|
Ethnobotanical
Leaflets 11: 173-194. 2007. Chemicals Detected in Plants Used
For Folk Medicine in South *Gordian
C. Obute and Godswill O. Adubor Department of Plant Science and Biotechnology, * E-Mail:
goddie_chi@yahoo.com Issued
ABSTRACT Plant species used for folk medicine from diverse
families of angiosperms employed by people in south eastern INTRODUCTION Medicinal
plant species are so regarded because they are sources of well known and medically useful secondary
products as wide-ranging as pain killers like morphine, stimulants like
nicotine, caffeine, cocaine and depressants with high potency in the
management of ailments in humans. Generally, drug plants are unique in
containing compounds that are end-products of long biosynthetic pathways and
are usually not needed in such plants’ metabolic processes. Davis and Heywood
(1963) reported that these compounds called
secondary metabolites include: alkaloids, glycosides, essential oils
and other organic constituents. These constituents are usually
produced in different parts of the plants like the root, leaves, fruits and
seeds and then translocated to other parts of plant for storage (Kochhar,
1981). Knowledge about these medicinally active constituents makes their
application in therapy possible as contained in the various pharmacopoeias.
Recently, in the field of ethno medicine it has been discovered that
therapeutic efficacy was more pronounced when the active compound was left in
a particular combination with other principles naturally present in plant
than when it was isolated and synthesized in the laboratory. In our first
work on medicinal plants, we made a check list of plant species with
medicinal value in the south eastern parts of Nigeria (Obute, 2005); this is
a follow up attempt at determining the types of flavonoids and amounts of
phenolic compounds present in these plant species. Perhaps it is this
discriminating occurrence that makes the various species efficacious in the
treatment of different ailments even if they belong to the same family. Flavonoids Flavonoids are 15-carbon compounds which
occur naturally and are widely distributed
in the plant kingdom appearing in flower, fruits, stems, leaves, roots
and plant derived beverages such as tea and wine. These
are ubiquitous in occurrence in nearly all plants; the ease with which they
are isolated and identified even from small amounts of plant materials as
well make this chemical the most used for medicinal purposes. Flavonoids
protect plants against external pathogens, ultra-violet light or heat. The
most important class of flavonoids include: anthocyanides flavones,
flavonoids, flavanones, flavan-3-01(also known as catechins). Anthocyanins
and coloured compounds in flowers, they facilitate pollination by attracting
insect and aid dispersal of seed in coloured fruits. The red, purple and blue
colours of most flowers and red colour of most fruits and autumn leaves are
due to anthocyanins, some yellow flowers tend to be due to carotenoids. The
anthocyanins are concentrated in the vacuoles, not in the plastids as
carotenoids are. Chemically anthocyanins are B-glycosides of anthocyanins. Flavonoids
possess anti-inflammatory properties and act as modulators of the immune
system in number of biological systems. This stems from the fact that they
are powerful antioxidants protecting biosystems against damaging effects of
free radicals. Most flavonoids belong to a group of chemicals, called
polyphenols, and their antioxidant properties are dependent on this
polyphenolic chemical structure. Phenols Phenols
are characterized by the presence of the hydroxyl group (-OH} and is derived
from hydrocarbons (aromatic hydrocarbon}. The reactivity of phenols is
predominantly determined by the presence of the hydroxyl group. Phenols
are generally referred to by their common names but may also be named as
benzene derivatives. Common examples of phenols include the following:
resorcinol, hydroquinone o-cresol, m-cresol, most of the phenols are noted
for their germicidal properties and cresol is used widely as a wood
preservative. Plants produce many thousands of compounds which contain one or
more phenolic residues, these compounds can be divided into major groups,
according to the number of carbon atom in their skeleton. The current effort
is targeted at listing the types of flavonoids and amounts of phenolic
products present in plant species already known to be medicinal but not yet
exploited by bioprospecting interests. MATERIALS The leaves used for
this study were obtained from different plant species growing in their natural
habitats. These plants as listed in Table 1, are, according to Obute (2005)
used in the ethno medicine of the peoples of the south eastern parts of
Nigeria. Plant collection was done from the premises of university of Port
Harcourt and Eagle Island and its environs close to Rivers State University
of Science and Technology in Port Harcourt Nigeria. Table 1: Species Used In the Study
Flavonoid compounds Leaf parts obtained
from the species were crushed separately and immersed in different glass
vials containing absolute ethanol solution (5mls). The mixtures were left for
two days to ensure adequate extraction. The samples were subjected to
separation protocols using the 2-D paper chromatographic method. A drop of
each solution was collected with a capillary tube and spotted on a designated
area on the chromatographic paper. A series of solvents Butanol-acetic acid
and water in the ratio of 4:1:5; Forestal (Conc. HCl-acetic acid and water)
in the ratio of 30:3:10 and 60:6:20ml and 50% acetic acid were used to carry
out the analysis. Each solvent was
poured into a trough in the chromatographic tank one at a time. The end of
the chromatographic paper nearest to the sample spots was folded
appropriately, dipped into the trough at the top of the chromatographic tank
and the rest of the paper made to hang vertically. Separation of samples
occurred as the solvent front was obtained then the chromatographic paper was
removed and hung to dry. Ammonia solution was used to spray the sheets and
the setup was left to air dry for about 15 minutes and observed under the UV
light to see colours produced. Finally, the RF values
for all the chromatographic papers were calculated by measuring the distance
from the origin to centre of the circle of the colour observed under UV light
divided by the distance between the origin and the solvents front (i.e. the
distance the solvent travelled) multiplied by 100. Distance migrated by
analyte (Da) 100
Distance migrated by the
solvent (Ds) 1 To determine the
flavonoids which may be present in the species, the RF value of each specimen
and their colours in the UV light were used according to the Harborne (1973)
method. Phenolic compounds The leaf samples were
crushed with mortar and pestle and 0.1g of each sample was poured into a
conical flask and 20ml of distilled water was added and the set up was left
to stand for about 10mins (for appropriate extraction) and then filtered into
different conical flasks. 2.5ml of the filtrate
was measured into another conical flask and 5ml of 0.1m NaOH was added. Then
the set up was warmed in a hot plate to 650 C. Then 2.5ml of
iodine was added to each of the samples to obtain brown colouration of the samples.
Then 0.5ml of Conc. HCL was added to the samples, after a drop or two of an
indicator (starch solution) was added and to make the colour change to dark
blue. The process was repeated using a blank (distilled water) titrated with
Na2S2O3 (sodium thiosulphate) until, it
become colourless. To determine the amount of phenolic compounds present in
the specimen, the method of King and
Armstrong (1934) was used and the formula below was used for the computation: Phenol mg/h = (Blank -
sample) x 1.567 x 4 x10 from other calculation the concentration of phenolic
compound. RESULTS It was observed that
most of the species contain flavonols and phenols. The type and amount of
these varied with the species (Tables 2 a&b). It did not follow any
particular phylogenetic pattern as members of the same family had different
types of flavonols while those from dissimilar ones had the same types. The
pattern of distribution of phenolic compounds also shows that there is no
particular order (Table 2b) whereas some had up to 4.76mg/g as in Anarcadium occidentale most showed
1.76mg/g as the least amount. Table 2 a: Chemical Compounds Detected in the species
Table 2 b. The amounts of phenolic compounds
found in each plant.
|
