Rational Design, Synthesis and Evaluation of Indole Nitrogen Hybrids as Photosystem II Inhibitors

Area of Science:

• Organic Chemistry
• Plant Physiology
• Biochemistry

Background:

• Photosystem II (PSII) is a critical complex in photosynthesis, making it a target for herbicide development.
• Indole derivatives have shown potential bioactivity, but their specific roles in inhibiting plant growth require further investigation.

Purpose of the Study:

• To synthesize and characterize novel indole derivatives.
• To evaluate the potential of these compounds as inhibitors of photosynthesis and plant growth.
• To elucidate the mechanism of action at the molecular level.

Main Methods:

• Fischer indole methodology for synthesis, followed by reduction/acetylation and amidation.
• Chlorophyll a (Chl a) fluorescence measurements to assess photosystem II (PSII) inhibition.
• In vivo studies on weed biomass reduction (Ipomoea grandifolia, Senna alata).
• Molecular docking to investigate interactions with the PSII protein D1.

Main Results:

• Twelve indole derivatives were synthesized and characterized.
• Compounds 15a (6-chloro-8-nitro-2,3,4,9-tetrahydro-1H-carbazole) and 15b (5-chloro-2,3-dimethyl-7-nitro-1H-indole) significantly inhibited PSII.
• These compounds reduced key fluorescence parameters (ABS/RC, TR0/RC, ET0/RC) and decreased weed dry biomass by approximately 40% and 37%, respectively.
• Molecular docking indicated that electron-withdrawing groups on the indole phenyl ring are crucial for binding to the PSII protein D1.

Conclusions:

• The synthesized indole derivatives, particularly 15a and 15b, show significant potential as herbicides.
• Inhibition of PSII electron transport is a key mechanism for their herbicidal activity.
• Further optimization of these molecular features could lead to the development of novel, potent herbicides.