Hydroxyl radical, hydrogen peroxide, singlet oxygen, super oxide anion and free radicals consist of reactive oxygen species. These reactive species will cause damage to the biological molecules. The damaged bio molecules might initiate certain diseases or might lead to the worsening of the existing diseases. Free radicals are reactive ions that can cause progression of diseases like diabetes, immunosuppression, metabolic injury, atherosclerosis, ischemic heart disease, Alzheimer's disease, aging, and Parkinson's disease.
Diseases that result from the oxidative stress could be prevented by the exogenous antioxidants such as tocopherols, flavonoids, vitamin C, carotenoids and various phenolic compounds. Some commonly used synthetic antioxidants are butylated hydroxyanisole, butylated hydroxytoluene (BHT). Natural antioxidants in plants can prevent the diseases by reducing the oxidative damage created by bio macromolecules.
Various harmful pathogens cause several diseases to human beings. When the defense mechanisms in the humans are not sufficient for fighting against the pathogens, certain chemotherapeutic drugs have been introduced. Haphazard usage of these drugs has led to the development of drug resistant strains. So, there is an extreme necessity to generate alternatives for synthetic drugs. The answer for this problem can emerge from the use of aromatic herbs and spices. Spices and aromatic herbs have antimicrobial and antioxidant features.
Nutmeg is the dried seed of the Myristica fragrans Houtt. It has anti-cancer, anti-inflammatory and anti-diarrheal properties. Nutmeg also acts as a memory enhancer and aphrodisiac. This study concentrates on investigating the antioxidant and antimicrobial properties of nutmeg with the help of extracts of methanol, ethanol, acetone, butanol and nutmeg aqueous extracts. All these solvents are chosen as they have various polarities. The extent of polarity of the solvents will determine the extent of solubility exhibited by the components of nutmeg.
The current investigation aims at estimating the antioxidant ability of the extracts of nutmeg, the antimicrobial ability of nutmeg extracts against the fungi and bacteria, the minimum inhibitory concentrations, and components of nutmeg that are actually involved in exhibiting antimicrobial and antioxidant properties.
The nutmegs are powdered and extracted into distilled water. The powdered sample is mixed with the solvents. After 72 hours duration, the supernatant and sediment are separated by vacuum filtration. The supernatant was dried and stored at -20 degrees centigrade. The amount of total phenolics, evaluation of reducing power, DPPH radical scavenging activity, Fe2+ chelating activity, beta-carotene bleaching activity, antimicrobial activity are measured for the sample prepared. The acetone extract was analyzed by gas chromatography-mass spectrometry (GC-MS).
Results of the study
Total phenolic content
Acetone solvent was found to be significantly effective compared to other solvents in extracting phenolic compounds. The total phenolic amount present in the extracts of nutmeg is measured using the Folin-Ciocalteu method. The phenolic compounds are extracted effectively in the solvents in the order of acetone>ethanol>methanol>aqueous>butanol. The quantity of phenolic compounds extracted by the acetone extract was 93.12+/-1.48 while through butanol extract was 49.82+/-1.26 mg GAE/100g dry weight of the nutmeg plant. It was reported that positive and significant correlation was observed to be present between the total phenolic content and antioxidant activity. Phenol antioxidants in the plants are synthesized through secondary metabolism. The antioxidant feature is dependent on the redox potential and the position of -OH in its chemical structure.
Reducing potential of the nutmeg extracts
The antioxidant activity of a compound can be determined also by its potential to reduce. The reducing compounds in the nutmeg extracts will reduce ferric ion to ferrous ion form by contributing an electron. The ferrous form can be measured by reading the absorbance of Perl Prussian blue color intensity at 700nm. The greater absorbance read at 700nm indicates the greater reducing power of the compound. Highest absorbance value was observed as 0.75+/-0.013 with acetone extract and lowest absorbance is observed as 0.33+/-0.019. The absorbance value of acetone extract was higher than that of other extracts while it is found to be lower than BHT extract (1.41+/-0.032).
DPPH radical scavenging activity
In this assay, the usage of DPPH, which is a stable free radical was measured in the various extracts of nutmeg. The antioxidant component of the extract reacts with DPPH by donating an H atom thereby resulting in the formation of diphenylpicrylhydrazine. The color of the reaction changes from purple to yellow and the absorbance takes place at 517nm. At 1mg/ml of sample concentration, the scavenging activity of free radical was observed in the acetone extract as 63.04+/-1.29percent and in the butanol extract as 36.21+/-1.31percent. This activity was observed as 94.2+/-1.41percent in the standard BHT.
Chelation of iron by nutmeg extracts is an excellent approach to restrict diseases triggered by oxidative stress. Highest chelating activity was shown by ethanol extract at the concentration of 1mg/ml as 72.11+/-1.54percent while the least is shown by aqueous extract as 48.34+/-1.85percent. EDTA standard could show 99.6+/-1.65percent of chelating activity of nutmeg extracts.
Beta-carotene bleaching assay
The free radicals react with beta-carotene by reducing it and bleaching its color. The antioxidants will reverse the process and hence the rate of antioxidation by the nutmeg extract is inversely related to the oxidation of beta-carotene. The acetone extract showed this activity as 74.36+/-1.94percent, and ethanol extract as 38.47+/-1.31percent. BHT showed this activity as 94.9+/-1.03percent.
Antimicrobial activity of the extracts
In this study, it is proved that nutmeg extracts showed antimicrobial activity against bacteria and fungi that are pathogenic.
GC-MS of acetone extract
The acetone extract of nutmeg seed consisted of the chemicals like sabinene, beta-pinene, myristicin, terpinen-4-ol, limonene, gamma-terpinene, p-menth-2-en-1-ol, elemicin, isoeugenol, p-menth-2-en-1-ol, myrcene, alpha-phellandrene, terpinolene, lonalool, and p-cymene.
In conclusion, the current study has elaborated the antimicrobial and antioxidant properties of different nutmeg extracts.
Ashish Deep Gupta, Vipin Kumar Bansal, Vikash babu, Nishi Maithil. Chemistry, antioxidant, and antimicrobial potential of Nutmeg (Myristica frangrans Houtt). Journal of Genetic Engineering and Biotechnology (2013) 11, 25-31.
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