Plants had been used for medicinal purposes long before recorded history. Ancient Chinese and Egyptian papyrus writings describe medicinal uses for plants as early as 3000BC. Indigenous cultures(such as African and Native Americans) used herbs in their healing rituals, while others developed traditional medical systems in which herbal therapies were used. Researchers found that people in different parts of the world tended to use the same or similar plants for the same purposes.Traditional medicine is the sum total of knowledge, skills and practices based on the theories, beliefs and experiences indigenous to different cultures that are used to maintain health, as well as to prevent, diagnose, improve or treat physical and mental illnesses (Pretty,2011).
Herbal medicines include herbs, herbal materials, herbal preparations, and finished herbal products that contain parts of plants or other plant materials as active ingredients. (W.H.O., 2008).
Recently, the World Health Organization estimated that 80% of people worldwide rely on herbal medicines for some part of their primary health care. The remaining 20% of individuals living in industrialized countries uses, in at least 25% of cases, pharmaceuticals which have been directly derived from plant products. The use of medicinal plants in complementary and alternative medicine has seen a great increase in recent years especially in Asia and Europe. One of the main reasons for the increasing use of traditional medicine is a growing trend for patients to take a more proactive approach to their own health and to seek out different forms of self-care. In the process, many consumers have turned to natural traditional medicinal products and practices, under the assumption that “natural means safe”(W.H.O, 2004). A vast family of plant kingdom has been explored from time immemorial for their medicinal values. These include: Euphorbiaceae, Fabaceae, Rubiaceae, Apocynaceae, Solanaceae, Sterculiaceae and many others. Many of these plants used as medicine were derived from ethnomedicinal plant sources.Plants have diverse pharmacological roles they play in the health of people, these pharmacological roles have depended on the occurrence of varieties of chemical components in the plants (Duke and Wain, 1981). Medicinal plants are sources of a number of novel chemical compounds(Boret al., 1998). The metabolites that have effects on human health are known as phytochemicals. Phytochemicals are compounds derived from plants which possess vast biological properties. They are divided into two major types: primary and secondary plant metabolites. Examples of primary plant metabolites include: carbohydrates, amino acids, fatty acids, lipids, steroids and phenolics.Secondary metabolites are responsible for the medicinal effects of plants (Deyu, 2007).Examples of such chemicals include alkaloids, flavonoids, saponins, phenol compounds, steroids and proteins (Negemet al., 1980)
Significance of Medicinal Plants to Man
- Many of medicines today are produced indirectly from medicinal plants. For example, reserpine from Rauwolfiavormitoria, Digoxin from Digitalislanata.
- Plants are directly used as medicine by a majority of cultures around the world. For example, Chinese medicine and Indian medicine.
- Many food crops have medicinal value, hence are sold to generate income. For example, cocoa.
- Medicinal plants are sources for new drugs. It is estimated that there are more than 250,000 flowering plant species of important medicinal value.
- Studying medicinal plants helps to understand plant toxicity and protect human and animals from natural poison.
- Cultivation and preservation of medicinal plants protect biological diversity, for example metabolic engineering of plants.
The study of medicinal plants has created an essential area for further studies and research, and the discovery of new lead compounds for drug development (Verpoorte, 2009).
1.1 FAMILY: FABACAEAE
The Fabaceae or Leguminosae commonly known as the legume, pea, or bean family, are a large and economically important family of flowering plants. It includes trees, shrubs and herbaceous plants perennials or annuals, which are easily recognized by their fruits (legume) and their compound, stipulated leaves. The group is widely distributed and is the third-largest land plant family in terms of number of species, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species (Judd et al., 2002). The largest genera are Astragalus(over 2,400 species), Acacia (over 950 species), Indigofera(around 700 species), Crotalaria (around 700 species), and Mimosa (around 500 species), which contain around 9.4% of all flowering plant species (Magalion and Sanderson, 2001). The Fabaceae is the most common family found in tropical rainforests and in dry forests in the Americans and Africa (Burhametal., 2004).
