Subscribe Now Subscribe Today
Research Article
 

Comparative in vitro Assessment of Drumstick (Moringa oleifera) and Neem (Azadiracta indica) Leaf Extracts for Antioxidant and Free Radical Scavenging Activities



U.B. Ekaluo, E.V. Ikpeme, O.U. Udensi, E.E. Ekerette, S.O. Usen and S.F. Usoroh
 
Facebook Twitter Digg Reddit Linkedin StumbleUpon E-mail
ABSTRACT

The current research was aimed at comparing the leaf extracts of two medicinal plants (Moringa oleifera and Azadiracta indica) for antioxidant and free radical scavenging potentials in different extracting solvents (absolute ethanol, 70 and 50% ethanol). Different in vitro assays such as total phenolic and flavonoid content, 2-2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, metal chelating activity, reducing power and total antioxidant capacity were employed in the study. The results revealed that A. indica contained more phenols and flavonoids than M. oleifera with the different extracting solvents. The amount of phenols and flavonoids in A. indica played a pivotal role in scavenging more of the DPPH radical at a lower inhibitory concentration, IC50 of 77.94 μg mL-1 than in M. oleifera at 118.96 μg mL-1 in absolute ethanol. Moringa oleifera was a better scavenger of the DPPH radical in 70 and 50% ethanol. In absolute ethanol, A. indica also chelated 50% of the metal ion at IC50 of 0.22 μg mL-1 which was even better than ascorbic acid (5.95 μg mL-1) and gallic acid (0.503 μg mL-1) standards. The values for A. indica were also comparably better than those of M. oleifera for reducing power and total antioxidant capacity at the respective concentrations. The results are indicative of the antioxidant and free radical scavenging potentials of M. oleifera and A. indica. Comparatively, A. indica was better than M. oleifera in doing the job and absolute ethanol extracts were better than 70 and 50% ethanol extracts in the scavenging potential.

Services
Related Articles in ASCI
Similar Articles in this Journal
Search in Google Scholar
View Citation
Report Citation

 
  How to cite this article:

U.B. Ekaluo, E.V. Ikpeme, O.U. Udensi, E.E. Ekerette, S.O. Usen and S.F. Usoroh, 2015. Comparative in vitro Assessment of Drumstick (Moringa oleifera) and Neem (Azadiracta indica) Leaf Extracts for Antioxidant and Free Radical Scavenging Activities. Research Journal of Medicinal Plants, 9: 24-33.

DOI: 10.3923/rjmp.2015.24.33

URL: https://scialert.net/abstract/?doi=rjmp.2015.24.33
 
Received: March 09, 2015; Accepted: April 27, 2015; Published: May 06, 2015



INTRODUCTION

Over the years, plants have been the major source of products for prevention and treatment of ailments in traditional medicine. This is because plants are naturally endowed with inherent bioactive compounds with medicinal properties capable of preventing or mitigating disease conditions. In recent time, with the advancement in molecular biology which has provided an indebt understanding of the molecular structures and actions of these bioactive compounds, much interest has been paved to medicinal plants occasioned by their invaluable medicinal properties. Worthy of note is the fact that some of these medicinal plants have been reported to exhibit oxidative stress mitigating properties on oxidative stress related diseases such as cancer, asthma, cardiovascular diseases, diabetes, arthritis, inflammation etc. (Kottaimuthu, 2008; Gomez-Flores et al., 2008; Koffi et al., 2009; Tripathy et al., 2010; Oluwole et al., 2011). This oxidative stress occur when there is an imbalance between the production of reactive oxygen species (free radicals) and the mechanism of detoxifying them (antioxidant production) in the body. When this occurs, the generated free radicals which are unstable atoms with unpaired valence electrons (Kadam et al., 2010; Aluko et al., 2013) will attack bio-molecules in the body transforming them into free radicals such as hydrogen peroxides (H2O2). This subsequently proliferates into the aforementioned disease conditions. Infertility has also been highly linked to the production of free radicals (Agarwal et al., 2008).

Generally, synthetic antioxidants are the commonest ways used in mopping the deteriorating effects of these free radicals in the body. The growing panics on the use of these synthetic antioxidants are the reported side effects orchestrated by their consumption (Kukic et al., 2006; Vijayakumar et al., 2012; Ikpeme et al., 2013). Due to this, there have been shifts from the use of synthetic antioxidants to natural antioxidants sourced from medicinal plants following reports on their safety, accessibility and affordability (Calixto, 2000; Ikpeme et al., 2011, 2012). Undoubtedly, the reported safety, cost effectiveness and accessibility of these medicinal plants on health has opened up a new field of research allowing research scholars to study different plants for their antioxidant potency as alternative measure to the synthetic antioxidants.

