The search for a novel pharmacotherapy from medicinal plants for neurodegenerative disorders has significantly advanced. Therefore, the present study was performed to evaluate the anticholinesterase activities of one hundred medicinal plants in Korea, where Terminalia chebula (T. chebula) fruits showed significant acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitions. Further bioassay monitored phytochemical exploration led to the isolation of 1,2,3,4,6-penta-O-galloyl-β-d-glucose (compound 1), which showed significant AChE and BChE inhibitory effects with IC50 values of 29.9 ± 0.3 µM and 27.6 ± 0.2 µM, respectively. The inhibitory effect of compound 1 towards acetylcholinesterase was also evaluated using TLC and compared with tacrine as the positive control; the positive effect was confirmed. Furthermore, compound 1 also displayed strong antioxidant activity by the FRAP assay (IC50 = 4.6 ± 0.2 µM). In conclusion, compound 1 may prove to be a potential natural anti-Alzheimer source based on noteworthy AChE and BChE inhibitions, and strong antioxidant activity.
The impacts of invasive alien plants (IAP) and their subsequent clearing by the Working for Water Programme (WfW) on (a) overstorey (woody plant) vegetation structure, (b) invasion intensity (overstorey aerial cover of woody alien plants) and (c) ground cover, in a temperate to subtropical riparian ecosystem were studied in 1996/7 and again in 2005, in order to provide a longer-term perspective on the effectiveness of WfW clearing. Forty 1000 m2 plots were surveyed and resurveyed, comparing between (a) higher altitude Grassland and lower altitude Savanna, (b) high (> 50% invasion intensity) versus low (< 50% invasion intensity) alien invasion sites, and (c) WfW cleared versus uncleared sites (the three ‘treatments’). Pre-clearing estimates from cut stumps in 1996/7 indicated high alien invasion intensities of 72 ± 8% in Grassland and 69 ± 11% in Savanna. From 1996/7 to 2005 there was a large decrease in aerial cover of alien trees of > 5 m and to a lesser extent 2–5 m in height, and a large increase in alien plants of < 2 m. Hence WfW was initially successful, with the original tall Eucalyptus grandis tree layer largely removed. However, total invasion intensity remained unchanged over the first decade (30.4 ± 4.6% in 1996/7, 31.9 ± 3.2% in 2005). From 1996/7 to 2005, grass and herbaceous cover decreased, while bare soil and litter increased, indicating reduced surface stability. This was in response to (a) the major flood event of February 2000, (b) the effects of IAP invasions and (c) WfW clearing. Total ground vegetation cover was negatively related to alien aerial cover in both biome reaches in 1996/7 and 2005. By 2005, there were no longer any differences in the aerial cover of woody alien plants in response to the original 1996/7 invasion intensity or clearing ‘treatments’, and hence progressive homogenization of IAP cover. Aerial cover of woody indigenous plants also responded negatively to increasing alien aerial cover in 1996/7 and 2005 in both Savanna and Grassland. In conclusion, the nature of the IAP problem has changed from dealing largely with relatively few large E. grandis trees in the mid-90s, to the present large suite of invasive species with numerous smaller individuals. This has implications for the time needed for clearing. This is one of few studies to have assessed the initial and longer-term (1995–2005) effectiveness of WfW clearing operations. It shows that improved IAP clearing protocols are needed. More follow-up treatments are recommended to ‘capture’ alien resprouts and new seedlings before they establish and reproduce. Secondly, integrating clearing with restoration of the tall indigenous riparian canopy tree species in heavily invaded sites would help to shade out many alien recruits.
The number of botany students, botany classes, botany departments in universities and botanists attending conventions has been declining over many years in North America. This is part of a general trend throughout the field of organismal biology, not just botany. The history leading up to the situation today in North America, is discussed and reasons are given for this trend over the last century of time. Seven ways to keep botany a viable occupation are discussed otherwise botany, in the 21st century, may go the way of the dinosaur.
