From covalent bonds to eco-physiological pharmacology of secondary plant metabolites

Potential clinical applications of Ashwagandha (Withania somnifera) in medicine and neuropsychiatry

INTRODUCTION

Ashwagandha (ASW) is the extract of the plant Withania somnifera. It is widely used in complementary, alternative, and integrative medicine (CAIM) but is little discussed in mainstream modern medical literature.

AREAS COVERED

We performed a review of potential pharmacotherapeutic properties of ASW. Studies were sourced from relevant online and offline databases. In animal models, ASW displays antioxidant activity. It has GABAergic and other neurotransmitter modulatory effects. It reduces apoptosis and promotes synaptic plasticity. It improves cognition and reverses induced cognitive deficits. It attenuates indices of stress. In human subjects, ASW enhances adaptogenesis in healthy adults. It modestly benefits generalized anxiety disorder and obsessive-compulsive disorder, and symptom severity in schizophrenia, substance use disorders, and attention deficit hyperactivity disorder. It improves sleep quality.

EXPERT OPINION

ASW may confer modest benefit in certain neuropsychiatric conditions. Its benefits may arise from induction of neuroplasticity, antioxidant and anti-inflammatory effects, and modulation of GABA and glutamate, as well as other neurotransmitters. The antioxidant and anti-inflammatory actions may also benefit neurodegenerative states. Reports of clinical benefit with ASW must be interpreted with caution, given the paucity of randomized clinical trials (RCTs). Greater methodological rigor is necessary before clinical recommendations on ASW can be confidently made.

Antibacterial Activity and Phytochemical Components of Leaf Extracts of Agave americana

Background

Ethiopian flora is a source of innumerable cures for several infections. The medicinal potential of A. americana has been evaluated in some studies. The current study aimed to investigate the antimicrobial effect of A. americana leaf extracts on selected bacterial strains and to determine the phytochemical components.

Purpose

To determine the phytochemical constituents and in vitro antibacterial activity of leaf extracts of Agave americana against Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella species, and Eshercia coli.

Methods

The macerated and Soxhlet crude extracts of Agave americana were further fractionated to petroleum ether, chloroform, acetone, and methanol fractions. The agar well diffusion method and disc diffusion methods were used to test the antibacterial effect and determine the minimum inhibitory concentration (MIC) of the plant extract. Standard methods of determination were used to determine the phytochemical components of Agave americana.

Results

The percentage yield of crude extracts of A. americana was 15.11%. Alkaloids, saponins, tannins, polyphenols, and flavonoids were identified as phytochemical constituents of A. americana. The crude and solvent fractions of A. americana have an antibacterial activity comparable to gentamycin, with zones of inhibition ranging from 17 to 40mm and minimum inhibitory concentration (MIC) of 2.5 mg mL for S. aureus, P. aeruginosa, and S. typhi strains and 10 mg mL for E. coli strains. S. aureus and E. coli were the most and least susceptible bacteria among the four bacterial test strains tested.

Conclusion

The crude and solvent fractions of A. americana have antibacterial activity against S. aureus, P. aeruginosa, and S. thyphi, comparable to gentamycin.

Kalanchoe brasiliensis Cambess., a Promising Natural Source of Antioxidant and Antibiotic Agents against Multidrug-Resistant Pathogens for the Treatment of Salmonella Gastroenteritis

Kalanchoe brasiliensis Cambess. is a native Brazilian plant popularly known as “saião”, and the juice of its fresh leaves is traditionally used to treat several disorders, including inflammatory and infectious processes such as dysentery. The goals of this study were to characterize the phytochemical composition and investigate the antioxidant activity, the antibiotic effect, and the mode of action against Salmonella of the hydroethanolic extracts from K. brasiliensis leaves collected in the summer and spring Brazilian seasons. These extracts had their chemical composition established by high-performance liquid chromatography with diode-array detection. Total phenolic and flavonoid contents were spectrophotometrically determined. 2,2-Diphenyl-1-picryl-hydrazyl radical scavenging, phosphomolybdenum reducing power and β-carotene bleaching assays were carried out to evaluate the antioxidant capacity. Antibiotic potential was assessed by minimal inhibitory concentration against 8 bacterial ATCC® and 5 methicillin-resistant Staphylococcus aureus and 5 Salmonella clinical strains. The mode of action was investigated by time-kill, bacterial cell viability, and leakage of compounds absorbing at 280 nm assays against Salmonella. Chromatographic profile and UV spectrum analyses suggested the significant presence of flavonoid type patuletin and eupafolin derivatives, and no difference between both periods of collection was noted. Significant amounts of total phenolic and flavonoid contents and a promising antioxidant capacity were observed. Hydroethanolic extracts (70%, summer and spring) were the most active against the tested Gram-positive and Gram-negative bacterial strains, showing the bacteriostatic action of 5000 μg/mL. Time-kill data demonstrated that these extracts were able to reduce the Salmonella growth rate. Cell number was reduced with release of the bacterial content. Together, these results suggest that K. brasiliensis is a natural source of antioxidant and antibacterial agents that can be applied in the research and development of new antibiotics for the treatment of Salmonella gastroenteritis because they are able to interfere in the Salmonella growth, probably due to cell membrane damage.

Effects of turmeric curcuminoids and metformin against central sensitivity to pain in mice

The reported experimental study was conducted to compare the effects of repeated daily oral doses of curcuminoids (CLE) with metformin as potential antidepressants and analgesics. Effects of a single and ten daily oral doses of CLE (5, 20, 80 mg/kg/day) and of 50 mg/kg/day metformin (MET) were compared in mice hot plate test (HPT) for analgesics. On the 11th treatment day, all animals were subjected to foot shock stress triggered hyperthermia test, and on the 12th treatment day to tail suspension test (TST) for antidepressants. Immediately thereafter, their blood levels of glucose, insulin and cortisol were quantified. Dose dependent analgesic activity of CLE was observed in HPT, whereas the metformin dose tested suppressed only pain hypersensitivity in the test. But statistically significant effects of both of them were observed in TST, and both of them also afforded protections against body weight loss and slight elevation in core temperatures induced by daily handling and repeated testing. CLE or metformin had no significant effects in foot shock stress triggered transient hyperthermic responses or on blood glucose, insulin and cortisol levels. Reported results reveal that curcuminoids as well as metformin are stress response modifiers with antidepressants like activities, but only low dose curcuminoids possess centrally acting analgesics like activities. They suggest that the bio-assay system used in this study is well suited for identifying curcuminoids like plant metabolites with analgesic and anti-stress activities, and that low dose curcuminoids are more effective as analgesics than low dose metformin.