Moringa oleifera is one of such medicinal plant reported with antioxidant properties (Siddhuraju and Becker, 2003; Iqbal and Bhanger, 2006). Moringa oleifera is reported to be effective in the treatment of rheumatism, infections, hiccough, influenza and internal abscess (Anwar et al., 2007; Mishra et al., 2011). The leaf extract is capable of reducing hyperglycemia (Mbikay, 2012). Nutritionally, the leaves contain essential amino acids, vitamins, minerals and β-carotene which have rendered it an invaluable commodity in the food industries (Sabale et al., 2008; Sharma et al., 2012). Azadirachta indica commonly known as neem is another medicinal plant of great importance in traditional medicine and fertility studies (Ekaluo et al., 2010). Neem oil, bark and leaf extracts are therapeutic in folk medicine for the control of leprosy, intestinal helminthiasis, respiratory disorders, constipation and skin infections (Biswas et al., 2002). Although antioxidant properties of M. oleifera and A. indica have been reported in recent researches, however, comparative reports of the antioxidant properties of these two commonly used medicinal plants are rare. Thus, the aim of the present research was to assess and compare the in vitro antioxidant activities and free radical scavenging potentials of M. oleifera and A. indica in different extracting solvents (absolute ethanol, 70 and 50% ethanol) to ascertain a more reliable antioxidant source between the two plants.

MATERIALS AND METHODS

Collection of plant materials and extraction: Fresh leaves of M. oleifera and A. indica were obtained from Staff Quarters, University of Calabar, Calabar and authenticated in the Herbarium Unit of the Department of Botany, University of Calabar. The fresh leaves were freed from dirts, air dried at room temperature for one week and then finely milled separately using a blender (Model: 5KSB655CCSO). Ten grams of the milled sample was soaked in 100 mL of the three different solvents (absolute ethanol, 70 and 50% ethanol) for 72 h at room temperature. The soaked samples were shaken intermittently during the extraction period and subsequently filtered using Whatman No. 1 filter paper. The resulting extracts were concentrated under vacuum in a rotary evaporator at 45°C for complete solvent removal. A stock solution of each crude extract was prepared and desired working concentrations were made by appropriate dilutions.

Determination of extract yield (%): The percentage yield of each extract was obtained by dividing the weight of the concentrated crude extract by the initial weight (10 g) of dry milled starting material and multiplying the ratio by 100.

Determination of Total Phenolic Content (TPC): The total phenolic contents of the extracts were determined by the Folin-Ciocalteau method according to Duarte-Almeida et al. (2006). One hundred microliter of Folin-Ciocalteau reagent was added to 500 μL of the different extract solutions containing 1000 μg mL-1 +6 mL of distilled water and shaken for one minute. Thereafter, 2 mL of 15% sodium carbonate was added to the mixture and shaken again for 30 sec. Finally, distilled water was added to the solution to make it up to 10 mL, then left to incubate for 1.5 h at room temperature. Thereafter, the absorbance at 750 nm was evaluated using a spectrophotometer (LABTECH UV/VIS Spectrophotometer, India-Single beam 295). Gallic acid monohydrate, a standard phenol, in the range of 5-150 μg mL-1 was used to prepare standard reference curve. The Total Phenol Contents (TPC) of the extracts were expressed as Gallic Acid Equivalents (GAE) from the linear regression curve of gallic acid.

Determination of Total Flavonoid Content (TFC): The total flavonoid contents of each extract concentration were determined using the aluminum chloride colorimetric method, according to Dewanto et al. (2002). The different extract solutions (1 mL containing 1000 μg mL-1) were diluted with 4 mL of distilled water in a 10 mL volumetric flask. Thereafter, 0.3 mL of 5% sodium nitrite (NaNO2) solution was added to each extract solution. Five minutes later, 0.3 mL of 10% aluminium chloride (AlCl3) was added; 1 min later, 2 mL of 1.0 M sodium hydroxide (NaOH) was added and finally, 2.4 mL of distilled water was added and mixed properly. Absorbance of the reaction mixture was read at 510 nm. Rutin, a standard flavonoid in the range of 10-150 μg mL-1 was used to prepare the standard reference curve. Total Flavonoid Content (TFC) of the extracts were expressed as Rutin Equivalents (RE) from the linear regression curve of Rutin.

