1. Introduction

Plants
have great importance in our lives as these are the source of shelter,
clothing, food, flavours and much more. In medicine plants have always been
considered as the basis of traditional medicine system among Chinese, Unani and
Ayurvedic. Various bioactive compounds are synthesized by plants which make them
so important in medicine, there are many plants which are medically important
as far as the presence of useful phytochemicals is concerned, and among such
medicinal plants is wild marigold (Tagetes
minuta). Plants have genes which are involved in the biosynthetic pathways
of medically important compounds and they are producing them naturally and the
environment also plays role in biosynthesis of those compounds. The biochemists
are looking for plants to know about compounds or new molecules of medicinal
importance which can lead to improvements in this area (Gurib-Fakim., et al 2006).Now a days a large world
population prefers natural products for treatments and preventions of diseases
of several kinds. Plant extracts are known for their antibacterial, antiviral,
antifungal, antioxidant and anti-inflammatory properties (Jassim and Naji 2003).

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Flavonoids, a class of polyphenol
secondary metabolites, are naturally found in plants and diet. From medicinal
point of view, they have great importance as these are very useful compounds
because of antiviral, anti-inflammatory, cardio-protective, anti-diabetic,
anti-cancer and other effects (Wang et al.,
2017). Flavonoids are actually derived from malonyl-CoA and the aromatic amino
acid phenylalanine approximately 8000 different flavonoid compounds have been
identified (Yeon et al, .2014).
Flavonols are secondary metabolites found in many plants whether they are
gymnosperms, angiosperms, mosses, ferns and liverworts, these are found to have
antibacterial activity against super bugs. A study indicated that the extracts
and isolated flavonols of T. minuta
have wide range of antibacterial activity (Shahzadi and Shah, 2015).

The flavonoid biosynthethic pathway is
one of the most extensively studied pathways of plant secondary metabolites (Winkel-Shirely,
2001).In Arabidopsis,maize,petunia,snapdragon,apple and grape the main
structural genes involved in flavonoid pathway have been identified and
characterized (Huang et al.,2013).

1.1 Tagetes
minuta

Tagetes
minuta (Wild marigold) belongs to sunflower (Asteraceae)
family and has been used for chest infections, coughs and repiratory
inflammations etc.  Tagetes minuta essential oil has the ability to work against both
gram-positive and gram- negative bacteria. The studies have also confirmed the
antifungal activities of Tagetes minuta essential oil against Aspergilus, Penicillium and Candida species
(Karimian et al., 2014). Essential
oil extracted from leaves had shown better antifungal activities against eight
phytopathogenic fungi including Alternaria solani (Gakuubi et al., 2016).

1.1.1
Taxonomy and Origin of Wild marigold

Tagetes minuta
 is annual aromatic herb belonging to the
Asteraceae (Compositeae) family and the genus Tagetes (Shahzadi et al., 2010; Gakuubi et al., 2016).This plant has many common
names such as Wild marigold, mexican marigold, stinkweed, stinking roger and
khaki bush (Gakuubi et al., 2016).Wild
marigold is indigenous to the temperate forest and mountain areas of the world.
It was coined in South America and spread around the globe as a weed. It has
been found in South Africa, Australia, Nigeria, India, Uruguay, East Africa
(Kenya), Brazil, Chile, France and the Chaco region of Paraguay. The oil of
this plant is famous and the main “Tagetes oil” producing countries are France,
Kenya, Argentina and Australia (Singh et
al., 2003). In Pakistan wild marigold is naturally found in North west
parts including swat and Hazara district in Khyber Pakhtunkhwa and it is
locally named as Gul-e- Sad Barga (Shahzadi et
al., 2010).

1.1.2
Morphology of Wild marigold

Tagetes minuta is aromatic, annual herb
with height reaching 50-150 cm (0.5-1.5m).The leaves are 3-30cm in lengh and
0.7-8cm wide. The color of leaves is dark-green to slightly glossy green and
contain 9-17 leaflets. The flowers heads are yellow in color and are arranged
in solitary clustered panicled branches (Figure 1.1).The underside of leaves
have multiple glands which produce aroma when ruptured (Gakuubi et al., 2016).