Characterization and Risk Assessment of Atmospheric PM2.5 and PM10 Particulate-Bound PAHs and NPAHs in Rwanda, Central-East Africa

Exposure to airborne particulates is estimated as the largest cause of premature human mortality worldwide and is of particular concern in sub-Saharan Africa where emissions are high and data are lacking. Particulate matter (PM) contains several toxic organic species including polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs). This study provides the first characterization and source identification for PM₁₀- and PM_2.5-bound PAHs and NPAHs in sub-Saharan Africa during a three-month period that spanned dry and wet seasons at three locations in Rwanda. The 24-h mean PM_2.5 and PM₁₀ concentrations were significantly higher in the dry than the wet season. PAH and NPAH concentrations at the urban roadside site were significantly higher than the urban background and rural site. Source identification using diagnostic ratio analysis and principal component analysis (PCA) revealed diesel and gasoline-powered vehicles at the urban location and wood burning at the rural location as the major sources of PAHs and NPAHs. Our analysis demonstrates that PM concentrations and lifetime cancer risks resulting from inhalation exposure to PM-bound PAHs and NPAHs exceed World Health Organization safe limits. This study provides clear evidence that an immediate development of emission control measures is required.

Traditional phytotherapy remedies used in Southern Rwanda for the treatment of liver diseases

ETHNOPHARMACOLOGICAL RELEVANCE

Liver diseases represent a major health problem due to their complications and limited treatment possibilities. In Rwanda, given low accessibility to modern treatments, most people still rely on traditional medicinal plants. The symptomatology of many hepatic troubles (icterus) is evident for traditional healers who have a high probability of selecting efficient herbal medicines.

OBJECTIVES

To document medicines used in the treatment of "hepatitis" in Southern Rwanda with the knowledge, attitudes and practices related to liver disorder recognition, control and treatment.

MATERIALS AND METHODS

56 traditional health practitioners, each a legal representative of an official association, were interviewed and participated in plant collection for the preparation of botanically identified herbarium specimens.

RESULTS

68 multi-component and 65 single-component herbal recipes were identified for the treatment of liver diseases with a total of 86 different herbs from 34 families identified. The most represented were the Asteraceae and the Lamiaceae. Crassocephalum vitellinum, Hypoestes triflora and Erythrina abyssinica were the most widely used plants. The principle of polymedication for complex (i.e. multifactorial) diseases ("Ifumbi" in Rwanda), is a constant in every traditional practice. It is striking that the Rwandese therapy of liver diseases proposes so many single-herb preparations (49% of all herbal preparations). Some of the recorded plants or other species from the same genus have previously been documented for liver protection using various in vivo and in vitro models.

CONCLUSION

Herbal remedies for hepatitis are widely used and highly diverse in Southern Rwanda; further chemical, pharmacological and toxicological studies are clearly required to rationally develop the most important remedies.

Chemical and Biological Components of Urban Aerosols in Africa: Current Status and Knowledge Gaps

Aerosolized particulate matter (PM) is a complex mixture that has been recognized as the greatest cause of premature human mortality in low- and middle-income countries. Its toxicity arises largely from its chemical and biological components. These include polycyclic aromatic hydrocarbons (PAHs) and their nitro-derivatives (NPAHs) as well as microorganisms. In Africa, fossil fuel combustion and biomass burning in urban settings are the major sources of human exposure to PM, yet data on the role of aerosols in disease association in Africa remains scarce. This review is the first to examine studies conducted in Africa on both PAHs/NPAHs and airborne microorganisms associated with PM. These studies demonstrate that PM exposure in Africa exceeds World Health Organization (WHO) safety limits and carcinogenic PAHs/NPAHs and pathogenic microorganisms are the major components of PM aerosols. The health impacts of PAHs/NPAHs and airborne microbial loadings in PM are reviewed. This will be important for future epidemiological evaluations and may contribute to the development of effective management strategies to improve ambient air quality in the African continent.

Tyrosinase modulation by five Rwandese herbal medicines traditionally used for skin treatment

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional herbal medicines provide an interesting, largely unexplored source for the development of potential new drugs and skin-care cosmetics. Some herbal extracts are known to be inhibitors of melanin formation, sometimes more potent than the classical inhibitors, hydroquinone/arbutin or kojic acid, and are not associated with melanocytes cytotoxicity or mutagenicity. Such plants are used in traditional medicine in many countries, particularly in Africa, for skin lightening.

AIM OF THE STUDY

To evaluate in vitro the ability of Rwandese medicinal plants, traditionally used for the treatment of skin (discoloration and attenuation of discolored spots), to modulate pigmentation and tyrosinase activity.