Investigation of the ethyl acetate leaf extract of Trichilia dregeana for anti-inflammatory activity using bioassay-guided fractionation led to the isolation of cycloart-23-ene-3,25-diol. The compound was tested for anti-inflammatory activity using the cyclooxygenase assays (COX-1 and COX-2), anti-cholinesterase activity using the microplate assay and investigated for potential mutagenic effects using the Ames test. In the cyclooxygenase assays, cycloart-23-ene-3,25-diol showed inhibitory activity against COX-2 (80%) at a concentration of 100 μM (IC50 was 40 μM). At the same concentration, the compound showed weak activity against COX-1 (56%) with an IC50 value of 97 μM. In the anti-cholinesterase test, the compound had a weak inhibitory effect against acetylcholinesterase (53%) when tested at a concentration of 0.4 mM. No potential mutagenic effects were observed in the Salmonella microsome assay (TA 98). Isolation of the bioactive compound and the activity observed in this study may explain in part the use of the tree in traditional medicine as a crude anti-inflammatory drug.
An account is given of pseudo-vivipary (vegetative apomixis) in South African Cyperaceae. Taxa exhibiting this reproductive strategy are tabled. Stress that effects plant population deterioration and eventual non-survival is attributed as causative; in particular water stress, either as maintained inundation or undue depletion. Habitat conditions appear to govern the balance between fruiting and pseudo-vivipary. This balance is changeable from season to season, area to area, species to species and within species. The viability of seeds within fruits formed upon inflorescences that also are in part pseudo-viviparous has not been tested.
The study evaluated the forage productivity and water use of four leguminous grasses namely alfalfa (Medicago sativa L.), vetch (Astragalus adsurgens Pall.), sainfoin (Onobrychis viciaefolia Scop.) and Lespedeza davurica grown in semiarid region on the Loess Plateau of China. The experiments were conducted in the years 2001–2004 where each grass was grown on four 7 m × 6 m experimental plots. The aboveground biomass production considered the sum of dry litter and standing parts was measured every year at the end of growth season. Soil water measurements were made from soil drill (Ø4 cm cores) every month for soil extending to a depth of 300 cm in the first and second year and up to 500 cm in the rest of the period.The yearly biomass production, soil water storage volume as well as its change, monthly rainfall and water consumption of each grass were statistically analyzed. A linear correlation was used to analyze the biomass production and total water used in evapo-transpiration. Stepwise regression was performed to evaluate the relationship between biomass production and monthly rainfall and soil water storage to explain the differences among grasses. The analysis showed that biomass production of both the vetch and L. davurica were significantly (P < 0.05) correlated with total precipitation of April to June while that of sainfoin and alfalfa was significantly (P < 0.05) correlated with total precipitation of the growth season (April to October). All four grasses exhibited positive (P < 0.05) aboveground biomass production response to soil water usage, but there is difference among. Alfalfa, vetch and sainfoin had a drying effect at a depth less than 2.0 m and consistently showed profiles with the lowest soil water content. Profiles with the lowest soil water content also had greater herbage growth and greater depths of water extraction.
