dioxide in urban air: a case study of Durban metropolis, South Africa

To devise and implement strategies to manage the quality of urban air, a metropolis needs air pollution data on which an air quality management plan can be formulated. Although air pollutants can come from several sources, many reports suggest that nitrogen dioxide from motor vehicle emissions is the major contributor to air pollution in cities. Since vehicles stop or move slowly through traffic intersections, concentrations of nitrogen dioxide (NO(2)) are expected to be relatively high at these sites. Inexpensive Ogawa passive samplers were placed at selected traffic intersections in the Durban Metropolis to trap the NO(2) which was then analysed by a sensitive laboratory-based method. The data obtained by this method was compared with data from sophisticated system comprising an active sampler cum on-line chemiluminescence detector. The sampling was done over a twelve month period to cover all seasons. Statistical analysis of the data showed that there was no significant difference between the means for the two methods. This study has established that an Ogawa passive sampler may be used as an economical and reliable collector for NO(2) in ambient air under varying climatic conditions. Further, the analysis method using a UV-Visible spectrophotometer was sensitive enough to detect NO(2) at the 10-20 ppb level. The cost of the method should be well within the budgets of most municipalities and it would motivate them to develop policies to alleviate traffic congestion.     

Elemental distribution in the edible leaves of Celosia trigyna from the western and northern regions of Nigeria

Celosia trigyna, which belongs to the plant family Amaranthaceae, is a plant used in traditional medicine to treat several conditions such as sores, chest pains, diarrhoea and menstrual cramps in many countries in Africa. It is also consumed by the local people in Nigeria as soups, sauces and stews. In this study, the distribution and bioaccumulation of the elements in C. trigyna species and growth soil from the western and northern regions of Nigeria was investigated to determine the effects of geographical location on the uptake of elements by the plant. Elemental concentrations in the leaves from the western region were found to be in decreasing order of Ca?>?Mg?>?Fe?>?Mn?>?Zn?>?Cu?>?Pb?>?As?>?Ni. Concentrations of elements in the leaves from the northern region were found to be in decreasing order of Ca?>?Mg?>?Fe?>?Mn?>?Zn?> Cu?>?As?>?Pb?>?Ni?>?Co?>?Cd. Proximate analysis of leaves from both regions compared well with the recommended dietary allowance making the leaves safe for human consumption. Principal component analysis was used to group elements having the same sources irrespective of their geographical locations. Cd, Co and Cr were not detected in the leaves from the western region. Concentrations of As and Pb were above maximum permissible limits in both regions, while Ayegunle and Bida (in the northern region) had the highest concentrations of Cd. The high level of these toxic metals may be attributed to anthropogenic activities. It is therefore important that the Nigerian agricultural extension system emphasizes the dangers of heavy metal contamination in leafy vegetables to farmers. Activities of the manufacturing industries in the study area should be adequately monitored under standard environmental protection laws.     

Impact of spiked concentrations of Cd,Pb, As and Zn in growth medium on elemental uptake of Nasturtium officinale (Watercress)

This study is aimed at investigating the impact of water quality on the uptake and distribution of three non-essential and toxic elements, namely, As, Cd and Pb in the watercress plant to assess for metal toxicity. The plant was hydroponically cultivated under greenhouse conditions, with the growth medium being spiked with varying concentrations of As, Cd and Pb. Plants that were harvested weekly for elemental analysis showed physiological and morphological symptoms of toxicity on exposure to high concentrations of Cd and Pb. Plants exposed to high concentrations of As did not survive and the threshold for As uptake in watercress was established at 5 ppm. Translocation factors were low in all cases as the toxic elements accumulated more in the roots of the plant than the edible leaves. The impact of Zn on the uptake of toxic elements was also evaluated and Zn was found to have an antagonistic effect on uptake of both Cd and Pb with no notable effect on uptake of As. The findings indicate that phytotoxicity or death of the watercress plant would prevent it from being a route of human exposure to high concentrations of As, Cd and Pb in the environment.     

Elemental composition and nutritional value of the edible fruits of coastal red-milkwood (Mimusops caffra) and impact of soil quality on their chemical characteristics

In this study, the elemental distribution of essential and toxic elements in the soil and fruits of the indigenous plant species, Mimusops caffra, from ten sites along the KwaZulu-Natal east coast was investigated using inductively coupled plasma-optical emission spectrometry. This was done to determine the nutritional value of the fruits as well as to evaluate the impact of soil quality on elemental uptake by the plant. The elemental concentrations in the fruits (in descending order) were found to be K > Na > Ca > Mg > Si > Al > Fe > Zn > Mn > Ni > Cr > Cu > Pb > Mo > Sb > As > Se > V > Cd > Co. The results show that approximately 10 g of fruit would contribute more than 85% towards the recommended dietary allowance for Fe and Si for most adults. The proximate chemical composition revealed the fruits to contain approximately 84% moisture, 4.7% ash, 6.9% protein, 1.7% oil and 2.7% carbohydrates. The study indicates that the fruits of this indigenous plant species are a good source of essential elements with low levels of potentially toxic elements (Pb, As and Cd) which makes the plant a good indigenous food source especially for vulnerable communities that need food security.     