MATERIALS AND METHODS

Based on an ethnopharmacological survey, five herbs [Brillantaisia cicatricosa Lindau (Acanthaceae), Chenopodium ugandae (Aellen) Aellen (Chenopodiaceae), Dolichopentas longiflora Oliv. (Rubiaceae), Protea madiensis Oliv. (Proteaceae) and Sesamum angolense Welw. (Pedaliaceae)] were selected. Twenty-seven extracts, obtained by treating the herbs with increasing polarities solvents, were investigated for their effects on cell viability (MTT test) and on pigmentation: inhibition of the enzyme tyrosinase (colorimetry of reaction products, measurement of enzyme activity, TLC-autography; studies on crude cellular extracts obtained from normal melanocytes and on a mushroom tyrosinase) and measurement of melanogenesis by human melanoma cells.

RESULTS

None of the tested plant extracts were cytotoxic on tested human melanoma cell lines, except for Dolichopentas longiflora (IC50 of leaves n-hexane extract, 4μg/ml for MM028 and 4.5μg/ml for MM001; IC50 of roots ethyl acetate extract, 0.8μg/ml for MM028 and 3.9μg/ml for MM001). Almost all extracts inhibited melanogenesis in a melanoma whole cells overall pigmentation assay, a model reflecting the entire cycle of melanogenesis. All the Protea madiensis extracts quite strongly inhibited melanogenesis and, surprisingly, one of the Dolichopentas longiflora leaves extracts was found to increase melanogenesis. These results were confirmed by the modulation of pigmentation reactions by crude cellular extracts obtained from normal melanocytes; interestingly, one of the extracts (Dolichopentas longiflora ethyl acetate extract) is even more active (61% at 500μg/ml) than kojic acid (<3% at 142μg/ml and 68% at 1421μg/ml). In a mushroom tyrosinase inhibition assay, data obtained on some extracts fairly agree with pigmentation inhibition measured on melanocytes proteins as, for example, the methanol extract of Protea madiensis. While a few others extract display discording data, this probably reflects either differences between human and mushroom tyrosinase, interference with melanocytes enzymes at later steps than tyrosinase or the simultaneous presence of compounds with conflicting activities in a given extract.

CONCLUSIONS

Ethnopharmacological data represent an efficient approach to discover active herbs. Some of the selected medicinal plants clearly show potent tyrosinase inhibitions while one extract significantly increases cell pigmentation; one extract contains potent growth melanocytes inhibitors.

An ethnobotanical survey of medicinal plants used in Rwanda for voluntary depigmentation

ETHNOPHARMACOLOGICAL RELEVANCE

Voluntary depigmentation, a very common practice in sub-Saharan Africa, often performed with pharmaceutical products diverted from their pharmacological use, may cause severe dermatological and systemic side effects. The present work aims at investigating whether and which herbs were used in Rwanda for similar purposes before the advent of the current depigmentation craze; this may give clues at herbal treatments possibly advantageous compared to current products.

MATERIAL AND METHODS

Sixty-one traditional healers, mostly representatives of their associations, were surveyed by questionnaires for knowledge and practice of voluntary depigmentation. Recipes or plants used, plant parts, harvest area, preparation methods, dosage and route of administration were recorded. Most of the cited herbs were harvested with the help of traditional healers and identified by comparison with voucher specimens; herbal vouchers of the five most cited herbs were deposited in official herbaria.

RESULTS

All surveyed traditional healers have knowledge of voluntary depigmentation; the population currently practicing do not recourse to their services but obtain bleaching products directly from the market. Traditional healers disclosed recipes prescribed or self-used (often by women) in their youth; others cited recipes are used to treat skin diseases with properties of "clarification", "black skin stain removal", in cases of hyperpigmentation, and/or "skin softening". Curiously, from the 28 recipes cited by traditional healers, all are mono-herbal preparations; most of the plants are mixed with butter for application to the skin.

CONCLUSION

Compared to other pathophysiological conditions, there is currently a very limited use of herbal preparations for depigmentation. Five herbs had a citation percentage equal or above to 50%, Brillantaisia cicatricosa Lindau (Acanthaceae), Chenopodium ugandae (Aellen) Aellen (Chenopodiaceae), Dolichopentas longiflora Oliv. (Rubiaceae), Protea madiensis Oliv. (Proteaceae) and Sesamum angolense Welw. (Pedaliaceae); in vitro experiments indicated a modulation of melanogenesis by these plant extracts, confirming the information obtained from traditional healers.