Large quantities of plants are traded annually in South Africa's traditional medicine or ‘muthi’ markets. A resource in high demand in the Faraday (Johannesburg) and Warwick (Durban) markets is uMavumbuka, a root holoparasite usually identified as either Hydnora africana Thunb. or Sarcophyte sanguinea Sparrm. subsp. sanguinea. However, rhizomes regularly observed in Faraday between 1994 and 2008 did not resemble either species, thereby suggesting that a third, and undocumented, species was being harvested. This was confirmed when the rhizomes were identified as H. abyssinica A.Br. by an American parasitic plant expert. An ethno-ecological study was initiated to verify its occurrence in selected muthi markets. The study further aimed to investigate the distribution of H. abyssinica through trader interviews, host species localities and some previously misidentified herbarium specimens. The study revealed that H. abyssinica was the only uMavumbuka species present in Faraday and Warwick in 2009. Furthermore, the rhizomes were being harvested in KwaZulu-Natal—an area not previously known to be part of its distribution range. Re-evaluated herbarium vouchers and recent photographs taken in the Kruger National Park have confirmed that H. abyssinica occurs in KwaZulu-Natal, Limpopo, Mpumalanga, Gauteng and Swaziland and hence eastern southern Africa. Fragments of Acacia xanthophloea Benth. roots were identified on 93% of the samples that had host roots attached, and we suspect that H. abyssinica follows the distribution of A. xanthophloea in suitable habitats north from KwaZulu-Natal and adjoining the South African border with Swaziland and Mozambique. Acacia karroo Hayne and A. grandicornuta Gerstner have also been positively identified as host species in South Africa from herbarium records. Plant harvesters in the markets cited the common names of several other species that uMavumbuka “grows under” that may be identified as hosts to H. abyssinica in the future. The collection of specimens in areas identified by the harvesters and in areas of suitable habitat is important to verify the occurrence, distribution and habitat of H. abyssinica in eastern southern Africa.Research Highlights►Hydnora abyssinica rhizomes were identified in traditional medicine markets in South Africa ►Rhizomes harvested in KwaZulu-Natal, further east than known from published distribution records ►Some H. abyssinica herbarium specimens had been incorrectly identified as H. africana ►Ethno-ecological validation of the occurrence of H. abyssinica in South Africa ►Distribution map updated to include new herbarium evidence and plant sightings
We examined pollination biology of Acacia nigrescens Oliver, flowering at the end of the dry season in Kruger National Park, South Africa. A. nigrescens produces small quantities of concentrated nectar, and has abundant pollen resources available to potential pollinators. We recorded large numbers of insect visitors and most fruit set on the tops of trees, beyond the reach of ungulate browsers such as giraffes (which consume a substantial proportion of A. nigrescens flowers). Wasps, flies and solitary bees were the most numerous visitors and are likely to play a significant role in pollination.
Salinity stress remains one of the world's oldest and the most serious environmental problem, which substantially hampers crop productivity in arid and semi arid areas. This problem has been addressed by expensive and energy depleting soil reclamation measures. However, a cheaper sustainable alternative lies in the development of salt tolerant crop cultivars. In this study, we tested salinity tolerances of 98 wheat accessions originating from Pakistan, India and Mexico from measurements of their shoot and root growth in cultures containing 0, 10 and 15 dS/m of NaCl. Genotypic responses were compared from measures of absolute and relative salt tolerances. Differential growth reductions to increased salinity were observed in the wheat accessions with those originating from Mexico exhibiting significantly greater salinity tolerances overall than those originating from Pakistan. No significant correlations were found between plant salinity tolerances and their vigour as measured by relative growth rates in controls; with relative growth rates of different genotypes grouped on the basis of different geographic origin and different genes of various stresses also not differing significantly from each other. Estimated broad-sense heritabilities indicated that phenotypic variance exceeded that of genotypic by nearly two orders of magnitude. These findings indicate that the genetic improvement of salt tolerance in wheat through selection will be problematic due to masking effects of the environment, and imply rigorous and careful selection of salt tolerant accessions.
The effect of employing a RITA® system in one or both of somatic embryo induction and germination stages was investigated, and it was deemed far superior to a semi-solid (agar) substrate in terms of in vitro plant yields for sugarcane genotype N41. Approximately 18,000 plants/leaf roll were obtained in vitro in 12 weeks, when both culture stages were undertaken using temporary immersion, compared with approximately 2000 plants/leaf roll produced on semi-solid medium. However, due to hyperhydricity, only ~ 34% of the plants produced in RITA® survived acclimatization. To overcome this, and realize the potential yields of the RITA® system, various culture conditions were investigated, viz. nutrient and sucrose supplies, a rockwool substrate and the immersion regime. Of these, increasing the resting time between immersions from 1 min/12 h to 1 min/72 h, and lowering MS nutrient to 1/2 strength, proved the most beneficial, resulting in 60% acclimation success. Genetic fidelity of these plants was investigated by AFLP analyses where only 0–0.9%, of polymorphic bands were scored compared with the conventionally- propagated N41 control. Phenotypic characterization of plants grown in the field for 6 months showed that, although all in vitro derived plants had a reduced stalk diameter relative to the control, there were no significant differences regarding stalk mass, height and population.Research highlights► Results confirm that in vitro yields are greater RITA® vessels instead of agar. ► 1/2 MS and 1 min/72 h immersion regime overcame shoot hyperhydricity in RITA®. ► The benefit of such a long resting time between immersions has not been reported. ► The established protocol yielded ± 6000 acclimated plants/leaf roll. ► AFLP and phenotypic tests showed few differences between ex-vitro and control plants.
