Moniliophthora perniciosa in Angola, Africa - the first record in the Eastern Hemisphere

Moniliophthora perniciosa causes a destructive disease known as witches' broom disease of cacao (WBDC). WBDC has been responsible for major reductions in production or even total abandonment of cacao plantations in most countries that it has invaded. To date, however, the disease is known only from the cacao-producing regions of South America, and a few Central American and Caribbean countries. It is not known from the Eastern Hemisphere and remains a major threat should it invade West Africa or Southeast Asia, where the majority of the world's chocolate production now occurs. In 2019 a pink pigmented mushroom was found fruiting from unidentified twigs in the Serra Vamba of Angola. The specimen was identified as M. perniciosa based on morphological and molecular analyses. Although Angola is not a major cacao-producing country, the presence of the fungus in the Eastern Hemisphere could be of global concern and may indicate the need for quarantine in Angola and vigilance in neighboring countries.

Anatomical and Biomechanical Properties of the Junction between Stem and Aerial Roots of Selenicereus undatus

Cacti have a distinct adaptation to arid conditions with a massive water storing tissue surrounding a weak central woody cylinder. However, they have not been studied as extensively as other plants have been. Selenicereus undatus is a hemi-epiphytic root climber that attaches itself to supporting plants or rocks with adventitious roots. The anatomy and biomechanics of the adventitious roots were studied using light microscopy, X-ray tomography and pullout and uniaxial tensile tests. The central cylinder of the roots is highly lignified and is connected to the vascular system of the shoot in a peculiar way. Xylem elements of the root turn 90 degrees towards the base of the shoot and merge laterally and below the junction with those from the shoot. Tensile and pull-out tests showed that failure occurs either at the root or junction, with the fracture surface mainly comprising the area where xylem elements from the root merge with those from the shoot. However, damage to the cortical tissue was minimal, and the measured forces showed that adventitious roots have a high safety factor. Even a complete failure of the junction after pullout does not result in severe injury to the cortex, which could lead to water loss or the entry of pathogens.

Extreme plastomes in holoparasitic Balanophoraceae are not the norm

BACKGROUND

Balanophoraceae plastomes are known for their highly condensed and re-arranged nature alongside the most extreme nucleotide compositional bias known to date, culminating in two independent reconfigurations of their genetic code. Currently, a large portion of the Balanophoraceae diversity remains unexplored, hindering, among others, evolutionary pattern recognition. Here, we explored newly sequenced plastomes of Sarcophyte sanguinea and Thonningia sanguinea. The reconstructed plastomes were analyzed using various methods of comparative genomics based on a representative taxon sampling.

RESULTS

Sarcophyte, recovered sister to the other sampled Balanophoraceae s. str., has plastomes up to 50% larger than those currently published. Its gene set contains five genes lost in any other species, including matK. Five cis-spliced introns are maintained. In contrast, the Thonningia plastome is similarly reduced to published Balanophoraceae and retains only a single cis-spliced intron. Its protein-coding genes show a more biased codon usage compared to Sarcophyte, with an accumulation of in-frame TAG stop codons. Structural plastome comparison revealed multiple, previously unknown, structural rearrangements within Balanophoraceae.

CONCLUSIONS

For the "minimal plastomes" of Thonningia, we propose a genetic code change identical to sister genus Balanophora. Sarcophyte however differs drastically from our current understanding on Balanophoraceae plastomes. With a less-extreme nucleotide composition, there is no evidence for an altered genetic code. Using comparative genomics, we identified a hotspot for plastome reconfiguration in Balanophoraceae. Based on previously published and newly identified structural reconfigurations, we propose an updated model of evolutionary plastome trajectories for Balanophoraceae, illustrating a much greater plastome diversity than previously known.

Morphology, anatomy and sleep movements of Ludwigia sedoides

The diurnal motion of higher plants, responding to the alternation of day and night, known as nyctinastic movements or "sleep movements", has been discussed frequently. We present the first description of the circadian rhythm of the water plant Ludwigia sedoides (Humb. & Bonpl.) H.Hara of the family Onagraceae, furthermore its morphology and anatomy. Our results indicate that the plant's movements are endogenous, although environmental factors certainly have an influence. The majority of plants with nyctinastic leaf movements have a pulvinus, as the crucial part of the plant enabling this movement. Although the basal section of the L. sedoides petiole is not swollen, the tissue functions similarly to a pulvinus. It consists of a central conducting tissue with thick-walled cells, which is surrounded by thin-walled motor cells that can undergo visible shrinking and swelling. Thus, the tissue functionally corresponds to a pulvinus. Examinations of cellular processes, like measurements of the turgor pressure in the petiole, need to be evaluated in future studies.

