The efficacy of methanolic extracts and powders of
12 spices (Pimpinella anisum, Scorodophleuszenkeii, Xy- lopiaparviflora, 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 to17.72 gGAE/100 gand 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.