Abstract

K. E. Ekpo*, A. O. Onigbinde and I. O. Asia

Macrotermes bellicosus (MB), Imbrasia belina larva (IBL), Oryctes rhinoceros larva (OR) and Rhynchophorus pheonicis (RP) larva oils were extracted, and the oils were physically and chemically characterized. The lipid content recorded for the insects were 31.46 ± 0.57%, 15.16 ± 0.18%, 14.87 ± 0.33% and 23.30 ± 0.33% (wet weight) for MB, IBL, OR and RP respectively. RP and OR insect oils were golden yellow, odourless and fluid at room temperature (26 ± 2 oC), while that extracted from IBL and MB were of a lighter yellow colour. The insect lipids all gave a low solidification temperature and high iodine number indicating a relatively high level of unsaturation of the insect/larval oils. Their saponification values were high suggesting the presence of a fair amount of fatty acids but their acid values were low pointing to the fact that these fatty acids were not free but esterified acids. The cholesterol values were also low but highest in MB with a value of 41.8 ± 0.15 mg/100 g lipid. For all the insects, the neutral lipid fraction was the major fraction in the insect oils. RP had the highest neutral lipid fraction of 88.40 while MB had the least value of 69.87. At the same time MB had the highest phospholipids and glycolipid fractions with values of 19.14 and 10.81 respectively while RP had the least phospholipids and glycolipid fractions with values of 8.20 and 2.60 respectively. For IBL, RP and OR (which are insect larvae) the major fatty acids in the oils were palmitic and oleic acids while for MB (mature insect) the major fatty acids were palmitic and linoleic acids. The insect/larval oils contained more unsaturated fatty acids which explained the high iodine number, low solidification values and the liquid nature of the oils at room temperature. OR recorded the highest level of unsaturation of 65.61 while MB had the least level of unsaturation of 50.02%. Further analysis revealed a refractive index ranging from 1.1 ± 0.01 to 1.3 ± 0.05, specific gravity of 0.84 ± 0.02 to 0.90 ± 0.01, solidification value of 10 - 14°C, total lipid phosphorus ranging from 31.0 ± 0.25 to 47.18 ± 0.03 g/gm lipid, acid value of 3.12 ± 0.55 to 3.6 ± 0.06, iodine value of 108 ± 0.15 to 140 ± 0.51, saponification value of 187.17 ± 0.55 to 198.9 ± 0.25 and unsaponifiable matter of 8.11 ± 0.02 to 12.04 ± 0.11. These values when compared with that observed in oils which have been considered to be of high quality and of much use in pharmaceutical industries suggest that these insect oils may have pharmaceutical potential.