The genus Landolphia P.Beauv. (Apocynaceae): A comprehensive review on its ethnobotanical utilizations, pharmacology and nutritional potential

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Landolphia is an important resource for African traditional medicine. Among the 60 different accepted species, nearly every plant part of the genus (bark, fruit, latex, leaf, leaf sap, root, rootbark, twig) from 13 species is utilized by traditional healers around Africa. Accordingly, many pharmacological studies (42) were performed on the most common species (11).

AIM OF THE STUDY

This comprehensive literature review summarizes all publications dealing on one of the 60 plant species from the genus Landolphia. An overview about already performed analysis is given and important aspects and knowledge gaps are highlighted for the direction of future research activities.

MATERIALS AND METHODS

A systematic web search taking into account the major platforms Web of Science, Scopus, PubMed, SciFinder and Google Scholar was performed for the term Landolphia. All relevant datasets, published between 1804 and 2022, were ordered according to their topics in different sections and compared to each other. A network visualization of the keywords via VOS Viewer was additionally performed.

RESULTS

In total, 209 publications were retrieved from the search engines, mainly written in English. Predominant are ethnopharmacological studies, which identified 292 phytochemicals in plant parts of the whole genus. Diverse biological activities were detected in different plant extracts, and five species were determined as of special interest for the treatment of malaria. Further research topics identified are botanical aspects, ethnobotanical utilizations, ecological aspects, the potential as source for human and animal nutrition, the manufacturing of rubber, economic aspects, biomechanical studies and others. L. owariensis is the most studied plant as it is abundant in continental Africa.

CONCLUSIONS

This review serves as a database for upcoming research on the genus Landolphia and directs existing knowledge gaps. A wide range of chemical components are already identified, but their exact content in the respective plant parts and their biological activity remains mainly unknown. Utilization patterns from traditional medicine are only partially analyzed as demonstrated for the applications as aphrodisiac, to treat skin diseases or as antidiabetic. Nutritional analyses likewise focus on several species of Landolphia and lack for the wide range of known edible fruits. The demand for new natural products in terms of medicine, rubber and nutrition is still high and the genus Landolphia seems to be a promising resource covering many aspects at once.

Mechanical investigations of the peltate leaf of Stephania japonica (Menispermaceae): Experiments and a continuum mechanical material model

Stephania japonica is a slender climbing plant with peltate, triangular-ovate leaves. Not many research efforts have been devoted to investigate the anatomy and the mechanical properties of this type of leaf shape. In this study, displacement driven tensile tests with three cycles on different displacement levels are performed on petioles, venation and intercostal areas of the Stephania japonica leaves. Furthermore, compression tests in longitudinal direction are performed on petioles. The mechanical experiments are combined with light microscopy and X-ray tomography. The experiments show, that these plant organs and tissues behave in the finite strain range in a viscoelastic manner. Based on the results of the light microscopy and X-ray tomography, the plant tissue can be considered as a matrix material reinforced by fibers. Therefore, a continuum mechanical anisotropic viscoelastic material model at finite deformations is proposed to model such behavior. The anisotropy is specified as the so-called transverse isotropy, where the behavior in the plane perpendicular to the fibers is assumed to be isotropic. The model is obtained by postulating a Helmholtz free energy, which is split additively into an elastic and an inelastic part. Both parts of the energy depend on structural tensors to account for the transversely isotropic material behavior. The evolution equations for the internal variables, e.g. inelastic deformations, are chosen in a physically meaningful way that always fulfills the second law of thermodynamics. The proposed model is calibrated against experimental data, and the material parameters are identified. The model can be used for finite element simulations of this type of leaf shape, which is left open for the future work.

