Spectroelectrochemical determination of the antioxidant properties of carpobrotus mellei and carpobrotus quadrifidus natural products

Philosophiae Doctor - PhDSouth African Carpobrotus species have been found to contain hydrolysable tannins,various flavonoids e.g. rutin and hyperoside, phytosterols and aromatic acids which have a diverse range of pharmacological properties including antimicrobial and, antioxidant activities. The main aim of the thesis was to determine the natural products in C. mellei and C. quadrifidus using chromatographic techniques and electrochemical analysis. The antioxidant activity of both Carpobrotus species was determined by using a superoxide dismutase (SOD) biosensor. ESI-LC-MS was used to separate and determine flavonoids in C. mellei and C. quadrifidus. 8 flavonoid compounds: catechin, epicatechin, epicatechin-epicatechin, coumarylquinic acid, isorhamnetin, quercetin-hexose (hyperoside), rutin and myricetin-deoxyhexose were identified. Cyclic and square wave voltammetry were used to detect flavonoids from C. mellei and C. quadrifidus. Catechin was detected in the ethyl acetate extract of C. mellei and C. quadrifidus. The oxidation potential of the plant extracts were observed at +150.6 mV to +1072.6 mV. The oxidation mechanism proceeds in sequential steps, related to the catechol moiety, -OH groups in C ring and the resorcinol group. The oxidation process of the catechol moiety involves a two electron - two proton reversible reaction and forms o-quinone. This occurs first at low potential and is a reversible reaction. The hydroxyl group in the C ring and resorcinol group oxidise there after and undergo an irreversible reaction. UV-vis and FTIR spectroscopy were used to confirm the presence of catechin in the ethyl acetate extract of both plants.UV-visible spectroelectrochemistry confirmed the oxidation process of catechin at constant potential. Since C. mellei and C. quadrifidus were confirmed to contain flavonoids by ESI-LC-MS and electrochemical analysis, the antioxidant activity was further investigated using a SOD biosensor. The superoxide dismutase (SOD) enzyme was immobilised with 1% Nafion on a platinum electrode. Detection limit and sensitivity of the SOD biosensor were found to be 0.03918 μmol L-1 and 1.44 μA(μmol L-1)-1, respectively. The results showed that C. mellei and C. quadrifidus have antioxidant activity, with relative antioxidant capacity (RAC) of 24% and 42%, respectively. May 200

Restoration of invaded Cape Floristic Region riparian systems leads to a recovery in foliage-active arthropod alpha- and beta-diversity

The Cape Floristic Region of South Africa is a global biodiversity hotspot threatened by invasive alien plants (IAPs). We assessed the effect of plant invasions, and their subsequent clearing, on riparian arthropod diversity. Foliage-active arthropod communities were collected from two native and one invasive alien tree species. Alpha- and beta-diversity of their associated arthropod communities were compared between near pristine, Acacia-invaded and restored sites. Arthropod alpha-diversity at near pristine sites was higher than at restored sites, and was lowest at invaded sites. This was true for most arthropod taxonomic groups associated with all native tree species and suggests a general trend towards recovery in arthropod alpha-diversity after IAP removal. Overall, arthropod species turnover among sites was significantly influenced by plant invasions with communities at near pristine sites having higher turnover than those at restored and invaded sites. This pattern was not evident at the level of individual tree species. Although arthropod community composition was significantly influenced by plant invasions, only a few significant differences in arthropod community composition could be detected between restored and near pristine sites for all tree species and arthropod taxonomic groups. Assemblage composition on each tree species generally differed between sites with similar degrees of plant invasion indicating a strong turnover of arthropod communities across the landscape. Results further suggest that both arthropod alpha- and beta-diversity can recover after IAP removal, given sufficient time, but catchment signatures must be acknowledged when monitoring restoration recovery

Setting the scene for achievable post-2020 convention on biological diversity targets: a review of the impacts of invasive alien species on ecosystem services in Africa

