Development of quality indicators of a new biostimulant from paracetamol waste

Introduction. In recent years, there has been a substantial rise in the utilization of biostimulants in agricultural crop production. The authors’ extensive research over the years has revealed that the byproduct of bacterial degradation of paracetamol exhibits a notable stimulatory effect on various medicinal and agricultural plants from different families. It serves as an inducer for the accumulation of biologically active substances in these plants, thereby making it a promising and efficient biostimulant.

The purpose of this study is to establish a comprehensive set of indicators and create a preliminary specification for the quality control of the bacterial degradation product of paracetamol, which serves as a new biostimulant for medicinal and agricultural plants.

Material and methods. For this study, we utilized the bacterial degradation product of paracetamol, derived from a pharmaceutical substance with an expired shelf life. The product was obtained from the Laboratory of Alkanotrophic Microorganisms, Perm Federal Research Center UB RAS (Perm). We employed various methods to analyze the product, including determining the melting point through the capillary method, assessing lead, cadmium, and arsenic content using an atomic absorption spectrometer with electrothermal atomization (MGA-915M, Lumex, Russia) and the Mga software on a personal computer running the Windows®-2000/XP operating system. Additionally, we recorded the IR spectrum using a Specord M80 IR spectrometer (Carl Zeiss Industrielle Messtechnik GmbH, Germany), and the electronic spectra were obtained with a Lambda EZ 201 spectrophotometer (PerkinElmer, USA). The quantification of phenolic hydroxyl and carboxyl groups was performed through back acid-base potentiometric titration.

Results: The product of bacterial degradation of paracetamol is practically insoluble in water, ether, very slightly soluble in chloroform, slightly soluble in hexane and acetonitrile, soluble in acetone and ethyl acetate, freely soluble in methyl alcohol, 95% ethyl alcohol and dimethyl sulfoxide. The melting point ranged from 150 to 206 °C, with decomposition. The heavy metal and arsenic content in samples of the product with varying shelf life complied with the standards outlined in general pharmacopoeia monograph 1.5.3.0009.15. The IR spectrum exhibited characteristic absorption bands of functional groups, including C–H aromatic (3042 cm^-1), –OH phenolic (3425 cm^-1), –NH– (3200 cm^-1), and C= N (1609 cm^-1). The electronic spectra of product solutions, in the concentration range of 5·10^-6 to 2.5·10^-5 g/cm³, displayed absorption maxima at λ=218 and λ=318 nm. The content of phenolic hydroxyls in the product composition ranged from 4.22 to 5.16 mmol-eq/g, while carboxyl groups ranged from 1.76 to 3.05 mmol-eq/g, comparable to the quantities found in humic acids.

Conclusions. We have established a comprehensive list of indicators and developed a preliminary specification for the quality control of the bacterial degradation product of paracetamol as a biostimulant for medicinal and agricultural plants.