Anatomy and Biomechanics of Peltate Begonia Leaves-Comparative Case Studies

Plants are exposed to various external stresses influencing physiology, anatomy, and morphology. Shape, geometry, and size of shoots and leaves are particularly affected. Among the latter, peltate leaves are not very common and so far, only few studies focused on their properties. In this case study, four Begonia species with different leaf shapes and petiole attachment points were analyzed regarding their leaf morphology, anatomy, and biomechanical properties. One to two plants per species were examined. In all four species, the petiole showed differently sized vascular bundles arranged in a peripheral ring and subepidermal collenchyma. These anatomical characteristics, low leaf dry mass, and low amount of lignified tissue in the petiole point toward turgor pressure as crucial for leaf stability. The petiole-lamina transition zone shows a different organization in leaves with a more central (peltate) and lateral petiole insertion. While in non-peltate leaves simple fiber branching is present, peltate leaves show a more complex reticulate fiber arrangement. Tensile and bending tests revealed similar structural Young's moduli in all species for intercostal areas and venation, but differences in the petiole. The analysis of the leaves highlights the properties of petiole and the petiole-lamina transition zone that are needed to resist external stresses.

Bioassay-Guided Isolation of Anti-Inflammatory Constituents of the Subaerial Parts of Cyperus articulatus (Cyperaceae)

Based on data from a previous ethnobotanical study in northern Angola, phytochemical investigations into the methanolic rhizomes and roots extract of Cyperus articulatus, monitored by in vitro assays, resulted in the recovery of 12 sesquiterpenes, 3 stilbenes, 2 phenolic acids, 1 monoterpene, and 1 flavonoid. Among them, 14 compounds were isolated for the first time from this species. Their inhibitory potential against nitric oxide (NO) production, as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, was evaluated in LPS-treated J774A.1 murine macrophages. Especially, both stilbene dimer trans-scirpusin B and trimer cyperusphenol B showed promising inhibitory activity against the production of the inflammatory mediator, NO, in a concentration-dependent manner (10−1 µM). The obtained data are the first results confirming the anti-inflammatory potential of C. articulatus and support its indigenous use as a traditional remedy against inflammation-related disorders.

Hunting techniques and their harvest as indicators of mammal diversity and threat in Northern Angola

Over-exploitation of wildlife especially bushmeat trade is the second most important threat to animal biodiversity. This also applies to Northern Angola but data on bushmeat and hunting techniques for this region are rare. Therefore, we study the most common hunting techniques, frequently captured species, and their economic value, and discuss the local resource use in relation to Angolan law and urgent global crises like the loss of biodiversity, the food supply in South African countries, and the risk of zoonoses. We recorded bushmeat hunting in 27 localities in the province of Uíge, accompanied hunters along their snare lines and interviewed additional 20 locals. Seven main types of snares and traps and their characteristics were defined. Hunters own on average 92 ± 128.7 snares and traps and capture about 25.3 ± 23.6 animals monthly. In total, respondents recognized 28 species of mammals of which one is considered as extinct and two as very rare. The majority of recorded species are hunted regularly. Rodents are most commonly caught followed by primates and duikers. Harvesting rates decrease with species’ body size, leading to high economic value of and achievable prices for rare, large animals. Overall, our results document the hunting pressure on mammals and the persisting popularity of bushmeat in Northern Angola which poses an imminent threat to remaining mammal populations. Moreover, it endangers ecosystem integrity, rural livelihoods, and human health through the risk of new zoonoses. Our findings underscore the urgent need for sustainable solutions. The Angolan government should play a more active role in enforcing existing hunting legislation to reduce illegal bushmeat trade.

Strengthening Structures in the Petiole-Lamina Junction of Peltate Leaves

Peltate- or umbrella- shaped leaves are characterised by a petiole more or less centrally attached to the lamina on the abaxial side. The transition from the petiole to lamina in peltate leaves resembles a significant and abrupt geometrical change from a beam to a plate in a very compact shape. Since these leaves have not been subject of many studies, the distribution of that specific leaf morphology in the plant kingdom was investigated. Furthermore, the connection between the petiole and lamina of several peltate species was studied anatomically and morphologically, focusing on the reinforcing fibre strands. We found peltate leaves in 357 species representing 25 orders, 40 families and 99 genera. The majority are herbaceous perennials growing in shady, humid to wet habitats mainly distributed in the subtropical–tropical zones. Detailed anatomical investigation of 41 species revealed several distinct principles of how the transition zone between the petiole and lamina is organised. In-depth analysis of these different types accompanied by finite element-modelling could serve as inspiration for supporting structures in lightweight construction.