Invasive alien species (IAS) are known to pose a serious threat to biodiversity, and reduce the ability of ecosystems to provide benefits to humans. In recognition of this threat and to address the impacts of IAS, Parties to the Convention on Biological Diversity (CBD) adopted Aichi Biodiversity Target 9, which is dedicated to the control or eradication of priority IAS and the management of their introduction pathways by 2020. The achievement of Target 9 relies strongly on the commitment and ability of Parties to set ambitious national or regional targets and achive them, the availability of information and the requisite expertise on invasion biology. Now that the global community is gearing for the post-2020 Biodiversity Framework, it is time to take stock and identify opportunities to improve the performance of the African region beyond 2020. We approached this task by reviewing information on the impacts of IAS on ecosystem services in Africa, as a large proportion of Africans directly rely on ecosystem services, particularly in rural areas. Furthermore, we assessed the expertise on IAS in Africa. Our data sources were National Reports of African countries to the CBD, as well as peer-reviewed scientific literature. National Reports under the CBD provide information on measures taken to implement the Convention at country level, as well as progress towards the achievement of set targets. We found National Reports for 48 (about 90%) countries of which 73% provided feedback on IAS indicating commitment to fight IAS. However, there were few studies within peer-reviewed scientific literature looking at impacts of IAS on ecosystem services in Africa and almost half of the authors were non-Africans. This alludes to limited scientific expertise to inform and support IAS management on the continent. Both the National Reports and scientific literature showed that provisioning services were the most negatively affected by IAS. Also, more than 100 species were listed as problematic. More efforts and resources are needed to document IAS impacts across different realms (e.g. marine, terrestrial and freshwater) and for sub-regional bodies so that more integrated strategies and approaches can be developed. This information is also needed to support the development and implementation of national legislative and regulatory initiatives, as well as to report on international obligations such as the Aichi Biodiversity Targets

Restoration of invaded Cape Floristic Region riparian systems leads to a recovery in foliage-active arthropod alpha- and beta-diversity

The Cape Floristic Region of South Africa is a global biodiversity hotspot threatened by invasive alien plants (IAPs). We assessed the effect of plant invasions, and their subsequent clearing, on riparian arthropod diversity. Foliage-active arthropod communities were collected from two native and one invasive alien tree species. Alpha- and beta- diversity of their associated arthropod communities were compared between near pristine, Acacia-invaded and restored sites. Arthropod alpha-diversity at near pristine sites was higher than at restored sites, and was lowest at invaded sites. This was true for most arthropod taxonomic groups associated with all native tree species and suggests a general trend towards recovery in arthropod alpha-diversity after IAP removal. Overall, arthropod species turnover among sites was significantly influenced by plant invasions with communities at near pristine sites having higher turnover than those at restored and invaded sites. This pattern was not evident at the level of individual tree species. Although arthropod community composition was significantly influenced by plant invasions, only a few significant differences in arthropod community composition could be detected between restored and near pristine sites for all tree species and arthropod taxonomic groups. Assemblage composition on each tree species generally differed between sites with similar degrees of plant invasion indicating a strong turnover of arthropod communities across the landscape. Results further suggest that both arthropod alpha- and beta- diversity can recover after IAP removal, given sufficient time, but catchment signatures must be acknowledged when monitoring restoration recovery.The DST/NRF Centre of Excellence in Tree Health Biotechnologyhttp://link.springer.com/journal/108412017-02-28hb2016Microbiology and Plant Patholog

Biodiversity and ecosystem services on the African continent – What is changing, and what are our options?

International audienceThroughout the world, biodiversity and nature's contributions to people are under threat, with clear changes evident. Biodiversity and ecosystem services have particular value in Africa– yet they are negatively impacted by a range of drivers, including land use and climate change. In this communication, we show evidence of changing biodiversity and ecosystem services in Africa, as well as the current most significant drivers of change. We then consider five plausible futures for the African continent, each underlain by differing assumptions. In three out of the five futures under consideration, negative impacts on biodiversity and ecosystem services are likely to persist. Those two plausible futures prioritizing environment and sustainability, however, are shown as the most likely paths to achieving long term development objectives without compromising the continent's biodiversity and ecosystem services. Such a finding shows clearly that achievement of such objectives cannot be separated from full recognition of the value of such services