1.2 GENUS: Albizia
Albizia is a genus of about 150 species of mostly fast-growing subtropical and tropicaltrees and shrubs in the subfamily Mimosoideae of the familyFabaceae. The genus is pantropical, occurring in Asia, Africa, Madagascar, America and Australia, but mostly in the Old World tropics. In some locations, some species are considered weeds. They are commonly called silk plants, silk trees, or sirises. Some species are commonly called mimosa, which more accurately refers to plants of genus Mimosa. Species from southeast Asia used for timber are sometime termed East Indian walnut. The leaves are pinnately or bipinnately compound. The small flowers are in bundles, with stamens much longer than the petals. The stamens are usually showy, although in some species such as A. canescens the flowers are inconspicuous. Unlike those of Mimosa, Albizia flowers have many more than 10 stamens. Albizia can also be told apart from another large related genus, Acacia, by its stamens, which are joined at the bases instead of separate. Albizias are important forage, timber, and medicinal plants, and many are cultivated as ornamentals for their attractive flowers ( Lowry et al., 1994)
1.3 SPECIE: ALBIZIA ZYGIA
English: West African albizia, West African walnut
Yoruba: Ayin-rela(Orwaet al., 2009)
1.3.1 Geographic distribution
Albiziazygia is widespread in tropical Africa, occurring from Senegal in the west to Kenya in the east and northern Angola and Tanzania in the south (Apertorgbor, 2007). Geographical area include: Benin, Cameroun, Central African Republic, Democratic Republic of Congo, Gabon, Gambia, Ghana, Guinea Bissau, Guinea, Ivory Coast, Kenya, Liberia, Mali, Mozambique, Nigeria, Senegal, Sudan, Tanzania, Uganda.(USDA, 2014)
Albiziazygia is a deciduous tree 9-30 m tall with a spreading crown and a graceful architectural form. Bark is grey and rough. Young branchlets are densely to very sparsely clothed with minute crisped puberulence, usually soon disappearing but sometimes persistent. Leaves pinnate, pinnae in 2-3 pairs and broadening towards the apex, obliquely rhombic or obovate with the distal pair largest, apex obtuse, 29-72 by 16-43 mm, leaves are glabrous or nearly so. Flowers subsessile, pedicels and calyx puberulous, white or pink; stamina tube exserted for 10-18 mm beyond corolla, Fruit pod oblong, flat or somewhat transversely plicate, reddish-brown in colour, the seeds of A. zygia are smaller (7.5-10 mm long and 6.5 to 8.5 mmwide) and flatter than either of the other Albizia species, but have the characteristic
round shape, with a slightly swollen center (Orwaet al 2009).
Albiziazygia occurs in lowland semi-deciduous and evergreen forest, in East Africa up to 1400 m altitude. In West Africa it is most common in secondary forest in the semi-deciduous foresst zone, but can also be found in lower numbers in both forested savanna and evergreen forest. It is locally common and shows no preference for wet or dry sites. It is tolerant to acid soils and shows some drought tolerance(Apertorgbor, 2007).
In traditional medicine, bark sap is instilled in the eyes to treat ophthalmia. A bark decoction is administered to treat bronchial diseases, fever (including malaria) and female sterility, and as a purgative, stomachic, antidote, vermifuge and aphrodisiac. Pounded or rasped bark is applied externally to treat yaws, sores, wounds and toothache(Apertorgbor, 2007).
Ground roots are added to food to treat cough and as an expectorant (Apertorgbor, 2007). It is also used as an antidote, cutaneous and sub-cutaneous parasitic infection (Burkill, 1985).
The roots have been reported to be used in the treatment of tuberculosis in Lake Victoria region in Kenya (Abereetal., 2014).
Leaf decoctions are used to treat fever and diarrhea, dysentery, insanity and pain killers (Apertorgbor, 2007; Burkill, 1985).
Albiziazygiahas been found to contain of bioactive xanthones, benzophenones and flavonoids in the stem bark of Albiziazygia (Oyewoet al., 2004)
The methanol extract of the stem bark contain alkaloid, saponins, glycosides, steroids, resins and reducing sugars, while flavonoid and cardio active glycosides were only observed with hexane extract (Oloyodeet al., 2013).
In addition to lupeol, chondrillasterol and p-hydroxybenzoic acid, three flavones were isolated for the first time from the bark of Albiziazygia. The latter compounds were identified as 3’,4’,7-trihydroxyflavone (1), 3-Omethoxyfisetin (2), and 3’,7-dihydroxyflavonone (3).Their structures were determined by Nuclear magnetic resonance and Mass spectrometry techniques and confirmed by comparison with the literature (Ndjakouet al., 2007).