Wenjing Lai1,2, Jianan Chen3,4, Ian Edwin Cock3,5, Matthew J. Cheesman1,6
1School of Parmacology, Gold Coast Campus, Griffith University, Parklands Drive, Southport, Queensland 4222, AUSTRALIA.
2College of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou 510006, CHINA.
3School of Environment and Science, Nathan Campus, Griffith University, 170 Kessels Rd, Nathan, Queensland 4111, AUSTRALIA.
4School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210046, CHINA.
5Environmental Futures Research Institute, Nathan Campus, Griffith University, 170 Kessels Rd, Nathan, Queensland 4111, AUSTRALIA.
6Menzies Health Institute Queensland, Quality Use of Medicines Network, Queensland 4222, AUSTRALIA.
Published: January 2018
Type: Original Article
Background: Withania somnifera (L.) Dunal roots are known for their anti-inflammatory and rejuvenative properties. This study focuses on the growth inhibitory activity of W. somnifera root extracts against some bacterial triggers of autoimmune inflammatory diseases, as well as the extracts in combination with conventional antibiotics. Methods: W. somnifera root powder was extracted with solvents of varying polarity and screened for inhibition of bacterial growth. Inhibition on agar was assessed by disc diffusion techniques, whilst the minimum inhibitory concentrations (MICs) were quantified by liquid dilution assays. To screen for combinatorial effects, the W. somnifera root extracts were combined with a range of conventional antibiotics and tested against each bacterial strain using liquid dilution assays. Extract toxicities was examined using Artemia nauplii bioassays, while their phytochemical profiles were determined using standard methodologies. Results: W. somnifera root extracts were unable to inhibit the growth of P. mirabilis, K. pneumonia, A. baylyi and Pseudomonas aeruginosa. However, the methanolic and aqueous extracts were good inhibitors of Y. enterocolitica, with MICs of 696 and 358 μg/mL respectively. These extracts also inhibited S. pyogenes growth, albeit with substantially higher MIC values indicative of only mild inhibition. Only small zones of inhibition were observed on agar for these extracts against both strains. Combinations of the W. somnifera extracts and conventional antibiotics generally produced additive or indifferent interactions, indicating that they are safe to use concomitantly without compromising the efficacy of either component. A single antagonistic combination (aqueous extract and tetracycline) against Y. enterocolitica was observed. All extracts were determined to be non-toxic as assessed in Artemia nauplii bioassays. Conclusions: Methanolic and aqueous W. somnifera extracts were strong inhibitors of Y. enterocolitica growth and mild inhibitors of S. pyogenes. These extracts were also non-toxic in the Artemia nauplii bioassay, indicating their potential for the prevention and treatment of Hashimoto’s disease.
Key words: Ashwagandha, Multi-drug resistant bacteria, Combinational therapies, Rheumatoid Arthritis, Hashimoto’s disease.