Vernonia colorata is used throughout Africa to treat various ailments. Its antiplasmodial activity has been widely reported. Using bioassay-guided fractionation, we isolated two antiplasmodial compounds — vernolide (IC50 = 1.87 μg/ml) and vernodalin (IC50 = 0.52 μg/ml) with selective indices of 1.02 and 2.79 for vernolide and vernodalin respectively. These compounds are non-specific towards parasites.
This study was designed to evaluate the antimycobacterial, anti-reverse transcriptase, radical scavenging and antitumor activities of the methanol extracts of the twigs and leaves of three plants of the genus Treculia, namely Treculia obovoidea, Treculia africana and Treculia acuminata. The DPPH radical scavenging assay was used for the antioxidant test while the crown gall tumor assay was used for antitumor evaluation. The INT colorimetry and microplate Alamar blue assay (MABA) were used for antimycobacterial investigations. The results of the antimycobacterial assays, showed that the leaf crude extract of the three Treculia species as well as that from the twigs of T. africana were able to prevent the growth of Mycobacterium smegmatis and Mycobacterium tuberculosis. The lowest MIC value (19.53 µg/ml) was recorded with extract of the leaves of T. africana on M. smegmatis, and those of T. africana and T. acuminata against M. tuberculosis. All studied extracts inhibited at various extents the anti-reverse transcriptase activity at 200 µg/ml. The best IC50 values, 31.1 µg/ml, 29.5 µg/ml and 21.1 µg/ml were recorded respectively with the extracts of the leaves of T. obovoidea, T. acuminata and T. africana. Results of the antioxidant activity indicate a dose-dependent ability of sample to scavenge the DPPH radical. The lowest IC50 values were obtained with extracts of the leaves of T. acuminata (56.3 µg/ml) and T. obovoidea (55.9 µg/ml). Pronounced tumor-reducing activity was observed with the extracts of the leaves of T. africana (89.67%), T. acuminata (92.16%), T. obovoidea (96.67%) and that of the twigs of T. acuminata (87.18%). The overall results provide evidence that plants of the genus Treculia might be potential sources of antitubercular, anti-HIV and antitumor compounds.
This study was designed to evaluate the antimycobacterial, antibacterial and antifungal activities of the methanol extract from the stem bark of Thecacoris annobonae Pax & K. Hoffm, that of aristolochic acid I (1) and other isolated compounds. The microplate alamar blue assay (MABA) and the broth microdilution method were used to determine the minimal inhibitory concentration (MIC) and minimal microbicidal concentration (MMC) of the above samples. The H+-ATPase-mediated proton pumping assay was used to evaluate a possible mechanism of action for both the methanol extract and aristolochic acid I. The results of the MIC determinations showed that the methanol extract and aristolochic acid I prevent the growth of all studied organisms. The results obtained in this study also showed that the methanol extract as well as aristolochic acid I inhibited the H+-ATPase activity. The overall results provided evidence that the methanol extract of T. annobonae might be a potential source of new antimicrobial drug against tuberculosis, and some bacterial and fungal diseases, but should be consumed with caution, bearing in mind that the main active component, aristolochic acid I is a potentially toxic compound.