DPPH radical scavenging activity: The ability of M. oleiferia and A. indica leaf extracts to scavenge stable DPPH radical was measured using the method of Mensor et al. (2001). Five different concentrations of each test extracts were prepared in methanol (20, 40, 60, 80, 100 μg mL-1). One milliliter of 0.3 mM of freshly prepared DPPH solution in methanol was added to 2.5 mL solution of each extract concentration and allowed to react in the dark at room temperature for 30 min. Absorbance of the resulting solution was measured at 518 nm. Methanol (1 mL) was added to 2.5 mL of each extract concentration was used as blank, while 1 mL of 0.3 mM DPPH solution added to 2.5 mL of methanol served as a negative control. Ascorbic acid and gallic acid were used as standard reference compounds (positive controls) for comparison. Percentage DPPH scavenging activities of the extracts and standards were determined using the following equation:

Image for - Comparative in vitro Assessment of Drumstick (Moringa oleifera) and Neem (Azadiracta indica) Leaf Extracts for Antioxidant and Free Radical Scavenging Activities

Where:
As = Absorbance of sample (extracts or reference standard)
Ab = Absorbance of blank
Ac = Absorbance of negative control

Results were expressed as inhibitory concentration, IC50 (concentration of extract or standard required to scavenge 50% of DPPH radicals) which were determined from a linear regression curve of concentration versus scavenging activity (%).

Metal (ferrous ion) chelating activity: The ferrous ion chelating activity of Moringa oleifera and A. indica leaf in different extracting solvents (Absolute ethanol, 70 and 50% ethanol) concentrations (Absolute, 70 and 50% ethanol) were determined by the method of Ebrahimzadeh et al. (2009). Here, the ability of the extracts to chelate ferrous ion (Fe2+) was estimated. Different concentrations (20-100 μg mL-1) of each extract were prepared and 1 mL of each concentration were mixed with 1 mL of FeSO4 (0.125 M) and 1 mL of ferrozine (0.3125 mM) and shaken vigorously. After incubating for 10 min at room temperature, the mixture solution was measured using a spectrophotometer at 562 nm against a blank containing the same components as stated above but the extracts were replaced with distilled water (1 mL of distilled water). The blank was incubated under the same conditions as the test samples. Sodium EDTA (Na2EDTA) was used as control. The percentage inhibitions of ferrozine (Fe2+) by the extracts were determined using the following equation:

Image for - Comparative in vitro Assessment of Drumstick (Moringa oleifera) and Neem (Azadiracta indica) Leaf Extracts for Antioxidant and Free Radical Scavenging Activities

Where:
Ac = Absorbance of control
As = Absorbance of sample

Results were expressed as IC50 (concentration of extract or standard required to chelate 50% of ferrous ions) which were determined from a linear regression curve of concentration versus chelating activity (%).

Total Antioxidant Capacity (TAC) assay: The Total Antioxidant Capacity (TAC) of M. oleifera and A. indica leaf extract in different extracting solvents (absolute ethanol, 70 and 50% ethanol) were determined by the phosphomolybdate method according to Jayaprakasha et al. (2002). An aliquot (30 μL) of different concentrations (20, 40, 60, 80 and 100 μg mL-1) of the test extracts were mixed with 3 mL of the reagent solution (0.6 M sulphuric acid, 28 mM sodium phosphate, 4 mM ammonium molybdate) taken in test tubes. The tubes were capped with aluminium foil and incubated in a boiling water bath at 95°C for 90 min. The reaction mixture was allowed to cool to room temperature and the absorbance of the solution was measured at 695 nm against a blank containing 3 mL of reagent solution and the appropriate volume of the dissolving solvents. The blank was incubated under the same conditions as the test samples. Ascorbic acid and gallic acid were used as standard reference compounds to compare the activities of the extracts.

Reducing power assay: Antioxidant activity of the leaf extract of Moringa oleifera and A. indica in different extracting solvents (absolute ethanol, 70 and 50% ethanol) were determined to assess their ferric ion (Fe3+) reducing ability according to the method of Anandjiwala et al. (2007). Different concentrations (20, 40, 60, 800, 100 μg mL-1) of each extract were prepared and 1 mL of each concentration was mixed with 2.5 mL of phosphate buffer (0.2 M, pH 6.8) and 2.5 mL of potassium ferricyanide. The mixture was incubated in a water bath at 50°C for 20 min. To this mixture, 2.5 mL of 10% trichloroacetic acid was added and then centrifuged at 3000 rpm for 10 min. The upper layer of the solution (2.5 mL) was mixed with 2.5 mL of distilled water and 0.5 mL of 0.1% ferric chloride was added. Absorbance of the Pert Prussian blue solution formed was measured at 700 nm. Ascorbic acid and gallic acid were used as standard reference compounds for comparison and prepared in same concentrations as the extracts.

Statistical analysis: Analysis of variance (ANOVA) was used to analyze absorbance values for total phenolic content, total flavonoid content, reducing power and total antioxidant capacity of the two medicinal plants against the reference standards. Mean separation was done using the Least Significant Difference (LSD) test.