Spectroelectrochemical determination of the antioxidant properties of carpobrotus mellei and carpobrotus quadrifidus natural products

Philosophiae Doctor - PhDSouth African Carpobrotus species have been found to contain hydrolysable tannins, various tlavonoids e.g. rutin and hyperoside, phytosterols and aromatic acids which have a diverse range of pharmacological properties including antimicrobial and, antioxidant activities. The main aim of the thesis was to determine the natural products in C. mellei and C. quadrifidus using chromatographic techniques and electrochemical analysis. The antioxidant activity of both Carpobrotus species was determined by using a superoxide dismutase (SOD) biosensor. ESI-LC-MS was used to separate and determine tlavonoids in C. mellei and C. quadrifidus. 8 tlavonoid compounds: catechin, epicatechin, epicatechin-epicatechin, coumarylquinic acid, isorhamnetin, quercetin-hexose (hyperoside), rutin and myricetin-deoxyhexose were identified. Cyclic and square wave voltammetry were used to detect tlavonoids from C. mellei and C. quadrifidus. Catechin was detected in the ethyl acetate extract of C. mellei and C. quadrifidus. The oxidation potential of the plant extracts were observed at +150.6 mV to +1072.6 mV. The oxidation mechanism proceeds in sequential steps, related to the catechol moiety, -OH groups in C ring and the resorcinol group. The oxidation process of the catechol moiety involves a two electron - two proton reversible reaction and forms o-quinone. This occurs first at low potential and is a reversible reaction. The hydroxyl group in the C ring and resorcinol group oxidise there after and undergo an irreversible reaction. UV-vis and FTIR spectroscopy were used to confirm the presence of catechin in the ethyl acetate extract of both plants. UV -visible spectroelectrochemistry confirmed the oxidation process of catechin at constant potential. Since C. mellei and C. quadrifidus were confirmed to contain flavonoids by ESI-LC-MS and electrochemical analysis, the antioxidant activity was further investigated using a SOD biosensor. The superoxide dismutase (SOD) enzyme was immobilised with 1% Nafion on a platinum electrode. Detection limit and sensitivity of the SOD biosensor were found to be 0.03918 umol L-' and 1.44 !lA (umol i.'):', respectively. The results showed that C. mellei and C. quadrifidus have antioxidant activity, with relative antioxidant capacity (RAC) of 24% and 42%, respectively

Tree health in near pristine, heavily invaded and restored riparian zones : the role of pests and fungal pathogens

