## 3 Bioactive Compounds in Peanut Skins
### Antimicrobial Activity  
As phenolic compounds are known to have antimicrobial properties, it is logical to examine the antimicrobial properties of peanut skin extracts. The first report used 80% ethanol in water to extract peanut skins [72]. The extract was used to determine the antioxidant power in meat when compared to synthetic antioxidants. While levels of 0.06% to 0.10% peanut skin extract had the equivalent power of 0.02% synthetic antioxidant in delaying the onset of rancidity in the meat samples, the inhibition of the microorganic growth was much less than a chemical antibiotic. Certain phenolic compounds including proanthocyanidins have proven antimicrobial properties. The study of extracts from peanut skins against certain bacterial strains has used this justification [68; 73; 74]. Peanut skins were initially extracted into boiling water, then portioned into ethyl acetate to isolate the proanthocyanidin fraction [73]. After solvent removal, the extracts were incorporated into growth media containing apple juice to create a model food system. _Saccharomyces cerevisiae_, _Zygosaccharomyces bailii_, and _Zygosaccharomyces bisporus_ were used as the test organisms in individual cultures. Although peanut skin extract proved to inhibit the yeast growth due to alteration of the cell membranes, the amount needed to be effective was thought to be too high for practical use in food. Using acetone in water acidified with acetic acid (70:28:2), hexane defatted peanut skins were extracted to recover the polyphenols [68]. Plated media were dosed with increasing amounts of the extracts in water from 250 to 1500 ppm. The plates were inoculated using _Salmonella typhimurium_, _E. coli_ OH157:H7, or _Listeria monocytogenes_ as the test organisms. No inhibition of _Listeria monocytogenes_ was seen by the addition of peanut skin extract and less inhibition was seen in the growth of the other organisms tested when compared to similar amounts of grape seed extracts. This was attributed to the B-type procyanidins present in grape seed extracts being more effective than the A-type procyanidins found in peanut skin extracts. Comparison of the antimicrobial effects of extracts from peanut skins with those from dry blanched peanuts used 70% acetone in water as the extractant [74]. The peanut skin extracts were found to be less effective in inhibiting the growth of a range of both gram-positive and gram-negative organisms by an order of magnitude. This was attributed to the phenolics from the blanched peanut extracts containing small phenolics rather than polymers of phenolic compounds. Peanut skins were extracted with 80% ethanol in water and then either freeze-dried or spray-dried with maltodextrin as a carrier [74]. The antimicrobial action against _Staphylococcus aureus_, _Listeria monocytogenes_, _Salmonella enterica_ subs. _Enterica_ serovar Enteritidis, and _Escherichia coli_ was evaluated. None of the powders showed any inhibition of Escherichia coliThe freeze-dried extract was the most effective in inhibiting the other pathogenic organisms. Although the spray-dried extracts were inhibitory as well, the lesser degree was attributed to the dilution of the phenolic content by the addition of maltodextrin in the preparation of the powders. Antiviral activity in peanut skin extracts has been demonstrated in cell culture trials when used in combination with antiviral drug compounds [75]. Pure ethanol was used to extract defatted peanut skins. The effect was most pronounced during the early stages of infection. The effect was attributed to the polyphenols present. The resveratrol content was also determined but not found to show concentration dependence. Fungal growth on grain producing mycotoxins has damaging health effects when consumed and reduce the acceptability of the crops. A study demonstrates the effect of peanuts skin extracts using 70% ethanol in the water on the growth of _Fusarium verticilliodes_ on maize [76].