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Isolation of Phomopsis Inhibitory Fraction of Allamanda Extract Removing Gum and Other Undesirable Compounds

F. Ahmed
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

F. Yasmin
Soil Science Division, Bangladesh Agricultural Research Institute, Joydevpur, Gazipur, Bangladesh

M. B. Meah
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Allamanda leaf extracts were made by three organic solvents hexane, methanol and ethyl acetate having different polarities. Thin layer chromatography (TLC) of the refluxing extracts showed each of them contained considerable number of different compounds. By observing Rf value of these extracts it was confirmed that the compounds present in different extracts are not same and two of them (methanol and ethyl acetate) extracts were distilled to remove solvent for bioactivity test. In growth inhibition test, methanol and ethyl acetate extracts of allamanda inhibited mycelial growth of Phomopsis vexans. Ethyl acetate extract at 0.2% and 0.3% concentration inhibited 100% mycelial growth of Phomopsis vexans while methanol extract was not effective in suppressing growth rather it arrested temporarily the growth of Phomopsis vexans. Eggplant seeds treated with ethyl acetate extract in blotter produced higher percentage of seed germination (85.00%) and healthy seedlings (88.36%) and lower percentage of dead seed (15.00%), and rotten seed (5.89%) than those treated with methanol extract. In most cases, seed quality was improved with the increasing of concentration of ethyl acetate extract. It may be summarized that higher amount of antifungal compounds were present in ethyl acetate extract in purified form where methanol also have some compounds that inhibited partially growth of Phomopsis vexans.

Keywords: Allamanda extract, Phomopsis vexans, Thin layer chromatography

Location: Plant Disease Diagnostic Clinic (PDDC), Department of Plant Pathology and Chemistry Laboratory, Department of Agricultural Chemistry, Bangladesh Agricultural University (BAU), Mymensingh

Start Date: 00-03-2011

End Date: 00-04-2012

Program Area: Pest Management

Commodity: Diseases

Objectives:

1. The present research was undertaken to remove gum, oil and other undesirable compounds except Phomopsis inhibitory compounds from allamanda leaf extract.

Methodology:

An experiment was conducted at the Plant Disease Diagnostic Clinic (PDDC), Department of Plant Pathology and Chemistry Laboratory, Department of Agricultural Chemistry, Bangladesh Agricultural University (BAU), Mymensingh, during March 2011 to April 2012. Allamanda extract preparation - For preparation of allamanda extract, 100 g dried and powdered allamanda leaves were taken in a thimble and 750 ml n-hexane was taken in a round bottom flask. The extraction was done by refluxing organic solvent (n-hexane) for about 10 hours in a water bath keeping the temperature not more than 65⁰C ± 2⁰C. At the end, allamanda extract was collected from refluxing apparatus and filtered). Then again the dried and extracted powder was taken in the thimble and 150ml n-hexane added in soxhlet apparatus. Extraction was continued for 15 hours in a water bath keeping the temperature not more than 65±2⁰C. At the end allamanda extract was collected from soxhlet apparatus and the thimble was washed. The leaf extract was labeled and preserved in a conical flask for further use. Same procedure was followed for the preparation of allamanda leaf extract by ethyl acetate and methanol by the same procedure. These three extracts were partially concentrated and used for bio-assay against Phomopsis vexans. Bio-assay of allamanda extracts - Isolate-22 of Phomopsis vexans collected from IPM Lab, Department of Plant Pathology, BAU was used for bio-assay. Laboratory experiment for bio-assay of methanol and ethyl acetate extracts against Phomopsis vexans was set following Completely Randomized Design (CRD) with four treatments with four replications for each extracts and both extracts were tested separately against Phomopsis vexans in vitro following growth inhibition technique. Inhibition percentage of the Phomopsis vexans was calculated by the following formula. % inhibition = (X - Y)/X x 100, Where, X = Mycelial growth/diameter of the colonies of Phomopsis vexans in absence of allamanda extracts i.e. control. Y = Diameter of the colonies of Phomopsis vexans in presence of allamanda extracts i.e. methanol and ethyl acetate extracts. Seed treatment with allamanda extracts - Eggplant seeds were left soaked in Phomopsis vexans suspension for 30 minutes. Then liquid was drained off and incubated in laminar air flow chamber for overnight. The sample seeds were dipped in the methanol and ethyl acetate extracts solution for 15 min. The liquid was drained off seeds, shade dried before plating. The experiment was set following Completely Randomized Design (CRD) with five treatments and four replications for each extract. The treatments were no treatment+ pathogen uninoculated (Control), no treatment+ pathogen inoculated (T1) and 0.1 (T2), 0.25 (T3) and 0.3% (T4) of both extracts were used. Treated seeds were incubated in blotter following blotter technique.

Source of Information: J. Environ. Sci. & Natural Resources, 5(2): 199 - 203 , 2012; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Allamanda extract may be used as alternatives to chemical pesticide for controlling Phomopsis blight and seedling disease of eggplant especially caused by Phomopsis vexans which might be economic, easy to use and eco-friendly. As the active ingredient may remain in purified allamanda extract so the formulation might be more active than before which will be also sustainable for our farmers.

Knowledge Management: Journal