Impact of Pteridium aquilinum on vegetation in Nyungwe Forest, Rwanda

Pteridium aquilinum acts as an important ecological filters in dominated communities. A study to investigate the effects of its dominance in the vegetation of Nyungwe was conducted. Sampling was done in Mubuga and Uwajerome mountains. A total of 53 alternate plots measuring 10 m × 10 m were sampled along a transect at regular interval of 10 m. In each plot, the species were identified and the cover abundance measured subjectively. Plant strategies, succession, biological forms, distribution and conservation status of each species were also determined. Data on species composition and cover abundance were analyzed using MVSP software and Shannon -Weiner index was used to determine diversity of communities. Descriptive statistics were used to assess the characteristics of the species. A total of 141 species belonging to 100 genera and 54 families and distributed in four plant communities were identified. Pteridium aquilinum, Macaranga kilimandischarica, Lycopodium clavatum and Microglossa parvifolia were dominant in communities I, II and III, with average cover of 31%, 6% and 4% respectively. The primary forest was dominated by Pavetta rwandensis and Allophyllus chaunostachys in community IV, with 21% and 10% coverage respectively. Shannon- Weiner and evenness indices were 1.538, 2.925, 3.251 and 2.940 and 0.436, 0.716, 0.791 and 0.768 in communities I, II, III and IV respectively. Species richness were 34, 36, 61 and 46 in communities I, II, III and IV respectively. Ruderal, chamaephytes, secondary, Africa tropical and least concerns plant species predominated in Pteridium vegetation areas with 76% 48%, 69%, 43% and 90% of total species respectively. Competitive, phanerophytes, primary, Afromontane and least concerns plant species dominated in non-dominated area with 54%, 52%, 58%, 40% and 88% of total species respectively. Pteridium aquilinum restricted the growth of trees as exhibited by the presence of few phanerophytes and enhanced the growth of ruderal species, both of which are indicators of disturbed forest. The tree species observed in P. aquilinum cut-areas was Macaranga kilimandischarica.

A New Method for Post-introduction Risk Assessment of Biological Invasions Among Introduced Shrubs in Developing Countries

Risk-assessment methods are useful in collecting data that can help decision making to prevent the introduction of new species that have the potential of invading as well as in management of established taxa. Not only the complexity and unaffordability of available pre-introduction risk-assessment models make them rarely or inconsistently applied in the least-developed countries, but also there is lack of tools to assess the status of already introduced plant species. In this study, an affordable and rapid method of assessment of invasiveness among introduced plant species was developed and tested in Rwanda. This method defines three invasion stages (potential, effective, and suppressive invaders) and four levels of risk assessment: post-introduction assessment of species inherent invasive potential (Level 1), post-establishment assessment of species capacity of regeneration (Level 2), post-naturalization assessment of species range of occurrence and ability for long-distance dispersal (Level 3), and post-naturalization assessment of species ability to outcompete other plants in the community and transform the landscape (Level 4). A review of invasive species in Rwanda was developed through desk review, examination of herbarium records, and vegetation surveys. This method should be applicable in other countries that lack the means for a more conventional scientific investigation or under any circumstance where a quick and inexpensive assessment is needed. The method could be useful to environmental managers for timely intervention with strategies specific to different stages of invasion (post-introduction, post-establishment, or post-naturalization) and allocate resources accordingly.

Data on vegetation sampling in areas dominated by Pteridium aquilinum in Nyungwe forest, Western Province of Rwanda

The data presented in this article describe plant traits (ecological strategy, plant succession, biological form, plant distribution and conservation status), cover-abundance scores of individualized communities after the application of Multivariate Statistical Package (MVSP) software and coverage percentage of species which compose the communities in areas sampled from Nyungwe forest. Taxonomic diversity indices (Shannon, Evenness and Richness) were also calculated and included in the dataset. The observed data can support the evaluation of Pteridium invasion in comparable forest types.

Urticaceae leaves with stinging trichomes were already present in latest early Eocene Okanogan Highlands, British Columbia, Canada

PREMISE

Paleontologists use tooth form to assess diets of fossil mammals. Plants would also be expected to adapt their morphology to respond to herbivory. Fossil nettle leaves with definitive stinging trichomes (tribe Urticeae, family Urticaceae) are described from the early Eocene upland lacustrine floras of the Okanogan Highlands, British Columbia, Canada. This is the first report of stinging trichomes in the fossil record. Their occurrence in western North America at a time of major large herbivorous mammal radiation suggests they acted, as they do today, as a deterrent for mammal herbivory.

METHODS

Fossil leaf compressions and extant leaves were photographed with standard methods. Focus-shift stacking was used to layer photos of the fossil leaves.

RESULTS

Urticaceous fossil leaves from the Okanogan Highlands greatly resemble their modern relatives in leaf morphology and particularly in both stinging and nonstinging trichomes. Nettles are common components of the flora of the Volcanoes National Park in Rwanda. This region is used as a modern analogue for the Okanogan Highlands, based on comparable elevation, equable conditions that host both similar floras and large folivores.

CONCLUSIONS

Nettles in tribe Urticeae (Urticaceae) producing leaves with stinging and nonstinging trichomes were already present in the early Eocene of western North America at a pivotal time during the early radiation of modern mammalian herbivore groups. They offer tantalizing evidence of a selective response that plants may have developed to protect themselves from the evolving mammalian herbivores of that time.