The aim of this study was to evaluate the antimicrobial activity of the crude extract of the twigs of Dorstenia turbinata (DTT) as well as that of five of the nine compounds isolated from this extract, namely 5-methoxy-3-[3-(ß-glucopyranosyloxy)-2-hydroxy-3-methylbutyl]psoralen (1), 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)psoralen (2), (2′S, 3′R)-3′-hydroxymarmesin (3), 4-hydroxy-3-methoxybenzaldehyde (4) and 4-methoxyphenol (5). Gram-positive, Gram-negative bacterial species as well as fungi were used. The agar disc diffusion test was used to determine the sensitivity of the tested samples while the well micro-dilution was used to determine the minimal inhibition concentrations (MIC) and the minimal microbicidal concentration (MMC) of the active samples. The results of the disc diffusion assay showed that the crude extract (DTT), compounds 1 to 3 were able to prevent the growth of all the tested pathogens at the tested concentrations. Compounds 4 and 5 showed moderate and selective activities. The results of MIC determinations indicated values ranging from 19.53 to 78.12 µg/ml for the DTT and from 9.76 to 78.12 µg/ml for compound 2. The MIC values recorded on 91% of the tested organisms for compounds 1 and 3. The lowest MIC value for the crude extract of D. turbinata (19.53 µg/ml) was noted on Trichophyton rubrum and Escherichia coli. The corresponding value for the tested compounds (9.76 µg/ml) was obtained with 2 and 3 on T. rubrum. The antimicrobial activity of this plant as well as that of compounds 1-2 is being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extracts from DTT as well as some of the isolated compounds in the treatment of bacterial and fungal infections.
The methanol extract from the stem bark of Terminalia superba (TSB), fractions (TSB1–7) and two compounds isolated following bio-assay guided fractionation namely 3,4′-di-O-methylellagic acid 3′-O-β-d-xylopyranoside (1) and 4′-O-galloy-3,3′-di-O-methylellagic acid 4-O-β-d-xylopyranoside (2) were evaluated for their antimycobacterial, antibacterial and antifungal activities. The broth microdilution, the microplate Alamar Blue assay (MABA) and the agar disc diffusion methods were used for the investigations. The results of the antimycobacterial assays showed that the crude extract, fractions TSB5–7 and compound 1 were able to prevent the growth of all the studied mycobacteria. The lowest minimal inhibitory concentration (MIC) value of 39.06 µg/ml for this extract was recorded on both M. smegmatis and M. tuberculosis MTCS2. The corresponding values were 19.53 µg/ml and 4.88 µg/ml for fractions and compounds respectively. The MIC determination results on other organisms indicated values ranging from 19.53 to 78.12 µg/ml for TSB and compound 2 on 90.9% of the tested organisms, meanwhile compound 1 as well as fractions TSB 6 and 7 exhibited detectable MIC values on all studied microorganisms. The overall results provide promising baseline information for the potential use of the crude extract from T. superba, fractions 6–7 and the tested compounds in the treatment of tuberculosis, bacterial and fungal infections.
Lippia javanica and Lippia scaberrima are used as herbal remedies and are commercially traded as health teas in southern Africa under the brands “Mosukujane” and “Musukudu”, respectively. This study evaluates the relationship between the presence of phenolic compounds and the antioxidant activities of infusions prepared from four Lippia species (L. javanica, L. scaberrima, L. rehmannii and L. wilmsii) indigenous to South Africa. The antioxidant activities of the infusions, determined by the 2,2-diphenylpycrylhydrazyl (DPPH) method, were also compared to those of popular black, green and herbal tea brands. Of the four indigenous species, infusions of L. javanica and L. wilmsii exhibited the highest antioxidant activities (EC50: 358 and 525 µg/ml, respectively) and contained the most phenolic compounds (14.8 and 14.5 mg/ml of dry weight gallic acid equivalent, respectively). Antibacterial activities of methanolic extracts of the four Lippia species were determined against four human pathogens (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa). The extract of L. javanica was the most active against all the pathogens tested. Those Lippia species (L. javanica and L. wilmsii) previously reported to produce higher levels of the pharmacologically active phenylethanoid glycosides verbascoside and isoverbascoside, portrayed stronger antioxidant and antibacterial activities. This study gives credence to the use of infusions of these Lippia species for their general health benefits.
