EVALUATION OF PHYSICO-CHEMICAL AND ANTIMICROBIAL STUDIES OF Delonix regia AND Piliostigma thonningii SEED OILS

Abstract

Delonix regia and Piliostigma thonningii seed oils were extracted with n-hexane using soxhlet extractor for six hours. The oils were concentrated over rotary evaporator to obtain golden yellow and greenish yellow coloured oils respectively. The oils were analysed for the following parameters: saponification value (142.08±1.00 and 129.45±0.47 mgKOH/g), iodine value (36.04±0.67 and 43.65±0.42 mg/iodine/100g), acid value (0.27±0.01 and 0.37±0.01 mg/KOH/g), specific gravity (0.79 and 0.81g/cm3), peroxide value (14±1.58 and 12±1.00 mg/KOH/g), and free fatty acid value (53.3±1.00 and 72.9±0.45 mgKOH/g) respectively. Preliminary antimicrobial screening of the oils against three different bacterial strains: Escherichia coli, Pseudomonas aeruginosa and Klebsiela oxytoca revealed that PTO exhibited high antimicrobial activity against E.Coli while DRO showed no significant effects; DRO showed significantly high antimicrobial activities against P.aeruginosa than PTO and the antimicrobial activities of PTO against K.oxytoca is very high compared to DRO. The DPPH antioxidant assay of the oils revealed that DRO exhibited higher antioxidant (IC50 = 0.013 μg/mL) activity than PTO, (IC50 = 0.646 μg/mL), but the IC50 of DRO is lower than those observed for the positive control. The result of GC-MS analysis showed the presence of 22 different compounds in DRO and 29 in PTO. The most abundant compound in DRO was 9,12-Octadecadienoic acid, methyl ester, (13.23 %). On the other hand, 9-octadecenoic acid (Oleic acid) was dominated in PTO by (15.4%). From this research finding, the seed oils of D.regia and P.thonningii may be of medicinally and industrially important and could also be used as a substitute for other oils or blended with other vegetable oils.