Microwave-Assisted Efficient Extraction and Stability of Juglone in Different Solvents from Juglans regia: Quantification of Six Phenolic Constituents by Validated RP-HPLC and Evaluation of Antimicrobial Activity

Abstract

In the present study, microwave-assisted extraction was compared with conventional approaches for the efficient extraction of juglone and other phenolics from Juglans regia bark. The effect of different solvents was also studied and ethyl acetate was found to be a better solvent in terms of juglone yield and stability. Further, a simple and fast RP-HPLC method was developed and validated for the determination of juglone and other bioactive phenolics like gallic acid, caffeic acid, quercetin, myricetin, and quercitrin in these extracts. In addition, the extracts were tested for antimicrobial activity against 16 microorganisms where all the extracts showed broad spectrum activity.

Keywords:

• Antimicrobial activity
• juglone
• Juglans regia
• microwave assisted extraction
• phenolic compounds
• RP-HPLC
• stability

The authors are grateful to the Council of Scientific & Industrial Research, New Delhi, India, for its financial support during the course of this project. The authors are also thankful to the Director, IHBT, for providing necessary facilities during the course of the work. N. Sharma and U. K. Sharma are thankful to CSIR, Delhi, for the award of the senior research fellowship.

Notes

^a No degradation.

^a antibiotics for bacteria.

^b antibiotics for fungi. MTCC No. in parenthesis.