Functional principles of baobab fruit pedicels - anatomy and biomechanics

BACKGROUND AND AIMS

Fruit pedicels have to deal with increasing loads after pollination due to continuous growth of the fruits. Thus, they represent interesting tissues from a mechanical as well as a developmental point of view. However, only a few studies exist on fruit pedicels. In this study, we unravel the anatomy and structural-mechanical relationships of the pedicel of Adansonia digitata, reaching up to 90 cm in length.

METHODS

Morphological and anatomical analyses included examination of stained cross-sections from various positions along the stalk as well as X-ray microtomography and scanning electron microscopy. For mechanical testing, fibre bundles derived from the mature pedicels were examined via tension tests. For establishing the structural-mechanical relationships, the density of the fibre bundles as well as their cellulose microfibril distribution and chemical composition were analysed.

KEY RESULTS

While in the peduncle the vascular tissue and the fibres are arranged in a concentric ring-like way, this organization shifts to the polystelic structure of separate fibre bundles in the pedicel. The polystelic pedicel possesses five vascular strands that consist of strong bast fibre bundles. The fibre bundles have a Young's modulus of up to 5 GPa, a tensile strength of up to 400 MPa, a high density (>1 g cm-3) and a high microfibril angle of around 20°.

CONCLUSIONS

The structural arrangement as well as the combination of high density and high microfibril angle of the bast fibre bundles are probably optimized for bearing considerable strain in torsion and bending while at the same time allowing for carrying high-tension loads.

Plants, food and treatments used by BaKongo tribes in Uíge (northern Angola) to affect the quality and quantity of human breast milk

Background

Angola has one of the highest annual under-five mortality rates in in the world and malnutrition poses a severe problem in the country. This study is the first to focus on the traditional knowledge of plants, foods, and treatments used by the local population in the province of Uíge to affect the quality and quantity of human breast milk, since decades of independence and civil war impeded ethnobotanical studies in this area.

Methods

This study was conducted in eight municipalities in the province of Uíge, Northern Angola in February and March 2018. In 265 semi-structured interviews, 360 informants in 40 rural villages were asked about plants, food, and treatments used to affect the quality and quantity of human breast milk. Additionally, information on child mortality and the duration of breastfeeding were collected. Whenever possible, plant specimens were collected for later identification. To determine the local importance of the collected plants, food, and treatments, the Relative Frequency of Citations was calculated.

Results

Most women reported to have no problems with their breast milk production. The duration of breastfeeding meets the recommendations of the World Health Organization (WHO). Across all use categories, 69 plants from 36 plant families, and 21 other foods and treatments could be identified.

Conclusions

The study shows an overview of a variety of plants, foods, and treatments used by mothers as galactagogues, to “clean” or to reduce their breast milk and those which they avoided to use during the lactation period. There is great potential for further research into this traditional knowledge. Also, further analysis of some of the plants could be of interest.

Stories told by plants on graveyards in Northern Angola

Background

Worldwide, different traditions of symbolic statements in graveyards can be found. However, studies on sub-Saharan Africa are rare. For BaKongo cemeteries, it is only known that they traditionally do not exhibit plants for decoration purposes. Our study wanted to inspect the influence of Portuguese culture due to the long shared colonial past.

Methods

During 2015 and 2019, plant use in 87 graveyards in 13 municipalities of the province Uíge was documented. Five expert interviews with the village eldest in five municipalities completed the data collection.

Results

While 24% of the graveyards didn´t have any planting, 27 plant species were found in the remaining ones, including a high percentage of alien species (59%), mainly from the Americas. The most abundant plant species are Euphorbia tirucalli (23%) and Agave sisalana (22%). With increasing distance from the city Uíge (especially towards the Democratic Republic of the Congo), the utilization of living plants in cemeteries is decreasing except along the road. In most of the cases, just one plant species per gravesite was found.

Conclusions

This unexpected high number of plants might be interpreted as a strong evidence of outside influence. Cultural symbols of the BaKongo cosmology and Christianism appear to coexist or coalesce. Furthermore, plants are used as a marker for graveyards. Modern influences like the use of concrete in proximity to urban areas indicate a certain wealth.