RESULTS

Extract yield, total phenolic content, total flavonoid content and inhibitory concentration (IC50) of M. oleifera and A. indica: Following the differences in concentration of the extracting solvents (absolute ethanol, 70 and 50% ethanol), there were concomitant differences in the percentage yield of the extracts. Moringa oleifera had the highest yield in 50% ethanol (23.12%) followed by 70% ethanol (21.89%) and absolute ethanol (11.79%). Azadiracta indica yield also increased as the concentration of the extracting solvent reduced; absolute ethanol (11.34%), 70% ethanol (17.84%), 50% ethanol (20.14%) as shown in Table 1. Results for total phenolic and flavonoid content revealed a concentration dependent relationship. Azadiracta indica had significant amount (p<0.05) of phenols than M. oleifera in the different extracting solvents. Flavonoid content of A. indica was significantly higher (p<0.05) in absolute ethanol (128.39 μg RE mg-1), 70% ethanol (42.83 μg RE mg-1), 50% ethanol (30.89 μg RE mg-1) than absolute ethanol (85.06 μg RE mg-1), 70% ethanol (25.05 μg RE mg-1) and 50% ethanol (8.95 μg RE mg-1) of M. oleifera. In DPPH radical scavenging, it required 77.94 μg mg-1 absolute concentration of A. indica to scavenge 50% of the radical compared to 118.96 μg mg-1 of M. oleifera at the same concentration. Azadiracta indica was also a better metal chelator (p<0.05) than M. oleifera since it required a lesser amount of its extract to chelate 50% of ferrous ion (Fe2+) in the respective extraction solvent concentration compare to M. oleifera (Table 1).

Concentration effect on free radical scavenging properties of M. oleifera, A. indica and standards: The result revealed significant differences in the free radical scavenging potential of M. oleifera and A. indica at the different concentration as shown in Table 2.

Table 1:Extract yield, phenolic content, flavonoid content, DPPH radical scavenging and metal chelating activities of M. oleifera and A. indica
Image for - Comparative in vitro Assessment of Drumstick (Moringa oleifera) and Neem (Azadiracta indica) Leaf Extracts for Antioxidant and Free Radical Scavenging Activities
Means with different superscript along the same horizontal array differ significantly (p<0.05) from each other. *IC50 values for ascorbic acid and gallic acids are 5.95±0.13 and 0.50±0.02 μg mL-1, respectively. **IC50 value for Na2 EDTA is 0.02±0.001 mg mL-1

Table 2:Concentration effect on reducing power and antioxidant capacity of M. oleifera, A. indica and standards
Image for - Comparative in vitro Assessment of Drumstick (Moringa oleifera) and Neem (Azadiracta indica) Leaf Extracts for Antioxidant and Free Radical Scavenging Activities
Means with different superscript along the same horizontal array differ significantly (p<0.05) from each other. -: Particular standard was not used

Although ascorbic acid, a standard reference was a better reducing agent than the test medicinal plants, however, the absorbance values of the medicinal plants indicated their scavenging potentials. At 20 μg mL-1, 70% ethanol extract of M. oleifera reduced significant amount (0.726) of the ferric ion (p<0.05) than A. indica but at 40 μg mL-1, 70% ethanol extract of A. indica was better than M. oleifera. There was no significant difference (p>0.05) in the reducing power of M. oleifera at 60 μg mL-1, absolute ethanol and 70% ethanol extracts (0.727 and 0.734) and 60 μg mL-1, absolute ethanol extract (0.733) of A. indica. At 100 μg mL-1, 50% ethanol extract of M. oleifera was better in reducing free radical while A. indica was better at 70% ethanol extract of the same concentration. Ascorbic and gallic acid standards showed significant antioxidant capacity than the test medicinal plant extracts. At 20 μg mL-1, 70 and 50% ethanol extracts of A. indica were the same (p>0.05). Absolute ethanol, 70 and 50% ethanol extracts of M. oleifera (0.027, 0.032 and 0.026) and 50% ethanol extract of A. indica (0.039) showed no significant difference at 20 μg mL-1. At 40, 60, 80 and 100 μg mL-1, A. indica showed high total antioxidant capacity than M. oleifera in the different extracting solvents.

DISCUSSION

Medicinal plants are regularly screened for free radical scavenging properties basically from the reports on their safety, efficacy and cost effectiveness (Calixto, 2000; Ikpeme et al., 2011, 2012) over synthetic antioxidants reported with side effects upon their consumption (Vijayakumar et al., 2012). As a result of this, various medicinal plants reported with antioxidant properties have been recommended for pharmaceutical industries and traditional medicine for the control and treatment of different kinds of ailments.