Thesis (PhDConsEcol)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Riparian zones represent an essential component of landscape biodiversity and are ecologically and socio-economically significant habitats. The riparian zones in South Africa are however threatened by numerous invasive alien plants (IAPs). These are dominated by several fast-growing Australian Acacias that are responsible for widespread replacement of native species. The impacts of IAPs on native ecosystems are widely acknowledged and have justified extensive eradication programmes such as the Working for Water (WfW) programme. To date, the WfW programme has only been partially successful in the eradication of IAPs in riparian zones in the short-term. However, studies that assess the success of this initiative seldom focus on the health of riparian tree communities. This under-representation of riparian tree health studies is largely because of a lack of knowledge of the diversity and abundance of pests and disease-causing agents associated with native plants in these systems. The aim of this study was to examine the role that folivorous insects and fungal pathogens play in tree health of riparian tree communities that differ in invasion treatments. The predominant two native riparian tree species Brabejum stellatifolium and Metrosideros angustifolia and one alien tree species Acacia mearnsii were selected. Three perennial river systems within the South-Western Cape Province were selected as study areas. Within study areas, nine sites of three invasion treatments were chosen: three near pristine; three heavily invaded (predominantly Acacia mearnsii) and three restored sites (seven years after clearing of A. mearnsii). The following were done to accomplish the main aim: (i) foliage-active arthropod communities were collected from selected tree species and compared in terms of alpha- and beta-diversity within and among sites with different invasion treatments, (ii) the levels of damage caused by leaf pathogens and folivorous insects on focal tree species were determined and compared among sites (iii) leaf damage patterns were studied in context of native plant diversity and host abundance, (iv) the influence of changes in predatory arthropod numbers and community composition, as well as changes in total leaf nitrogen and phosphorus levels on the numbers of free-feeding folivorous insects (sap-sucking and leaf-chewing), in relation to the level of invasion were investigated, and (v) physiological parameters and nutrients in Brabejum stellatifolium leaves with varying levels of fungal infection and folivore damage were investigated. Heavily invaded sites had low arthropod species richness and abundance as compared to restored and near pristine sites, which were more similar. Beta-diversity was also influenced by invasion treatment. However few significant differences in arthropod community composition could be detected between restored and near pristine sites, and this pattern was similar for all tree species and arthropod taxonomic groups. Arthropod richness and community composition are therefore potential indicators of ecosystem health after restoration. Comparison of sites within each invasion treatment revealed that rivers have distinct signatures in terms of their arthropod communities. A study of different damage levels caused by leaf pathogens and folivorous insects showed that on native trees, folivore and fungal pathogen damage was significantly higher at restored and heavily invaded sites than at near pristine sites. For A. mearnsii, damage caused by both folivores and pathogens increased at heavily invaded sites, but returned to near pristine site levels at restored sites. Differences in native plant diversity did not explain these patterns, as restored sites had similar diversity levels to the near pristine sites. Surprisingly, as native host abundance increased, respective damage caused by fungal pathogens and folivores decreased. For A. mearnsii, increased host abundance was significantly correlated to increased folivore and pathogen damage. Insects and diseases not only reduced leaf area but also affected balances of physiological processes, thereby possibly delaying their recovery in a restoration scenario. Photosynthetic rate and other physiological parameters generally decreased with increasing damage severity caused by weevils and fungal pathogens in the canopy leaves of mature trees. Folivorous insect densities associated with tree species showed different responses to changes in predator densities and plant nutritional status. Brabejum stellatifolium and Acacia mearnsii had highest leaf nitrogen levels at restored and heavily invaded sites respectively, as compared to near pristine sites. Increased folivore abundance was only significantly and positively correlated to levels of leaf nitrogen content for B. stellatifolium and A. mearnsii. The results suggest that leaf nitrogen content is important for folivore