Adansonia digitata germination tests. Elephants or heat: what causes scarification of seed to facilitate germination?

BACKGROUND

The dormancy of Adansonia digitata seeds is well known. For propagation purposes, plenty of germination tests were conducted, however, rarely taking the ecology of baobab into account. Our main goal, therefore, is to identify the decisive natural trigger for breaking the dormancy. We therefore performed 31 different tests and their influence on the germination rate (time to germination and proportion of seeds germinating).

RESULTS

The highest germination rates were reached in the heat tests while elephant's digestion seems to stimulate germination of Adansonia digitata only to a limited extent. The chalazal slit of the seed represents the primary site of water entry. Tannins concentrated in this region that are influenced by temperature play an important role for inhibiting the germination.

CONCLUSION

As a result, the hypothesis is formulated that germination success strongly depends on heat, provoked by wildfires or prolonged exposition to the sun causing decomposition of tannins by high temperatures rather than on digestion.

At the edge of extinction: a first herpetological assessment of the proposed Serra do Pingano Rainforest National Park in Uíge Province, northern Angola

We systematically assess the herpetofaunal diversity of the Serra do Pingano Forest Ecosystem (SPFE) and additional localities throughout the northern Angolan province of Uíge during four independent Rapid Assessment (RA) field campaigns held between 2013 and 2019. These assessments represent the first systematic surveys of amphibians and reptiles from the province, and thus we provide the first province-wide species list. We collected data on the status and current threats to amphibians and reptiles in the proposed Serra do Pingano Rainforest National Park and were able to document 33 species of reptiles from Uíge province. Of the 33 species recorded from the province, 10 species are exclusively found in the SPFE. Amphibian surveys yielded 47 amphibian species from the province. These include 14 new country records and additional records that may represent undescribed species. This raises the amphibian count for Angola to at least 133 species, which includes 18 species exclusively found within the SPFE. Species-richness estimators indicate that more species should be detected if survey efforts are intensified. The species composition in the SPFE is unique and consists of a high proportion of forest specialists with restricted ranges and species found nowhere else in the country. This emphasizes today’s paramount importance of the SPFE, which is threatened by increasing agricultural encroachment and uncontrolled timber extraction and charcoal production. These principal factors need to be controlled and/or abandoned in already impacted areas. Conservation strategies should particularly consider the strict protection of remaining intact forests and both lentic and lotic aquatic systems. They are not only crucial for safeguarding a significant number of species that depend on these habitats for reproduction; they also provide key ecosystem services to the local population. Angola, and Uíge province in particular, is at a crossroads concerning decisions and trade-offs among utilization, conservation, and preservation of its forests and, thus, substantial parts of the country’s biodiversity. The establishment of a National Protected Area in the Serra do Pingano Ecosystem is therefore a necessary and urgently needed first step towards protecting Angola’s national biodiversity heritage.

Unraveling the Phylogenomic Relationships of the Most Diverse African Palm Genus Raphia (Calamoideae, Arecaceae)

Palms are conspicuous floristic elements across the tropics. In continental Africa, even though there are less than 70 documented species, they are omnipresent across the tropical landscape. The genus Raphia has 20 accepted species in Africa and one species endemic to the Neotropics. It is the most economically important genus of African palms with most of its species producing food and construction material. Raphia is divided into five sections based on inflorescence morphology. Nevertheless, the taxonomy of Raphia is problematic with no intra-generic phylogenetic study available. We present a phylogenetic study of the genus using a targeted exon capture approach sequencing of 56 individuals representing 18 out of the 21 species. Our results recovered five well supported clades within the genus. Three sections correspond to those based on inflorescence morphology. R. regalis is strongly supported as sister to all other Raphia species and is placed into a newly described section: Erectae. Overall, morphological based identifications agreed well with our phylogenetic analyses, with 12 species recovered as monophyletic based on our sampling. Species delimitation analyses recovered 17 or 23 species depending on the confidence level used. Species delimitation is especially problematic in the Raphiate and Temulentae sections. In addition, our clustering analysis using SNP data suggested that individual clusters matched geographic distribution. The Neotropical species R. taedigera is supported as a distinct species, rejecting the hypothesis of a recent introduction into South America. Our analyses support the hypothesis that the Raphia individuals from Madagascar are potentially a distinct species different from the widely distributed R. farinifera. In conclusion, our results support the infra generic classification of Raphia based on inflorescence morphology, which is shown to be phylogenetically useful. Classification and species delimitation within sections remains problematic even with our phylogenomic approach. Certain widely distributed species could potentially contain cryptic species. More in-depth studies should be undertaken using morphometrics, increased sampling, and more variable markers. Our study provides a robust phylogenomic framework that enables further investigation on the biogeographic history, morphological evolution, and other eco-evolutionary aspects of this charismatic, socially, and economically important palm genus.