Structure and antioxidant activity of phenolic compounds isolated from the edible fruits and stem bark of Harpephyllum caffrum

Antioxidant activity in edible fruits is an important characteristic in the choice of fruits for human consumption, and has profound influence on nutrition and health. Two pharmacologically active triterpenoids, β-sitosterol and lupeol, and the powerful flavan-3-ol antioxidant, (+)-catechin, were isolated from the edible fruits of Harpephyllum caffrum while a mixture of cardanols, an alkyl p-coumaric acid ester, and (+)-catechin were isolated from the stem bark. This is the first report of these compounds being isolated from this plant. The antioxidant capacity of (+)-catechin was higher than the other isolated compounds as well as the known antioxidant, ascorbic acid.     

Cytotoxic activity of the bioactive principles from Ficus burtt-davyi

Ficus burtt-davyi (Moraceae) is a medicinal plant species indigenous to Southern Africa. In this study, a phytochemical and cytotoxic investigation on F. burtt-davyi was conducted to evaluate its ethno-medicinal use. The phytochemical study of the fruits yielded triterpenoids (lupeol and α-amyrin). The cytotoxic evaluation was done on the methanolic extracts and selected compounds, lupeol, α-amyrin, lupeol acetate and (+)-catechin isolated from F. burtt-davyi stem bark and fruits. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay was carried out against two human cancer cell lines, breast adenocarcinoma (MCF-7) and colorectal adenocarcinoma (Caco-2), and normal human embryonic kidney cells (HEK293). The methanol extract from the stem bark was significantly cytotoxic to MCF-7 and Caco-2 cell lines (p < 0.05) in a concentration-dependent manner with IC₅₀ values of 6.6 and 8.1 µg mL^?1, respectively relative to the control. Lupeol and (+)-catechin showed cytotoxic activity against MCF-7 cell lines with IC₅₀ values of 22.6 and 29.8 µg mL^?1, respectively and greater cytotoxic activity against Caco-2 cell lines with IC₅₀ values of 10.7 and 9.0 µg mL^?1, respectively. Data from this study suggests that F. burtt-davyi exhibits cytotoxicity with no significant inhibitory effects against HEK293. The results also indicate that (+)-catechin and lupeol, the most abundant bioactive principles in the stem bark, are responsible for the synergistic cytotoxic effects against tested human cancer cell lines. This study provides evidence on the pharmaceutical potential of the medicinal plant, F. burtt-davyi, as a chemotherapeutic agent against cancer.     

Pharmaceuticals as emerging organic contaminants in Umgeni River water system,KwaZulu-Natal,South Africa

The occurrences of pharmaceuticals and personal care products as emerging organic contaminants (EOCs) have been reported in several countries of the world except from African countries. This study was therefore conducted to investigate the occurrence of nine antibiotics, five antipyretics, atenolol, bezafibrate, and caffeine in wastewater and surface water samples from the Umgeni River. The water samples were extracted with solid-phase extraction using hydrophilic-lipophilic balance (HLB) and C-18 cartridges for the acidic and neutral drugs, respectively. The quantification was carried out with high-performance liquid chromatography-diode array detector (HPLC-DAD) using the standard addition method. The method limits of detections were in the range of 0.14–0.97 μg/L while the recoveries were between 53.8 and 108.1 %. The wastewater had 100 % occurrence of the analytes studied, with caffeine having the highest concentration at 61?±?5 μg/L and nalidixic acid being the most observed antibiotic at 31?±?3 μg/L. The waste treatment process reduced the influent concentrations by 43.0–94.2 % before discharge except for atenolol removal that is lower. The concentrations of the analytes were lower in the surface water with most compounds having concentrations below 10 μg/L except acetaminophen and atenolol. The estuary mouth and Blue Lagoon had the highest concentrations of some of the compounds in surface water which depict downstream load. The factors governing the fate and mobility of these compounds in this environment are not fully understood yet and will require further studies.     

Chemical composition of selected seaweeds from the Indian Ocean,KwaZulu-Natal coast,South Africa

The chemical composition of three edible seaweeds (Codium capitatum, Hypnea spicifera and Sargassum elegans) and two inedible seaweeds (Halimeda cuneata and Spyridia hypnoides) from the Indian Ocean along the KwaZulu-Natal East Coast, South Africa were investigated as a function of seasonal variation. The proximate compositions of the edible seaweeds were determined. In edible seaweeds, the moisture level ranged from 85.4 to 89.5%, protein from 6.1 to 11.8%, lipids from 7.5 to 13.1% and carbohydrates from 37.8 to 71.9%. Elemental concentrations in the five studied seaweeds varied significantly with season (P < 0.05) with mean elemental concentrations (in µg g^?1, dry weight) being: Ca (29 260), Mg (6 279), Fe (1 086), Cu (145.9), Mn (48.32), As (24.29), Zn (15.65), Ni (9.83), Cr (5.78), Pb (4.84), Co (0.87) and Se (0.86). The concentrations of As were particularly high in S. elegans, ranging from 94.70 ± 6.6 µg g^?1 in winter to 65.10 ± 2.3 µg g^?1 in summer. Hierarchical cluster analysis showed similar distribution of elements in edible seaweeds which was dissimilar to that in inedible seaweeds. This study suggests that edible macro alga, C. capitatum and H. spicifera, could be potential sources of most essential nutrients and may contribute positively to the diet without posing the risk of adverse health effects due to low concentrations of toxic elements. However, due to high levels of As in S. elegans, its consumption should be moderated to reduce dietary exposure to this toxic element.