Introduction

Trees and shrubs are the source of many products beside timber. Their extracts have been used to combat several diseases¹. Africans from earlier times had learned to extract natural colours from trees and shrubs for a number of end uses such as cosmetics and small scale textile handicraft.

Bixa orellana popularly called “Annatto” of the family Bixaceae is a tropical plant of a small tree or shrub. The seed yielded the orange dye used for colouring foodstuffs, soaps and various fabrics². Morinda lucida, family Rubiaceae, is a medium sized tree grown in tropical Africa. Its wood produce a yellow dye of high molar absorptivity³. Zanthoxylum zanthoxyloides belongs to the family Rutaceae and its stem/root bark yields red dyes. The colouring potential of the dye on cotton fabric had been reported⁴. Zingiber officinale (Ginger) is a perennial tropical herb with underground branching stems called rhizomes. It belongs to the Zingiberaceae family. The rhizomes yield the yellow dye which had been characterised⁵. Popoola et al., had found the colourant useful in textile and non textile applications. Pterocarpus erinaceous belong to the family Papilionaceae. It is one of the various species of red wood known as Barwood⁷. P. erinaceous is the common species in Western Nigeria and is popularly known as African Rose wood. The wood also yields a red dye. Sorghum caudatum is of the most important cereals after rice and maize in the tropics. It belongs to the family Gramineae and its leaves yields a red dye⁷.

The present work reports the phytochemical and antibacterial properties of these six dye plants’ extracts.

Materials and Methods

Source & Extraction

The plants part (Table 1) were purchased at ‘Oja Oba’ market at Akure, Ondo State and identified. The samples were cleansed, dried in an oven at 105°C for 6hr and pulverised. Each sample was extracted at a solute-solvent ratio of 1:25 for 6hr in a Soxhlet extractor.

Phytochemical screening

The extracts were evaluated for the presence of alkaloids, glycosides, reducing sugars, saponins, tannins, flavonoids and phlobatanins⁸.

Table 1 : Dye Plants evaluated for

phytochemical and antimicrobial activity

Alkaloids

About 0.2g of the extracts were warmed with 2% H₂SO₄ for two minutes. It was filtered and few drops of Dragencloff’s reagent were added. Orange red precipitate indicates the presence of alkaloids.

Glycosides

The extract was hydrolysed with dilute HCl solution and neutralized with sodium hydroxide solution. A drop of Fehling’s solution A and B were added. Red precipitate indicates the presence of glycosides.

Reducing sugars

The extract was shaken with distilled water and filtered. The filtrate was boiled with drops of Fehling’s solution A and B for two minutes. An orange red precipitate indicates the presence of reducing sugars.

Saponins

About 0.2g of the extract was shaken with 5ml of distilled water and then heated to boil. Frothing (appearance of creamy mass of small bubbles) shows the presence of saponins.

Tannins

Small quantity of extract was mixed with water and heated on water bath. The mixture was filtered and ferric chloride was added to the filtrate. A dark green solution indicates the presence of tannins.

Flavonoids

Extract (0.2 g) was dissolved in diluted NaOH and HCl was added. A yellow solution that turns colourless indicates the presence of flavonoids.

Phlobatanins

The extract (0.5 g) was dissolved in distilled water and filtered. The filtrate was boiled with 2% HCl solution. Red precipitate shows the presence of Phlobatanins.

Antibacterial Screening

Preparation of Medium

Nutrient Agar (LAB M) used for the antagonistic test was prepared according to Manufacturer’s instruction and sterilized at 121°C for 15 minutes.

Indicator Bacteria

Stock culture of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were obtained from the Microbiology Department, Federal University of Technology, Akure. The cultures were maintained throughout the duration of the work on agar slant.

Table 2 : Inhibition of bacterial growth by the dye plants extracts Zone of Inhibition (mm)

Table 3 : Phytochemical analysis of the ethanol extract of the dye plants

Antibacterial Assay

The agar well diffusion for antibacterial test described by Schillinger and Lucke was adopted⁹. Overnight broth culture of the indicator bacteria were used to seed agar before pouring into plates. This was done in triplicate for each of the indicator bacteria. Two wells were made on the seeded agar plate with the aid of sterile cork borer of diameter 12mm. One well which contain sterile ethanol serves as control while the other was filled with the ethanol extract of the plant.

Results and Discussion

The antibacterial assay showed that the ethanol extract of Z. zanthoxyloides, Zingiber officinale and Morinda lucida were able to inhibit the growth of the three indicator bacteria with the zone of inhibition between 0.50-11.6mm (Table 2). The extract of Sorghum caudatum, Bixa orellana and Pterocarpus erinaceous could not inhibit all the bacteria. Extract of Zanthoxylum zanthoxyloides was found to be more active against Staphylococcus aureus with a zone of inhibition of 11.6mm.

The result of the phytochemical screening reveals that the dye extracts contain either two or one of tannins and flavonoids. This may be responsible for their antibacterial properties¹⁰. Pamplona Roger¹¹ had earlier reported that plant extracts containing chemicals with antibacterial properties have been useful in treating bacterial and fungal infections.

In addition, inhibitory properties of these dye extracts may also enhance the stability of these plants colourants as added additives to polymer substrate.

References

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2. Kochnar, S.L. Tropical Crops: A textbook of economy botany, Macmillan Pub. Ltd., London, 268-271 (1981)
3. Adetuyi, A.O., Popoola, A.V. and Lajide, L. Isolation, Purification, and UV-Visible Spectroscopic study of the colourant from Morinda lucida plant. Journal of Applied Science, 5(4) 3173-3185 (2002)
4. Adetuyi, A.O. and Popoola, A.V. Extraction and Dye ability potential studies of the colourant in Zanthoxylum zanthoxyloides plant on cotton fabric, Journal of Science Engineering Technology, 8(2), 3291-3299 (2001)
5. Adetuyi, A.O., Popoola, A.V. and Ipinmoroti, K.O. Extraction and structural elucidation of the colouring pigment (Dye) in Ginger (Zingiber officinale) rhizome, Journal of Science Engineering and Technology, 7(4), 2870-2880 (2000
6. Popoola, A.V, Ipinmoroti, K.O., Adetuyi, A.O. and Ogumoroti, T.O. Extraction, Spectroscopic and colouring potential studies of the dye of Ginger ( officinale) rhizome. Pakistan Journal of Science and Industrial Research, 37(5), 217-220 (1994)
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9. Schillinger, U. and Lucke, F. Antibacterial activity of Lactobacillus sake from meat. Applied and Environmental Microbiology, 55, 1901-1906 (1989)
10. Sofowora, A. Medicinal Plants and Traditional medicine in Africa, 2nd edn., John Wiley and Sons, New York, 6-56 (1993)
11. Pamploma – Roger, G.D. The Encyclopedia of Medicinal plants, Education and Health Library, 2nd edn. Spain, 76-97 (1999)