Hydroquinone; A Novel Bioactive Compound from Plant-Derived Smoke Can Cue Seed Germination of Lettuce

Abstract

Plant-derived smoke has been known to play an important role in distribution and growth of vegetation. Using a proficiently designed furnace, we extracted smoke from the leaves of four plant viz. Helianthus annuus,Aloe vera,Ginkgo biloba, and Cymbopogon jwarancusa. Smoke dilutions obtained from these plants were obtained in different concentrations to identify potential lettuce growth promoting smoke solution. Results revealed that smoke obtained from G. biloba significantly enhanced the lettuce seed germination. This solution was then partitioned into ethyl acetate, dichloromethane, n-hexane, chloroform and ether fractions. Ethyl acetate fraction was found to be potent to enhance seed germination. This fraction was subjected to column chromatography and spectroscopic techniques to obtain compound 1. This compound was identified as hydroquinone using 1D and 2D NMR techniques. At low concentrations (5, 10, and 20 ppm), compound 1 enhanced the lettuce seed germination; however, higher concentrations inhibited its growth as compared to control.

Keywords: Ginkgo biloba; column chromatography; hydroquinone; lettuce; plant-derived smoke; secondary metabolites; seed germination.

Figure 1

Furnace design for extraction of plant-derived smoke. A specialized furnace was designed to extract plant derived smoke. An electric heater was used to produce heat for making smoke of plant material inside the furnace. The smoke was collected in to a glass beaker, containing 1 L DW. The concentrated smoke solution was diluted for further use. The background of the picture was changed for more clarity.

Figure 2

Effect of various dilutions of smoke solution extracted from Helianthus annuus, Aloe vera, Ginkgo biloba, and Cymbopogon jwarancusa. The smoke extracts diluted with autoclaved distilled water with 1:50, 1:100 and 1:500; while sole distilled water was used as control. For each set of treatment, the different letters indicates significant differences (P < 0.05) between smoke extracts and control treatments as evaluated by Duncan Multiple Range Test. Error bars refers to SE.

Figure 3

Effects of Ginkgo biloba derived smoke extracts (50, 100, 300, and 500 ppm concentration) of n-hexane, ether, dichloromethane, chloroform, and ethyl acetate on lettuce seed germination rate. Sole distilled water was used only as control against smoke of various concentration extracted in n-hexane, ether, dichloromethane, chloroform and ethyl acetate. For each set of treatment, the different letters indicates significant differences (P < 0.05) between smoke extracts and control treatments as evaluated by Duncan Multiple Range Test. Error bars refers to SE.

Figure 4

Effects of various concentrations of bioactive hydroquinone on the germination and growth of lettuce seed; the experiment was repeated three times comprising three replicates having 20 seeds. (A,B,C) Seed germination response of lettuce seeds in response to 5, 10, 20, 50, and 100 ppm of the bioactive compound 1 (hydroquinone) pictorial presentation shows the data taken after each 24 h. (D) Comparative root/shoot length of all tested dilutions of the hydroquinone, compared with control.

Figure 5

Structure of compound 1. Compound 1 was identified as 1,4-dihydroxybenzene also known as hydroquinone by using 1D and 2D NMR spectral data along with the GC/MS analysis and co-TLC with the authentic sample. At low concentrations (5, 10, and 20 ppm) compound 1 enhanced the lettuce seed germination; however, higher concentrations inhibited its growth as compared to control.

Figure 6

Germination and growth assay of commercially available hydroquinone on lettuce seeds. (A) Germination rate of lettuce under the indicated hydroquinone treatments. (B) Shoot and (C) root length of lettuce in response to the indicated treatments. All the treatments are in ppm. 0 mean control plants treated with distilled water only. The error bars represents ± SE and different letters indicates significant differences (P < 0.05).