Umbrella leaves-Biomechanics of transition zone from lamina to petiole of peltate leaves

In this study we aim to show how the peltate leaves of Colocasia fallax Schott and Tropaeolum majus L., despite their compact design, achieve a rigid connection between petiole and lamina. We have combined various microscopy techniques and computed tomography (CT) scanning for the analysis of the basic structure of the plant's stabilization system. Mechanical tests yielded key mechanical parameters and allowed us to assess the mode of failure. The results of the tests were further processed in a finite element method (FEM) analysis. We were able to show that both plants are able to endure high loads irrespective of the different composition of the supporting structure. C. fallax forms many separate branched strands, whereas T. majus forms fewer strands of greater diameter interconnected in the centre of the transition area, forming a bundle of irregular orientation. This results in different ways to dissipate loads on the lamina. In C. fallax we observed the outer strands of the strengthening tissue under high stress while the inner bundle carries little load. In T. majus the load is distributed more evenly through the juncture in the middle of the transition area. Potential applications include the construction of biomimetical flying roofs.

First large-scale ethnobotanical survey in the province of Uíge, northern Angola

BACKGROUND

Angola suffered a long-lasting military conflict. Therefore, traditional knowledge of plant usage is still an important part of cultural heritage, especially concerning the still very poor health care system in the country. Our study documents for the first time traditional knowledge of plant use of local Bakongo communities in the northern province of Uíge on a large scale with a focus on medicinal plants and puts data in context to different parameters of age, gender and distance to the provincial capital.

METHODS

Field work was carried out during nine field trips in 13 municipalities between October 2013 and October 2016. In 62 groups, 162 informants were interviewed. Herbarium specimens were taken for later identification. Database was analysed using Relative Frequency of Citations, Cultural Importance Index, and Informant Consensus Factor. Furthermore, significances of influence of age, gender and distance were calculated.

RESULTS

Our study presents 2390 use-reports, listing 358 species in 96 plant families, while just three out of 358 mentioned species are endemic to Angola about one-fifth are neophytes. The larger the distance, the higher the number of use citations of medical plants. Although women represent just a fifth of all citations (22%), their contribution to medicinal plants was proportionally even higher (83%) than those of men (74%). Fifty percent of all plants mentioned in the study were just listed by men, 12% just by women. We made some new discoveries, for example. Gardenia ternifolia seems to be promising for treatment of measles, and Annona stenophylla subsp. cuneata has never been ethnobotanically nor phytochemically investigated.

CONCLUSIONS

While the study area is large, no significant influence of the distance in regard to species composition in traditional healer's concepts of the respective village was pointed out. Although several plants were just mentioned by women or men, respectively, no significant restriction to gender-specific illnesses in medical plant use could be found. Merely concerning the age of informants, a slight shift could be detected. Visual representation of the ethnobotanical study in Uíge, northern Angola.

Medicinal plants of northern Angola and their anti-inflammatory properties

ETHNOPHARMACOLOGICAL RELEVANCE

32 plants, from which 30 are used in local traditional medicine - identified by interviews with the resident population - in the province of Uíge in northern Angola for the treatment of inflammation related disorders, were screened on different anti-inflammatory parameters. Three extracts were selected for a detailed ethnobotanical, pharmacological and phytochemical investigation based on their in vitro activity.

AIM OF THE STUDY

We aimed to assess the in vitro anti-inflammatory activity of these plants and highlight the active principles of the three most promising candidates.