An investigation of leaf indumentum, the identification of the essential oil components and assessment of various biological activities of Salvia albicaulis and S. dolomitica essential oils were carried out. Non-glandular and both peltate and capitate glandular trichomes were identified using scanning electron microscopy. The essential oil of S. albicaulis was dominated by oxygen-containing sesquiterpenes (47%), with viridiflorol (25%), 1,8-cineole (9%) and limonene (9%) as major components. S. dolomitica oil was mainly composed of oxygen-containing monoterpenes (72%), with geraniol (20%), linalyl acetate (20%) and linalool (17%) being the major components. The in vitro pharmacological properties of the essential oils were also evaluated. Antibacterial activity was assessed against Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 11778), Escherichia coli (ATCC 8739) and Klebsiella pneumoniae (NCTC 9633). The oils showed poor activity against E. coli (MIC value > 32 mg ml− 1), while moderate activity was obtained against the other pathogens (MIC values between 2 and 12 mg ml− 1). The results of the antiplasmodial activity evaluated against the chloroquine-resistant FCR-3 strain showed that both S. albicaulis and S. dolomitica essential oils exhibited antiplasmodial activity with IC50 values of 6 ± 2 and 5 ± 1 μg ml− 1, respectively. The two oils also displayed anti-inflammatory activity (IC50 value: 39 ± 4 and 65 ± 6 μg ml− 1, respectively). Poor anti-oxidant activity was obtained against the DPPH·and the ABTS·+ radicals (IC50 values > 100 μg ml− 1). The toxicity profile of the two oils evaluated against the human kidney epithelium cells indicated some degree of toxicity in comparison to 5′-fluoro-uracil.
Eucomis species having considerable horticultural potential are used in African traditional medicine to treat various ailments. The effects of environmental and physiological parameters on the initiation and growth of bulblets using leaf explants were investigated. These included the effect of temperature (10, 15, 20, 25 and 30 °C), photoperiod (8 h light, 16 h light, continuous light and continuous dark), carbohydrates (sucrose, fructose and glucose) at different concentrations and combinations as well as various plant growth regulators; gibberellic acid (GA3), indole-3-butyric acid (IBA), napthaleneacetic acid (NAA), N6-benzyladenine (BA), zeatin and others. Liquid shake and liquid static cultures versus solid cultures were investigated. Maximum number of bulblets per leaf explant was obtained at 20 °C, with an average of 3 bulbs per leaf explants and a bulblet mass of 57 mg. An 8 h light cycle produced 1.38 bulbs per leaf explant, at a mass of 42 mg. Fructose at 3% produced an average of 1.18 bulbs per leaf explant, 3.39 mm wide and weighing 56.6 mg. Of the plant growth regulators, 4.90 µM IBA was found to be the optimum treatment for bulblet induction, with an average bulb diameter of 4.36 mm and a mean bulblet mass of 79.07 mg. Liquid shake cultures exhibited poor growth while bulblet, leaf and root growth was improved in liquid static cultures. Successful micropropagation from leaf explants established that leaf explants can be used as an alternative explant source to bulbs. This protocol allows for the fast and economic mass propagation of Eucomis plants.
Boophone disticha L. Herb (Amaryllidaceae) is used in traditional medicine for treatment of painful wounds, headaches, skin disorders, inflammatory conditions, rheumatic pains and anxiety. At least eight alkaloids have been characterized and reported in the literature. Of these buphanidrine and buphanamine have affinity to the serotonin transporter (SERT). Alkaloids from other Amaryllidaceae species have also shown affinity to SERT. In this study, an ethanol extract was prepared from dry bulbs. Through HPLC–UV separation five peaks were collected and characterized by LC-MS and 1H NMR and led to the identification of crinine, buphanamine, buphanidrine, distichamine and buphanisine. The activity of these compounds was tested in a binding assay using [3H]-citalopram as ligand and a functional SERT inhibition assay utilizing COS-7 cells expressing hSERT. The four active compounds, buphanamine, buphanidrine, buphanisine and distichamine, had IC50-values of 55 µM, 62 µM, 199 µM and 65 µM respectively, in the binding assay. The alkaloids also showed activity in the functional assay, buphanidrine and distichamine being the most active with IC50-values of 513 µM and 646 µM, respectively.
