Chemicals Detected in Plants Used For Folk Medicine in South Eastern Nigeria

*Gordian C. Obute and Godswill O. Adubor

Department of Plant Science and Biotechnology, University of Port Harcourt, Choba, Port Harcourt Nigeria

* E-Mail: goddie_chi@yahoo.com

ABSTRACT

Plant species used for folk medicine from diverse families of angiosperms employed by people in south eastern Nigeria were analysed for the basic chemical compounds that make them medicinal. It was observed that flavonols and Phenolic compounds were widespread in these plants. However, the types and amounts of these chemicals varied for even species in the same family.

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 AND METHODS

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

S/N	Name of species used in medicine	Family
1	Persea americana Mil.	Lauraceae
3	Newbouldia laevis (P. Beaux) Seeman Ex Bureau	Bignoniaceae
4	Phyllanthus amarus Schum and Thonn	Euphorbiaceae
5	Costus lucanusianus L.	Costaceae
6	Chromoleana odorota (L) K R	Asteraceae
7	Ageratum conyzoides L.	Asteraceae
14	Vernonia amygdalina Del.	Asteraceae
2	Aspilia africana (Pers) C.D. Adams	Asteraceae
8	Carica papaya L	Caricaceae
9	Anacardium occidentale L.	Anacardiaceae
10	Psidium guajava L.	Myrtaceae
11	Telfairia occidentalis Hook. fil.	Cucurbitaceae
12	Mangifera Indica L	Anacardiaceae
13	Caesalpinia pulcherima (L) SW.	Caesalpiniaceae
15	Cymbopogon citratus (DC) Staps.	Poaceae
16	Avicennia germinans L.	Avicenniaceae (Verbenaceae)
17	Rhizophora racemosa G. F. W. Meyer	Rhizophoraceae
18	Rhizophora mangle L.	Rhizophoraceae
19	Nypa fruticans (Wumb).	Arecaceae (Palmae)
20	Senna alata L. Syn. Cassia alata, Herpetica alata	Fabaceae

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

RF = X

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

S/N	Name of plants	Family	Flavonoid Present
1	Persea americana Mil.	Lauraceae	Myricetin (Flavonols)
2	Aspilia africana (Pers) C.D. Adams	Asteraceae	Gossypetin (Flavonols)
3	Newbouldia laevis (P. Beaux) Seeman E.X. Bureau	Bignoniaceae	Quercetin (Flavonols)
4	Phyllanthus amarus Schum & Thonn	Euphorbiaceae	Kayaflavone (Biflavonyl) Chrysoeriol (Flavonols)
5	Costus lucanusianus L	Costaceae	Myricetin (Flavonols)
6	Chromoleana odorota (L) K.R	Asteraceae	Isorhamnetin (Flavonols)
7	Ageratum conyziodes L	Asteraceae	Luteolin (Flavones)
8	Carica papaya L.	Caricaceae	Kaempferol (Flavonols)
9	Anacardium occidentale L	Anacardiaceae	Keampferol (Flavonols)
10	Psidium guajava L	Myrtaceae	Kayaflavone (Biflavonyls)
11	Telfairia occidentalis Hooker .F.	Cucurbitaceae	Isorhomnetin (Flavone)
12	Mangifera indica L	Anarcadiaceae	Querecetin (Flavonols)
13	Caesalpinia pulcherrima (L) Sw	Caesalpiniaceae	Azaleatin (Flavonols)
14	Vernonia amygdalina	Asteraceae	Myricetin (Flavonols)
15	Lemon grass (Dc) Staps	Poaceae	Azaleatin (Flavonols)
16	Rhizophora mangle	Rhizophoraceae	Gossypetin (Flavonols)
17	Rhizophora racemosa G.F.W Mayer	Rhizophoraceae	Querecetin (Flavonols)

Table 2 b. The amounts of phenolic compounds found in each plant.

S/N	Plant species Amount of phenolic product
1	Newbouldia laevis 1.76mg/g
2	Anacardium occidentale 4.76 mg/g
3	Chromoleana odorota 3.51mg/g
4	Ageratum conyzoides 1.76mg/g
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