## 2 Extraction of Peanut Skins
### Compound Identification
\begin{table}
\begin{tabular}{c c c} \hline
**Extract a** & **Extraction Percentage b** & **Phenolic Total Content b** \\ \hline ME & 17.9 (cd) \(\pm\) 0.6 & 148.7 (d) \(\pm\) 3.6 \\ EE & 18.5 (cd) \(\pm\) 0.2 & 114.8 (c) \(\pm\) 5.9 \\ KE & 19.4 (de) \(\pm\) 0.6 & 61.4 (a) \(\pm\) 1.4 \\ AE & 9.9 (a) \(\pm\) 0.1 & 58.5 (a) \(\pm\) 2.4 \\ dME & 17.1 (cd) \(\pm\) 0.9 & 165.6 (a) \(\pm\) 16.2 \\ dEE & 16.2 (c) \(\pm\) 1.1 & 150.4 (d) \(\pm\) 9.1 \\ dKE & 13.1 (b) \(\pm\) 0.1 & 65.5 (a) \(\pm\) 1.8 \\ dAE & 10.0 (a) \(\pm\) 0.3 & 90.7 (b) \(\pm\) 1.1 \\ \hline \end{tabular}  
* Abbreviations: ME = Methanbolic extract, EE = Ethanolic extract, KE = Acetonic extract, AE = Aqueous extract. The addition of the letter “d” signifies detailed peanut skins. b Means followed by the same letter within each column are not significantly different at \(\alpha\) = 0.05.  
\end{table} 
Table 1: Extraction percentages (wt %) of antioxidant components and phenolic total contents (mg/g) of the extracts from peanut skins using different solvents [17]. two compounds had never been isolated from a natural source. Other compounds identified were several flavonoid glycosides. Further research with this extraction technology allowed for the isolation and identification of several oligomeric proanthocyanidins [21]. The activity of the flavan-3-ols, catechin and epicatechin and their oligomers, and the proanthocyanidins has been the subject of research in cocoa sources and tea [22]. As those found in peanut skins are composed of the A linkage form compared to the B or C forms in those other sources, comparison studied have investigated the comparative activity. The difference in the 3-dimensional structure of the compounds due to the extra 2\(\beta\)-O7 linkage in the A-type found in peanut skins could affect their interaction with membrane phospholipids (Figure 1). As this has proven to influence membrane fluidity and thus the ability of the compounds to interact with free radicals within the cell, the action of the different forms was examined [23]. A system using fluorescent probes that could be oxidized by peroxyl radicals that were induced by the assay on liposomes was used. The effectiveness was found to be dependent on the number of available flavanol monomers present, so no significant differences were seen between the types of dimers and trimers. The A-type dimer did have a different effect on the ordering of the core, with different rigidification indicating a different type of reaction with this form of the dimer. It has been proposed that the rigidity of the A-type due to the additional bond between the adjoining flavan-3-ols plays a role in their interaction with large biomolecules [24]. The color of peanut skins has been proven to have a relationship with the composition of the phenolic compound present [25; 26; 27; 28; 29]. In an examination of all the market types with skin colors from light brown to dark red, total flavonoids were not found to be as closely correlated to skin color as they were to growing location. The statistical relationship between the total flavonoids and the procyanidin content indicated that these compounds are the major flavonoids present. This indicates these compounds are more sensitive to stress conditions. The total phenols were more closely related to the hue of the skin color. Only the peanuts with the black seed coats were found to contain cyanidin-3-O-sambubioside both free and in glucosides [27]. Black seed coated peanuts were used to study the genetic control of peanut seed coat color [30]. In this report, the flavonoids present in white, red, and striped peanut skins in addition to those in the black peanut seed coats were extracted using 75% methanol in water acidified with 0.5% acetic acid. Figure 1: Structures of the procyanidin dimers. (**a**) The A-form found in peanut skins. (**b**) The B-form found in cocoa. The extracts were filtered, and the flavonoids were identified and quantified using High-Pressure Liquid Chromatography-Mass Spectrometry-Time of Flight (HPLC-MS-TOF).