MATERIALS AND METHODS

Plant material was collected in northern Angola during eight field trips from 2013 to 2015 based on data documented in 61 interviews with 142 local informants. 36 methanol (MeOH) extracts were prepared and tested at different concentrations (100, 50, 10µg/mL) to evaluate their inhibition on cyclooxygenase (COX)-2 expression and on nitric oxide (NO) release in lipopolysaccharide (LPS)-stimulated J774A.1 macrophages. Five selected extracts were additionally tested at the lower concentrations of 5, 2.5, and 1.25µg/mL and for their potential on inhibition of tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) release. The major compounds of three of those five extracts were either identified by HPLC coupled with (tandem) mass spectrometry and comparison with data from literature or isolated from the respective extracts and confirmed by NMR experiments (one and two dimensional).

RESULTS

30 plant species with in total 161 citations were mentioned by the informants to have anti-inflammatory properties. The predominantly used plant part is the leaf (39%), followed by underground organs like roots and rhizomes (25%), bark (18%) as well as fruits and seeds with 15%. With 47%, decoction is the most frequent preparation form. A large number of the MeOH extracts showed promising activities in our preliminary screening for the inhibition of COX-2 expression and NO release. Five extracts with high activities in both assays showed also concentration dependent inhibition at lower concentrations and a decreased release of two additional pro-inflammatory mediators (IL-6 and TNF-α) vs. LPS. Three leaf extracts where chosen for a detailed investigation, which lead to the identification of several constituents: verbascoside and isoverbascoside (Acanthus montanus), geraniin, chebulagic acid and a large flavonoid fraction (Alchornea cordifolia) as well as the four flavonoids astilbin, isovitexin, isoorientin and swertisin (Chaetocarpus africanus). Their implication in the observed biological activity was proved by comparison with published data of these compounds in identical or similar pharmacological models.

CONCLUSIONS

The indigenous use of these plants against inflammation related ailments could be - at least partly - verified by our in vitro models for many of the investigated extracts. Acanthus montanus and Alchornea cordifolia particularly stood out with their high activity in all four performed assays, which was in accordance with pharmacological studies of their major constituents in literature. In addition, this study was the first phytochemical investigation of Chaetocarpus africanus and first description of the occurrence of the ellagitannins geraniin and chebulagic acid in Alchornea cordifolia. These results support the traditional use and should encourage further investigations of medicinal plants of northern Angola.

Adansonia digitata and Adansonia gregorii fruit shells serve as a protection against high temperatures experienced during wildfires

The thick and woody shell of the fruit of Adansonia species cannot be explained solely by adaptation to zoochory or hydrochory. Since the trunks of Adansonia possess a thick and fire-resistant bark and wildfires occur regularly in its habitat (savannah), we examined with the African Adanonia digitata and the Australian Adansonia gregorii whether the fruit offers protection against high heat typically experienced in wildfires. Heat-resistance tests were conducted by applying a simple heat test based on known temperature and temperature residence times occurring in savannah fires and complemented by tests to reveal the impact of heat on germination since long-term seed dormancy is known for Adansonia. Germination tests with acid treated and heat treated seeds were performed to establish if heat also increased germination rate as effectively as acid treatments have been found to do. Heat was found to increase germination rate, but not as effectively as treatment with acid, therefore fruits exposed to high temperatures experienced in wildfires may have a better chance of germination than fruits that were not exposed to wildfires. The ability of the investigated fruits to protect seeds from high temperatures suggests that wildfires may have played a role in the evolution of the hard-shell structure typically found in Adansonia.

Plants from disturbed savannah vegetation and their usage by Bakongo tribes in Uíge, Northern Angola

BACKGROUND

This study represents the first in-depth ethnobotanical study in the province of Uíge in northern Angola and documents the traditional knowledge of the Bakongo people living in the area. Due to deforestation and frequent fires, degraded savannahs dominate the landscape in the study region. Here we provide a list of useful plants from these savannahs including quantitative data about cultural importance of the respective species, aiming on the one hand to conserve the local knowledge and on the other hand to create a reliable basis for research projects in the region.

METHODS

Field work was conducted in April and May 2014 in 5 municipalities of Uíge province. The study is based on 32 semi-structured and free-listing interviews, group discussions of varying scope and 14 field trips, involving a total of 82 informants. Throughout the course of the study herbarium specimens of the useful species were collected for later identification. Cultural importance index was applied to analyse the data sets recorded and to determine the best-known useful species in the region. All data sets were compared to the literature available for the region.

