Antioxidant potential of methanolic extracts and powders of some Cameroonian spices during accelerated storage of soybean oil

The efficacy of methanolic extracts and powders of 12 spices (Pimpinella anisum, Scorodophleuszenkeii, Xylopiaparviflora, Eugenia caryophyllus, Fagara leprieurii, Fagara macrophylla, Monodora myristica, Olax subscorpioidea, Xylopiaaethiopica, Allium sativum, Zinziber officinale and Cinnamomum zeylanicum) in stabilizing crude soyabean oil during accelerated storage was assessed. The phytochemical screening revealed the presence of phenols in all the spices except that of Allium sativum. Total phenolic content (TPC) and DPPH radical scavenging activity of the extracts varied significantly (p < 0.01) ranging from 1.34 to 17.72 g GAE/100 g and 18.91% to 96.39% respectively. Extract of Zinziber officinale, Olax subscorpioidea, Fagaramacrophylla, Eugenia caryophyllus and Xylopia parviflora, which offered the highest TPC, exhibited superior antioxidant activity with regard to the DPPH. Furthermore, the antioxidant effectiveness of the extracts and powders was assessed using crude soyabean oil (CSO) as the oxidation substrate. CSO samples stabilized with extracts at a concentration of 500 ppm (w/w) and powders at a concentration of 1000 ppm were subjected to accelerated storage (65 ̊C, oven heating, 24 days, 8 h heating cycle per day), and analyzed periodically for the extent of oxidative alterations following the measurement of iodine and peroxide value. CSO + BHT at 200 ppm served as standards besides the control. Results reveal Zinziberofficinale, Cinnamomum zeylanicum, Scorodophleuszenkerii, Monodora myristica, Xylopiaaethiopica, Allium sativum, Fagara leprieurii extracts and powders and the powder of Pimpinella anisum to be potent antioxidants for stabilization of crude soyabean oil.