Alchornea laxiflora AQUEOUS LEAF EXTRACT: ITS ALLELOPATHIC POTENTIAL AND BIOACTIVE AGENTS
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Date
2017-12
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UNIVERSITY OF ILORIN
Abstract
The dangers posed by synthetic herbicides necessitated the need to search for eco-friendly alternatives in some plants by exploring their allelopathic property. Allelopathic plants have the ability to inhibit the growth and survival of surrounding plants. The aim of this experiment was therefore to evaluate the allelopathic potential of Alchornealaxiflora and to isolate the bioactive agents responsible. The objectives of the study were to: (i) screen Alchornealaxiflora aqueous leaf extract for the presence of secondary metabolites; (ii) examine the growth inhibitory, germination inhibitory and genotoxic effects of the extract; (iii) determine the effects of the extract on some photosynthetic and lipid synthesis parameters; (iv) determine the effects of the extract on oxidative stress parameters; (v) determine the effect of the extract on some osmotic stress indicators; (vi) carry out a bioactivity-guided isolation and identification of the bioactive agents; (vii) conduct an autodock analysis using enzymes.
The extract was first subjected to Alliumcepa test to evaluate the growth-inhibitory and genotoxic effects (reduction of mitotic index, chromosomal aberration), then tomato seedlings were used to further evaluate its germination inhibitory and other phytotoxic effects (photosynthesis inhibition, lipid synthesis inhibition, oxidative stress induction, osmotic stress induction)with atrazine as standard. Thereafter, it was subjected to standard chromatographic techniques involving bioactivity-guided fractionations, thin layer chromatography and high performance liquid chromatography as well as isolate the bioactive agents responsible for the allelopathic property. Finally, the isolated compounds were subjected to molecular docking techniques using enzymes (Ferredoxin NADP-reductase and Acetyl CoA carboxylase and alpha amylase) to further confirm the bioactive agents. Data were subjected to Analysis of Variance Test at p˂0.05.
The findings of the studywere that the extract:
i. contained a number of secondary metabolites including alkaloids, phenol, phlobatannins, terpenes, tannin andflavonoids.
ii. caused significant reductions (p˂0.05) in growth, germination,and abnormalities in chromosomal activities in tomato seedlingsandAlliumcepa root cells.
iii. caused significant reductions (p˂0.05) inChlorophyll contents and activities of Ferredoxin NADP-reductase and Acetyl CoA carboxylase enzymes of tomato seedlings.
iv. caused significant increases (p˂0.05) in Malondialdehyde concentrations and decreasesin activities of antioxidant enzymes (Superoxide dismutase, Catalase andPeroxidase).
v. caused significant increases (p˂0.05) in protein, proline and total soluble sugarconcentrations.
vi. contained Rutin and Quercetrin as its Allelochemicals.
vii. contained Rutin and Quercetrin which interacted favourably with the amino acid residues on Alpha amylase, Acetyl-coA carboxylase and Ferredoxin NADP-reductase.
The study concluded that Rutin and Quercetrin are partly responsible for the allelopathic activity exhibited by Alchornealaxifloraaqueous leaf extract. It is therefore recommendedthat Alchornealaxifloramay be used as a source of templates for the development of bio-herbicides.
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Keywords
Alchornea laxiflora, AQUEOUS LEAF EXTRACT, ALLELOPATHIC POTENTIAL, BIOACTIVE AGENTS, Allelopathic plants