RESULTS

The study documents a total of 498 citations for the use of 122 plants from 48 families, 34.0 % of which were unknown according to the literature used for comparison. The high amount (71 %) of medical use-reports indicates that plants still play a crucial role in rural health care. We identified 14 plant species of special interest for pharmacological analysis. Species of highest cultural importance are Annona senegalensis Pers. and Sarcocephalus latifolius (Sm.) E.A., both of which are frequently found in disturbed savannahs.

CONCLUSIONS

The study points out the importance of savannahs even if degraded in terms of useful plants and provides a valuable addition to current knowledge of plant use in Northern Angola. This is not only essential for further studies, i.e. regarding pharmaceutical agents, but also for the design of a planned botanical garden of the University Kimpa Vita in Uíge, which aims at communicating the findings to the local people.

Relicts of a forested past: Southernmost distribution of the hairy frog genus Trichobatrachus Boulenger, 1900 (Anura: Arthroleptidae) in the Serra do Pingano region of Angola with comments on its taxonomic status

The monotypic genus Trichobatrachus, with its sole representative, the hairy frog, Trichobatrachus robustus Boulenger, 1900, could be considered one of the most well-known frogs of Africa. Despite its broad recognition and the fact that it is considered wide-spread and locally common (Amiet & Burger 2004), surprisingly little is known about the actual distribution and the specific occurrence patterns of the species. It was originally described by Boulenger (1900) from the Benito River, previously erroneously stated to be located in Gabon. However, Lötters et al. (2001) clarified that the type locality was actually situated in Equatorial Guinea, then part of French Congo, and subsequently provided the first confirmed country record for Gabon. Hairy frogs were previously included in the herpetofaunal lists of Cameroon (Parker 1936; Perret & Mertens 1957), the Democratic Republic of Congo (Laurent 1956), and Nigeria (Schiøtz 1963). More recently published accounts list them for Cameroon (Euskirchen et al. 1999; Herrmann et al. 2005; Gonwouo & Rödel 2008), Equatorial Guinea (De la Riva 1994; Lasso et al. 2002), Gabon (Lötters et al. 2001; Rödel & Pauwels 2003; Burger et al. 2004; Pauwels & Rödel 2007; Bell et al. 2011), and the Democratic Republic of Congo (DRC, Fretey et al. 2011), and speculate about their potential occurrence in Congo and the Cabinda enclave of Angola (Amiet & Burger 2004). The DRC record so far represented the most southerly distribution, while the most northerly account comes from the Adamaoua Province of northern Cameroon (Tadpole voucher MHNG-AMP/ERPI-1035.006 from Bénoué source, Northern cliff Ngaoundéré, Adamaoua, Cameroon/Adamaoua Province, cf. Perret 1966). Specimens stored in the collection at the Royal Museum of Central Africa, Tervuren (RMCA) under collection numbers RMCA B 90060.0004-11 confirm the occurrence of the species in Congo. To our knowledge, these specimens represent yet unpublished first country records.

How to become a tree without wood--biomechanical analysis of the stem of Carica papaya L

Carica papaya L. does not contain wood, according to the botanical definition of wood as lignified secondary xylem. Despite its parenchymatous secondary xylem, these plants are able to grow up to 10-m high. This is surprising, as wooden structural elements are the ubiquitous strategy for supporting height growth in plants. Proposed possible alternative principles to explain the compensation for lack of wood in C. papaya are turgor pressure of the parenchyma, lignified phloem fibres in the bark, or a combination of the two. Interestingly, lignified tissue comprises only 5-8% of the entire stem mass. Furthermore, the phloem fibres do not form a compact tube enclosing the xylem, but instead form a mesh tubular structure. To investigate the mechanism of papaya's unusually high mechanical strength, a set of mechanical measurements were undertaken on whole stems and tissue sections of secondary phloem and xylem. The structural Young's modulus of mature stems reached 2.5 GPa. Since this is low compared to woody plants, the flexural rigidity of papaya stem construction may mainly be based on a higher second moment of inertia. Additionally, stem turgor pressure was determined indirectly by immersing specimens in sucrose solutions of different osmolalities, followed by mechanical tests; turgor pressure was between 0.82 and 1.25 MPa, indicating that turgor is essential for flexural rigidity of the entire stem.