The genus Artemisia consists of about 500 species, occurring throughout the world. Some very important drug leads have been discovered from this genus, notably artemisinin, the well known anti-malarial drug isolated from the Chinese herb Artemisia annua. The genus is also known for its aromatic nature and hence research has been focussed on the chemical compositions of the volatile secondary metabolites obtained from various Artemisia species. In the southern African region, A. afra is one of the most popular and commonly used herbal medicines. It is used to treat various ailments ranging from coughs and colds to malaria and diabetes. Although it is one of the most popular local herbal medicines, only limited scientific research, mainly focussing on the volatile secondary metabolites content, has been conducted on this species. The aim of this review was therefore to collect all available scientific literature published on A. afra and combine it into this paper. In this review, a general overview will be given on the morphology, taxonomy and geographical distribution of A. afra. The major focus will however be on the secondary metabolites, mainly the volatile secondary metabolites, which have been identified from this species. In addition all of the reported biological activities of the extracts derived from this species have been included as well as the literature on the pharmacology and toxicology. We aim at bringing together most of the available scientific research conducted on this species, which is currently scattered across various publications, into this review paper.
Artemisia afra is one of the most widely used medicinal plants in African traditional medicine and is commonly administered in polyherbal combinations to treat respiratory infections. Focussing on plant volatiles, the aim of this study was to provide scientific evidence for the antimicrobial activity of A. afra (principle plant) in combination with essential oils from three medicinal aromatic plants; Agathosma betulina, Eucalyptus globulus and Osmitopsis asteriscoides. In vitro minimum inhibitory concentration (MIC) assays were undertaken on four pathogens (Enterococcus faecalis ATCC 29212, Moraxella catarrhalis ATCC 23246, Klebsiella pneumoniae NCTC 9633 and Cryptococcus neoformans ATCC 90112) to determine antimicrobial efficacy of the oils and their combinations. The fractional inhibitory concentration (FIC) and isobolograms were used to interpret pharmacodynamic interactions such as synergy, antagonism or additive profiles. The antimicrobial activity of the individual oils mostly displayed moderate activity. Predominantly, additive interactions were noted. The most prominent synergistic interaction (FIC value of 0.5) was observed when A. afra was combined with O. asteriscoides in the 8:2 ratio (eight parts A. afra with two parts O. asteriscoides) against C. neoformans. No antagonistic interactions were evident.
The impacts of habitat fragmentation and reduced population sizes on ecological processes deserve more attention. In this study we examine pollination in rural and urban populations of Brunsvigia litoralis (Amaryllidaceae), an endangered endemic and a flagship species for plant conservation in South Africa. B. litoralis has flowers conforming to the bird-pollination syndrome, but the only flower visitor at the urban sites, the Greater Double-collared Sunbird (Cinnyris afra) (1.6 visits/flower/hour), is unable to access the nectar in the usual way due to a long perianth tube (38.8 mm) and resorts to robbing. Supplemental hand pollination was used to test for pollen limitation of seed set at the urban sites flowers were pollen-supplemented. Seed set in supplemented plants increased by more than an order of magnitude relative to controls. The longer-billed Malachite Sunbird (Nectarinia famosa) was observed as the sole pollinator of B. litoralis at the rural site where seed set was significantly higher. Although B. litoralis plants are long lived, the absence of pollinators in these urban fragments might place populations at an extinction risk.Research highlights► Brunsvigia litoralis is specialized for pollination by the Malachite Sunbird, Nectarinia famosa. ► Shorter-billed Greater Double-collared Sunbird, Cinnyris afra, obtained nectar through robbing. ► Low seed set in small, urban, Malachite Sunbird absent populations.
