Dose-dependent Inhibition of Singlet Oxidation in Olive Oil by African Nutmeg (Monodora myristica) Crude Extract

Cleaned, dried and deshelled African Nutmeg Monodora myristica was ground and extracted with methanol. Doses of 0.0g, 0.5g, 1.0g, 1.5g, 2.0g of the Monodora myristica crude extract were added to each of five sets of reaction mixtures, prepared by dissolving 2g of olive oil in 10 % methanol/dichloromethane to which 5mg of methylene blue was added as photosensitizer. Each reaction mixture, except its corresponding control, was subjected to singlet oxidation for a total of 10hours, removing 10ml aliquots every 2 hours to determine its Peroxide Value (PV) using the International Diary Federation (IDF) method. Samples of the reaction mixtures were also analyzed using the Fourier Transform Infrared Spectrophotometer. The peroxide value of the reaction mixtures containing 0.0g, 0.5g, 1.0g, 1.5g, and 2.0g amounts of the crude Monodora myristica increased from 9.56Meq/Kg before photoxidation (i. e. control) to 9.77Meq/Kg, 9.56Meq/Kg, 9.71Meq/Kg, 9.67Meq/Kg, and 9.67Meq/Kg respectively after 2hours of photoxidation. Further oxidation did not show any significant increase in PV of the reaction mixtures. The FTIR Spectra showed that the plant extract protected the C=C double bond whose absorption band was at 732cm-1. This protection was optimal in the reaction mixture with 0.5g of the extract. However, the reaction mixture with the 1.5g dose of extract had pronounced peaks of both the C=C double bond group at 732cm-1 and C=O group at 1022.27cm-1.