food plant selection on B. stellatifolium and A. mearnsii, but not on M. angustifolia. There was no relationship between leaf damage and nitrogen levels or altered arthropod communities on M. angustifolia Therefore, individual plant species should be treated as separate entities when assessing plant health in a restoration scenario. Combined, these results indicate that; (i) native plant species and arthropod communities recover after alien plant clearing. Recovered arthropod assemblages may indicate the recovery of crucial processes like pollination, decomposition, and seed dispersal thereby strengthening the significance of conservation of arthropods from maintenance of biodiversity and ecosystem function and structure, (ii) the responses of sites to plant invasion treatment are site-specific, and therefore important to consider rivers individually when conceptualising activities of restoration, (iii) the role of fungal pathogens and folivorous insects in riparian ecosystems is more important than previously understood and there is a need for more research to provide better insights on why certain fungal pathogens and folivorous insects become major pests and diseases once the IAPs are cleared, (iv) folivorous insect responses to plant nutritional quality and predator densities is plant species-specific. Hence, individual plant species should be treated as separate entities when assessing plant health in a restoration scenario, and (v) insect feeding on vegetative parts of the plant and leaf fungal pathogens infections are damaging to the host plants. This may pose a serious threat to riparian tree communities already stressed by invasive alien plants, thereby delaying their recovery in a restoration scenario. Results of this study have potential to serve as valuable tools in riparian ecosystem management in South Africa.AFRIKAANSE OPSOMMING: Oewergebiede verteenwoordig ‟n noodsaaklike komponent van landskapbiodiversiteit en is vanuit ‟n ekologiese en sosio-ekonomiese oogpunt belangrike habitats. Die oewergebiede van Suid-Afrika word egter deur verskeie indringer uitheemse plante (IUP). Hierdie word gedomineer deur verskeie vinnig groeiende Australiese akasias wat verantwoordelik is vir die wydverspreide vervanging van inheemse spesies. Die impak van IUP‟e op inheemse ekosisteme word allerweë erken en het as regverdiging gedien vir uitgebreide uitroeiingsprogramme soos dié van Werk vir Water (Working for Water (WfW)). Tot op hede was die WfW-program slegs gedeeltelik suksesvol in die uitroei van IUP‟e in oewergebiede in die kort termyn. Studies wat die sukses van hierdie inisiatief ondersoek, fokus egter selde op die gesondheid van oewerboom-gemeenskappe. Hierdie onderverteenwoordiging van oewerboom-gesondheid is grootliks as gevolg van ‟n gebrek aan kennis oor die diversiteit en volopheid van plae en siekteveroorsakende agente wat met inheemse plante in hierdie stelsels geassosieer word. Die doel van hierdie studie was om die rol van blaarvretende insekte en swampatogene in die boomgesondheid van oewerboom-gemeenskappe wat op grond van die behandeling van indringers verskil, te ondersoek. Die vernaamste twee inheemse boomspesies op oewers is Brabejum stellatifolium en Metrosideros angustifolia, en een uitheemse boomspesie, Acacia mearnsii, is gekies. Drie standhoudende rivierstelsels in die Suidwestelike Kaap Provinsie is as studiegebiede gekies. Binne die studiegebiede is nege liggings van drie verskillende behandelings van indringers gekies: drie feitlik ongerep; drie wat swaar ingedring is (hoofsaaklik Acacia mearnsii) en drie gerestoureerde liggings (sewe jaar na die verwydering van A. mearnsii). Die volgende is onderneem om die doel te bereik: (i) blaar-aktiewe geleedpotige gemeenskappe is uit geselekteerde boomspesies versamel en vergelyk in terme van alfa- en beta-diversiteit binne en tussen liggings met verskillende behandelings van indringers, (ii) die vlakke van skade wat deur blaarpatogene en blaarvretende insekte op die boomspesies waarop gefokus is, veroorsaak is, is bepaal en tussen liggings vergelyk, (iii) die patrone van blaarskade is in die konteks van inheemse plantdiversiteit en gasheervolopheid ondersoek, (iv) die invloed van veranderinge in die getal roofgeleedpotiges en gemeenskapsamestelling, asook veranderinge in die totale vlakke van stikstof en fosfor in die blare, op die getal vryvoedende blaarvretende insekte (die wat sap suig en wat blare kou) is ondersoek in verhouding tot die vlak van indringing, en (v) fisiologiese parameters en voedingstowwe in Brabejum stellatifolium blare met verskillende vlakke van swambesmetting en blaarskade is ondersoek. Swaar ingedringde liggings het lae rykheid en volopheid van geleedpotige spesies gehad in vergelyking met gerestoureerde en feitlik ongerepte liggings, wat meer eenders was. Beta-diversiteit is ook deur die behandeling van indringers beïnvloed. Minder beduidende verskille in geleedpotige gemeenskapsamestelling kon egter tussen