Spatial specificity of radical scavenging ability in Moringa oleifera varieties from selected countries
Authors: Oluewu M. M  , Walker LT  
Published: December 2024

Moringa oleifera (MO) is widely recognized for its rich content of bioactive compounds, which possess significant antioxidant and anti-inflammatory properties. However, variations in the phytochemical composition of MO seeds, influenced by geographical origin and processing methods, have not been fully explored. This study investigates the radical scavenging abilities of MO seeds from Nigeria, Ghana, Haiti, and India, all grown under controlled conditions at the Winfred Thomas Agricultural Research Station (WTARS) at Alabama A and M University. The primary objective of this study was to assess the variation in radical scavenging abilities, specifically DPPH (1,1-diphenyl-2-picrylhydrazyl) activity, across different MO seed varieties and processing methods. This was done to determine if spatially specific dose-response behaviors exist and to identify which combinations of seed origin and preparation yield the highest antioxidant activity.
MO seeds were collected from four countries: Nigeria, Ghana, Haiti, and India, and subjected to three different processing methods—raw, boiled, and fermented. The seeds were then extracted using two solvents, 70% ethanol and 80% methanol. The DPPH radical scavenging activity was measured using the Brand-Williams method with slight modifications, and the results were expressed as micromoles of Trolox Equivalent (TE) per gram of sample. The study revealed significant variability in the antioxidant activity of MO seeds based on their geographical origin and processing methods. Among the four countries, MO seeds from India exhibited the highest average DPPH value (8018.87 µmol/g), followed by Haiti (6741.10 µmol/g), Nigeria (6349.98 µmol/g), and Ghana (6068.87 µmol/g). Raw seeds consistently showed the highest radical scavenging ability across all locations and solvents, with the highest recorded value in Haitian raw seeds extracted with 70% ethanol (9720 µmol/g). In contrast, fermented seeds exhibited the lowest antioxidant activity, with the least value observed in Ghanaian seeds extracted with 80% methanol (306.33 µmol/g).
The choice of solvent also played a crucial role, with 70% ethanol outperforming 80% methanol in preserving or extracting antioxidants, particularly in raw and boiled seeds. The study also found significant dose-response relationships, with raw seeds showing the steepest increase in DPPH activity with higher extract concentrations. In contrast, fermented seeds demonstrated a weaker dose-response, indicating diminished radical scavenging ability after fermentation. The ANOVA results further highlighted the significant effects of the country of origin, treatment method, and their interaction on antioxidant activity. The interaction between geographical origin and processing methods was particularly noteworthy, suggesting that the optimal method for maximizing antioxidant activity varies depending on the seed's origin. The findings underscore the importance of considering both the geographical origin and the processing method when evaluating the antioxidant properties of MO seeds. Indian and Haitian MO seeds, particularly in their raw form and extracted with 70% ethanol, offer the highest antioxidant potential. The study also demonstrates that minimal processing is crucial for preserving the radical scavenging ability of MO seeds.
Further research should focus on the specific phytochemical compounds responsible for the antioxidant activity in MO seeds from different regions. Additionally, farmers and producers should optimize cultivation and processing methods based on local environmental conditions to maximize the nutritional and medicinal benefits of MO seeds. Finally, public awareness programs should be initiated to promote the health benefits of MO seeds, particularly those with high antioxidant activity.