The results of the current research revealed the presence of reasonable amount of phenols and flavonoids in both medicinal plant extracts. Polyphenolic and flavonoid compounds are very important secondary metabolites in plants and are reported to be responsible for the variation in antioxidant activities in plants (Demiray et al., 2009; Basma et al., 2011; Uyoh et al., 2013) and are capable of fighting against free radicals by inactivating lipid free radicals or preventing decomposition of hydrogen peroxide into free radicals due to their redox properties, chelate metal ions, quenching singlet and triplet oxygen (Pokorny et al., 2001; Maisuthisakul et al., 2007; Balasundram et al., 2006; Javanmardi et al., 2003). This may undoubtedly suggest that plants with high quantity of polyphenols and flavonoids are good antioxidant sources although quantifying phenols and flavonoids are not the only yardstick for measuring antioxidant capacity of a substrate as many in vitro antioxidant assays are always required for a more categorical conclusion. Approximately, Azadiracta indica contained more phenols and flavonoids in absolute ethanol extract than Moringa oleifera which suggest why it required lesser amount of the extract (97.94 μg mL-1) to scavenge 50% of DPPH radical compare to M. oleifera at the same concentration (Table 1). The DPPH, a synthetic free radical have been used to measure in vitro ability of a test substance to scavenge free radicals. The effects of phenolic compounds on DPPH radical scavenging are thought to be due to their hydrogen donating ability (Ghimeray et al., 2009) to the unstable DPPH free radical that accepts an electron or hydrogen to become a stable diamagnetic molecule (Siddaraju and Dharmesh, 2007). It is most likely that the decrease in absorbance of DPPH radical caused by phenolic compound in our result is due to reaction between antioxidant molecules in the extracts and the radicals. Although the amount of DPPH scavenged by the two plants in the respective extracting solvents are not equivalent to ascorbic and gallic acid standards, however, this amount is adequate to suggest the extract potential in scavenging free radicals.

According to Ghimeray et al. (2009) transition metals have played a pivotal role in the generation of oxygen free radicals in living organisms. These transition elements such as iron and copper are able to kick start free radical generation because they are oxidation reaction catalyst due to unpaired electrons on their valence shells which makes them structurally unstable. The unstable nature of these metals often orchestrate the conversion of H2O2 to OH in the Fenton reaction and in decomposition of alkyl peroxides to heavy reactive alkyl and hydrogen radicals (Hsu et al., 2006). Interestingly, chelating agents such as antioxidants may inactivate metal ions and potentially inhibit the metal dependent processes (Finefrock et al., 2003) by donating electrons to these unstable-electron-deficient metals. From Table 1, with only 0.22 μg mL-1, A. indica chelated 50% of ferrous ions in absolute concentration of ethanol showing even more chelating capacity than ascorbic and gallic acid standards which chelated 50% of the metal ion at higher concentrations (5.95 and 0.503 μg mL-1, respectively). In 70 and 50% ethanol, A. indica extracts also showed good metal chelating capacity comparable to the two standards. This result suggest that rather than depending completely on ascorbic acid, gallic acid and other synthetic antioxidant sources to mitigate the deteriorating effect of free radicals in the body, a more readily and cost effective source such as A. indica leaf extracts could be adopted. Although M. oleifera extracts did not show good metal chelating potential, its antioxidant properties is worth recommending as reflected from its DPPH scavenging capacity in absolute ethanol.

Reducing power is the measure of the extract ability to donate electrons in order to facilitate the reduction of ferric ion (Fe3+) to ferrous ion (Fe2+). The absorbance values indicate the concentration of Fe2+, thus, the higher the absorbance values the higher the concentration of Fe2+ which indicate the ability of the extract to donate electrons as an antioxidant reservoir (Laandrault et al., 2001; Yen et al., 2000). This may probably suggest that both M. oleifera and A. indica extracts are good electron donors (antioxidant sources) following their absorbance values at the respective concentration of the extracting solvents.

It has been reported that damages mediated by free radicals such as superoxide anion (O2¯), hydroxyl radical (OH) and peroxyl radical (ROO¯) result in the disruption of membrane fluidity, protein denaturation, lipid peroxidation which brings about generation of oxidative stress evidenced in many chronic diseases (Biglari et al., 2008; Ikpeme et al., 2014). Polyphenols from plant origin have the capacity to quench these radicals due to their ability to stabilize unpaired electrons (Anokwuru et al., 2011) and may have implication in prevention and/or curing oxidative stress diseases (Shukla et al., 2009). Although antioxidant activities of M. oleifera and A. indica obtained from the various in vitro assays in this study may not be completely obtainable in vivo, the results probably indicate that the extract of these two medicinal plants can scavenge and/or prevent free radical generation thereby mitigating oxidative stress mediated diseases in the body.

