Protein profile and antioxidant activity of Moringa oleifera seed

Abstract

Moringa oleifera is one of the common plants found in different parts of the world with medicinal and nutritional properties. Many studies have proved the edibility of all parts of the tree such as leaves, pods, and seeds which have the ability to treat and prevent diseases making it a highly valued plant. To date, no proteomics and antioxidant studies are available on different parts of the fresh and naturally sun-dried seeds which are the whole seed, seed and seed coat. Hence, this study focuses on the One-dimensional (1D) electrophoretic pattern of the fresh and dry seed in three different parts determined using Sodium dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Protein identification was further analysed using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) analysis for the seed samples with the highest band count. Next, antioxidant activity was carried out for the protein extract using 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and Ferric Reducing Antioxidant Power (FRAP) assay. As for the crude extract, antioxidant activity was tested using FRAP and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay. Based on the electrophoretic pattern obtained, there were approximately 16-29 bands in all the samples in which the dry seed had the highest band count followed by the fresh seed. As for the protein identification, a total of 328 proteins for the fresh seed and 326 proteins for the dry seed was identified. The proteins were further classified according to their functional groups based on GoMapMan database. The highest functional groups for both samples were protein biosynthesis, followed by metabolism and RNA biosynthesis. In terms of antioxidant activity, the dry seed coat had the highest antioxidant value for protein extract tested on both assays. Meanwhile, for the crude extract, the dry whole seed resulted in the highest antioxidant value for DPPH assay while the dry seed coat had the highest FRAP assay. Overall, the seed coat exhibits good antioxidant activity in both protein and crude extract. The findings obtained provide information on the proteins and antioxidant activity found in fresh and dry seed of Moringa oleifera. Thus, this information could work as a platform for further analysis on the protein identification of other seed parts influenced by environmental conditions. In addition, the information could be used for comparisons with commercialized Moringa seed products for better understanding on the effect of drying method on the nutrient content of plant seeds.