Antimicrobial activity of the extracts and physalin D from Physalis alkekengi and evaluation of antioxidant potential of physalin D

Abstract

Physalis alkekengi L. (Solanaceae) is a popular plant in traditional European and Chinese folk medicine, and it has been reported to have many ethnopharmacological properties including antifungal, anti-cough, anti-inflammatory, analgesic, and febricide activities. Some active components from Physalis species have been investigated. However, no antimicrobial activity studies on extracts and physalins of P. alkekengi have been carried out. In this study, we attempted to identify the possible antimicrobial activities of the methanol extract from aerial parts of P. alkekengi and the dichloromethane extract from calyces of the plant. The extracts were tested against five Gram-positive and five Gram-negative bacteria and five Candida species by using disk diffusion and broth microdilution methods. The extracts were fractionated to isolate physalins using chromatographic techniques, and physalin D was isolated from the extracts. The structure of the compound was elucidated on the basis of ¹H-NMR spectroscopic study, and confirmed by comparison with a reference sample and literature data. Results indicated that all the extracts and physalin D were characterized by antibacterial action, especially against Gram-positive bacteria, with MIC values between 32 and 128 μg/mL. The methanol extract had moderate activity against fungi at MICs ranging from 128 to 512 μg/mL, but the dichloromethane extract and physalin D had low activity against fungi at MICs ranging from 256 to 512 μg/mL. Additionally, the antioxidant activity of physalin D was evaluated by qualitative DPPH (1,1-diphenyl-2-picrylhydrazyl) radical and TBA (thiobarbituric acid) assays. Physalin D showed low antioxidant activity with an IC₅₀ value of ≥ 10 ± 2.1.

Keywords::

• Antimicrobial activity
• antioxidant activity
• extraction
• isolation
• physalin D
• Physalis alkekengi

Acknowledgements

The financial support of the research fund of the University of Mersin (project number: BAP-SBE EMB (SH) 2003-2YL) is gratefully acknowledged. The authors thank Assoc. Prof. Ayşe Everest (Department of Biology, Faculty of Arts and Sciences, University of Mersin, Mersin, Turkey) for identification of the plant material. The authors are grateful to Prof. H. Yamamura, Graduate School of Engineering, Nagoya Institute of Technology, for ¹H-NMR measurements.

Declaration of interest: The authors report no conflicts of interest.