CONCLUSION

Comparatively, the leaf extract of A. indica had more phenols and flavonoids than M. oleifera in all the extracting solvents. This culminated why A. indica was able to scavenge 50% of the DPPH radical in absolute ethanol and also chelated 50% of the metal ion at a lower concentration than M. oleifera. The absorbance values for reducing power and total antioxidant capacity of A. indica were also comparably better than M. oleifera. Thus, the results indicate that A. indica leaf extract is a better antioxidant and free radical scavenger over M. oleifera mostly in absolute ethanol although more comparative antioxidant studies of the two plant extracts are required to further authenticate this claim.

REFERENCES
1:  Agarwal, A., K. Makker and R. Sharma, 2008. Clinical relevance of oxidative stress in male factor infertility: An update. Am. J. Reprod. Immunol., 59: 2-11.
CrossRef  |  PubMed  |  Direct Link  |  

2:  Aluko, B.T., O.I. Oloyede and A.J. Afolayan, 2013. Polyphenolic contents and free radical scavenging potential of extracts from leaves of Ocimum americanum L. Pak. J. Biol. Sci., 16: 22-30.
CrossRef  |  PubMed  |  Direct Link  |  

3:  Anokwuru, C.P., O. Ajibaye and A. Adesuyi, 2011. Comparative antioxidant activity of water extract of Azadiractha indica stem bark and Telfairia occidentalis leaf. Curr. Res. J. Biol. Sci., 3: 430-434.
Direct Link  |  

4:  Anwar, F., S. Latif, M. Ashraf and A.H. Gilani, 2007. Moringa oleifera: A food plant with multiple medicinal uses. Phytother. Res., 21: 17-25.
CrossRef  |  PubMed  |  Direct Link  |  

5:  Balasundram, N., K. Sundram and S. Samman, 2006. Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence and potential uses. Food Chem., 99: 191-203.
CrossRef  |  Direct Link  |  

6:  Basma, A.A., Z. Zakaria, L.Y. Latha and S. Sasidharan, 2011. Antioxidant activity and phytochemical screening of the methanol extracts of Euphorbia hirta L. Asian Pac. J. Trop. Med., 4: 386-390.
CrossRef  |  PubMed  |  Direct Link  |  

7:  Biglari, F., A.F.M. AlKarkhi and A.M. Easa, 2008. Antioxidant activity and phenolic content of various date palm (Phoenix dactylifera) fruits from Iran. Food Chem., 107: 1636-1641.
CrossRef  |  Direct Link  |  

8:  Biswas, K., I. Chattopadhyay, R.K. Banerjee and U. Bandyopadhyay, 2002. Biological activities and medicinal properties of neem (Azadirachta indica). Curr. Sci., 82: 1336-1345.
Direct Link  |  

9:  Calixto, J.B., 2000. Efficacy, safety, quality control, marketing and regulatory guidelines for herbal medicine (phytotherapeutic agents). Braz. J. Med. Biol. Res., 33: 179-189.
CrossRef  |  

10:  Demiray, S., M.E. Pintado and P.M.L. Castro, 2009. Evaluation of phenolic profiles and antioxidant activities of Turkish medicinal plants: Tilia argentea, Crataegi folium leaves and Polygonum bistorta roots. World Acad. Sci. Eng. Technol., 54: 312-317.
Direct Link  |  

11:  Dewanto, V., X. Wu, K.K. Adom and R.H. Liu, 2002. Thermal processing enhances the nutritional value of tomatoes by increasing total antioxidant activity. J. Agric. Food Chem., 50: 3010-3014.
CrossRef  |  Direct Link  |  

12:  Duarte-Almeida, J.M., A.V. Novoa, A.F. Linares, F.M. Lajolo and M.I. Genovese, 2006. Antioxidant activity of phenolics compounds from sugar cane (Saccharum officinarum L.) juice. Plant Foods Hum. Nutr., 61: 187-192.
CrossRef  |  PubMed  |  Direct Link  |  

13:  Ebrahimzadeh, M.A., S. Ehsanifar and B. Eslami, 2009. Sambucus ebulus elburensis fruits: A good source for antioxidants. Pharmacognosy Maga., 4: 213-218.
Direct Link  |  

14:  Ekaluo, U.B., E.V. Ikpeme, O. Udensi, A.A. Markson, B.E. Madunagu, G. Omosun and E.J. Umana, 2010. Effect of aqeous leaf extract of neem (Azadirachta indica) on the hormonal milieu of male rats. Int. J. Curr. Res., 7: 1-3.

