The Utilization Of Natural Products For Agricultural Benefits

Abstract

The invasive species Psidium cattleianum, termed strawberry guava, poses a major problem for the State of Hawaii. It outcompetes native plants, with the dominance of strawberry guava potentially due to allelopathy, which is the biochemical inhibition of one plant by another. To isolate potential allelochemicals, water extracts from both varieties of strawberry guava (red and yellow), were tested and found to reduce dicot and monocot growth. The yellow variety of strawberry guava produced an Inhibition constant of 50% lethality (IC50) of 10.74mg/mL for lettuce and 12.2 mg/mL for green onion, while the red variety produced a IC50 of 9.57mg/mL for lettuce and 6.54 mg/mL for green onion. In soil trials, it has been found that Psidium cattleianum leaf chemicals reduced the germination rate of the monocot (Echinochloa sp.) more relative to the dicot (Amaranthus retroflexus). High performance liquid chromatography bioassay mediation fractionation and tandem mass spectroscopy found that the phenolic acid, gallic acid, is a constituent for Psidium cattleianum’s allelopathy. Additionally, in-silica molecular docking was conducted with the enzymatic molecular target site, hydroxyphenylpyruvate dioxygenase, to create a predictive model. The trends showed that, based upon 2-acyl-cyclohexane-1,3-diones with simple aliphatic side chains, the perfect R1 tail length is an undecyl 11-C. Too short a tail did not fully utilize the binding pocket, while too long of a tail did not fit within the binding pocket properly, showcased by having a more positive binding energy and a less efficient IC50 value. This class, along with cyclohexane-1,3-diones with phenyl side chains or phenylene side chains also followed another trend, where the addition of an R2 methyl group again made a more positive binding energy and a less efficient IC50 value, possibly due to sterics. This showed proof of concept that it is possible to correlate binding energy and measured IC50 values to create this predictive model that can be adapted to other molecular target sites and ligands. In addition, while only strawberry guava was investigated within the course of this work, there remains multiple suspected allelopathic species than can be further analyzed following strawberry guava’s path as a blueprint for future studies.