die gerestoureerde en feitlik ongerepte liggings waargeneem word, en hierdie patroon was eenders vir al die boomspesies en taksonomiese groepe van geleedpotiges. Die rykheid en gemeenskapsamestelling van geleedpotiges is dus potensiële aanwysers van ekosisteemgesondheid ná restourasie. Die vergelyking van liggings binne elke verskillende behandeling van indringers het getoon dat riviere duidelike „handtekeninge‟ het in terme van hulle geleedpotige gemeenskappe. ‟n Studie van verskillende vlakke van skade wat deur blaarpatogene en blaarvretende insekte veroorsaak is, het getoon dat blaar- en patogeenskade op inheemse bome beduidend hoër was op die gerestoureerde en swaar ingedringde liggings as op die feitlike ongerepte liggings. Vir A. mearnsii het die skade wat deur beide blaarvreters en patogene veroorsaak is, noemenswaardig op die hoogs ingedringde liggings vermeerder, maar dit het omgekeer na feitlik ongerepte vlakke op die gerestoureerde liggings. Verskille in inheemse plantdiversiteit het nie hierdie patrone verklaar nie, aangesien gerestoureerde liggings soortgelyke diversiteitsvlakke gehad het as die feitlik ongerepte liggings. Wat verbasend was, was dat soos inheemse gasheer volopheid toegeneem het, die skade wat deur swampatogene en blaarvreters veroorsaak het, onderskeidelik verminder het. Vir A. mearnsii was ‟n toename in gasheervolopheid beduidend gekorreleer met ‟n toename in blaar- en patogeenskade. Insekte en siektes het nie net blaaroppervlak verminder nie, maar het ook die balanse van fisiologiese prosesse beïnvloed en het daardeur moontlik hul herstel in ‟n restourasie-scenario vertraag. Die tempo van fotosintese en ander fisiologiese parameters het oor die algemeen verminder met ‟n verhoging in die erns van die skade wat deur kalanders en swampatogene in die blaardak van volwasse bome veroorsaak is. Die digtheid van blaarvretende insekte wat met boomspesies verband hou, het verskillende reaksies op veranderinge in roofdierdigthede en plant voedingstatus getoon. Brabejum stellatifolium en Acacia mearnsii het die hoogste blaarstikstofvlakke gehad in die gerestoureerde en swaar ingedringde liggings onderskeidelik, in vergelyking met die liggings wat feitlik ongerep was. Verhoogde blaarvretervolopheid was slegs vir B. stellatifolium en A. mearnsii beduidend en positief gekorreleer met vlakke van stikstofinhoud in die blare. Die resultate stel voor dat blaar stikstofinhoud belangrik is vir blaarvretende voedselplantseleksie op B. stellatifolium en A. mearnsii, maar nie op M. angustifolia nie. Daar was geen verhouding tussen blaarskade en stikstofvlakke of veranderde geleedpotige gemeenskappe op M. angustifolia nie. Individuele plantspesies moet dus as aparte entiteite beskou word wanneer plantgesondheid in ‟n restourasie-scenario geassesseer word. Saam toon hierdie resultate dat: (i) inheemse plantspesies en geleedpotige gemeenskappe herstel ná uitheemse plante opgeruim is. Groepe herstelde geleedpotiges dui moontlik op die herstel van belangrike prosesse soos bestuiwing, ontbinding, en saadverspreiding, wat dus dui op hoe belangrik die bewaring van geleedpotiges is vir die behoud van biodiversiteit en ekosisteemfunksie en -struktuur, (ii) die reaksies van liggings op die behandeling van plant indringers is liggingspesifiek en dit is dus belangrik om riviere individueel te oorweeg wanneer restourasie-aktiwiteite konseptualiseer word, (iii) die rol van swampatogene en blaarvretende insekte in oewer-ekosisteme is belangriker as voorheen begryp en dit is nodig dat meer navorsing onderneem word om beter insigte te verkry in hoekom sekere swampatogene en blaarvretende insekte vername plae en siektes word wanneer IUP‟e opgeruim word, (iv) blaarvretende insekresponse op die voedingskwaliteit van plante en roofdierdigtheid is plantspesie spesifiek. Dus moet individuele plantspesies as afsonderlike entiteite behandel word wanneer plantgesondheid in ‟n restourasie-scenario geassesseer word, en (v) insekvoeding op vegetatiewe plantdele en blaar swampatogeniese infeksies beskadig die gasheerplante. Dit kan ‟n ernstige bedreiging inhou vir oewerboomgemeenskappe wat reeds onder stres is as gevolg van indringer uitheemse plante en wat dus hulle herstel in ‟n restourasie-scenario kan vertraag. Die resultate van hierdie studie het die potensiaal om as belangrike gereedskap in oewer-ekosisteembestuur in Suid-Afrika te dien

Studies on some biologically active natural products from Tulbaghia Alliacea

Doctor EducationisIt is believed that early humans had knowledge of how to use traditional medicinal plants, but the knowledge has been partially lost as society underwent various changes leading to new civilizations. The aim of this study was to isolate and identify natural product constituents from Tulbaghia Alliacea. There has not yet been any scientifically conducted investigation on the plant. Tulbaghia Alliacea is used for fever and colds, asthma, pulmonary tuberculosis and stomach problems.South Afric