15:  Ghimeray, A.K., C. Jin, B.K. Ghimine and D.H. Cho, 2009. Antioxidant activity and quantitative estimation of azadirachtin and nimbin in azadirachta indica A. Juss grown in foothills of Nepal. Afr. J. Biotechnol., 8: 3084-3091.
Direct Link  |  

16:  Gomez-Flores, R., C. Arzate-Quintana, R. Quintanilla-Licea, P. Tamez-Guerra, R. Tamez-Guerra, E. Monreal-Cuevas and C. Rodriguez-Padilla, 2008. Antimicrobial activity of Persea americana Mill (Lauraceae) (avocado) and gymnosperma glutinosum (Spreng.) Less (Asteraceae) leaf extracts and active fractions against Mycobacterium tuberculosis. Am. Euras. J. Scient. Res., 3: 188-194.
Direct Link  |  

17:  Hsu, B., I.M. Coupar and K. Ng, 2006. Antioxidant activity of hot water extract from the fruit of the Doum palm, Hyphaene thebaica. Food Chem., 98: 317-328.
CrossRef  |  

18:  Ikpeme, E.V., U.B. Ekaluo, M.E. Kooffreh and O. Udensi, 2011. Phytochemistry and heamatological potential of ethanol seed leaf and pulp extracts of Carica papaya (Linn.). Pak. J. Biol. Sci., 14: 408-411.
CrossRef  |  PubMed  |  Direct Link  |  

19:  Ikpeme, E.V., A.I. Nta, U.B. Ekaluo and O. Udensi, 2012. Phytochemical screening and haematological evaluation of Parkia biglobosa and Gonglonema latifolium. J. Basic Applied Res., 2: 2599-2606.
Direct Link  |  

20:  Ikpeme, E.V., O.U. Udensi, E.E. Ekerette and P.N. Chukwurah, 2013. Optimization of plant factory for sourcing natural antioxidants: A paradigm shift. Int. J. Adv. Res., 1: 7-15.
Direct Link  |  

21:  Ikpeme, E.V., U.B. Ekaluo, O.U. Udensi and E.E. Ekerette, 2014. Screening fresh and dried fruits of avocado pear (Persea Americana) for antioxidant activities: An alternative for synthetic antioxidant. J. Life Sci. Res. Discovery, 1: 19-25.
Direct Link  |  

22:  Iqbal, S. and M.I. Bhanger, 2006. Effect of season and production location on antioxidant activity of Moringa oleifera leaves grown in Pakistan. J. Food Comp. Anal., 19: 544-551.
CrossRef  |  Direct Link  |  

23:  Javanmardi, J., C. Stushnoff, E. Locke and J.M. Vivanco, 2003. Antioxidant activity and total phenolic content of Iranian Ocimum accessions. Food Chem., 83: 547-550.
CrossRef  |  Direct Link  |  

24:  Jayaprakasha, G.K., B.S. Jena, P.S. Negi and K.K. Sakariah, 2002. Evaluation of antioxidant activities and antimutagenicity of turmeric oil: A byproduct from curcumin production. Z. Naturforsch. C, 57: 828-835.
PubMed  |  Direct Link  |  

25:  Koffi, N., A.K. Ernest and S. Dodiomon, 2009. Effect of aqueous extract of Persea americana seeds on the glycemia of diabetic rabbits. Eur. J. Scient. Res., 26: 376-385.
Direct Link  |  

26:  Kottaimuthu, R., 2008. Ethnobotany of the valaiyans of karandamalai, Dindigul district, Tamil Nadu, India. Ethnobot. Leaflets, 12: 195-203.
Direct Link  |  

27:  Kukic, J., S. Petrovic and M. Niketic, 2006. Antioxidant activity of four endemic Stachys taxa. Biol. Pharmaceut. Bull., 29: 725-729.
CrossRef  |  Direct Link  |  

28:  Laandrault, N., P. Pouchert, P. Ravel, F. Gase, G. Cros and P.L. Teissedro, 2001. Antioxidant activities and phenolic level of French wines from different varieties and vintages. J. Agric. Food Chem., 49: 3341-3343.
CrossRef  |  Direct Link  |  

29:  2012. Therapeutic potential of Moringa oleifera leaves in chronic hyperglycemia and dyslipidemia: A review. Front. Pharmacol., Vol. 3
CrossRef  |  

30:  Mensor, L.L., F.S. Menezes, G.G. Leitao, A.S. Reis, T.C. dos Santos, C.S. Coube and S.G. Leitao, 2001. Screening of Brazilian plant extracts for antioxidant activity by the use of DPPH free radical method. Phytother. Res., 15: 127-130.
CrossRef  |  PubMed  |  Direct Link  |  

31:  Mishra, G., P. Singh, R. Verma, S. Kumar, S. Srivastav, K.K. Jha and R.L. Khosa, 2011. Traditional uses, phytochemistry and pharmacological properties of Moringa oleifera plant: An overview. Der Pharmacia Lettre, 3: 141-164.

