Invasive species could lead to their control while

Invasive plant species are defined as native or non-native
species that colonize a specific habitat and negatively impact on it
ecologically, environmentally or economically (Schoonover, 2010). Introduced
plant species may become invasive if it out-competes indigenous species for
resources such as light, nutrient, water or food, thereby altering the biotic
and abiotic components of the entire ecosystem (Weidenhamer and Callaway,
2010).  Biological invasions by exotic plant species
are worldwide common phenomenon and constitutes one of the main threats to natural ecosystem and biological diversity as a whole
(Jabeen et al., 2015). The effects of invasive plant
species on agriculture, forestry, human health, fisheries and other human activities have
been documented (Joshi et al., 2016).

 

The
economic, social and ecological contributions of invasive plant species have
been reported (Abhijith and Binu, 2017). They have become alternative
sources of utilization where the indigenous vegetation has been destroyed
through over-exploitation. These species are being extensively used by many
people for a variety of functional and aesthetic purposes. Commercial
utilization of these plant species could lead to their control while providing
ecosystem services to poor rural communities (Semenya et al., 2012). For example, invasive plants species like Lantana camara, Opuntia ficus-indica, Caesalpinia
decapetala, Ricinus communis, solanum
mauritianum and Rhus succedanea have
been used traditionally in treating diarrhea, blood pressure, excessive
bleeding, insect bites, sexually transmitted diseases, fever, diabetes and
toothache amongst other ailments. Moreover, the fruits of Opuntia ficus-indica are consumed as part of daily nutrition (Semenya
et al., 2012; Shedbalkar et al., 2010). Therefore, the significant
environmental and economic costs of invasive plants make them an important and
timely topic of study (Schoonover, 2010).

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According to
Lambertini et al. (2010), invasive
plant species are of evolutionary concern because of their success in habitats
where they have invaded, sometimes despite little genetic diversity as compared
to their indigenous range. This success could
be due to multiple introductions, polyploidy, large numbers of founder
individuals and gene flow among populations, resulting to genetically distinct
genotypes (Piya et al., 2014). Introduced plant species are
capable of offsetting the adverse consequences of genetic barriers and establish
genetic diversity in the new environment. In such cases, genotypes from diverse
geographical regions are reshuffled or recombined, thereby yielding superior genotypes
not present in the local range (Lambertini et
al., 2010). The study on origin of invasive plant species is fundamental in ascertaining
their beginnings as a consequence
of single or multiple introductions in a specific environment. Assessment of genetic
diversity and structure, as well as introduction histories and invasion
pathways is critical in the management of invasive plants (Nater et al., 2013).

 

The plant under
study, Parthenium hysterophorus Linn,
is an invasive weed which is globally distributed and belongs to the family
Asteraceae (Bagchi et al., 2016). Parthenium hysterophorus is a persistent, annual or transient flowery weed of subtropical
and tropical areas. This
dynamic weed is commonly known as feverfew, carrot weed, bitter weed, congress
grass or false ragweed (Joshi et al.,
2016). In Kisumu County, the weed is referred to as ‘mafua’ (flower), ‘akech’
(bitter) or ‘odagwa / buya’ (weed). The plant species has been reported to
possess different classes of compounds (Roy and Shaik, 2013). Though regarded
as a destructive weed,
P. hysterophorus has been shown possess
numerous medicinal properties (Joshi et
al., 2016) and could be used in treating malaria and other infectious
diseases among local communities in Kenya.

 

Malaria is one of the main
contributors to the worldwide burden of disease and a considerable barrier to
the socio-economic progress in underprivileged and developing countries
(Machumi, 2010). Studies
have indicated that approximately 300 to 660 million new pathological attacks
of malaria happens globally every year and results in nearly 1 to 3 million
deaths yearly (Machumi, 2010). More than 90% of these deaths occur in Africa and are mostly
reported in pregnant women and children below five years of age (Kumari et al., 2016). Malaria has huge impact on health
of children, pregnant women and immunocompromised people and is a major
predisposing factor to ailments associated with diarrheal diseases,
malnutrition, viral illnesses and respiratory tract infections amongst other diseases
(Shantz-Dunn and Nour, 2009). In fact, malaria is ranked third globally among the most frequent causes
of infectious disease-related deaths after tuberculosis and pneumococcal acute
respiratory tract infection (Shantz-Dunn and Nour, 2009).

 

The use of natural product-derived drugs and
synthetic drugs in treating malaria has been faced with several challenges.
These include rapid growth and multiplication of parasites in the human host
blood cells, emergence of drug resistant parasites and complications arising
from oxidative stress during malaria infections (Machumi, 2010). Oxidative
stress has been linked to several malaria complications such as cerebral and
pulmonary edema, anemia and poor eyesight. Most fatalities associated with
oxidative stress are caused by high production of free radicals in host cells
(Percario et al., 2012). Efforts to
treat the disease are hampered by the increased resistance of malaria parasites
to readily available drugs. Therefore, new drugs or drug combinations with
antioxidant properties are urgently needed to treat malaria. The drugs should be
safe, possess novel modes of action or be chemically distinct from the drugs
currently in use (Ramalhete et al.,
2008). In this regard, genetic diversity, antimalarial, antioxidant and cytotoxicity
as well as phytochemical profiles of the leaf extracts of P. hysterophorus will be investigated. This will form the basis of utilization
of the weed as a medicinal plant in Kenya.