Riparian zones are complex disturbance-mediated systems that are highly susceptible to invasion by alien plants. They are prioritized in most alien-plant management initiatives in South Africa. The current practice for the restoration of cleared riparian areas relies largely on the unaided recovery of native species from residual individuals and regeneration from soil-stored seed banks. Little is known about the factors that determine the effectiveness of this approach. We need to know how seed banks of native species in riparian ecosystems are affected by invasion, and the potential for cleared riparian areas to recover unaided after clearing operations. Study sites were selected on four river systems in the Western Cape: the Berg, Eerste, Molenaars and Wit Rivers. Plots were selected in both invaded (> 75% Invasive Alien Plant (IAP) canopy cover) and un-invaded (also termed reference, with < 25% IAP canopy cover) sections of the rivers. Replicate plots were established at two elevations (mountain stream and foothill) and in three moisture regimes (dry, wet and transitional bank zones). Soil samples were taken, surveys were done of the aboveground vegetation, and comparisons were made between invaded and non-invaded sites. Seed bank communities were clearly defined by the state of the river (reference or invaded) and moisture regimes (wet and dry bank zones). Comparisons at a landscape scale showed no clear pattern, as the composition of both aboveground and seed bank species assemblages were strongly influenced by site history, especially the extent of invasion and fire frequency. Even after heavy and extensive invasion, riparian seed banks have the potential to initiate the restoration process. However, not all riparian species are represented in the seed bank. Based on these results, restoration recommendations are outlined for alien-invaded riparian zones.
Annual stem circumference growth rates of 23 woody species of the Sand Forest and woodland in Maputaland are presented for the first time. The rare Sand Forest, has been identified as an endemic, diverse vegetation type that is under threat from land transformation and human utilisation outside conservation areas. The growth rate of the selected woody species was evaluated over a 71-month survey that encompassed climatic extremes, oscillating from heavy rainfall to drought in a short period of time. The mean annual stem circumference growth rate among the investigated species varied thirteen fold, from a low of 2.04 mm/yr for Brachylaena huillensis to 26.28 mm/yr for Garcinia livingstonei. When the data of all species were considered, there was a significant positive relationship between stem circumference and growth rate, but no significant relationship between wood density and growth rate. The present results suggest that there is no significant difference in terms of mean annual growth rate between the Sand Forest and woodland vegetation types. In general, woodland species showed larger fluctuations in growth rate and the temporal pattern of Sand Forest species seemed to lag behind that of the woodland species. These trends can in part be ascribed to the woodland species all being deciduous, whereas the Sand Forest suite included both deciduous and evergreen species. Annual growth rates measured from dry season to dry season were not related to the seasonal rainfall pattern, but appeared to be highly dependent on the water availability at the time of the enumeration. The larger size classes reacted sooner to decreased water availability and a reduction in growth of larger trees was accompanied by an increase in growth in the smaller size classes.
Petroleum ether, dichloromethane, ethanol (70%) and water extracts of 12 South African plants were screened using microdilution assays against Gram-positive (Bacillus subtilis, Staphylococcus aureus), Gram-negative (Escherichia coli) bacteria, and the fungus Candida albicans. No antimicrobial activity was observed in water extracts. The ethanol extracts of Becium obovatum leaves showed the best antibacterial activity with a minimum inhibitory concentration value of 0.074 mg/ml against B. subtilis. The petroleum ether extract of leaves of Cucumis hirsutus, Haworthia limifolia and Protea simplex showed good antibacterial activity with MIC values ranging between 0.098 and 0.780 mg/ml against all the test bacteria. The petroleum ether extract of P. simplex leaves showed the best anti-candidal activity with a minimum fungicidal concentration value of 0.014 mg/ml. The ethanol extracts of Agapanthus campanulatus (leaves and root), Dissotis princeps and Gladiolus dalenii as well as the dichloromethane extract of P. simplex leaves showed good anti-candidal activity with minimum fungicidal concentration values ranging between 0.037 and 0.39 mg/ml. Mutagenicity tests conducted on extracts that showed good antimicrobial activity suggest the plants are probably safe for consumption. The results obtained in this study show that some of the traditional plants may indeed be effective for the treatment of ailments related to gastro-intestinal disorders that may be due to the test pathogens.