Radhika Dhakal

Bio: Radhika Dhakal is an academic researcher from Yeungnam University. The author has contributed to research in topics: Amino acid & Fermentation. The author has an hindex of 7, co-authored 8 publications receiving 358 citations. Previous affiliations of Radhika Dhakal include University of Illinois at Chicago.

Metabolic alternation in the accumulation of free amino acids and γ-aminobutyric acid in postharvest mature green tomatoes following irradiation with blue light

Abstract: Tomatoes (Solanum lycopersicum L.) are known as a super food because they contain many compounds beneficial to human health. To elucidate the role of specific wavelength of light on the accumulation of free amino acids and -aminobutyric acid (GABA) in postharvest tomato fruits, mature green tomato fruits were treated with darkness, or blue or red light by using light emitting diode (LED) for seven days. All free amino acids, except glutamic and aspartic acids, increased more in fruits treated with blue light than in those treated with either darkness or red light. The GABA, a non-protein amino acid and having health beneficial effects, increased in the blue light treatment with the maximum content being observed on the third day. Taken together, these findings indicate that irradiation with blue light has an effect in increasing the GABA contents in postharvest tomato fruits.

Bactericidal Effect of Extracts and Metabolites of Robinia pseudoacacia L. on Streptococcus mutans and Porphyromonas gingivalis Causing Dental Plaque and Periodontal Inflammatory Diseases

Abstract: The mouth cavity hosts many types of anaerobic bacteria, including Streptococcus mutans and Porphyromonas gingivalis, which cause periodontal inflammatory diseases and dental caries. The present study was conducted to evaluate the antibacterial potential of extracts of Robinia pseudoacacia and its different fractions, as well as some of its natural compounds against oral pathogens and a nonpathogenic reference bacteria, Escherichia coli. The antibacterial activity of the crude extract and the solvent fractions (hexane, chloroform, ethyl acetate and butanol) of R. pseudoacacia were evaluated against S. mutans, P. gingivalis and E. coli DH5α by standard micro-assay procedure using conventional sterile polystyrene microplates. The results showed that the crude extract was more active against P. gingivalis (100% growth inhibition) than against S. mutans (73% growth inhibition) at 1.8 mg/mL. The chloroform and hexane fractions were active against P. gingivalis, with 91 and 97% growth inhibition, respectively, at 0.2 mg/mL. None of seven natural compounds found in R. pseudoacacia exerted an antibacterial effect on P. gingivalis; however, fisetin and myricetin at 8 µg/mL inhibited the growth of S. mutans by 81% and 86%, respectively. The crude extract of R. pseudoacacia possesses bioactive compounds that could completely control the growth of P. gingivalis. The antibiotic activities of the hexane and chloroform fractions suggest that the active compounds are hydrophobic in nature. The results indicate the effectiveness of the plant in clinical applications for the treatment of dental plaque and periodontal inflammatory diseases and its potential use as disinfectant for various surgical and orthodontic appliances.

Soybean (Glycine max L. Merr.) sprouts germinated under red light irradiation induce disease resistance against bacterial rotting disease.

Abstract: Specific wavelengths of light can exert various physiological changes in plants, including effects on responses to disease incidence. To determine whether specific light wavelength had effects on rotting disease caused by Pseudomonas putida 229, soybean sprouts were germinated under a narrow range of wavelengths from light emitting diodes (LEDs), including red (650–660), far red (720–730) and blue (440–450 nm) or broad range of wavelength from daylight fluorescence bulbs. The controls were composed of soybean sprouts germinated in darkness. After germination under different conditions for 5 days, the soybean sprouts were inoculated with P. putida 229 and the disease incidence was observed for 5 days. The sprouts exposed to red light showed increased resistance against P. putida 229 relative to those grown under other conditions. Soybean sprouts germinated under red light accumulated high levels of salicylic acid (SA) accompanied with up-regulation of the biosynthetic gene ICS and the pathogenesis- related (PR) gene PR-1, indicating that the resistance was induced by the action of SA via de novo synthesis of SA in the soybean sprouts by red light irradiation. Taken together, these data suggest that only the narrow range of red light can induce disease resistance in soybean sprouts, regulated by the SA-dependent pathway via the de novo synthesis of SA and up-regulation of PR genes.

Health Benefits of Fermented Foods

Abstract: In the past, the beneficial effects of fermented foods on health were unknown, and so people primarily used fermentation to preserve foods, enhance shelf life, and improve flavour Fermented foods became an important part of the diet in many cultures, and over time fermentation has been associated with many health benefits Because of this, the fermentation process and the resulting fermented products have recently attracted scientific interest In addition, microorganisms contributing to the fermentation process have recently been associated with many health benefits, and so these microorganisms have become another focus of attention Lactic acid bacteria (LAB) have been some of the most studied microorganisms During fermentation, these bacteria synthesize vitamins and minerals, produce biologically active peptides with enzymes such as proteinase and peptidase, and remove some non-nutrients Compounds known as biologically active peptides, which are produced by the bacteria responsible for fermentation, are also well known for their health benefits Among these peptides, conjugated linoleic acids (CLA) have a blood pressure lowering effect, exopolysaccharides exhibit prebiotic properties, bacteriocins show anti-microbial effects, sphingolipids have anti-carcinogenic and anti-microbial properties, and bioactive peptides exhibit anti-oxidant, anti-microbial, opioid antagonist, anti-allergenic, and blood pressure lowering effects As a result, fermented foods provide many health benefits such as anti-oxidant, anti-microbial, anti-fungal, anti-inflammatory, anti-diabetic and anti-atherosclerotic activity However, some studies have shown no relationship between fermented foods and health benefits Therefore, this paper aims to investigate the health effects of fermented foods

The effects of probiotics on depressive symptoms in humans: a systematic review.

Abstract: Patients suffering from depression experience significant mood, anxiety, and cognitive symptoms. Currently, most antidepressants work by altering neurotransmitter activity in the brain to improve these symptoms. However, in the last decade, research has revealed an extensive bidirectional communication network between the gastrointestinal tract and the central nervous system, referred to as the “gut–brain axis.” Advances in this field have linked psychiatric disorders to changes in the microbiome, making it a potential target for novel antidepressant treatments. The aim of this review is to analyze the current body of research assessing the effects of probiotics, on symptoms of depression in humans. A systematic search of five databases was performed and study selection was completed using the preferred reporting items for systematic reviews and meta-analyses process. Ten studies met criteria and were analyzed for effects on mood, anxiety, and cognition. Five studies assessed mood symptoms, seven studies assessed anxiety symptoms, and three studies assessed cognition. The majority of the studies found positive results on all measures of depressive symptoms; however, the strain of probiotic, the dosing, and duration of treatment varied widely and no studies assessed sleep. The evidence for probiotics alleviating depressive symptoms is compelling but additional double-blind randomized control trials in clinical populations are warranted to further assess efficacy.