32:  Oluwole, F.S., S.A. Onasanwo and S.B. Olaleye, 2011. Effects of aqueous and methanolic extracts of Persea Americana leaf (Avocado pear) on gastric acid secretion in male albino rats. Eur. J. Scient. Res., 61: 474-481.

33:  Maisuthisakul, P., M. Suttajit and R. Pongsawatmanit, 2007. Assessment of phenolic content and free radical-scavenging capacity of some thai indigenous plants. Food Chem., 100: 1409-1418.
CrossRef  |  Direct Link  |  

34:  Pokorny, J., N. Yanishlieva and M.H. Gordon, 2001. Antioxidants in Food: Practical Applications. Taylor and Francis, Boston, USA., ISBN-13: 9780849312229, Pages: 288.

35:  Sabale, V., V. Patel, A. Paranjape, C. Arya, S.N. Sakarkar and P.M. Sabale, 2008. Plant review Moringa oleifera (Drumstick): An overview. Pharmacogn. Rev., 2: 7-13.
Direct Link  |  

36:  Sharma, N., P.C. Gupta and C.V. Rao, 2012. Nutrient content, mineral content and antioxidant activity of Amaranthus viridis and Moringa oleifera leaves. Res. J. Med. Plant, 6: 253-259.
CrossRef  |  Direct Link  |  

37:  Anandjiwala, S., M.S. Bagul, H. Srinivasa, J. Kalola and M. Rajani, 2007. Antioxidant activity of stem bark of Tespesia populnea Soland ex Corr. J. Nat. Remedies, 7: 135-141.
Direct Link  |  

38:  Shukla, S., A. Mehta, V.K. Bajpai and S. Shukla, 2009. In vitro antioxidant activity and total phenolic content of ethanolic leaf extract of Stevia rebaudiana Bert. Food and Chem. Toxicol., 47: 2338-2343.
CrossRef  |  Direct Link  |  

39:  Siddaraju, M.N. and S.M. Dharmesh, 2007. Inhibition of gastric H+, K+-ATPase and Helicobacter pylori growth by phenolic antioxidants of Curcuma amada. J. Agric. Food Chem., 55: 7377-7386.
CrossRef  |  Direct Link  |  

40:  Siddhuraju, P. and K. Becker, 2003. Antioxidant properties of various solvent extracts of total phenolic constituents from three different agroclimatic origins of drumstick tree (Moringa oleifera Lam.) leaves. J. Agric. Food Chem., 51: 2144-2155.
CrossRef  |  PubMed  |  Direct Link  |  

41:  Tripathy, S., D. Pradhan and M. Anjana, 2010. Anti-inflammatory and antiarthritic potential of Ammania baccifera Linn. Int. J. Pharm. Biosci., 1: 1-7.
Direct Link  |  

42:  Uyoh, E.A., P.N. Chukwura, I.A. David and A.C. Bassey, 2013. Evaluation of antioxidant capacity of two Ocimum species consumed locally as spices in Nigeria as a justification for increased domestication. Am. J. Plant Sci., 4: 222-230.
CrossRef  |  Direct Link  |  

43:  Vijayakumar, S., R. Dhanapal, I. Sarathchandran, A.S. Kumar and J.V. Ratna, 2012. Evaluation of antioxidant activity of Ammania baccifera (L.) whole plant extract in rats. Asian Pac. J. Trop. Biomed., 2: S116-S119.
CrossRef  |  Direct Link  |  

44:  Kadam, V.J., Y.M. Joshi, H.P. Sawant and T.A. Jadhav, 2010. Free radical scavenging activity of aqueous solution of black salt. Int. J. Pharm. Pharmaceut. Sci., 2: 95-96.
Direct Link  |  

45:  Yen, G.C., P.D. Duh and D.Y. Chuang, 2000. Antioxidant activity of anthraquinones and anthrone. Food Chem., 70: 437-441.
CrossRef  |  Direct Link  |  

46:  Finefrock, A.E., A.I. Bush and P.M. Doraiswamy, 2003. Current status of metals as therapeutic targets in Alzheimer's disease. J. Am. Ger. Soc., 51: 1143-1148.
CrossRef  |  Direct Link  |  

©  2021 Science Alert. All Rights Reserved